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UNIVERSIDADE ESTÁCIO DE SÁ 
 
 
 
 
 
 
Hélio Pereira Lopes 
 
 
 
 
 
 
Influência do Tipo de Movimento de Rotação na Vida Útil 
em Fadiga de Instrumentos Endodônticos 
de Níquel-Titânio Mecanizados 
 
 
 
 
 
 
 
 
 
 
Rio de Janeiro 
2015 
ii 
 
HÉLIO PEREIRA LOPES 
 
 
 
 
INFLUÊNCIA DO TIPO DE MOVIMENTO DE ROTAÇÃO NA VIDA ÚTIL 
EM FADIGA DE INSTRUMENTOS ENDODÔNTICOS 
DE NÍQUEL-TITÂNIO MECANIZADOS 
 
 
 
 
 
 
 
 
 
Tese apresentada à Faculdade 
de Odontologia da Universidade 
Estácio de Sá, visando à 
obtenção do grau de Doutor em 
Odontologia (Endodontia). 
 
 
 
 
 
 
ORIENTADOR 
Prof. Dr. José Freitas Siqueira Jr. 
 
 
 
 
 
UNIVERSIDADE ESTÁCIO DE SÁ 
RIO DE JANEIRO 
2015 
iii 
 
 
DEDICATÓRIA 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Aos meus filhos, Marcelo, Isabela e 
aos meus netos, Lucas, Daniel e 
Davi pelo estímulo permanente para 
que eu possa prosseguir nessa 
minha longa caminhada. 
iv 
 
AGRADECIMENTOS 
 
À Isabelita, minha esposa, pelo amor, amizade e companheirismo que me 
incentivam a seguir em frente, mesmo diante das adversidades encontradas. 
 
Ao professor e amigo José Freitas Siqueira Júnior, por ser referência 
mundial de pesquisador e professor. Pelo exemplo de determinação e amor ao 
que faz. Com sua genialidade tem contribuído mundialmente para tornar a 
endodontia uma especialidade mais científica. Minha eterna gratidão pela 
parceria em textos e livros científicos que temos publicado. 
 
Ao professor e amigo Carlos Nelson Elias, por sua extraordinária 
competência, perseverança e incansável dedicação ao ensino e a pesquisa. 
Seu profundo conhecimento na área de ciência dos materiais muito tem 
contribuído para o avanço científico da Odontologia. Obrigado por compartilhar 
todo o seu valioso conhecimento com extraordinária simplicidade, humildade e 
tolerância. 
 
À professora Márcia Valéria Boussada Vieira, pela dedicação e competência 
a que se dedica à difícil missão de formar e informar novos endodontistas. 
Agradeço pela valiosa colaboração no desenvolvimento e execução deste 
trabalho, assim como valorosos conhecimentos compartilhados. 
 
Aos professores Victor Talarico e Letícia Chaves, pela colaboração 
criteriosa na execução dos ensaios mecânicos realizados em laboratório. 
Obrigado pela disponibilidade e valiosa colaboração. 
 
À professora Isabela das Neves Roças Siqueira, pelo incentivo, amizade e 
confiança depositada. 
 
Ao Instituto Militar de Engenharia, pela cessão de seus laboratórios. 
 
v 
 
À secretária Angélica Pedrosa, pela gentileza e amizade. 
 
À professora de português, Nina Rosa Leitão de Carvalho Lima, por sua 
correção e revisão deste trabalho. 
 
Os meus agradecimentos a todos os colaboradores que participaram na 
elaboração e publicação dos artigos pertinentes à confecção deste trabalho. 
 
 
vi 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
É fácil descrever técnica endodôntica. 
Difícil é executá-la. 
 
vii 
 
ÍNDICE 
 
Pág. 
RESUMO viii 
ABSTRACT ix 
LISTA DE SIGLAS E ABREVIATURAS x 
1.INTRODUÇÃO 1 
2.JUSTIFICATIVA 11 
3.HIPÓTESE 12 
4.OBJETIVOS 13 
5.ARTIGOS PUBLICADOS 14 
6.DISCUSSÃO 57 
7.CONCLUSÕES 73 
8. REFERÊNCIAS BIBLIOGRÁFICAS 75 
viii 
 
RESUMO 
 
Objetivo: Este estudo avaliou e comparou a influência dos movimentos de 
rotação reciprocante e de rotação contínua na vida útil em fadiga de 
instrumentos endodônticos de niquel-titânio (NiTi) mecanizados, quando 
submetidos a ensaios de flexão rotativa estáticos e dinâmicos. 
Métodos: Os dispositivos empregados nos ensaios mecânicos de flexão 
rotativa estático e dinâmico, assim como os canais artificiais, foram os mesmos 
utilizados em todos os trabalhos avaliados e analizados nesse estudo. 
Resultados: Os resultados obtidos demonstraram diferenças estatísticas entre 
os movimentos de rotação reciprocante e de rotação contínua. Também 
ocorreram diferenças significantes em relação ao modelo de ensaio de flexão 
rotativa estático e dinâmico. 
Conclusão: Os resultados obtidos revelaram que os instrumentos 
endodônticos de NiTi mecanizados, quando acionados com o movimento de 
rotação reciprocante no modelo dinâmico, apresentaram maior vida útil em 
fadiga, quando comparados ao movimento de rotação contínua no modelo 
estático. 
 
 
Palavras-chave: instrumentos endodônticos de níquel-titânio; movimento de 
rotação reciprocante; movimento de rotação contínua; fratura em flexão 
rotativa; ensaio estático; ensaio dinâmico. 
ix 
 
ABSTRACT 
 
Aim: This study evaluated and compared the influence of the reciprocating and 
the continuous rotation movements on the fatigue life of rotary nickel-titanium 
(NiTi) instruments subjected to static and dynamic cyclic fatigue assays. 
Methods: The devices used in the mechanic assays of static and dynamic 
cyclic fatigue as well as the artificial canals were the same used in all the 
experiments evaluated and analyzed in this study. 
Results: Findings showed statistic difference between the reciprocating and the 
continuous rotation movements. There was also a significant difference related 
to the use static and dynamic cyclic fatigue tests. 
Conclusion: The present results revealed that the rotary NiTi endodontic 
instruments working in reciprocating rotation in the dynamic model showed 
longer fatigue life when compared to the continuous rotation movement in the 
static model. 
 
 
Key words: nickel-titanium endodontic instruments; reciprocating movement; 
continuous rotation movement; rotation bending fracture; static assay; dynamic 
assay. 
 
 
 
 
x 
 
LISTA DE SIGLAS E ABREVIATURAS 
 
AISI - American Iron and Steel Institute 
D0 - diâmetro da ponta da parte de trabalho de um instrumento endodôntico 
D3 - diâmetro medido na parte de trabalho do instrumento endodôntico 
distando 3 mm da ponta 
D13 - diâmetro medido na parte de trabalho do instrumento endodôntico 
distando 13 mm da ponta 
D16 - diâmetro medido junto do intermediário de instrumentos endodônticos 
com comprimento de 16 mm na parte de trabalho 
HV - microdureza Vickers 
ISO - International Organization for Standardization 
MEV - microscopia eletrônica de varredura 
NCF - número de ciclos até a fratura 
NiTi - liga níquel-titânio 
NiTiNOL - Níquel-Titânio-Naval Ordenance Laboratory 
NOL - Naval Ordenance Laboratory em Silver Springs, EUA 
 
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1. INTRODUÇÃO 
 
Instrumento endodôntico é uma ferramenta de natureza metálica 
empregada como agente mecânico na instrumentação de canais radiculares. 
(LOPES et al., 2010a). 
A ocorrência de falhas de um material normalmente é o resultado de 
deficiências do projeto, processamento inadequado dos materiais, de 
deterioração em uso e operação incorreta pelo profissional. 
A fratura dos instrumentos endodônticos consiste na separação em duas 
partes, devido à aplicação de cargas externas. Pode ser induzida pela 
aplicação de cargas em torção ou em flexão rotativa (LOPES et al., 2000; 
ELIAS & LOPES, 2007; LOPES et al., 2007; CHEUNG, 2009). 
A resistência à fratura dos materiais depende basicamente das forças de 
coesão entre seus átomos e a presença de defeitos nos materiais. Não existe 
material sem defeito. Sabendo-se desta limitação, os materiais (instrumentos 
endodônticos) são submetidos aos diferentes ensaios mecânicos para a 
determinação de suas propriedades mecânicas e previsão de seu desempenho 
clínico. A despeito disso, às vezes, os materiais podem apresentar fratura com 
carregamento abaixo do seu limite de resistência, obtido em ensaios 
mecânicos(CALLISTER, 2002). 
Os instrumentos endodônticos são fabricados com ligas de aço 
inoxidável ou com ligas níquel-titânio (NiTi) convencional e modificadas. O 
grande diferencial entre os instrumentos endodônticos de NiTi e de aço 
inoxidável é a flexibilidade. Os instrumentos de NiTi apresentam flexibilidade 
2 
 
500% maior do que os de aço inoxidável; esta maior flexibilidade aumenta a 
resistência em fadiga de um instrumento endodôntico, quando submetido ao 
ensaio de flexão rotativa. Esta propriedade também permite que estes 
instrumentos acompanhem a curvatura de um canal com facilidade, reduzindo 
o deslocamento apical e mantendo a forma original do mesmo, com menor 
movimentação do eixo central do canal radicular durante a instrumentação 
(SERENE et al., 1995; BERUTTI et al., 2012; BÜRKLEIN & SCHÄFER, 2013). 
Apesar disto, o risco de fratura dos instrumentos endodônticos continua a ser 
um problema durante a instrumentação de canais radiculares curvos. 
A fratura dos instrumentos endodônticos pode ocorrer por torção ou por 
flexão rotativa. A fratura por torção ocorre quando a ponta ou qualquer parte de 
um instrumento fica imobilizada no interior de um canal radicular, enquanto sua 
haste de acionamento continua a girar. Nesta condição, o limite elástico do 
material é ultrapassado e o instrumento endodôntico sofre deformação plástica. 
A continuidade do carregamento (giro), estando o instrumento em deformação 
plástica, pode levá-lo a falha (fratura por torção). 
Já a fratura por flexão rotativa promove a fratura por fadiga de um 
instrumento endodôntico. A fratura por flexão rotativa ocorre quando um 
instrumento endodôntico gira no interior de um canal curvo. Nesta condição, o 
instrumento é submetido a tensões trativas e compressivas concentradas na 
região de curvatura máxima do canal. Esta concentração de tensões trativas e 
compressivas podem promover mudanças microestruturais na liga metálica, 
promovendo a falha por fadiga do instrumento endodôntico. 
3 
 
A fratura por fadiga ocorre sem que haja qualquer sinal visível de 
deformação plástica anteriormente. A vida útil em fadiga de um instrumento 
endodôntico é diretamente proporcional à intensidade das tensões a que são 
submetidos. A intensidade das tensões varia em função da geometria dos 
canais, da geometria dos instrumentos endodônticos e da flexibilidade da liga 
metálica empregada na fabricação dos instrumentos (PRUETT, 1997; HAIKEL 
et al., 1999; LOPES et al., 2013a). 
Com o objetivo de reduzir a intensidade das tensões aplicadas em um 
instrumento endodôntico, durante a instrumentação de um canal curvo, tem 
sido propostas mudanças no tipo de movimento a ele aplicado. Assim a 
crescente proposta é o acionamento de instrumentos endodônticos com 
dispositivos mecânicos (motores e contra ângulos especiais), por meio do 
movimento de rotação reciprocante. Este movimento pode aumentar a vida útil 
em fadiga de instrumentos endodônticos, quando comparado com o movimento 
de rotação contínua, estático ou dinâmico (WAN et al., 2011; KIM et al., 2012; 
LOPES et al., 2013b, LOPES et al., 2013c). 
O uso de contra-ângulos especiais com o objetivo de obter o movimento 
reciprocante data de 1928 (Cursor Filing Contra-Angle; W&H, Bürmoos, 
Áustria). Desde então, outros contra ângulos tem sido desenvolvidos com o 
propósito de acionar os instrumentos endodônticos por meio de movimento de 
rotação reciprocante (YARED & RAMLI, 2013). 
 
 
 
4 
 
Movimentos dos instrumentos endodônticos 
Durante a instrumentação de canais radiculares, os instrumentos 
endodônticos podem promover o desgaste da dentina (ampliação do canal 
radicular) por meio dos movimentos (limagem, alargamento ou alargamento e 
limagem) aplicados a eles, obtidos manualmente ou por dispositivos 
mecânicos. O movimento de alargamento ou limagem está relacionado à 
geometria da parte de trabalho, ao comportamento mecânico do instrumento e 
à anatomia dos segmentos de canais radiculares (LOPES et al., 2010a). 
 
Movimento de alargamento 
Alargamento é um processo mecânico de usinagem destinado a ampliar 
por meio do corte de um material, o diâmetro de um furo (canal radicular) pré-
existente. 
Alargadores endodônticos são instrumentos de natureza metálica cuja 
haste de corte, geralmente, é cônica. Os alargadores endodônticos são 
instrumentos (ferramentas) projetados exclusivamente para alargar canais 
radiculares (LOPES et al., 2010a). 
O alargamento consiste no giro (movimento de rotação) e no 
deslocamento compressivo (movimento de avanço) simultâneos de um 
alargador no interior de um furo. Para que ocorra o alargamento de um canal 
radicular (corte do material), é necessário que o instrumento trabalhe justo no 
interior de um furo, ou seja, o diâmetro do instrumento deve ser maior do que o 
do furo e o círculo de corte complete todo o contorno do furo. Os alargadores 
endodônticos de NiTi são indicados para a realização do movimento de 
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alargamento empregado na instrumentação de canais radiculares (LOPES et 
al., 2010b). 
Em endodontia, os alargadores endodônticos podem executar o 
movimento de alargamento, por meio de uma rotação parcial à direita, de uma 
rotação parcial alternada ou reciprocante (com rotação à direita e à esquerda 
ou à esquerda e à direita) ou de uma rotação contínua à direita (LOPES et al., 
2010b). 
O movimento de alargamento parcial à direita é realizado manualmente. 
O movimento de alargamento parcial reciprocante pode ser realizado 
manualmente ou por dispositivos mecânicos. Quando os instrumentos 
endodônticos apresentam hélices da direita para a esquerda, o instrumento 
deve ser acionado inicialmente à direita, com o objetivo de cortar a dentina e, à 
esquerda, para libertar o instrumento endodôntico do esforço de corte. Quando 
os instrumentos endodônticos apresentam hélices da esquerda para a direita, o 
instrumento deve ser acionado inicialmente à esquerda com o objetivo de 
cortar a dentina e, à direita, com o objetivo de libertar o instrumento do esforço 
de corte (LOPES et al., 2010b). 
O movimento de alargamento parcial reciprocante por meio de 
dispositivos mecânicos pode ser programado para funcionar com diferentes 
ângulos de rotação. O ângulo de rotação reciprocante pode variar ou ser 
constante. Quando variável é maior no sentido de corte da dentina. Quanto 
maior o ângulo de rotação reciprocante menor será a resistência em flexão 
rotativa (vida útil em fadiga) do instrumento endodôntico. (WAN et al., 2011; 
KIM et al., 2012; PLOTINO et al., 2012; GAMBARINI et al., 2012a; LOPES et 
6 
 
al., 2013b; LOPES et al., 2013c) A frequência das oscilações pode variar com a 
velocidade de giro do dispositivo mecânico. A posição do ângulo de corte pode 
se situar na mesma região em relação ao círculo de corte ou pode se deslocar 
sucessivamente completando o contorno do círculo de corte. 
No movimento de alargamento contínuo, o instrumento endodôntico 
deve girar continuamente à direita. É executado por meio de dispositivos 
mecânicos (motores e contra ângulos especiais); porém, podem ser acionados 
manualmente. A velocidade de giro é variável e normalmente indicada pelo 
fabricante. Quanto maior a velocidade de giro, menor será a vida útil em fadiga 
do instrumento empregado (LOPES et al., 2009; KIM et al., 2012). 
O movimento de alargamento contínuo, em comparação ao alargamento 
reciprocante, induz maior tensão trativa e compressiva na região crítica (ponto 
de maior tensão) em flexão rotativa, reduzindo a vida útil em fadiga do 
instrumento endodôntico (LOPES et al., 2013b; LOPES et al., 2013c). 
 
Fratura por flexão rotativa 
A fratura por flexão rotativa ocorre quando um instrumento endodôntico 
gira no interior de um canal curvo, estando ele dentro do limite elástico do 
material. Na região de flexão rotativa de um instrumento endodôntico são 
induzidas tensões alternadas trativas e compressivas.A repetição destas 
tensões promove mudanças microestruturais acumulativas, que induzem a 
fratura por fadiga do instrumento endodôntico. 
A fadiga é um fenômeno que ocorre quando são aplicados 
carregamentos dinâmicos repetidos ou flutuantes a um material metálico e o 
7 
 
mesmo se rompe com uma carga muito menor que a equivalente a sua 
resistência estática. A fadiga é importante no sentido de que ela é a maior 
causa individual de falhas em metais, sendo estimado que ela compreenda 
aproximadamente 90% de todas as falhas metálicas (LOPES & ELIAS, 2001; 
CHEUNG, 2009; RODRIGUES et al., 2011). 
A fratura por fadiga de um instrumento pode ser avaliada e analisada por 
meio de ensaio mecânico por flexão rotativa. 
Para a realização do ensaio mecânico de flexão rotativa é necessário o 
uso de dispositivos específicos (PRUETT et al., 1997; LI et al., 2002; LOPES et 
al., 2013a). O instrumento gira no interior de um canal artificial curvo com raio 
de curvatura, posição e comprimento do arco pré-determinados (LOPES et al., 
2013a). É considerado ensaio destrutivo, ou seja, é realizado até ocorrer a 
fratura do instrumento endodôntico. O canal artificial deve possuir diâmetro 
maior do que o do instrumento a ser ensaiado. O instrumento endodôntico é 
acionado a uma velocidade pré-determinada, empregando-se um contra ângulo 
acoplado a um micromotor elétrico. O conjunto canal artificial, contra ângulo / 
micromotor elétrico é fixado em um dispositivo suporte, tendo como objetivo 
principal eliminar a interferência do operador na indução de tensões sobre os 
instrumentos endodônticos, durante o ensaio de flexão rotativa (LOPES et al., 
2013a). 
Na endodontia, o ensaio mecânico de flexão rotativa pode ser 
considerado estático ou dinâmico. É considerado estático, quando um 
instrumento endodôntico gira no interior de um canal artificial curvo, 
permanecendo numa mesma distância, ou seja, sem deslocamento longitudinal 
8 
 
de avanço e retrocesso (PRUETT et al., 1997; HAIKEL et al., 1999; LOPES et 
al., 2007). Quando um instrumento, durante o ensaio, é movimentado 
longitudinalmente com avanço e retrocesso, é considerado dinâmico. Em 
ambas as condições os instrumentos podem ser ensaiados por meio de 
rotação reciprocante ou contínua (LI et al., 2002; LOPES et al., 2010c; LOPES 
et al., 2013c). 
De acordo com TOBUSHI et al. (1998), o ensaio de flexão rotativa é um 
método simples e eficaz para determinar o comportamento mecânico em fadiga 
dos instrumentos endodônticos de NiTi. 
 
Intensidade das tensões 
A intensidade das tensões (força) a que um instrumento endodôntico fica 
submetido durante um ensaio mecânico de flexão rotativa, ou durante o uso 
clínico, está relacionada à geometria dos canais, à geometria dos instrumentos 
endodônticos e ao tipo de movimento empregado (LOPES et al., 2010c; 
LOPES et al., 2013a). 
Quanto à geometria dos canais, o profissional não pode mudá-la. Porém, 
os instrumentos e o tipo de movimento selecionados estão atrelados ao 
conhecimento do profissional. 
Quanto à geometria dos canais, destacam-se o comprimento do raio, o 
comprimento do arco e a posição do arco ao longo do comprimento do canal 
(LOPES et al, 2013a). Quanto menor o comprimento do raio, quanto maior o 
arco e quanto mais para cervical estiver o arco, maior será a intensidade das 
tensões que um instrumento endodôntico ficará submetido no ensaio de flexão 
9 
 
rotativa. Este aumento da intensidade das tensões induzirá a fratura do 
instrumento endodôntico por um tempo menor de uso (LOPES et al., 2013a). 
Em relação à geometria dos instrumentos endodônticos, destacamos o 
diâmetro D0, a conicidade das hastes helicoidais, o comprimento da parte de 
trabalho e o número de hélices (SCHÄFER & TEPEL, 2001; ZHANG et al., 
2010). 
Quanto maior o diâmetro em D0, quanto maior a conicidade, quanto 
menor o comprimento da parte de trabalho e quanto menor o número de 
hélices, maior será a intensidade das tensões a que um instrumento 
endodôntico ficará submetido durante o ensaio de flexão rotativa (LOPES et al., 
2013c). O aumento da intensidade de tensões reduz o tempo de vida útil de um 
instrumento endodôntico. Também devemos ressaltar outros fatores, como a 
forma e a área da seção reta transversal e a flexibilidade de um instrumento 
endodôntico (SCHÄFER & TEPEL, 2001; ELIAS & LOPES, 2007; ZHANG et 
al.,2010). Como os instrumentos endodônticos apresentam a haste helicoidal 
cônica, há aumento de seu diâmetro de D0 para D16; com isto, ocorre redução 
de sua flexibilidade, à medida que se aproxima de D16. Consequentemente a 
redução da flexibilidade aumentará a frequência de fratura por fadiga de um 
instrumento submetido ao ensaio de flexão rotativa. 
 Com o objetivo de reduzir a intensidade das tensões em um instrumento 
endodôntico ao girar no interior de um canal curvo, tem sido proposto o 
acionamento do instrumento por meio do movimento de alargamento com 
rotação reciprocante como alternativa ao movimento de alargamento com 
rotação contínua (GAMBARINI et al., 2012a; GAMBARINI et al., 2012b; 
10 
 
GAMBARRA-SOARES et al., 2013; LOPES et al., 2013b; LOPES et al., 2013c; 
YARED & RAMLI, 2013) 
Durante o preparo químico mecânico de um canal radicular, os 
instrumentos endodônticos são submetidos a severo estado de tensão e 
deformação, que variam com a anatomia do canal, com as propriedades e 
comportamento mecânico dos instrumentos endodônticos e com o tipo de 
movimento aplicado (LOPES et al., 2010b). 
Assim, a presente proposta sugere a avaliação, em laboratório, da 
influência do movimento reciprocante aplicado aos instrumentos endodônticos 
de níquel-titânio mecanizados, quando submetidos ao ensaio de flexão rotativa 
contínua estático e dinâmico. 
 
11 
 
2. JUSTIFICATIVA 
 
O conhecimento da influência do tipo de movimento aplicado em um 
instrumento endodôntico de NiTi mecanizado é essencial na sua vida útil em 
fadiga. Em função do exposto, este trabalho buscou, por meio da realização de 
ensaios mecânicos estáticos e dinâmicos, com o movimento de rotação 
reciprocante e com o movimento de rotação contínua, avaliar a vida útil em 
fadiga de instrumentos endodônticos de NiTi mecanizados, quando 
empregados em canais curvos. 
 
12 
 
3. HIPÓTESE 
 
Os resultados esperados devem respaldar a hipótese de que o 
movimento de rotação reciprocante no modelo dinâmico aumenta a vida útil em 
fadiga de um instrumento endodôntico de NiTi mecanizado, em comparação ao 
movimento de rotação contínua. 
 
13 
 
4. OBJETIVOS 
 
Este estudo teve como objetivos: 
 
1- Realizar ensaios de flexão rotativa com o movimento de rotação 
reciprocante e movimento de rotação contínua e comparar os resultados 
obtidos, para determinar que tipo de movimento rotatório promove maior vida 
útil em fadiga de um instrumento ensaiado. 
2- Realizar ensaio de flexão rotativa com o movimento de rotação 
reciprocante e com o movimento de rotação contínua nos modelos de ensaios 
estáticos e dinâmicos, para determinar qual modelo promove maior vida útil em 
fadiga de um instrumento ensaiado. 
3- Analisar, por meio da microscopia eletrônica de varredura (MEV), as 
superfícies de fraturas e as configurações das hastes helicoidais cônicas dos 
instrumentos, nos ensaios estáticos e dinâmicos com o movimento de rotação 
reciprocante e com o movimento de rotação contínua. 
 
14 
 
5. ARTIGOS PUBLICADOS 
 
ARTIGO N° 1 
Lopes HP, Britto IMO, Elias CN, Oliveira JCM, Neves MS, Moreira EJL, 
Siqueira JF Jr (2010d). Cyclic fatigue resistance of ProTaper Universal 
instruments when subjected to static and dynamic tests. Oral Surg Oral Med 
Oral Pathol Oral Radiol Endod 110: 401-404. 
ARTIGO N° 2 
Rodrigues RCV, Lopes HP, Elias CN, Amaral G, Vieira VTL, De Martin AS 
(2011). Influence of different manufacturing methods on the cyclic fatigue of 
rotary nickel-titanium endodontic instruments. J Endod37: 1553-1557. 
ARTIGO N° 3 
Gambarra-Soares T, Lopes HP, Oliveira JCM, Souza LC, Vieira VT, Elias CN 
(2013). Dynamic or static fatigue tests: which best determines the lifespan of 
endodontic files? ENDO 7: 101-104. 
ARTIGO N° 4 
De-Deus G, Moreira EJL, Lopes HP, Elias CN (2010). Extended cyclic fatigue 
life of F2 ProTaper instruments used in reciprocating movement. Int Endod J 
43: 1063-1068. 
ARTIGO N° 5 
Lopes HP, Vieira MVB, Elias CN, Siqueira Jr JF, Mangelli M, Lopes WSP et al. 
(2013b). Fatigue life of WaveOne and ProTaper instruments operated in 
15 
 
reciprocating or continous rotation movements and subjected to dynamic and 
static tests. ENDO 7: 217-222. 
ARTIGO N° 6 
Lopes HP, Elias CN, Vieira MVB, Siqueira Jr JF, Mangelli M, Lopes WSP et al. 
(2013c). Fatigue life of Reciproc and Mtwo instruments subjected to static and 
dynamic tests. J Endod 39: 693-696. 
ARTIGO N° 7 
De-Deus G, Vieira VTL, Nogueira da Silva EJ, Lopes HP, Elias CN, Moreira EJ 
(2014). Bending resistance and dynamic and static cyclic fatigue life of Reciproc 
and WaveOne Large instruments. J Endod 40: 575-579. 
16 
 
ARTIGO N° 1 
Lopes HP, Britto IMO, Elias CN, Oliveira JCM, Neves MS, Moreira EJL, 
Siqueira JF Jr (2010d). Cyclic fatigue resistance of ProTaper Universal 
instruments when subjected to static and dynamic tests. Oral Surg Oral Med 
Oral Pathol Oral Radiol Endod 110: 401-404. 
 
 
 
 
 
 
 
 
 
 
 
 
 
Cyclic fatigue resistance of ProTaper Universal instruments
when subjected to static and dynamic tests
Hélio P. Lopes, DDS, LD,a Izabelle M.O. Britto, DDS,a Carlos N. Elias, PhD,b
Julio C. Machado de Oliveira, DDS, PhD,a Mônica A.S. Neves, DDS, MSc,a
Edson J.L. Moreira, DDS, PhD,c and José F. Siqueira Jr., DDS, PhD,a Rio de Janeiro, Brazil
ESTÁCIO DE SÁ UNIVERSITY, MILITARY INSTITUTE OF ENGINEERING, AND GRANDE RIO UNIVERSITY
Objective. This study evaluated the number of cycles to fracture of ProTaper Universal S2 instruments when subjected
to static and dynamic cyclic fatigue tests.
Study design. ProTaper Universal S2 instruments were used until fracture in an artificial curved canal under rotational
speed of 300 rpm in either a static or a dynamic test model. Afterward, the length of the fractured segments was
measured and fractured surfaces and helical shafts analyzed by scanning electron microscopy (SEM).
Results. The number of cycles to fracture was significantly increased when instruments were tested in the dynamic
model (P � .001). Instrument separation occurred at the point of maximum flexure within the artificial canals, i.e., the
midpoint of the curved canal segment. SEM analysis revealed that fractured surfaces exhibited characteristics of the
ductile mode. Plastic deformation was not observed in the helical shaft of fractured instruments.
Conclusions. The number of cycles to fracture ProTaper Universal S2 instruments significantly increased with the use
of instruments in a dynamic cyclic fatigue test compared with a static model. These findings reinforce the need for
performing continuous pecking motions during rotary instrumentation of curved root canals. (Oral Surg Oral Med
Oral Pathol Oral Radiol Endod 2010;110:401-404)
Root canal preparation methods have changed substan-
tially since the introduction of nickel-titanium (NiTi)
alloy. The physical properties of NiTi have enabled
manufacturing endodontic instruments with different
cross-sectional designs and greater tapered working
shafts. Another great breakthrough accompanying the
introduction of NiTi instruments was the development
and further widespread use of rotary instruments and
techniques for root canal instrumentation, especially of
curved root canals.1-3
The NiTi alloy presents a lower modulus of elasticity
than stainless steel files; therefore, NiTi instruments
exhibit a greater elasticity and higher resistance to
plastic deformation. The advent of NiTi endodontic
instruments has made it possible to attain preparations
that are larger at the apical part, more centered, and
with reduced incidence of deviations compared with
stainless-steel instruments.1,3-5 Current evidence indi-
aDepartment of Endodontics, Faculty of Dentistry, Estácio de Sá
University.
bDepartment of Materials Science, Military Institute of Engineering.
cDepartment of Endodontics, Faculty of Dentistry, Grande Rio Uni-
versity.
Received for publication Apr 25, 2010; returned for revision May 11,
2010; accepted for publication May 15, 2010.
1079-2104/$ - see front matter
© 2010 Published by Mosby, Inc.
doi:10.1016/j.tripleo.2010.05.013
cates that larger apical preparations enhance irrigation
efficacy, disinfection, and quality of the obturation.6-9
The major concern during clinical use of rotary NiTi
instruments under continuous reaming rotation is the
low-cycle fatigue fracture. Fatigue fracture is consid-
ered to be low cycle when it occurs in �104 cycles, and
this type of instrument failure develops when instru-
ments are subjected to rotating bending stress in curved
canals.10 The resistance to low-cycle fatigue fracture
refers to the number of cycles that an instrument can
endure under a specific loading condition before frac-
ture occurs.11,12
Cyclic fatigue tests can be static or dynamic.10-13 In
the static test, the instrument rotates within a curved
canal at a fixed length, i.e., with no axial oscillation.
The dynamic model of cyclic fatigue test consists of
moving the instrument back and forth in the curved
canal. The aim of the present study was to assess the
number of cycles to fracture of ProTaper Universal S2
instruments when subjected to static and dynamic cy-
clic fatigue tests.
MATERIALS AND METHODS
Twenty-four ProTaper Universal rotary NiTi end-
odontic instruments (Dentsply/Maillefer, Ballaigues,
Switzerland) size S2 were used in this experiment.
These instruments present nominal tip diameter of 0.20
mm and 25 mm of useful length. The taper of this
instrument is variable along its shaft, increasing from
401
OOOOE
402 Lopes et al. September 2010
0.04 mm/mm (D1) to 0.08 mm/mm (D12) and then
decreasing to 0.05 mm/mm (D16).
An artificial canal was made out of a cylindric tube
of stainless steel having the inner diameter of 1.4 mm,
total length of 19 mm, arc located between the two
straight segments of the canal, and a curvature radius of
6 mm. The arc measured 9 mm, the longest straight part
was 7 mm and the shortest straight part was 3 mm. The
curvature radius of the artificial canal was measured by
taking into account the concave surface of the interior
of the tube (Fig. 1). During the tests, the artificial canal
was filled with glycerin to reduce the friction of the
instrument against the canal wall and to minimize the
release of heat. A bench vise was used to hold the
stainless steel tube during tests.
Twelve ProTaper Universal S2 instruments were
used in the static test. Each instrument was placed in a
contra-angle at speed reduction of 16:1 (TC-Motor
3000; Nouvag, Goldach, Switzerland) and introduced
into the canal from the longest straight tube segment
until the tip of the instrument reached the entire length
of the canal. The contra-angle was hand-held by an
experienced operator, and the instruments were worked
in clockwise rotation at nominal speed of 300 rpm until
fracture. The time to fracture was measured by the
same operator using a digital stopwatch (Leroy) and
was established when there was visual observation of
the instrument separation. The number of cycles to
fracture was attained by multiplying the rotational
speed by the time (in seconds) that fracture of each
instrument occurred.
Another set of 12 ProTaper Universal S2 instruments
was used in the dynamic test. The instruments were
subjected to the same protocol as in the static test,
except that in this group the operator promoted back-
and-forth axial movements with the endodontic instru-
ments inside the artificial curved canal until fracture
was observed. The amplitude of axial movements was
Fig. 1. Artificialcanal used in the cyclic fatigue experiment.
Schematic drawing.
3 mm, with about 2 seconds for every displacement.
Data obtained on the number of cycles to fracture of
ProTaper Universal S2 instruments when subjected to
static or dynamic cyclic fatigue tests were statistically
analyzed by the Student t test with significance level set
at 5% (P � .05).
The length of the separated instrument fragments
was measured by using a digital vernier caliper (Mitu-
toyo Sul-Americana, Suzano, SP, Brazil). The fractured
surface and the helical shaft of the separated instru-
ments were examined under scanning electron micros-
copy (SEM) (JSM 5800; Jeol, Tokyo, Japan) to deter-
mine the type of fracture.
RESULTS
Table I depicts the means and standard deviations of
the time and number of cycles to fracture of ProTaper
Universal S2 instruments subjected to static or dynamic
tests. Statistical analyses showed that the number of
cycles to fracture was significantly increased when the
instruments were tested in the dynamic model (P �
.001).
The average lengths of the separated segments mea-
sured from the instrument’s tips were 8.87 mm and 8.97
mm after the static and dynamic tests, respectively. At
these points, the instrument taper is the same (0.06
mm/mm) and the diameters are 0.69 mm and 0.7 mm,
respectively. Instrument separation occurred at the
point of maximum flexure within the artificial canals,
i.e., the midpoint of the curved segment of the artificial
canal.
The SEM analysis revealed that the fractured sur-
faces had ductile morphologic characteristics (Figs. 2A
and 2B). The presence of dimples with varied shapes
was identified on the fractured surfaces. Plastic defor-
mation was not observed in the helical shaft of frac-
tured instruments (Figs. 3A and 3B). The different
cyclic fatigue tests (static or dynamic) had no influence
on SEM results.
DISCUSSION
Cyclic fatigue resistance is measured by the number
of cycles that an instrument endures during the fatigue
test. The number of cycles is cumulative and relates to
the intensity of compressive and tensile stresses, which
Table I. Mean (SD) of the time and the number of
cycles to fatigue fracture (NCF) of ProTaper Universal
S2 instruments
Test n Time, s NCF
Static 12 68.1 (14.7) 340.5 (73.65)
Dynamic 12 125.1 (13.4) 625 (67.2)
in turn are related to the curvature radius, arc length,
OOOOE
Volume 110, Number 3 Lopes et al. 403
and instrument size.10-12,14 According to Tobushi et
al.,15 the cyclic fatigue test is a simple and reliable
approach to determine the fatigue behavior of instru-
ments manufactured from NiTi alloy. In the present
study, a metallic tube was used to standardize the entire
length of the canal, the length of the curvature radius
and the length of the arc. However, one should bear in
mind that the actual lengths of arc and radius of the
cylindric curved canal are not the same as the instru-
ment positioned inside the tube.16 It is also important to
point out that because the inner diameter of the tube
was larger than that of the endodontic instrument and
a lubricant was used throughout the experiments, in-
struments were allowed to rotate within the canal with-
out significant resistance during the cyclic fatigue
tests.10,11,14,17
This study was intended to evaluate whether cyclic
fatigue resistance of ProTaper Universal S2 instruments
Fig. 2. Fractured surfaces of instruments showing morpho-
logic characteristics of the ductile type. A, Static test; B,
dynamic test (original magnification �1,500).
was different when these instruments were subjected to
either static or dynamic test. The results demonstrated
that the number of cycles to fracture were significantly
higher in the dynamic test. These results are consistent
with those reported by Li et al.13
Because in the static test the endodontic instrument is
not subjected to an axial movement, the alternating
compressive and tensile stresses are concentrated at the
same area of the instrument.13 These stresses are cu-
mulative and induce microstructural changes in the
metallic alloy. The present results indicated that stress
concentration at the same area of the instrument shaft
significantly reduced the number of cycles to fracture.
On the other hand, in the dynamic test, compressive and
tensile stresses are distributed along the tapered helical
shaft of the instruments, owing to the axial movement
of the instruments within the curved canal. Therefore,
by avoiding stress concentration at the same instrument
area, the fatigue fracture resistance was augmented.
Fig. 3. Fractured surfaces. No plastic deformation is ob-
served on the helical shaft. A, Static test; B, dynamic test
(original magnification �100).
The present results and those from Li et al.13 indicate
OOOOE
404 Lopes et al. September 2010
that this principle conceivably holds for other instru-
ments.
The SEM analysis of fractured ProTaper Universal
S2 instruments did not reveal any morphologic differ-
ence between the cyclic fatigue tests. No evidence of
plastic deformation in the helical shafts of fractured
instruments was observed. The fracture surface of the
instruments tested had morphologic characteristics of
the ductile type, which is in consonance with several
earlier studies.10,11,14,18,19
The average length of the separated instrument seg-
ments was not influenced by the different cyclic fatigue
tests. All instruments tested fractured at the point of
movement flexure within the curved segment of the
tube. At this point, the stress on the instrument was
conceivably greater.
In conclusion, the results of the present study showed
that the number of cycles to fracture ProTaper Univer-
sal S2 instruments under rotary bending test increased
with the use of instruments in a dynamic cyclic fatigue
test compared with a static model. These findings rein-
force the need for performing continuous pecking mo-
tions during rotary instrumentation of curved root ca-
nals. No plastic deformation was visible along the
helical shaft of the fractured instruments, and the frac-
tured surfaces were of the ductile type.
REFERENCES
1. Coleman CL, Svec TA. Analysis of Ni-Ti versus stainless steel
instrumentation in resin simulated canals. J Endod 1997;23:
232-5.
2. Peters OA. Current challenges and concepts in the preparation of
root canal systems: a review. J Endod 2004;30:559-67.
3. Hulsmann M, Peters OA, Dummer PMH. Mechanical prepara-
tion of root canals: shaping goals, techniques and means. Endod
Topics 2005;10:30-76.
4. Short JA, Morgan LA, Baumgartner JC. A comparison of canal
centering ability of four instrumentation techniques. J Endod
1997;23:503-7.
5. Yoshimine Y, Ono M, Akamine A. The shaping effects of three
nickel-titanium rotary instruments in simulated S-shaped canals.
J Endod 2005;31:373-5.
6. Siqueira JF, Jr Lima KC, Magalhaes FA, Lopes HP, de Uzeda M.
Mechanical reduction of the bacterial population in the root canal
by three instrumentation techniques. J Endod 1999;25:332-5.
7. Rollison S, Barnett F, Stevens RH. Efficacy of bacterial removal
from instrumented root canals in vitro related to instrumentation
technique and size. Oral Surg Oral Med Oral Pathol Oral Radiol
Endod 2002;94:366-71.
8. Card SJ, Sigurdsson A, Orstavik D, Trope M. The effectiveness
of increased apical enlargement in reducing intracanal bacteria. J
Endod 2002;28:779-83.
9. Usman N, Baumgartner JC, Marshall JG. Influence of instrument
size on root canal debridement. J Endod 2004;30:110-2.
10. Pruett JP, Clement DJ, Carnes DL Jr. Cyclic fatigue testing of
nickel-titanium endodontic instruments. J Endod 1997;23:77-85.
11. Lopes HP, Ferreira AA, Elias CN, Moreira EJ, de Oliveira JC,
Siqueira Jr JF. Influence of rotational speed on the cyclic fatigue
of rotary nickel-titanium endodontic instruments. J Endod 2009;
35:1013-6.
12. Yao JH, Schwartz SA, Beeson TJ. Cyclic fatigue of three types
of rotary nickel-titanium files in a dynamic model. J Endod
2006;32:55-7.
13. Li UM, Lee BS, Shih CT, Lan WH, Lin CP. Cyclic fatigueof
endodontic nickel titanium rotary instruments: static and dy-
namic tests. J Endod 2002;28:448-51.
14. Lopes HP, Moreira EJ, Elias CN, de Almeida RA, Neves MS.
Cyclic fatigue of ProTaper instruments. J Endod 2007;33:55-7.
15. Tobushi H, Shimeno Y, Hachisuka T, Tanaka K. Influence of
strain rate on superelastic properties of TiNi shape memory alloy.
Mechanics Mater 1998;30:141-50.
16. Plotino G, Grande NM, Mazza C, Petrovic R, Testarelli L,
Gambarini G. Influence of size and taper of artificial canals on
the trajectory of NiTi rotary instruments in cyclic fatigue studies.
Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:
e60-6.
17. Inan U, Aydin C, Tunca YM. Cyclic fatigue of ProTaper rotary
nickel-titanium instruments in artificial canals with 2 different
radii of curvature. Oral Surg Oral Med Oral Pathol Oral Radiol
Endod 2007;104:837-40.
18. Wei X, Ling J, Jiang J, Huang X, Liu L. Modes of failure of
ProTaper nickel-titanium rotary instruments after clinical use. J
Endod 2007;33:276-9.
19. Haikel Y, Serfaty R, Bateman G, Senger B, Allemann C. Dy-
namic and cyclic fatigue of engine-driven rotary nickel-titanium
endodontic instruments. J Endod 1999;25:434-40.
Reprint requests:
José F. Siqueira Jr., PhD
Faculty of Dentistry
Estácio de Sá University
Av. Alfredo Baltazar da Silveira, 580/cobertura, Recreio
Rio de Janeiro, RJ
Brazil 22790-701
siqueira@estacio.br
mailto:siqueira@estacio.br
21 
 
ARTIGO N° 2 
Rodrigues RCV, Lopes HP, Elias CN, Amaral G, Vieira VTL, De Martin AS 
(2011). Influence of different manufacturing methods on the cyclic fatigue of 
rotary nickel-titanium endodontic instruments. J Endod 37: 1553-1557. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Basic Research—Technology
Influence of Different Manufacturing Methods
on the Cyclic Fatigue of Rotary Nickel-Titanium
Endodontic Instruments
Renata C.V. Rodrigues, DDS,* H�elio P. Lopes, LD,† Carlos N. Elias, PhD,‡ Georgiana Amaral, PhD,§
Victor T.L. Vieira, DDS,
‡
and Alexandre S. De Martin, PhD*
Abstract
Introduction: The aim of this study was to evaluate, by
static and dynamic cyclic fatigue tests, the number of
cycles to fracture (NCF) 2 types of rotary NiTi instru-
ments: Twisted File (SybronEndo, Orange, CA), which
is manufactured by a proprietary twisting process, and
RaCe files (FKG Dentaire, La Chaux-de-Fonds,
Switzerland), which are manufactured by grinding.
Methods: Twenty Twisted Files (TFs) and 20 RaCe files
#25/.006 taper instruments were allowed to rotate
freely in an artificial curved canal at 310 rpm in a static
or a dynamic model until fracture occurred. Results:
Measurements of the fractured fragments showed that
fracture occurred at the point of maximum flexure in
the midpoint of the curved segment. The NCF was signif-
icantly lower for RaCe instruments compared with TFs.
The NCF was also lower for instruments subjected to
the static test compared with the dynamic model in
both groups. Scanning electron microscopic analysis re-
vealed ductile morphologic characteristics on the frac-
tured surfaces of all instruments and no plastic
deformation in their helical shafts. Conclusions: Rotary
NiTi endodontic instruments manufactured by twisting
present greater resistance to cyclic fatigue compared
with instruments manufactured by grinding. The frac-
ture mode observed in all instruments was of the ductile
type. (J Endod 2011;37:1553–1557)
Key Words
Cyclic fatigue, endodontic instruments, nickel-titanium,
Twisted File, RaCe
From the *Department of Endodontics, S~ao Leopoldo Man-
dic, Dental Research Center, Campinas, S~ao Paulo;
†Department of Endodontics, Faculty of Dentistry, Est�acio de
S�a University, Rio de Janeiro, Rio de Janeiro; ‡Department of
Materials Science, Military Institute of Engineering, Rio de
Janeiro, Rio de Janeiro; and §Department of Endodontics, S~ao
Leopoldo Mandic, Dental Research Center, Rio de Janeiro, Rio
de Janeiro, Brazil.
Address requests for reprints to Dr Alexandre S. De Martin,
Av Julio de Mesquita, 983/92, Campinas, SP, Brazil CEP 13025-
063. E-mail address: a-sigrist@uol.com.br
0099-2399/$ - see front matter
Copyright ª 2011 American Association of Endodontists.
doi:10.1016/j.joen.2011.08.011
JOE — Volume 37, Number 11, November 2011
Most nickel-titanium (NiTi) rotary endodontic instruments are machined bygrinding although some are produced by twisting the alloy after heat treatment
(1). Low-cycle fatigue fracture is a concern during the clinical use of rotary NiTi instru-
ments (2–4). Fracture is defined as low cycle when it occurs in less than 104 cycles. This
type of failure may be induced by rotating bending stresses when instrumenting curved
canals (5). Resistance to fracture is determined by the number of cycles an instrument
can endure under a specific loading condition before fracture occurs (6–8).
Cyclic fatigue tests can be static or dynamic (5, 9, 10). In static tests, the instrument
rotates at a fixed length (ie, with no axial oscillation) (5, 6, 10), whereas in the dynamic
model the instrument is moved back and forth within the canal (7, 11, 12). The aim of
this study was to assess the influence of the manufacturing process (grinding or
twisting) on the number of cycles to fracture (NCF) of rotary NiTi instruments
through static and dynamic fatigue tests.
Materials and Methods
Forty-four rotary NiTi instruments were used in this study: 22 Twisted files (TFs)
(SybronEndo, Orange, CA), which are machined by twisting, and 22 RaCe files (FKG
Dentaire, La Chaux-de-Fonds, Switzerland), which are manufactured by grinding.
Both sets of files had a nominal size of 0.25 mm at D0, a taper of 0.06 mm/mm, and
a triangular cross-section. The RaCe files had a total length of 25 mm, and the TFs
had a total length of 27 mm.
Instrument Geometry (Design Features)
For standardization of the instruments tested, 10 files of each brand were exam-
ined under a stereomicroscope (Pantec-Panambra, Cambuci, SP, Brazil) to determine
their diameters at D3 and D13; the number of spirals in the working portion; and their
helical angle at D3, D6, and D13. The taper of the working portion was calculated by
subtracting the diameters at D3 and D13 as described by Stenman and Spangberg (13)
using the following equation:
Taper ðTÞ ¼ D13� D3=10
The diameter at D0 was calculated based on the values of D3 and T using the
following equation:
D0 ¼ D3� T� 3
The helical angle is the acute angle formed by the spiral and the long axis of the
instrument. It was obtained by tracing a line tangent to the spirals; this line formed
an acute angle with the plane containing the instrument axis. The number of spirals
per millimeter was obtained by dividing the number of spirals by the length of the
working portion. Two instruments of each brand were embedded in acrylic resin
and prepared for scanning electron microscopic (SEM) analysis of their cross-
sections (JSM 5800; JEOL, Tokyo, Japan).
Cyclic Fatigue of 2 Types of NiTi Rotary Instruments 1553
mailto:a-sigrist@uol.com.br
http://dx.doi.org/10.1016/j.joen.2011.08.011
Figure 1. A schematic representation of the artificial canal used in the cyclic
fatigue tests.
Figure 2. An apparatus used for the cyclic fatigue test.
Basic Research—Technology
Bending Resistance Tests
The bending resistance was evaluated using a universal testing
machine (DL 10.000; Emic, S~ao Jos�e dos Pinhais, Brazil) as
described in previous studies (14, 15). A 20-N load was applied
at 15 mm/min by means of a flexible stainless steel wire with 1
end fastened to the testing machine head and the other end attached
3 mm from the instrument tip until it displayed a 45� deflection.
The maximum load to bend each file was recorded, and data
were statistically analyzed by the Student t test, with the significance
level set at 5%. Bending resistance was tested in 10 instruments of
each brand.
Cyclic Fatigue Tests
For these tests, an artificial canal measuring 1.4 mm in diameter
and 19 mm in total length was fabricated from a stainless steel tube. A 9-
mm-long curved segmentwith a 6-mm radius (measured at the internal
concave surface of the tube) was created between 2 straight segments
that measured 7 mm and 3 mm (Fig. 1).
Static Test
A stainless steel apparatus with a square base and a vertical axis
was constructed. The vertical axis allowed for the fixture and move-
ment of a handpiece. At the base, a bench vise held the artificial
canal. A gap at the base of the apparatus allowed the bench vise
TABLE 1. The Mean Values for the Working Portion Length (WP); the Diameter at D3
the Diameter at D0; and the Number of Spirals per Millimeter in the Working Port
Instruments No.
Taper
(mm/mm)
Diameter (mm)
D0 D3 D13
RaCe 10 0.06 0.30 0.48 1.09
TF 10 0.06 0.22 0.40 0.98
1554 Rodrigues et al.
to move horizontally while maintaining the axis of the instrument
aligned with the straight segment of the artificial canal created
between 2 straight segments that measured 7 mm and 3 mm.
(Fig. 2). The canal was filled with glycerin to reduce friction, mini-
mizing the release of heat. Each file was attached to a contra-angle/
micromotor handpiece with 10:1 gear reduction (TC–Motor 3000;
Nouvag AG/AS/LTD, Goldach, Switzerland) and introduced into the
canal until the file tip touched a shield positioned at the simulated
apical foramen. Ten instruments of each brand were rotated clock-
wise at 310 rpm until fracture. The time of fracture was recorded
by the same operator using a digital stopwatch (Leroy) and estab-
lished by visual observation of instrument separation. The NCF was
obtained by multiplying the rotational speed by the time (in seconds)
when fracture occurred.
Dynamic Test
Another set of 10 instruments of each brand was used for the
dynamic test. The instruments were subjected to the same protocol
described in the static test, but for these experiments a mechanical
device promoted back and forth axial movements while the files
rotated inside the canal. The amplitude of the axial movements was
3 mm, with approximately 2 seconds between oscillations. Data ob-
tained from the static and dynamic tests for both brands of files
were statistically analyzed by the Student t test, with the significance
level set at 5%. The fractured surfaces and the helical shaft of the
separated instruments were analyzed under SEM (JSM 5800) to
determine the type of fracture and the presence of plastic deformation
in the shaft.
and D13; the Helical Angle at D3, D6, and D13; the Number of Spirals; the Taper;
ion of the Files
WP (mm)
Helical angle
No. of
spirals Per mmD3 D6 D13
17.61 14.55 17.73 19.56 7 0.4
15.36 20.64 24.97 31.16 11 0.7
JOE — Volume 37, Number 11, November 2011
TABLE 2. Means (� standard deviation) of the Maximum Load (g) to Bend
RaCe and TF Instruments
Instruments
No. of
instruments Maximum load (g)
RaCe 10 333.4 (16.5)
TF 10 218.2 (15.26)
TABLE 3. Mean (� standard deviation) of the Time(s) and Numbers of Cycles
to Fracture (NCF) for the Instruments Tested
Test
Time NCF
RaCe TF RaCe TF
Static 25.2
(5.43)
80.4
(8.57)
130.03
(28.03)
414.86
(44.27)
Dynamic 45.4
(14.41)
153.25
(36.53)
234.26
(26.33)
790.77
(188.5)
Basic Research—Technology
Results
Instrument Geometry (Design Features)
The mean length of the working portion; the diameter at D3 and
D13; the helical angle at D3, D6, and D13; the number of spirals in
the working portion; the mean taper; the diameter at D0; and the
number of spirals per millimeter in the working portion of the files
are shown in Table 1. SEM analyses of fractured surface showed that
TFs and RaCe files had a triangular cross-section.
Bending Resistance
The mean bending resistance, represented by the maximum load
(in grams) to bend the instruments, is shown in Table 2. A significant
difference was observed between the 2 groups (P = 0). Statistically
less force was required for TFs with respect to RaCe files in the
bending test.
Cyclic Fracture
The means and standard deviation for the time (in seconds)
and NCF are shown in Table 3. TFs presented a significantly higher
NCF compared with RaCe files (P = 0). SEM analysis revealed that
both brands of files displayed ductile morphologic characteristics
on the fracture surfaces. No plastic deformation occurred in the
helical shaft of the instruments (Figs. 3 and 4). The cyclic
fatigue testing model (static or dynamic) had no influence on the
SEM results.
Figure 3. The fractured surface of TFs subjected to static (A to B) and dynamic (C
TF (100� magnification). (B and D) Cracks following machining grooves are obs
JOE — Volume 37, Number 11, November 2011
Discussion
The NCF of rotary NiTi endodontic files is affected by their shape,
dimensions, and bending resistance. Therefore, these were the param-
eters evaluated in the present study. Slight variations in design may have
a significant impact on the behavior of endodontic instruments (13).
The greater diameter at D0 and the lower flexibility of RaCe files
compared with TFs may partly explain their lower resistance to cyclic
fatigue (5, 6, 16–19).
The performance of rotary instruments in cyclic fatigue assays is
directly related to their bending resistance (6, 20, 21). In our
experiments, RaCe files required significantly greater loads than TF to
display 45� deflection. Therefore, it can be inferred that RaCe files
are less flexible than TFs. Rigid instruments present lower a NCF
because of the buildup of tensions at the point of maximum flexure,
as observed in the present work and in previous studies (19, 22–24).
According to Yao et al (7), the use of standardized artificial canals
in cyclic fatigue experiments minimizes the influence of other variables.
In the present study, a metallic tube was used to standardize the entire
length of the canal, the length of the curvature radius, and the length of
the arc. However, one should bear in mind that the actual lengths of the
arc and the radius of the cylindric curved canal are not the same as the
instrument positioned inside the tube (25). It is also important to point
out that because the inner diameter of the tube was larger than that of
the endodontic instrument and a lubricant was used throughout the
experiments, instruments were allowed to rotate within the canal
without significant resistance during the cyclic fatigue tests. Friction
to D) tests. (A and C) The absence of plastic deformation in the helical shaft of
erved near the fractured surface of TF (1,000�).
Cyclic Fatigue of 2 Types of NiTi Rotary Instruments 1555
Figure 4. RaCe instruments fractured in the static (A to B) and dynamic (C to D) tests. (A and C) The absence of plastic deformation in the helical shaft (100�
magnification). (B and D) No cracks were observed on RaCe instruments (1,600� and 1,000� magnification, respectively).
Basic Research—Technology
was further reduced by using a lubricant throughout the assays (5, 6,
14, 21, 25).
The TF instruments displayed significantly higher NCF values than
RaCe files in both fatigue assays (static and dynamic), as observed in
previous studies with similar methodologies (26–28). Our
observations suggest that the new manufacturing process involving
twisting coupled with heat treatment along with the unique
longitudinal features of TF files (ie, the helical angle, arrangement
and number of spirals/mm in the fluted portion, and longitudinally
oriented surface texture) may have positively affected their
performance (26). The number of spirals in the working portion
may have favored the higher flexibility and fatigue resistance of TFs
compared with RaCe files. The morphological features of NiTi rotary
instruments and their effect on cyclic fatigue resistance have been the
object of several studies (17, 18, 26–28).
According to the manufacturer, Twisted File instruments are
produced by a proprietary process of heating and cooling of
NiTi that leads to a molecular structure known as the R phase.
In this state, NiTi can be twisted, resulting in instruments with opti-
mized properties (29). The alloy in the R phase displays super
elasticity and shape memory, allowing theproduction of more flex-
ible instruments compared with their ground counterparts
(26, 29).
Regardless of the instrument brand and manufacturing process, in
the present work, the NCF was significantly higher during dynamic versus
static fatigue testing; our findings, which are similar to those from other
studies (7–11), indicate that a concentration of stresses in the same area
of the instrument shaft significantly reduces the NCF. Because in the static
test the file does not move axially, alternating compressive and tensile
stresses are concentrated in one area of the instrument. These
cumulative stresses induce microstructural changes in the alloy. In
contrast, in the dynamic model, the file moves axially within the canal,
allowing stresses to be distributed along the instrument shaft. By
preventing stress concentration in the same area, resistance to fracture
1556 Rodrigues et al.
is enhanced. Our results along with those from Li et al (9) and Lopes
et al (10) suggest that this principle may hold true for other types of
instruments.
SEM analysis of the instruments showed that both file types had
a triangular cross-section. Analysis of the fractured surfaces did not reveal
morphologic differences between the 2 types of instruments or between
instruments fractured during static versus dynamic tests. Moreover, no
evidence of plastic deformation was detected in the helical shafts of
any fractured instruments. All fracture surfaces displayed ductile
morphologic characteristics as observed by other authors (5, 21, 26).
In conclusion, TF endodontic instruments, which are manufac-
tured by a twisting technology, display higher NCF values compared
with RaCe instruments, which are manufactured by grinding. The NCF
for both instruments was higher in the dynamic fatigue test than in
the static model. Therefore, it can be inferred that TFs are more flexible
than RaCe files. These results highlight the importance of applying
a continuous pecking motion during rotary instrumentation of curved
root canals in order to avoid concentration of stresses in the same
area of the instrument shaft.
Acknowledgments
The authors thank FKG Dentaire for providing the instruments
used in this study.
The authors deny any conflicts of interest related to this study.
References
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nology and clinical use: a review. Quintessence Int 2010;41:479–88.
2. Martin B, Zelada G, Varela P, et al. Factors influencing the fracture of nickel-titanium
rotary instruments. Int Endod J 2003;36:262–6.
3. Zelada G, Varela P, Martin B, et al. The effect of rotational speed and the curvature of
root canals on the breakage of rotary endodontic instruments. J Endod 2002;28:
540–2.
JOE — Volume 37, Number 11, November 2011
Basic Research—Technology
4. Varela-Pati~no P, Iba~nez-P�araga A, Rivas-Mundi~na B, et al. Alternating versus continuous
rotation: a comparative study of the effect on instrument life. J Endod 2010;36:157–9.
5. Pruett JP, Clement DJ, Carnes DL Jr. Cyclic fatigue testing of nickel-titanium
endodontic instruments. J Endod 1997;23:77–85.
6. Lopes HP, Ferreira AA, Elias CN, et al. Influence of rotational speed on the cyclic
fatigue of rotary nickel-titanium endodontic instruments. J Endod 2009;35:1013–6.
7. Yao JH, Schwartz SA, Beeson TJ. Cyclic fatigue of three types of rotary nickel-titanium
files in a dynamic model. J Endod 2006;32:55–7.
8. Kramkowski TR, Bahcall J. An in vitro comparison of torsional stress and cyclic
fatigue resistance of ProFile GT and ProFile GT Series X rotary nickel-titanium files.
J Endod 2009;35:404–7.
9. Li UM, Lee BS, Shih CT, et al. Cyclic fatigue of endodontic nickel-titanium rotary
instruments: static and dynamic tests. J Endod 2002;28:448–51.
10. Lopes HP, Britto IMO, Elias CN, et al. Cyclic fatigue resistance of Protaper Universal
instruments when subjected to static and dynamic tests. Oral Surg Oral Med Oral
Pathol Oral Radiol Endod 2010;110:401–4.
11. Dederich DN, Zakariasen KL. The effects of cyclical axial motion on rotary
endodontic instrument fatigue. Oral Surg Oral Med Oral Pathol 1986;61:192–6.
12. Ray JJ, Kirkpatrick TC, Rutledge RE. Cyclic fatigue of EndoSequence and K3 rotary
files in a dynamic model. J Endod 2007;33:1469–72.
13. Stenman E, Spangberg LSW. Root canal instruments are poorly standardized.
J Endod 1993;19:327–34.
14. Lopes HP, Elias CN, Vieira VTL, et al. Effects of electropolishing surface treatment on
the cyclic fatigue resistance of BioRace nickel-titanium rotary instruments. J Endod
2010;36:1653–7.
15. Serene TP, Adams JD, Saxena A. Nickel-titanium instruments applications in
endodontics. St Louis, MO: Ishiyaku Euroamerica Inc; 1995.
16. Parashos P, Messer HH. Rotary NiTi instrument fracture and its consequences.
J Endod 2006;32:1031–43.
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17. Cheung GSP, Shen Y, Darvell BW. Effect of environment on low-cycle fatigue of
a nickel-titanium instrument. J Endod 2007;33:1433–7.
18. Cheung GSP, Darvell BW. Low-cycle fatigue of NiTi rotary instruments of various
cross-sectional shapes. Int Endod J 2007;40:626–32.
19. Hani OF, Salameh Z, Al-Shalan T, et al. Effect of clinical use on the cyclic fatigue
resistance of ProTaper nickel-titanium rotary instruments. J Endod 2007;33:
737–41.
20. Callister WD Jr. Cîencia e engenharia de materiais: uma introduç~ao. 5th ed. Rio de
Janeiro: LTC; 2002.
21. Lopes HP, Moreira EJ, Elias CN, et al. Cyclic fatigue of ProTaper instruments. J Endod
2007;33:55–7.
22. Walia HM, Brantley WA, Gerstein H. An initial investigation of bending and torsional
properties of nitinol root canal files. J Endod 1988;14:346–51.
23. Ullmann CJ, Peters OA. Effect of cyclic fatigue on static fracture loads in ProTaper
nickel-titanium rotary instruments. J Endod 2005;31:183–6.
24. Inan U, Aydin C, Tunca YM. Cyclic fatigue of ProTaper rotary nickel titanium instru-
ments in artificial canals with 2 different radii of curvature. Oral Surg Oral Med Oral
Pathol Oral Radiol Endod 2007;104:837–40.
25. Plotino G, Grande NM, Cordaro M, et al. A review of cyclic fatigue testing of nickel-
titanium rotary instruments. J Endod 2009;35:1469–76.
26. Kim HC, Yum J, Hur B, Cheung GS. Cyclic fatigue and fracture characteristics of
ground and twisted nickel-titanium rotary files. J Endod 2010;36:147–52.
27. Larsen CM, Watanabe I, Glickman GN, He J. Cyclic fatigue analysis of a new gener-
ation of nickel titanium rotary instruments. J Endod 2009;35:401–3.
28. Gambarini G, Grande NM, Plotino G, et al. Fatigue resistance of engine-driven rotary
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29. Park SY, Cheung GSP, Yum J, et al. Dynamic torsional resistance of nickel-titanium
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Cyclic Fatigue of 2 Types of NiTi Rotary Instruments 1557
27 
 
ARTIGO N° 3 
Gambarra-Soares T, Lopes HP, Oliveira JCM, Souza LC, Vieira VT, Elias CN 
(2013). Dynamic or static fatigue tests: which best determines the lifespan of 
endodontic files? ENDO 7: 101-104. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
32 
 
ARTIGO N° 4 
De-Deus G, Moreira EJL, Lopes HP, Elias CN (2010). Extended cyclic fatigue 
life of F2 ProTaper instruments used in reciprocating movement. Int Endod J 
43: 1063-1068. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Extended cyclic fatigue life of F2 ProTaper
instruments used in reciprocating movement
G. De-Deus1, E. J. L. Moreira2, H. P. Lopes3 & C. N. Elias4
1Veiga de Almeida University, Rio de Janeiro; 2UNIGRANRIO School of Dentistry, Rio de Janeiro; 3ABE/RJ and UNESA, Rio de
Janeiro; and 4Military Institute of Engineering, Biomaterials Laboratory, Rio de Janeiro, RJ, Brazil
Abstract
De-Deus G, Moreira EJL, Lopes HP, Elias CN. Extended
cyclic fatigue life of F2 ProTaper instruments used in recipro-
cating movement. International Endodontic Journal, 43, 1063–
1068, 2010.
Aim To evaluate the cyclic fatigue fracture resistanceof engine-driven F2 ProTaper instruments under recip-
rocating movement.
Methodology A sample of 30 NiTi ProTaper F2
instruments was used. An artificial canal was made
from a stainless steel tube, allowing the instruments to
rotate freely. During mechanical testing, different
movement kinematics and speeds were used, which
resulted in three experimental groups (n = 10). The
instruments from the first group (G1) were rotated at a
nominal speed of 250 rpm until fracture, whilst the
instruments from the second group (G2) were rotated
at 400 rpm. In the third instrument group (G3), the
files were driven under reciprocating movement. The
time of fracture for each instrument was measured, and
statistical analysis was performed using parametric
methods.
Results Reciprocating movement resulted in a
significantly longer cyclic fatigue life (P < 0.05). More-
over, operating rpm was a significant factor affecting
cyclic fatigue life (P < 0.05); instruments used at a
rotational speed of 400 rpm (approximately 95 s) failed
more rapidly than those used at 250 rpm (approxi-
mately 25 s).
Conclusions Movement kinematics is amongst the
factors determining the resistance of rotary NiTi
instruments to cyclic fracture. Moreover, the recipro-
cating movement promoted an extended cyclic fatigue
life of the F2 ProTaper instrument in comparison with
conventional rotation.
Keywords: cyclic fatigue, instruments, ProTaper,
reciprocating movement.
Received 17 October 2009; accepted 25 April 2010
Introduction
Endodontic NiTi instruments have the shape memory
effect and superelasticity of NiTi alloy that make them
suitable for the enlargement of curved root canals. NiTi
rotary instruments with varying cross-sectional designs
and tapers have been developed and marketed in the
past two decades. However, despite their clear advan-
tages, NiTi instruments may undergo premature failure
by fatigue (Grande et al. 2006, Inan et al. 2007, Lopes
et al. 2007, Ounsi et al. 2007, Whipple et al. 2009),
which is the life-limiting factor for its clinical use. As a
consequence, the performance of NiTi rotary systems is
under constant evaluation (Peters 2004, De-Deus &
Garcia-Filho 2009).
Recently, a new approach to the use of the ProTaper
F2 instrument in a reciprocating movement was
reported (Yared 2008). The concept of using a single
NiTi instrument to prepare the entire root canal is
interesting; the learning curve is reduced considerably
as the technique is simplified. Moreover, the use of only
one NiTi instrument is more cost-effective than the
conventional multi-file NiTi rotary systems.
Although the first clinical impressions of the single-
file NiTi technique appear promising, other important
parameters remain to be assessed by both laboratory
and clinical studies. The fracture of an endodontic
instrument happens as a result of torsional or bending
Correspondence: Gustavo De-Deus, Av. Henrique Dodsworth,
85 ap. 808, Lagoa, 22061-030 Rio de Janeiro, RJ, Brazil
(e-mail: endogus@gmail.com).
doi:10.1111/j.1365-2591.2010.01756.x
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 1063–1068, 2010 1063
fatigue (Sattapan et al. 2000, Guilford et al. 2005, Xu &
Zheng 2006, Inan et al. 2007, Ounsi et al. 2007) and is
a complex event. Thus, a drastic change in the
movement kinematics, as proposed by Yared (2008),
needs to be assessed in terms of cyclic facture
resistance. The hope of better fracture resistance with
a new movement kinematic requires systematic eval-
uation.
The purpose of this study was to evaluate the cyclic
fatigue life of the F2 ProTaper instrument, engine-
driven under reciprocating movement. The conven-
tional rotary movement (continuous rotation) was used
as a reference for comparison. The null hypothesis
tested was that there are no differences in the fatigue
fracture resistance between the two movements. The
instrument surface fracture morphology and the helical
shaft of the instruments were made to determine the
fracture patterns of the instruments.
Materials and methods
A sample of 30 NiTi ProTaper F2 instruments (25 mm
in length; Maillefer SA, Ballaigues, Switzerland) from
six different lots was used. During mechanical testing,
different movement kinematics and speed settings were
used, which resulted in three experimental groups
(n = 10). The instruments were randomly distributed
with the aid of a free computer algorithm (http://
www.random.org).
One artificial canal was made from stainless steel
tube with an inner diameter of 1.04 mm, a total length
of 20.0 mm, and arcs on the tips with a curvature
radius of 6.0 mm. The arc of the tube measured
9.4 mm and the straight portion 10.6 mm, whereas
the curvature radius was approximately 90� and was
measured taking into consideration the concave sur-
face of the interior of the tube (Figure 1a and 1b).
A stainless steel apparatus was fabricated with a
square base and a vertical axis (Lopes et al. 2009). The
vertical axis contained a structure that allowed for the
fixture and movement of a micromotor/contra-angle
headpiece; a bench vice held the stainless steel tubes.
A gap at the base of the apparatus allowed for the
movement of the bench vice in a horizontal direction,
allowing for a connection between the axis of the
instrument and the straight part of the stainless steel
canal (Sattapan et al. 2000). The lengths of the
instruments were measured using a digital vernier
calliper (Mitutoyo Sul-Americana Ltd., Suzano, SP,
Brazil). The lengths of the metallic handles (L) of the
instruments were computed by subtracting the blade
length from the total length.
The instruments rotated freely within the stainless
tube, which was filled with glycerin to reduce friction
and heat production. Each instrument was positioned
in a contra-angle handpiece and introduced into the
canal until the tip touched a shield positioned at the
other extremity. This shield was subsequently removed,
as it was used to standardize the instrument penetra-
tion into the canal.
Three NiTi file groups were tested. The instruments
from the first group (G1) were rotated at a nominal
speed of 250 rpm until fracture, whilst the instruments
from the second group (G2) were rotated at 400 rpm.
The instruments from groups G1 and G2 were driven in
right-hand rotation by an electric motor (X-Smart
(a) (b)
Figure 1 (a) An overview of the stainless steel apparatus used. The structure at the vertical axis allowed for the fixture and
movement of the micromotor/contra-angle. (b) Closer view of the artificial root canal (stainless steel tube) used.
Cyclic fatigue life of F2 ProTaper instrument De-Deus et al.
International Endodontic Journal, 43, 1063–1068, 2010 ª 2010 International Endodontic Journal1064
model; Tulsa/Dentsply, Tulsa, OK, USA) using a 1 : 20
reduction contra-angle handpiece. For both G1 and G2,
the instruments were driven following the manufac-
turer’s instructions.
For the third instrument group (G3), the files were
used following the method of Yared (2008); the
nominal speed was set at 400 rpm and the instruments
were driven with an ATR Teknica electric micromotor
(Pistoia, Tuscany, Italy) using reciprocating move-
ment.
The time of fracture of each instrument was
measured by the same operator for all groups, using
a digital chronometer. The instance of fracture was
based on visual observation of the fracture occurring in
the instrument. An analysis for each fractured instru-
ment was performed under SEM (JEOL JSM 5800; JEOL,
Mitaka, Tokyo, Japan) to determine the mode of
fracture.
As the preliminary analysis of the raw pooled data
revealed a bell-shaped distribution (D’Agostino &
Person omnibus normality test), the statistical analysis
was performed using parametric methods: one-way
analysis of variance. Post hoc pair-wise comparisons
were performed using Tukey test for multiple compar-
isons. The alpha-type error was setat 0.05. SPSS 11.0
(SPSS Inc., Chicago, IL, USA) and Origin 6.0 (Microcal
Software, Inc., Northampton, MA, USA) were used as
analytical tools.
Results
The average length of the Pro Taper F2 instruments
was 25 mm.
SEM evaluation demonstrated that fractured
surfaces had ductile morphological characteristics
(Fig. 3a,c). Dimples with varied forms were identified.
In all the samples, although there were small
increases in length, plastic deformation in the helical
shaft of the fractured instruments was not observed
(Fig. 3b).
The number of cycles until fracture was a function of
the movement kinematics (reciprocate and continuous
rotation). Under continuous rotation, instrument frac-
ture occurred after an average of 160 cycles at
250 rpm and 120 cycles at 400 rpm. Under the
reciprocating movement, fracture occurred after an
average of 126 completed rotations at 400 rpm, which
results in 630 cycles.
The average, the minimal and the maximal values,
as well as the standard deviation, of the time until the
fracture are shown in Fig. 2. Based on the statistical
analysis, the instruments used in the reciprocating
movement revealed a significantly longer cyclic fatigue
life (P < 0.05). Moreover, speed of rotation had a
significant effect on the cyclic fatigue life in the two
rotary movement groups (P < 0.05).
Figure 3a,b,c shows representative SEM micrographs
illustrating the surface morphology of the fractured
instruments.
Discussion
The results demonstrated that movement kinematics
had a significant influence on the cyclic fatigue life of
F2 ProTaper instruments. Therefore, the null hypoth-
esis can be rejected.
From a mechanical viewpoint, stress fracture in
rotary endodontic instruments results from continued
repetitive loading (cyclic fatigue). Research has shown
that fatigue failure occurs by the formation of micro-
cracks, usually at the surface of a file, with the growth
of this crack increasing by small increments during
each loading cycle (Christ 2008). This behavior is
commonly observed in any material submitted to
fatigue loading. In clinical conditions, tensile stress
induces a crack nucleation and propagation in instru-
ment surface irregularities, which present a region of
concentrated stress (Ounsi et al. 2007, Wei et al.
2007). All new endodontic instruments show irregu-
larities on the surface (Anderson et al. 2007, Wei et al.
2007). Experimental data has shown that there are
Figure 2 Box-plot showing the average, median, the minimal
and maximal values, as well as the standard deviation, of the
time until instrument fracture occurred. Different letters
indicate significant statistical differences between groups;
P < 0.05.
De-Deus et al. Cyclic fatigue life of F2 ProTaper instrument
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 1063–1068, 2010 1065
large variances in fracture strength of endodontic
instruments resulting from a distribution of pre-existing
defects on the surface (Anderson et al. 2007, Wei et al.
2007). Consequently, the instrument fatigue life can be
regarded as a function of the tensile value, irregularities
and the size of cracks on the surface.
The fatigue behavior of endodontic instruments and
stress analysis during canal treatment is illustrated in
Fig. 4. At point 1, the concave part of the instrument is
submitted to tensile stress and the crack is opened. At
point 3, the convex part of the instrument is under
compressive stress and the crack is closed. When the
part of the instrument at point 1 turns 180 degrees, the
position changes to point 3 and the material is
submitted to a compressive stress and the crack closes.
On the other hand, when point 3 turns 180 degrees, it
undergoes tensile stress at point 1. At each cycle, the
maximum tensile stress occurs at point 1 and maxi-
mum compressive stress occurs at point 3. The instru-
ment fails after ‘‘N’’ cycles, which is the instrument’s
fatigue life. When the rotation speed increases, the
instruments’ average time of fracture decreases, but the
number of cycles does not change. Figure 2 shows that
the fatigue life reduced when the rotation speed
increased from 250 to 400 rpm. This can be viewed
as a further finding of this study. Several reports have
noted the effect of the rotational speed on NiTi
instrument fracture, with these results being in line
with the present findings, which indicate that instru-
ments rotated at higher speeds are more susceptible to
fracture than when used at lower rotational speeds
(Gambarini 2001, Zelada et al. 2002).
Figure 4b also shows that when the instrument is
submitted to a reciprocating movement, the average
time until fracture increases. It is well known that
greater bending deflection of the instrument in each
cycle results in a reduction in the number of cycles
needed to break the file (Xu & Zheng 2006). Many
(a) (b)
(c)
Figure 3 (a) Ductile surface fracture morphology. It is possible to observe dimples. (b) Surface fracture in the helical shaft of the
fractured instrument with an absence of plastic deformation. (c) Ductile surface fracture morphology. It is possible to observe
dimples.
Cyclic fatigue life of F2 ProTaper instrument De-Deus et al.
International Endodontic Journal, 43, 1063–1068, 2010 ª 2010 International Endodontic Journal1066
cycles would be required for fracture if the root canal
constraint was able to produce only elastic deforma-
tion. During just one reciprocating movement (Yared
2008), the instrument turns clockwise 0.4 of the cycle
(144 degrees) and returns 0.2 part of the cycle (72
degrees), which means that after five reciprocating
movements, the instrument completes one entire rota-
tion (360 degrees). The fatigue life is measured by the
number of times that the crack closes and opens.
During one cycle, the crack opens and closes once. This
movement rationale acts to extend the fatigue life of F2
ProTaper instruments.
There are no previous reports on the effect of
reciprocating movement on the cyclic fatigue life of
the F2 ProTaper instrument, and further studies are
needed to confirm the extended fatigue life of the F2
ProTaper instrument driven with reciprocating move-
ment.
The present results indicate that movement kine-
matics is included amongst the factors determining the
resistance of rotary NiTi instruments to cyclic fracture
resistance. Under the present experimental framework,
reciprocating movement extends the cyclic fatigue life
of F2 ProTaper instruments when compared to the
conventional rotary movement. In addition, the influ-
ence of speed on the fatigue life is confirmed when the
F2 instrument was driven under rotary movement.
Further clinical studies are required to determine the
relationship of the present experimental data with the
efficacy of the F2 ProTaper file used in reciprocating
movement in vivo.
References
Anderson ME, Price JW, Parashos P (2007) Fracture resis-
tance of electropolished rotary nickel-titanium endodontic
instruments. Journal of Endodontics 33, 1212–26.
Christ HJ (2008) Fundamental mechanisms of fatigue and
fracture. Student Health Technology Information 133, 56–67.
De-Deus G, Garcia-Filho P (2009) The influence of the NiTi
rotary system on the debridement quality of the root canal
space. Oral Surgery Oral Medicine Oral Pathology Oral
Radiology and Endodontics 108, 71–6.
Gambarini G (2001) Cyclic fatigue of nickel-titanium rotary
instruments after clinical use with low- and high-torque
endodontic motors. Journal of Endodontics 27, 772–4.
(a) (b)
Figure 4 (a) Schematic drawing of the root canals used in the study; Angle 90 degrees and arc 9.4 mm. (b) Schematic drawing
showing that when the instrument is submitted to a reciprocating movement, the average time of fracture increases.
De-Deus et al. Cyclic fatigue life of F2 ProTaper instrument
ª 2010 International Endodontic Journal International Endodontic Journal, 43, 1063–1068,2010 1067
Grande NM, Plotino G, Pecci R, Bedini R, Malagnino VA,
Somma F (2006) Cyclic fatigue resistance and three-
dimensional analysis of instruments from two nickel-
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Guilford WL, Lemons JE, Eleazer PD (2005) A comparison of
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Inan U, Aydin C, Tunca YM (2007) Cyclic fatigue of ProTaper
rotary nickel-titanium instruments in artificial canals with 2
different radii of curvature. Oral Surgery Oral Medicine Oral
Pathology Oral Radiology and Endodontics 104, 837–40.
Lopes HP, Ferreira AA, Elias CN, Moreira EJ, de Oliveira JC,
Siqueira JF Jr. (2009) Influence of rotational speed on the
cyclic fatigue of rotary nickel-titanium endodontic instru-
ments. Journal of Endodontics 35, 1013–6.
Lopes HP, Moreira EJ, Elias CN, de Almeida RA, Neves MS
(2007) Cyclic fatigue of ProTaper instruments. Journal of
Endodontics 33, 55–7.
Ounsi HF, Salameh Z, Al-Shalan T et al. (2007) Effect of
clinical use on the cyclic fatigue resistance of ProTaper
nickel-titanium rotary instruments. Journal of Endodontics
33, 737–41.
Peters OA (2004) Current challenges and concepts in the
preparation of root canal systems: a review. Journal of
Endodontics 30, 559–67.
Sattapan B, Nervo GJ, Palamara JE, Messer HH (2000) Defects
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Endodontics 26, 161–5.
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use. Journal of Endodontics 33, 276–9.
Whipple SJ, Kirkpatrick TC, Rutledge RE (2009) Cyclic fatigue
resistance of two variable-taper rotary file systems: ProTaper
universal and V-Taper. Journal of Endodontics 35, 555–8.
Xu X, Zheng Y (2006) Comparative study of torsional and
bending properties for six models of nickel-titanium root
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instrument: preliminary observations. International Endodon-
tic Journal 41, 339–44.
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(2002) The effect of rotational speed and the curvature of
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International Endodontic Journal, 43, 1063–1068, 2010 ª 2010 International Endodontic Journal1068
39 
 
ARTIGO N° 5 
Lopes HP, Vieira MVB, Elias CN, Siqueira Jr JF, Mangelli M, Lopes WSP et al. 
(2013b). Fatigue life of WaveOne and ProTaper instruments operated in 
reciprocating or continous rotation movements and subjected to dynamic and 
static tests. ENDO 7: 217-222. 
 
 
 
 
 
 
 
 
 
 
 
 
 
46 
 
ARTIGO N° 6 
Lopes HP, Elias CN, Vieira MVB, Siqueira Jr JF, Mangelli M, Lopes WSP et al. 
(2013c). Fatigue life of Reciproc and Mtwo instruments subjected to static and 
dynamic tests. J Endod 39: 693-696. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Basic Research—Technology
Bending Resistance and Dynamic and Static Cyclic Fatigue
Life of Reciproc and WaveOne Large Instruments
Gustavo De-Deus, DDS, MS, PhD,* Victor Talarico Leal Vieira, PhD,*
Emmanuel Jo~ao Nogueira da Silva, PhD,* Helio Lopes, PhD,† Carlos Nelson Elias, PhD,‡
and Edson Jorge Moreira, PhD*
Abstract
Introduction: The aim of the present study was to eval-
uate the bending resistance and the dynamic and static
cyclic fatigue life of Reciproc R40 and WaveOne large in-
struments.Methods: A sample of 68 nickel-titanium in-
struments (25 mm in length) for use under reciprocation
movement (Reciproc and WaveOne) from 3 different lots
was tested. Reciproc R40 and WaveOne Large files, both
of which had a nominal size of 0.40 mm at D0, were
selected. The bending resistance was performed in 10
instruments of each system by using a universal testing
machine. Dynamic and static models for cyclic fatigue
testing were performed by using a custom-made device.
For these tests, an artificial canal measuring 1.4 mm in
diameter and 19 mm total length was fabricated from
a stainless steel tube. Scanning electron microscopy
analysis was performed to determine the mode of frac-
ture. Statistical analysis was performed by using para-
metric methods, 1-way analysis of variance. Post hoc
pair-wise comparisons were performed by using Tukey
test for multiple comparisons. Results:WaveOne instru-
ments presented significantly higher bending resistance
than Reciproc (P < .05). Moreover, Reciproc revealed a
significantly longer cyclic fatigue life (P < .05) in both
static and dynamic tests (P < .05). Conclusions: Recip-
roc R40 instruments resisted dynamic and static cyclic
fatigue significantly more than WaveOne Large instru-
ments. Furthermore, WaveOne instruments presented
significantly less flexibility than Reciproc. (J Endod
2014;40:575–579)
Key Words
Cyclic fatigue, instruments, NiTi, Reciproc, reciprocating
movement, WaveOne
From the *Department of Endodontology, Grande Rio Uni-
versity (UNIGRANRIO), Duque de Caxias, RJ; †Est�acio de S�a Uni-
versity (UNESA), Rio de Janeiro; and ‡Military Institute of
Engineering, Biomaterials Laboratory, Rio de Janeiro, Rio de Ja-
neiro, Brazil.
Address requests for reprints to Prof Gustavo Andr�e de
Deus Carneiro Vianna, Av. Henrique Dodsworth, 85 ap. 808, La-
goa, Rio de Janeiro, RJ, Brazil 22061-030. E-mail address:
endogus@gmail.com
0099-2399/$ - see front matter
Copyright ª 2014 American Association of Endodontists.
http://dx.doi.org/10.1016/j.joen.2013.10.013
JOE — Volume 40, Number 4, April 2014
Nickel-titanium (NiTi) rotary instruments have become a fundamental tool formechanical root canal preparation mainly because of their superelastic behavior.
However, despite their advantages, NiTi rotary instruments may undergo premature fail-
ure by flexion and/or torsion (1). Cyclic fatigue fracture occurs as consequence of the
continuous rotation of an instrument in a curved space in the absence of binding. In this
condition, the instrument under elastic deformation is subjected to a mechanical load
represented by alternating tensile and compressive stresses (2). The cyclical repetition
of the load leads to instrument fracture through low-cycle fatigue (3, 4). The cyclic
fatigue resistance comprises the number of cycles that an instrument can endure
under a specific loading condition until fracture occurs. Because NiTi instruments
may show no visible signs of permanent deformation during cyclic fatigue,
instrument separation may occur unexpectedly (5).
In 2008, a new approach to the use of the ProTaper F2 (DENTSPLY Ltd, Addlestone,
UK) instrument in a reciprocating movement was reported as an alternative to the
conventional continuous rotation (6). The reciprocation motion relieves stress on the
instrument by special counterclockwise (cutting action, the instrument advances in
the canal and engages dentin to cut it) and clockwise (release of the instruments,
the instrument is immediately disengaged) movements and therefore extends the NiTi
instrument life span, hence resistance to fatigue, in comparison with continuous rotation
(7, 8). Two reciprocation NiTi systems were introduced into themarket: Reciproc (VDW,
Munich, Germany) and WaveOne (Dentsply Maillefer, Ballaigues, Switzerland). The
manufacturers recommended the use of these files driven by a specific motor with a
preset reciprocation mode (‘‘RECIPROC ALL’’ for Reciproc and ‘‘WAVEONE ALL’’ for
WaveOne). These instruments travel a shorter angular distance than rotary
instruments, which are subject to lower stress values, rendering an extended fatigue
life (9–11).
One point to highlight is that the extended cyclic fatigue life promoted by the recip-
rocationmovement can play a role in achieving larger apical preparations. There is some
evidence that larger apicalpreparations allow a greater reduction of intracanal bacteria
load and less hard tissue debris, mainly as result of more effective irrigation (12–14).
However, achieving a larger apical diameter is not an easy clinical challenge task,
essentially in curved, narrow, and long root canals. One point of concern is about the
higher instrument fracture risk because the larger the instrument is, the lower
the flexibility, and flexibility can directly interfere with instrument’s performance in the
cyclic fatigue fracture resistance (2, 15).
The aim of the present study was to evaluate the bending resistance and the
dynamic and static cyclic fatigue life of Reciproc R40 and WaveOne large instru-
ments. The null hypotheses tested were as follows:
1. That there are no differences in the static fatigue fracture resistance between the Re-
ciproc R40 and WaveOne large instruments
2. That there are no differences in the dynamic fatigue fracture resistance between the
Reciproc R40 and WaveOne large instruments
3. That there are no differences in the bending resistance between the Reciproc R40
and WaveOne large instruments
The instrument surface fracture morphology and the helical shaft of the instru-
ments were examined to determine the fracture patterns of the instruments.
Bending and Cyclic Fatigue Life of Reciproc and WaveOne 575
Delta:1_given name
Delta:1_surname
Delta:1_given name
Delta:1_surname
Delta:1_given name
Delta:1_surname
mailto:endogus@gmail.com
http://dx.doi.org/10.1016/j.joen.2013.10.013
Figure 1. (A) Box plot showing the average, median, minimal, and maximal
values and the standard deviation of the maximum strength. (B) Box plot
showing point-to-point strength distribution. Different letters indicate signifi-
cant statistical differences between groups (P < .05).
Basic Research—Technology
Materials and Methods
A sample of 68 NiTi instruments (25 mm in length) for use under
reciprocation movement (Reciproc and WaveOne) from 3 different lots
was tested. Reciproc R40 and WaveOne Large files, both of which had a
nominal size of 0.40 mm at D0, were selected. The former have a
nominal taper at the first apical millimeters of 0.06 mm/mm, whereas
the latter has 0.08 mm/mm. For standardization and reliability of the
experiment, the instruments tested were examined for defects or defor-
mities under a stereomicroscope.
Bending Resistance Test
The bending resistance was performed in 10 randomly selected
instruments of each system by using a universal testing machine (DL
10.000; Emic, S~ao Jos�e dos Pinhais, Brazil) as described in previous
studies (2, 16). A 20-N load was applied at 15 mm/min by means of
a flexible stainless steel wire with 1 end fastened to the testing machine
head and the other end attached 3 mm from the instrument tip until it
displayed a 45� deflection. The maximum load to bend each file was
recorded and statistically analyzed. The force values were acquired in
3 points corresponding to positions 17�, 34�, and 45� for a more
detailed analysis.
Cyclic Fatigue Tests
The instruments were randomly distributed with the aid of a free
computer algorithm (http://www.random.org) in 4 experimental
groups (n = 12). Dynamic and static models for cyclic fatigue testing
were performed by using a custom-made device. For these tests, an
artificial canal measuring 1.4 mm in diameter and 19 mm total length
was fabricated from a stainless steel tube. A 9-mm-long curved segment
with 6-mm radius (measured at the internal concave surface of the
tube) was created between 2 straight segments that measured 7 mm
and 3 mm (17). The canal was filled with glycerin, reducing friction
and heat release. Fatigue tests were performed under static or dynamic
conditions.
Static Test
Twelve instruments of each reciprocate system were activated by
using a 6:1 reduction handpiece (Sirona Dental Systems GmbH, Ben-
sheim, Germany) powered by a torque-controlled motor (Silver Recip-
roc; VDW) by using the pre-setting programs for each one (‘‘RECIPROC
ALL’’ for Reciproc and ‘‘WAVEONE ALL’’ for WaveOne). All instruments
were reciprocated following the manufacturer’s instructions until a
fracture occurred. A stainless steel apparatus was fabricated with a
square base and a vertical axis (8). The vertical axis contained a struc-
ture that allowed for the fixture and movement of a micromotor/contra-
angle headpiece; a bench vise held the stainless steel tubes. A gap at the
base of the apparatus allowed for the movement of the bench vise in a
horizontal direction, allowing for a connection between the axis of the
instrument and the straight part of the stainless steel canal (5). The
lengths of the instruments were measured by using a digital vernier
caliper (Mitutoyo Sul-Americana Ltd, Suzano, SP, Brazil). The lengths
of the metallic handles of the instruments were computed by subtracting
the blade length from the total length.
The instruments rotated freely within the stainless tube that was
filled with glycerin to reduce friction and heat production. Each instru-
ment was positioned in a contra-angle handpiece and introduced into
the canal until the tip touched a shield positioned at the other extremity.
This shield was subsequently removed, because it was used to stan-
dardize the instrument penetration into the canal. The time was
recorded and stopped as soon as a fracture was detected visually
and/or audibly. To avoid human error, video recording was performed
576 De-Deus et al.
simultaneously, and the recordings were then observed to cross-check
the time of file separation (9).
Dynamic Test
Another set of 12 instruments of each reciprocate system was
used for the dynamic test. The instruments were subjected to the
same protocol described in the static test, but for these experiments,
a mechanical device promoted back-and-forth axial movements
while the files rotated inside the canal. The amplitude of the axial
movements was 3 mm, with approximately 2 seconds between oscil-
lations.
The fractured surfaces and the helical shaft of the separated
instruments in both static and dynamic tests were analyzed under scan-
ning electron microscopy (JSM 5800; JEOL, Tokyo, Japan) to deter-
mine the type of fracture and the presence of plastic deformation in
the shaft.
Statistics
Because the preliminary analysis of the raw pooled and isolated
data revealed a bell-shaped distribution (D’Agostino and Person
omnibus normality test), statistical analysis was performed by using
parametric methods, 1-way analysis of variance. Post hoc pair-wise
comparisons were performed by using Tukey test for multiple compar-
isons. The alpha-type error was set at 0.05. SPSS 11.0 (SPSS Inc,
JOE — Volume 40, Number 4, April 2014
http://www.random.org
Basic Research—Technology
Chicago, IL) and Origin 6.0 (Microcal Software, Inc, Northampton, MA)
were used as analytical tools.
Results
WaveOne instruments presented significantly higher bending
resistance than Reciproc (P < .05) (Fig. 1). Moreover, Reciproc
revealed a significantly longer cyclic fatigue life (P < .05) in both static
and dynamic tests (P < .05). The average, the minimal and maximal
values, and the standard deviation of the bending, static, and dynamic
tests are shown in the graphs of Figure 2.
Scanning electron microscopy visual inspection of the fractured
surface indicated that all instruments showed morphologic character-
istics of ductile fracture. Wide-ranging forms of dimples were identified
overall, and no plastic deformation in the helical shaft of the fractured
instruments was observed (Fig. 3).
Discussion
The first results of this study showed that the dynamic and static
cyclic fatigue of Reciproc R40 instrument was significantly higher
than that of the WaveOne larger instrument. Therefore, the first and sec-
ond null hypotheses were rejected. Previous studies demonstrated that
Reciproc R25 instrument has a higher cyclic fatigue resistance than
WaveOne primary files (18–22); however, to the best of the authors’
knowledge, this is the first attempt to evaluatethe bending resistance
and the dynamic and static cyclic fatigue by using Reciproc and
WaveOne large files (tip #40).
The dynamic cyclic fatigue average time of Reciproc instruments
showed an increase of 31% compared with static test, whereasWaveOne
instruments showed 22% improvement in time. Thus, it is important to
note that even by using the reciprocating motion, the instrument should
not be static inside the root canal to reduce the risk of fracture.
Figure 2. Box plot showing the average, median, minimal, and maximal values and
letters indicate significant statistical differences between groups (P < .05). (A) Dyna
One, (C) dynamic WaveOne versus static WaveOne, (D) dynamic Reciproc versus
JOE — Volume 40, Number 4, April 2014
The average fatigue time of Reciproc instrument was 69% and 73%
greater than the WaveOne for the static and dynamic tests, respectively.
The percentages of time difference of either instrument were very
similar in both types of fatigue test, and this shows that the experimental
model used has enough sensitiveness to detect the odds of the instru-
ments Reciproc at the 2 tested conditions. Theoretically, this advantage
should be similar even with the change of kinematics of the experiment,
and this difference was approximately 4%.
The third result from the current study indicated that WaveOne
files required significantly greater loads than Reciproc to reach 45�
deflection. This means that WaveOne larger instruments are less flexible
than Reciproc R40 ones. Thus, the third null hypothesis was also
rejected. Overall, rigid instruments present a lower number of cycles
to fracture because of the buildup of tensions at the point of maximum
flexure, as observed in the present study and in line with previous
studies (23, 24). Within our knowledge, there is only limited
information about flexibility of WaveOne and Reciproc instruments.
Therefore, the current results can be used to shine some light on the
mechanical behavior of these larger instruments specifically designed
to be driven under reciprocation movement.
The tip sizes (diameter at D0) of Reciproc R40 and WaveOne Large
were the same, although the taper differed. A design point of Reciproc
and WaveOne instruments is that the former have a nominal taper at the
first apical millimeters of 0.06 mm/mm, whereas the latter has 0.08
mm/mm. This difference also helps to explain the greater stiffness of
WaveOne instruments. Both reciprocating file systems are made of
the same NiTi alloy (M-wire); however, they have different cross sec-
tions. Reciproc instruments have an S-shaped cross section with 2 cut-
ting blades, whereas WaveOne instruments have a modified convex
triangular cross section and the tip and a convex triangular cross sec-
tion in the middle and coronal portions. It has been reported that the
larger the cross-sectional area is, the higher the flexural and torsional
stiffness (25, 26); in this way, file design (cross-sectional shape,
the standard deviation of the time until instrument fracture occurred. Different
mic Reciproc versus dynamic WaveOne, (B) static Reciproc versus static Wave-
static Reciproc.
Bending and Cyclic Fatigue Life of Reciproc and WaveOne 577
Figure 3. Fractured surfaces of instruments showing morphologic characteristics of the ductile type. (A) Reciproc static test, (B) WaveOne static test, (C)
Reciproc dynamic test, (D) WaveOne dynamic test (original magnification, �150).
Basic Research—Technology
diameters of core, etc) would have a significant influence on the
torsional and bending (hence, fatigue) resistance (26).
The current study compared the bending resistance and the
dynamic and static cyclic fatigue of Reciproc R40 and WaveOne Large
instruments. The rationale behind the selection of these instruments
to test is the current trend to promote larger apical preparations with
the purpose of optimizing root canal disinfection (12–14, 27) and
thus rendering better conditions for tissue repair (28).
The best way of reproducing this type of fatigue is repeating the
movement for all tested files under well-standardized experimental con-
ditions, mainly in terms of predefined curvature. Experimental models
where the instruments can bind should be avoided because additional
torsional stress points will appear (21). Although the use of extracted
teeth simulates clinical situations, they are not ideal for the analysis
of cyclic fatigue because they are not anatomically standardized, and
there may be other confounding factors (21). A metallic tube was
used in the present study to standardize the entire length of the canal,
the length of the curvature radius, and the length of the arc. One
limitation of the metallic simulators is that the instrument works in a
passive way, whereas clinically it can lock on dentin, leading to torsional
fracture.
Static and dynamic models were used to test the cyclic fatigue resis-
tance in the present study. Regardless of the instrument brand, the cyclic
fatigue was significantly higher during dynamic versus static fatigue test.
This result is similar to previous studies (17, 21, 22, 29, 30), suggesting
that a concentration of stress in a small area of the instrument reduces the
cyclic fatigue of the instrument. As in the dynamic model, the file moves
axially within the canal; a better distribution of stress along the instrument
reduces the compressive and tensile stresses’ concentration at the
instrument area located at the center of the metallic tube curve,
enhancing fracture resistance (17).
The scanning electron microscopy analysis showed typical fracto-
graphic appearances of cyclic fatiguewith nomorphologic differences be-
tween the 2 types of instruments or between instruments fractured during
578 De-Deus et al.
static versus dynamic tests. All fracture surfaces displayed ductilemorpho-
logic characteristics as observed in previous studies (3, 8, 17, 19).
Under the present experimental framework, Reciproc R40 instru-
ments resisted dynamic and static cyclic fatigue significantly more than
WaveOne Large instruments. Furthermore, WaveOne instruments pre-
sented significantly less flexibility than Reciproc.
Acknowledgments
The authors deny any conflicts of interest related to this study.
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51 
 
ARTIGO N° 7 
De-Deus G, Vieira VTL, Nogueira da Silva EJ, Lopes HP, Elias CN, Moreira EJ 
(2014). Bending resistance and dynamic and static cyclicfatigue life of Reciproc 
and WaveOne Large instruments. J Endod 40: 575-579. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Basic Research—Technology
Bending Resistance and Dynamic and Static Cyclic Fatigue
Life of Reciproc and WaveOne Large Instruments
Gustavo De-Deus, DDS, MS, PhD,* Victor Talarico Leal Vieira, PhD,*
Emmanuel Jo~ao Nogueira da Silva, PhD,* Helio Lopes, PhD,† Carlos Nelson Elias, PhD,‡
and Edson Jorge Moreira, PhD*
Abstract
Introduction: The aim of the present study was to eval-
uate the bending resistance and the dynamic and static
cyclic fatigue life of Reciproc R40 and WaveOne large in-
struments.Methods: A sample of 68 nickel-titanium in-
struments (25 mm in length) for use under reciprocation
movement (Reciproc and WaveOne) from 3 different lots
was tested. Reciproc R40 and WaveOne Large files, both
of which had a nominal size of 0.40 mm at D0, were
selected. The bending resistance was performed in 10
instruments of each system by using a universal testing
machine. Dynamic and static models for cyclic fatigue
testing were performed by using a custom-made device.
For these tests, an artificial canal measuring 1.4 mm in
diameter and 19 mm total length was fabricated from
a stainless steel tube. Scanning electron microscopy
analysis was performed to determine the mode of frac-
ture. Statistical analysis was performed by using para-
metric methods, 1-way analysis of variance. Post hoc
pair-wise comparisons were performed by using Tukey
test for multiple comparisons. Results:WaveOne instru-
ments presented significantly higher bending resistance
than Reciproc (P < .05). Moreover, Reciproc revealed a
significantly longer cyclic fatigue life (P < .05) in both
static and dynamic tests (P < .05). Conclusions: Recip-
roc R40 instruments resisted dynamic and static cyclic
fatigue significantly more than WaveOne Large instru-
ments. Furthermore, WaveOne instruments presented
significantly less flexibility than Reciproc. (J Endod
2014;40:575–579)
Key Words
Cyclic fatigue, instruments, NiTi, Reciproc, reciprocating
movement, WaveOne
From the *Department of Endodontology, Grande Rio Uni-
versity (UNIGRANRIO), Duque de Caxias, RJ; †Est�acio de S�a Uni-
versity (UNESA), Rio de Janeiro; and ‡Military Institute of
Engineering, Biomaterials Laboratory, Rio de Janeiro, Rio de Ja-
neiro, Brazil.
Address requests for reprints to Prof Gustavo Andr�e de
Deus Carneiro Vianna, Av. Henrique Dodsworth, 85 ap. 808, La-
goa, Rio de Janeiro, RJ, Brazil 22061-030. E-mail address:
endogus@gmail.com
0099-2399/$ - see front matter
Copyright ª 2014 American Association of Endodontists.
http://dx.doi.org/10.1016/j.joen.2013.10.013
JOE — Volume 40, Number 4, April 2014
Nickel-titanium (NiTi) rotary instruments have become a fundamental tool formechanical root canal preparation mainly because of their superelastic behavior.
However, despite their advantages, NiTi rotary instruments may undergo premature fail-
ure by flexion and/or torsion (1). Cyclic fatigue fracture occurs as consequence of the
continuous rotation of an instrument in a curved space in the absence of binding. In this
condition, the instrument under elastic deformation is subjected to a mechanical load
represented by alternating tensile and compressive stresses (2). The cyclical repetition
of the load leads to instrument fracture through low-cycle fatigue (3, 4). The cyclic
fatigue resistance comprises the number of cycles that an instrument can endure
under a specific loading condition until fracture occurs. Because NiTi instruments
may show no visible signs of permanent deformation during cyclic fatigue,
instrument separation may occur unexpectedly (5).
In 2008, a new approach to the use of the ProTaper F2 (DENTSPLY Ltd, Addlestone,
UK) instrument in a reciprocating movement was reported as an alternative to the
conventional continuous rotation (6). The reciprocation motion relieves stress on the
instrument by special counterclockwise (cutting action, the instrument advances in
the canal and engages dentin to cut it) and clockwise (release of the instruments,
the instrument is immediately disengaged) movements and therefore extends the NiTi
instrument life span, hence resistance to fatigue, in comparison with continuous rotation
(7, 8). Two reciprocation NiTi systems were introduced into themarket: Reciproc (VDW,
Munich, Germany) and WaveOne (Dentsply Maillefer, Ballaigues, Switzerland). The
manufacturers recommended the use of these files driven by a specific motor with a
preset reciprocation mode (‘‘RECIPROC ALL’’ for Reciproc and ‘‘WAVEONE ALL’’ for
WaveOne). These instruments travel a shorter angular distance than rotary
instruments, which are subject to lower stress values, rendering an extended fatigue
life (9–11).
One point to highlight is that the extended cyclic fatigue life promoted by the recip-
rocationmovement can play a role in achieving larger apical preparations. There is some
evidence that larger apical preparations allow a greater reduction of intracanal bacteria
load and less hard tissue debris, mainly as result of more effective irrigation (12–14).
However, achieving a larger apical diameter is not an easy clinical challenge task,
essentially in curved, narrow, and long root canals. One point of concern is about the
higher instrument fracture risk because the larger the instrument is, the lower
the flexibility, and flexibility can directly interfere with instrument’s performance in the
cyclic fatigue fracture resistance (2, 15).
The aim of the present study was to evaluate the bending resistance and the
dynamic and static cyclic fatigue life of Reciproc R40 and WaveOne large instru-
ments. The null hypotheses tested were as follows:
1. That there are no differences in the static fatigue fracture resistance between the Re-
ciproc R40 and WaveOne large instruments
2. That there are no differences in the dynamic fatigue fracture resistance between the
Reciproc R40 and WaveOne large instruments
3. That there are no differences in the bending resistance between the Reciproc R40
and WaveOne large instruments
The instrument surface fracture morphology and the helical shaft of the instru-
ments were examined to determine the fracture patterns of the instruments.
Bending and Cyclic Fatigue Life of Reciproc and WaveOne 575
Delta:1_given name
Delta:1_surname
Delta:1_given name
Delta:1_surname
Delta:1_given name
Delta:1_surname
mailto:endogus@gmail.com
http://dx.doi.org/10.1016/j.joen.2013.10.013
Figure 1. (A) Box plot showing the average, median, minimal, and maximal
values and the standard deviation of the maximum strength. (B) Box plot
showing point-to-point strength distribution. Different letters indicate signifi-
cant statistical differences between groups (P < .05).
Basic Research—Technology
Materials and Methods
A sample of 68 NiTi instruments (25 mm in length) for use under
reciprocation movement (Reciproc and WaveOne) from 3 different lots
was tested. Reciproc R40 and WaveOne Large files, both of which had a
nominal size of 0.40 mm at D0, were selected. The former have a
nominal taper at the first apical millimeters of 0.06 mm/mm, whereas
the latter has 0.08 mm/mm. For standardization and reliability of the
experiment, the instruments tested were examined for defects or defor-
mities under a stereomicroscope.
Bending Resistance Test
The bending resistance was performed in 10 randomly selected
instruments of each system by using a universal testing machine (DL
10.000; Emic, S~ao Jos�e dos Pinhais, Brazil) as described in previous
studies (2, 16). A 20-N load was applied at 15 mm/min by means of
a flexible stainless steel wire with 1 end fastened to the testing machine
head and the other end attached 3 mm from the instrument tip until it
displayed a 45� deflection. The maximum load to bend each file was
recorded and statistically analyzed. The force values were acquired in
3 points corresponding to positions 17�, 34�, and 45� for a more
detailed analysis.
Cyclic Fatigue Tests
The instruments were randomlydistributed with the aid of a free
computer algorithm (http://www.random.org) in 4 experimental
groups (n = 12). Dynamic and static models for cyclic fatigue testing
were performed by using a custom-made device. For these tests, an
artificial canal measuring 1.4 mm in diameter and 19 mm total length
was fabricated from a stainless steel tube. A 9-mm-long curved segment
with 6-mm radius (measured at the internal concave surface of the
tube) was created between 2 straight segments that measured 7 mm
and 3 mm (17). The canal was filled with glycerin, reducing friction
and heat release. Fatigue tests were performed under static or dynamic
conditions.
Static Test
Twelve instruments of each reciprocate system were activated by
using a 6:1 reduction handpiece (Sirona Dental Systems GmbH, Ben-
sheim, Germany) powered by a torque-controlled motor (Silver Recip-
roc; VDW) by using the pre-setting programs for each one (‘‘RECIPROC
ALL’’ for Reciproc and ‘‘WAVEONE ALL’’ for WaveOne). All instruments
were reciprocated following the manufacturer’s instructions until a
fracture occurred. A stainless steel apparatus was fabricated with a
square base and a vertical axis (8). The vertical axis contained a struc-
ture that allowed for the fixture and movement of a micromotor/contra-
angle headpiece; a bench vise held the stainless steel tubes. A gap at the
base of the apparatus allowed for the movement of the bench vise in a
horizontal direction, allowing for a connection between the axis of the
instrument and the straight part of the stainless steel canal (5). The
lengths of the instruments were measured by using a digital vernier
caliper (Mitutoyo Sul-Americana Ltd, Suzano, SP, Brazil). The lengths
of the metallic handles of the instruments were computed by subtracting
the blade length from the total length.
The instruments rotated freely within the stainless tube that was
filled with glycerin to reduce friction and heat production. Each instru-
ment was positioned in a contra-angle handpiece and introduced into
the canal until the tip touched a shield positioned at the other extremity.
This shield was subsequently removed, because it was used to stan-
dardize the instrument penetration into the canal. The time was
recorded and stopped as soon as a fracture was detected visually
and/or audibly. To avoid human error, video recording was performed
576 De-Deus et al.
simultaneously, and the recordings were then observed to cross-check
the time of file separation (9).
Dynamic Test
Another set of 12 instruments of each reciprocate system was
used for the dynamic test. The instruments were subjected to the
same protocol described in the static test, but for these experiments,
a mechanical device promoted back-and-forth axial movements
while the files rotated inside the canal. The amplitude of the axial
movements was 3 mm, with approximately 2 seconds between oscil-
lations.
The fractured surfaces and the helical shaft of the separated
instruments in both static and dynamic tests were analyzed under scan-
ning electron microscopy (JSM 5800; JEOL, Tokyo, Japan) to deter-
mine the type of fracture and the presence of plastic deformation in
the shaft.
Statistics
Because the preliminary analysis of the raw pooled and isolated
data revealed a bell-shaped distribution (D’Agostino and Person
omnibus normality test), statistical analysis was performed by using
parametric methods, 1-way analysis of variance. Post hoc pair-wise
comparisons were performed by using Tukey test for multiple compar-
isons. The alpha-type error was set at 0.05. SPSS 11.0 (SPSS Inc,
JOE — Volume 40, Number 4, April 2014
http://www.random.org
Basic Research—Technology
Chicago, IL) and Origin 6.0 (Microcal Software, Inc, Northampton, MA)
were used as analytical tools.
Results
WaveOne instruments presented significantly higher bending
resistance than Reciproc (P < .05) (Fig. 1). Moreover, Reciproc
revealed a significantly longer cyclic fatigue life (P < .05) in both static
and dynamic tests (P < .05). The average, the minimal and maximal
values, and the standard deviation of the bending, static, and dynamic
tests are shown in the graphs of Figure 2.
Scanning electron microscopy visual inspection of the fractured
surface indicated that all instruments showed morphologic character-
istics of ductile fracture. Wide-ranging forms of dimples were identified
overall, and no plastic deformation in the helical shaft of the fractured
instruments was observed (Fig. 3).
Discussion
The first results of this study showed that the dynamic and static
cyclic fatigue of Reciproc R40 instrument was significantly higher
than that of the WaveOne larger instrument. Therefore, the first and sec-
ond null hypotheses were rejected. Previous studies demonstrated that
Reciproc R25 instrument has a higher cyclic fatigue resistance than
WaveOne primary files (18–22); however, to the best of the authors’
knowledge, this is the first attempt to evaluate the bending resistance
and the dynamic and static cyclic fatigue by using Reciproc and
WaveOne large files (tip #40).
The dynamic cyclic fatigue average time of Reciproc instruments
showed an increase of 31% compared with static test, whereasWaveOne
instruments showed 22% improvement in time. Thus, it is important to
note that even by using the reciprocating motion, the instrument should
not be static inside the root canal to reduce the risk of fracture.
Figure 2. Box plot showing the average, median, minimal, and maximal values and
letters indicate significant statistical differences between groups (P < .05). (A) Dyna
One, (C) dynamic WaveOne versus static WaveOne, (D) dynamic Reciproc versus
JOE — Volume 40, Number 4, April 2014
The average fatigue time of Reciproc instrument was 69% and 73%
greater than the WaveOne for the static and dynamic tests, respectively.
The percentages of time difference of either instrument were very
similar in both types of fatigue test, and this shows that the experimental
model used has enough sensitiveness to detect the odds of the instru-
ments Reciproc at the 2 tested conditions. Theoretically, this advantage
should be similar even with the change of kinematics of the experiment,
and this difference was approximately 4%.
The third result from the current study indicated that WaveOne
files required significantly greater loads than Reciproc to reach 45�
deflection. This means that WaveOne larger instruments are less flexible
than Reciproc R40 ones. Thus, the third null hypothesis was also
rejected. Overall, rigid instruments present a lower number of cycles
to fracture because of the buildup of tensions at the point of maximum
flexure, as observed in the present study and in line with previous
studies (23, 24). Within our knowledge, there is only limited
information about flexibility of WaveOne and Reciproc instruments.
Therefore, the current results can be used to shine some light on the
mechanical behavior of these larger instruments specifically designed
to be driven under reciprocation movement.
The tip sizes (diameter at D0) of Reciproc R40 and WaveOne Large
were the same, although the taper differed. A design point of Reciproc
and WaveOne instruments is that the former have a nominal taper at the
first apical millimeters of 0.06 mm/mm, whereas the latter has 0.08
mm/mm. This difference also helps to explain the greater stiffness of
WaveOne instruments. Both reciprocating file systems are made of
the same NiTi alloy (M-wire); however, they have different cross sec-
tions. Reciproc instruments have an S-shaped cross section with 2 cut-
ting blades, whereas WaveOne instruments have a modified convex
triangular cross section and the tip and a convex triangular cross sec-
tion in the middle and coronal portions. It has been reported that the
larger the cross-sectional area is, the higher the flexural and torsional
stiffness (25, 26); in this way, file design (cross-sectional shape,
the standard deviation of the time until instrument fracture occurred. Different
mic Reciproc versusdynamic WaveOne, (B) static Reciproc versus static Wave-
static Reciproc.
Bending and Cyclic Fatigue Life of Reciproc and WaveOne 577
Figure 3. Fractured surfaces of instruments showing morphologic characteristics of the ductile type. (A) Reciproc static test, (B) WaveOne static test, (C)
Reciproc dynamic test, (D) WaveOne dynamic test (original magnification, �150).
Basic Research—Technology
diameters of core, etc) would have a significant influence on the
torsional and bending (hence, fatigue) resistance (26).
The current study compared the bending resistance and the
dynamic and static cyclic fatigue of Reciproc R40 and WaveOne Large
instruments. The rationale behind the selection of these instruments
to test is the current trend to promote larger apical preparations with
the purpose of optimizing root canal disinfection (12–14, 27) and
thus rendering better conditions for tissue repair (28).
The best way of reproducing this type of fatigue is repeating the
movement for all tested files under well-standardized experimental con-
ditions, mainly in terms of predefined curvature. Experimental models
where the instruments can bind should be avoided because additional
torsional stress points will appear (21). Although the use of extracted
teeth simulates clinical situations, they are not ideal for the analysis
of cyclic fatigue because they are not anatomically standardized, and
there may be other confounding factors (21). A metallic tube was
used in the present study to standardize the entire length of the canal,
the length of the curvature radius, and the length of the arc. One
limitation of the metallic simulators is that the instrument works in a
passive way, whereas clinically it can lock on dentin, leading to torsional
fracture.
Static and dynamic models were used to test the cyclic fatigue resis-
tance in the present study. Regardless of the instrument brand, the cyclic
fatigue was significantly higher during dynamic versus static fatigue test.
This result is similar to previous studies (17, 21, 22, 29, 30), suggesting
that a concentration of stress in a small area of the instrument reduces the
cyclic fatigue of the instrument. As in the dynamic model, the file moves
axially within the canal; a better distribution of stress along the instrument
reduces the compressive and tensile stresses’ concentration at the
instrument area located at the center of the metallic tube curve,
enhancing fracture resistance (17).
The scanning electron microscopy analysis showed typical fracto-
graphic appearances of cyclic fatiguewith nomorphologic differences be-
tween the 2 types of instruments or between instruments fractured during
578 De-Deus et al.
static versus dynamic tests. All fracture surfaces displayed ductilemorpho-
logic characteristics as observed in previous studies (3, 8, 17, 19).
Under the present experimental framework, Reciproc R40 instru-
ments resisted dynamic and static cyclic fatigue significantly more than
WaveOne Large instruments. Furthermore, WaveOne instruments pre-
sented significantly less flexibility than Reciproc.
Acknowledgments
The authors deny any conflicts of interest related to this study.
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57 
 
6. DISCUSSÃO 
 
Fratura de instrumento endodôntico 
A fratura de um instrumento endodôntico, durante o uso clínico ou em 
laboratório, consiste na separação do mesmo em duas partes, devido à 
aplicação de cargas externas (LOPES et al., 2010c). 
A fratura de um instrumento endodôntico no interior de um canal 
radicular durante o uso clínico pode causar danos diretos ou indiretos. Danos 
diretos são representados pelo custo do instrumento endodôntico. Danos 
indiretos são causados pela retenção do segmento do instrumento fraturado no 
interior de um canal radicular. A presença desse segmento fraturado pode 
causar, durante a instrumentação do canal radicular, iatrogenias como desvios 
e perfurações radiculares. 
A presença de um fragmento metálico no interior de um canal radicular 
pode levar o tratamento endodôntico ao fracasso clínico principalmente nos 
casos de necrose pulpar previamente existente (SPILLI et al., 2005). 
SPILLI et al. (2005) analisaram o impacto da permanência de um 
instrumento endodôntico fraturado no interior de um canal radicular no 
resultado de um tratamento endodôntico realizado. Foram avaliados 277 
dentes contendo um ou mais fragmentos de instrumentos (total = 301 
fragmentos). Destes 235 (78,1%) eram de instrumentos de NiTi mecanizados, 
48 (15,9%) de instrumentos manuais de aço inoxidável, 12 (4,0%) de espiral 
Lentulo e 6 (2%) de espaçadores endodônticos digitais. Quanto a localização 
do fragmento 1 (0,5%) estava no segmento cervical, 57 (18,9%) no segmento 
58 
 
médio, 232 (77,1%) no segmento apical e em 11 (3,7%), a extremidade do 
fragmento estava além do forame apical. Quanto à condição perirradicular, 153 
(52,2%) dentes eram portadores de lesão perirradicular pré-operatória 
enquanto que 124 (44,8%) não tinham lesão perirradicular. No estudo de 
controle, foi avaliado, um grupo de 146 dentes com instrumento fraturado retido 
no interior do canal e outro de 146 dentes controle equiparado. O percentual de 
sucesso foi de 91,8% para o grupo contendo instrumento fraturado e de 94,5% 
para o grupo controle equiparado. Para ambos os grupos o percentual de 
sucesso foi de 86,7% para dentes portadores de lesão perirradicular pré-
operatória, contra 92,9% para dentes não portadores de lesão perirradicular. 
Finalizando, concluíram que a permanência de um instrumento fraturado no 
interior de um canal radicular tratado endodonticamente não teve nenhuma 
influência adversa no resultado. A presença de uma lesão perirradicular pré-
operatória foi clinicamente um indicador de prognóstico mais significativo, do 
que a presença de um fragmento de um instrumento retido no interior de um 
canal radicular tratado endodonticamente. 
 
Ensaios Mecânicos 
Ensaios mecânicos são procedimentos mecânicos com o objetivo de 
quantificar e/ou qualificar o comportamento mecânico de um corpo-de-prova ou 
de um instrumento no estado como comercializado (instrumentos endodônticos 
acabados) (ELIAS & LOPES, 2007). 
Os corpos-de-prova apresentam formas e dimensões padronizadas e 
são testados em máquinas e equipamentos especiais. São preparados com 
59 
 
base nas especificações das normas existentes. Os instrumentosendodônticos 
são testados como são comercializados (acabados) (ELIAS & LOPES, 2007). 
Os corpos-de-prova empregados nos ensaios mecânicos têm dimensões 
e formas rigorosamente padronizadas. Normalmente a forma do corpo-de-
prova é diferente do produto acabado (instrumento endodôntico). 
Os instrumentos endodônticos utilizados como corpo-de-prova 
apresentam variações entre as dimensões nominais e reais, defeitos de 
acabamento superficial (ranhuras, rebarbas e micro cavidades), variações da 
forma e da área das seções retas transversais das hastes de corte helicoidais 
cônicas, que atuam como variáveis e interferem nos resultados dos ensaios 
mecânicos realizados. Assim, quando do emprego de instrumentos 
endodônticos devemos buscar o máximo de uniformizações em relação a 
geometria (forma e dimensão) dos instrumentos empregados nos ensaios 
mecânicos. Além disso, é aconselhável o uso de um número mínimo de 10 
instrumentos (ELIAS & LOPES, 2007). 
O uso clínico para o estudo da fratura de instrumentos endodônticos em 
dentes humanos permite a combinação de tensões por torção e flexão rotativa 
além de acrescentar inúmeras variáveis em relação à anatomia do canal 
radicular (raio do arco, comprimento do arco, posição do arco, dupla curvatura 
e dureza da dentina), ao conhecimento, experiência e habilidade do 
profissional. Assim sendo, optamos, para o estudo da fratura de instrumentos 
endodônticos, o ensaio mecânico de flexão rotativa estático e dinâmico em 
laboratório que permite a padronização dos carregamentos para todos os 
grupos ensaiados. 
60 
 
Os ensaios mecânicos de laboratórios não retratam os carregamentos 
reais dos instrumentos durante a instrumentação dos canais de dentes 
humanos, entretanto, são empregados nos ensaios por flexão rotativa para a 
avaliação do número de ciclos suportados pelo instrumento endodôntico até a 
fratura. Esses valores são fundamentais no estudo comparativo das 
propriedades mecânicas e da resistência à fratura entre os diversos 
instrumentos, na seleção da liga metálica usada na fabricação do instrumento e 
para o ajuste de motores elétricos, quanto ao torque e à velocidade de giro. 
Além disso, podemos afirmar que os ensaios mecânicos de laboratório 
fornecem valores e comparações entre os instrumentos endodônticos avaliados 
que podem e devem ser aplicados durante o uso clínico de instrumentação de 
um canal radicular. Em função do exposto, é provável que os resultados 
conflitantes existentes na literatura sejam oriundos de inúmeras variáveis 
existentes quanto às metodologias empregadas e ao uso de instrumentos 
acabados de diferentes geometrias e marcas comerciais como corpo-de-prova. 
Um único canal metálico foi utilizado nos estudos executados para 
padronizar as tensões induzidas nos instrumentos e para excluir outras causas 
para a falha do instrumento durante o ensaio de flexão rotativa que não a 
fratura por fadiga. 
O canal metálico usado durante os ensaios de flexão rotativa apresentou 
diâmetro interno de 1,4 mm o que permitiu o giro livre do instrumento sem ser 
submetido às tensões de torção ou de flambagem (ELIAS & LOPES, 2007). 
Cada instrumento posicionado em um canal artificial curvo pode seguir 
uma trajetória com uma curvatura diferente daquela do canal artificial. 
61 
 
Entretanto, é preciso ressaltar que instrumentos diferentes podem não 
descrever a mesma trajetória, quando posicionados no interior de um canal 
artificial cilíndrico e curvo (PLOTINO et al. 2010). Este resultado irá depender 
da flexibilidade do instrumento e da relação diâmetro do instrumento/ diâmetro 
do canal artificial. Essa diferença pode contribuir para as variações na vida útil 
em fadiga de instrumentos endodônticos (LOPES et al., 2010a; LOPES et al., 
2013c). 
Quanto à integridade geométrica e dimensional do instrumento 
endodôntico, o ensaio mecânico é considerado: destrutivo, quando provoca a 
inutilização parcial ou total do instrumento. Exemplos; ensaio de torção e de 
flexão rotativa; não destrutivo, quando não compromete a integridade do 
instrumento. Exemplo, ensaio de flexão em cantilever (ELIAS & LOPES, 2007). 
Com os resultados obtidos nos ensaios mecânicos, é possível estimar e 
prever o desempenho de um instrumento endodôntico durante o seu uso 
clínico. Todavia o profissional, geralmente, ignora isso e seleciona o 
instrumento pelo D0 (diâmetro virtual) e conicidade, e não pelo comportamento 
mecânico do instrumento obtido em ensaios laboratoriais. 
 
Ensaio de flexão rotativa: Estático e Dinâmico 
Os resultados do presente estudo evidenciaram diferença significante 
entre os dois modelos de ensaios mecânicos. A vida útil em fadiga de um 
instrumento endodôntico submetido ao ensaio mecânico de flexão rotativa 
dinâmico, é maior quando comparado ao ensaio estático. 
62 
 
Para LOPES et al. (2010d) a vida útil em fadiga para ocorrer a fratura de 
um instrumento ProTaper Universal S2 (Dentsply, Maillefer, Ballaigues, Suíça) 
acionado com o movimento de rotação contínua, foi maior com o uso do ensaio 
de flexão rotativa dinâmico em comparação com o modelo estático. A 
separação do instrumento ocorreu no ponto máximo de flexão no interior de um 
canal, isto é, próximo ao ponto médio do arco de um canal. Estes resultados 
reforçam a necessidade de, durante a instrumentação de um canal radicular, 
realizar contínuos avanços e retrocessos do instrumento endodôntico em 
sentido apical de um canal radicular curvo. 
Segundo LI et al. (2002) durante o ensaio mecânico de flexão rotativa 
dinâmico, empregando-se uma mesma velocidade, foi propiciado ao 
instrumento endodôntico um intervalo de tempo maior, antes que ele passasse 
novamente pela área crítica de maior concentração de tensão. O avanço e 
retrocesso no interior de um canal curvo tem como objetivo evitar a 
concentração de tensão em uma determinada área do instrumento 
endodôntico. 
RODRIGUES et al. (2011) concluíram que os instrumentos TF 
(SybronEndo, Orange, CA, EUA), que são fabricados por torção, evidenciaram 
maior vida útil em fadiga, quando comparados aos instrumentos RaCe (FKG, 
Dentaire, Suíça) fabricados por usinagem. A vida útil em fadiga para ambos os 
instrumentos acionados com o movimento de rotação contínua foi maior no 
ensaio dinâmico quando comparado ao estático. Estes resultados são 
consistentes com outros reportados na literatura (LI et al., 2002; LOPES et al., 
2010d). Este resultado realça a importância do avanço e retrocesso em sentido 
63 
 
apical de um instrumento endodôntico, durante a instrumentação de canais 
radiculares com segmentos curvos. Com este procedimento, reduzimos a 
concentração de tensões trativas e compressivas em uma mesma área do 
instrumento endodôntico. É necessário ressaltar que a natureza da liga 
metálica NiTi fase R para os instrumentos TF e NiTi convencional para os 
instrumentos RaCe assim como o processo de fabricação dos instrumentos 
ensaiados (TF torção, RaCe usinagem) influenciaram nos resultados obtidos. 
GAMBARRA-SOARES et al. (2013), realizaram um estudo procurando 
esclarecer qual o modelo de ensaio de flexão rotativa, estático ou dinâmico 
seria mais favorável na determinação da vida útil em fadiga de um instrumento 
endodôntico. De acordo com os autores, o ensaio dinâmico representa melhor 
opção clínica de uso já que, durante a instrumentação mecanizada dos canais 
radiculares, é preconizado realizar movimentos de avanço e retrocesso no 
interior de um canal curvo, sem deixar o instrumento girando na mesma 
posição no sentido do comprimento do canal. O movimento axial (avanço e 
retrocesso) proporcionado pelo ensaio dinâmico permite uma melhor 
distribuição das tensões trativas e compressivas ao longo da haste helicoidal 
cônica do instrumento endodôntico, evitando a concentração das tensões em 
apenas uma área. A melhor distribuição das tensões trativas e compressivas 
ao longo da haste helicoidalcônica do instrumento endodôntico induz aumento 
de sua vida útil em fadiga (LOPES et al., 2010d; GAMBARRA-SOARES et al., 
2013; LOPES et al., 2013b; LOPES et al., 2013c). Estes autores concluíram 
que o ensaio de flexão rotativa dinâmico favorece resultados mais próximos da 
realidade clínica do que o ensaio de flexão rotativa estático. 
64 
 
Este trabalho corroborou com estudos prévios (LI et al., 2002; YAO et 
al., 2006; LOPES et al.,2010d, OH et al., 2010) que relacionaram o aumento da 
vida útil em fadiga de instrumentos endodônticos, quando estes são 
submetidos a um movimento axial de acesso e retrocesso (dinâmico). Contudo, 
trabalhos recentes têm proposto a instrumentação de canais radiculares com 
movimento único e progressivo em sentido apical (YARED, 2008; MALLET & 
DIEMER, 2009). Todavia, não foi possível elucidar o porquê desta orientação. 
Porém, é importante salientar que a velocidade de avanço único em sentido 
apical de um canal radicular é clinicamente difícil de ser controlada induzindo 
um maior risco de imobilização da ponta do instrumento endodôntico no interior 
de um canal radicular. Estando a ponta imobilizada e na outra extremidade do 
instrumento (haste de acionamento), seja aplicado um torque superior ao limite 
de resistência do material, ocorrerá a fratura do instrumento endodôntico por 
torção. Para impedir a imobilização da ponta de um instrumento endodôntico 
no interior de um canal radicular é necessário que a velocidade de rotação 
(velocidade de corte da dentina) seja maior do que a velocidade de avanço do 
instrumento em sentido apical. Entretanto, esta relação entre a velocidade de 
rotação e a velocidade de avanço é clinicamente muito difícil de ser obtida. 
Também, sendo a velocidade de avanço maior do que a velocidade de corte, 
poderá induzir a flambagem do instrumento. Consequentemente, a flambagem 
pode induzir a fratura por flexão rotativa (fadiga) de um instrumento 
endodôntico. A maior velocidade de avanço pode também induzir o roscamento 
do instrumento no interior de um canal radicular. 
65 
 
Flambagem é a deformação elástica (temporária) apresentada por um 
instrumento endodôntico, quando submetido a um carregamento compressivo 
na direção de seu eixo (axial). Durante esse tipo de carregamento, o 
instrumento encurva e forma um arco. Nesta condição, há um aumento da 
intensidade das tensões trativas e compressivas que reduz a vida útil em fadiga 
do instrumento endodôntico empregado na instrumentação de um canal 
radicular. 
A fadiga de um componente (instrumento endodôntico) é gerada através 
de uma carga induzida por ciclos repetitivos, que geram trincas e que são 
propagadas até chegar a um tamanho crítico para a integridade deste 
componente. Com a contínua indução da carga em ciclos, o crescimento da 
trinca dominante irá se propagar até o momento em que uma parte íntegra 
(seção resistente) do componente não suportar a carga induzida. Neste 
momento a resistência do material é excedida e o núcleo central remanescente 
experimenta uma fratura rápida (PARASHOS & MESSER, 2006; ELIAS & 
LOPES, 2007; LOPES et al., 2007; SHEN et al., 2012). 
 
Movimento de rotação Contínua x Reciprocante 
De acordo com DE-DEUS et al. (2010), o tipo de movimento aplicado 
nos instrumentos endodônticos mecanizados, durante o ensaio mecânico de 
flexão rotativa, está entre os fatores preponderantes na resistência à fratura por 
fadiga apresentada pelos instrumentos endodônticos. Além disso, o movimento 
reciprocante em comparação ao movimento de rotação contínua aumentou a 
66 
 
vida útil em fadiga de instrumentos endodônticos ensaiados em flexão rotativa 
estática. 
As pesquisas têm mostrado que a falha por fadiga ocorre pela formação 
de micro trincas presentes usualmente na superfície do instrumento. O 
crescimento das trincas por pequenos incrementos durante cada ciclo de flexão 
rotativa induz a fratura do instrumento endodôntico (CHRIST, 2008; DE-DEUS 
et al., 2010; LOPES et al., 2010d). Em condição clínica a tensão trativa induz a 
nucleação e a propagação da trinca até a falha do instrumento (ELIAS & 
LOPES, 2007; OUNSI et al., 2007; WEI et al., 2007). 
Consequentemente, a vida útil em fadiga de um instrumento pode ser 
considerada como sendo função dos valores das tensões, dos defeitos de 
acabamento superficial (ranhuras) e do tamanho das trincas (OUNSI et al., 
2007; WEI et al., 2007; LOPES et al., 2010d). 
LOPES et al. (2013c) avaliando a vida útil em fadiga de instrumentos 
Reciproc e Mtwo fabricados pela VDW, Munique, Alemanha, concluíram que a 
vida útil em fadiga do instrumento Reciproc foi maior do que a do instrumento 
Mtwo. Este achado revelou que o tempo de fratura de um instrumento 
endodôntico acionado no interior de um canal curvo foi significativamente maior 
para o instrumento de maior flexibilidade, e para o uso do movimento de 
rotação reciprocante, quando submetido ao ensaio de flexão rotativa dinâmico. 
Os resultados obtidos nos ensaios de flexão rotativa foram avaliados de 
acordo com dois parâmetros: modelo do ensaio (estático e dinâmico) e o tipo 
de movimento aplicado ao instrumento (rotação contínua ou rotação 
reciprocante). Desconsiderando a marca do instrumento, o tipo de movimento 
67 
 
(reciprocante ou contínuo) e natureza da liga metálica empregada na 
fabricação dos instrumentos endodônticos, o tempo até a fratura por fadiga foi 
significativamente maior para o ensaio modelo dinâmico, do que no ensaio de 
flexão rotativa modelo estático (LOPES et al., 2013c). Esses resultados estão 
de acordo com outros trabalhos existentes na literatura (YAO et al., 2006; LI et 
al., 2012; PLOTINO et al., 2012). Desconsiderando a marca do instrumento, o 
modelo de ensaio de flexão rotativa (estático ou dinâmico) e a natureza da liga 
metálica empregada na fabricação do instrumento endodôntico, o tempo até a 
fratura por fadiga foi significativamente maior quando o instrumento foi 
acionado pelo movimento de rotação reciprocante em comparação ao 
movimento de rotação contínua. 
LOPES et al. (2013b) avaliando a vida útil em fadiga de instrumentos 
Wave One e ProTaper (Dentsply Maillefer, Bellaigues, Suiça) concluíram que 
os instrumentos operados em movimento de rotação reciprocante e no modelo 
dinâmico prolongaram a vida em fadiga dos instrumentos WaveOne. Este 
resultado está de acordo com outros trabalhos que utilizaram outros 
instrumentos (GAMBARINI et al., 2012a; GAMBARINI et al., 2012b; GAVINI et 
al., 2012; KIM et al., 2012). 
Para LOPES et al. (2013b) a análise por meio do MEV revelou que a 
superfície de fratura apresentou característica do tipo dúctil. Resultados esses 
em consonância com outros estudos (WEI et al.,2007; CASTELLÓ-ESCRIVA et 
al., 2012). Afirmaram também que a característica morfológica da superfície de 
fratura não foi afetada pelo modelo do ensaio de flexão rotativa estático ou 
68 
 
dinâmico e pelo tipo de movimento (reciprocante ou contínuo) empregados no 
acionamento do instrumento endodôntico ensaiado. 
Independentemente do instrumento usado (WaveOne Primário ou 
ProTaper F2), do tipo de movimento (reciprocante ou giro contínuo) e da liga 
NiTi (M-Wire ou convencional), o ensaio de flexão rotativa dinâmico revelou 
uma vida útil maior em fadiga do que o ensaio de flexão rotativa estático. Vida 
útil em fadiga prolongada no ensaio dinâmico está provavelmente relacionada 
com o fato de que o instrumento é movido axialmente ao longo da curvatura 
(arco) e isso permite uma melhor distribuição dos esforços de compressão e de 
tração ao longo do eixo dos instrumentos, enquanto que as tensões em um 
ensaio estático se acumulam em uma única região do instrumento e isto 
predispõe à ocorrência de fraturas em um tempo significativamente menor 
(LOPES et al., 2013b). 
LOPES et al. (2010a) reforçaram a importância do movimento de avanço 
e retrocesso durante a instrumentação mecanizada de canaiscurvos. Os 
autores utilizaram o instrumento ProTaper Universal S2 em ensaio de flexão 
rotativa estático e dinâmico. Os instrumentos foram submetidos a uma 
velocidade de rotação de 300 rpm em ambos os ensaios, posicionados no 
interior de um canal metálico de 6 mm de raio de curvatura para determinar o 
número de ciclos até a fratura. No ensaio estático não houve movimento axial, 
enquanto que no dinâmico houve um movimento axial de avanço e retrocesso 
de amplitude de 3 mm com 2 segundos para cada deslocamento. O estudo 
demonstrou que o ensaio dinâmico obteve um número de ciclos até a fratura do 
instrumento significativamente maior que o ensaio estático, e a fratura ocorreu 
69 
 
no ponto de maior flexão no interior do canal artificial. Os autores concluíram 
que o movimento axial aumenta significativamente a vida útil em fadiga do 
instrumento endodôntico. 
Neste estudo os instrumentos WaveOne primários acionados em 
movimento reciprocante tiveram uma vida útil significativamente mais longa à 
fadiga, quando comparados com os instrumentos ProTaper F2 acionados em 
rotação contínua (LOPES et al., 2013b). Isto está de acordo com vários 
estudos (GAVINI et al., 2012; KIM et al., 2012; PLOTINO et al., 2012; LOPES 
et al., 2013b) e pode ser explicado pelo fato de que, quando os instrumentos 
estão trabalhando com o movimento reciprocante estático ou dinâmico, em 
cada ciclo as tensões de tração são distribuídas em torno de diferentes pontos 
da haste helicoidal cônica do instrumento. Quando os instrumentos são 
submetidos à rotação contínua, os pontos de tensão se concentram na mesma 
área do instrumento, o mais próximo do centro do arco (LOPES et al., 2013b). 
Consequentemente, os instrumentos acionados com movimentos reciprocantes 
têm uma vida útil à fadiga maior que os instrumentos acionados com rotação 
contínua (WAN et al., 2011; CASTELLÓ- ESCRIVA et al., 2012; LOPES et al., 
2013b). 
Para DE-DEUS et al. (2014) o instrumento Reciproc (R40), quando 
submetido ao ensaio de flexão rotativa estático e dinâmico, apresenta maior 
resistência à fratura por fadiga do que o instrumento WaveOne (Large). Este 
resultado pode ser atribuído à maior flexibilidade (menor rigidez) apresentada 
pelo instrumento Reciproc (R40) em comparação ao instrumento WaveOne 
(Large). 
70 
 
Diferentes estudos com outros instrumentos endodônticos e com outros 
ângulos de rotação reciprocante têm revelado que os instrumentos acionados 
por meio do movimento reciprocante têm apresentado maior vida útil à fadiga 
do que quando acionados por meio do movimento de giro contínuo (WAN et al., 
2011; LOPES et al., 2013). 
Isto pode ser explicado pelo fato de que quando os instrumentos 
endodônticos estão acionados com o movimento reciprocante (estático ou 
dinâmico), em cada ciclo, as tensões trativas e compressivas são distribuídas 
em torno de diferentes pontos da haste helicoidal cônica do instrumento 
endodôntico. Quando os instrumentos são acionados com rotação contínua, os 
pontos de tensões trativas e compressivas se concentram na mesma área 
circundante do instrumento, o mais próximo do centro do arco de um canal 
curvo. Consequentemente, os instrumentos acionados com movimentos de 
rotação reciprocante tem uma vida útil à fadiga maior que os instrumentos 
acionados com rotação contínua (WAN et al., 2011; LOPES et al., 2013b). 
No movimento de rotação reciprocante quanto menor o ângulo de 
rotação, independentemente do modelo estático ou dinâmico, maior será a vida 
útil em fadiga de um instrumento endodôntico (WAN et al., 2011; LOPES et al., 
2013b). 
Consequentemente, um instrumento endodôntico operando em 
movimento de rotação reciprocante pode ser empregado por um maior tempo 
na instrumentação de canais radiculares antes da falha. 
 
Análise por meio do MEV 
71 
 
A análise por microscopia eletrônica de varredura das hastes de corte 
helicoidais dos instrumentos analisados não mostrou deformação plástica. Este 
fato é explicado pela característica de superelasticidade da liga níquel-titânio 
que aumenta o grau de deformação elástica e também na utilização de um 
canal artificial que possui um diâmetro maior que o dos instrumentos 
ensaiados, garantindo a redução da resistência ao giro do instrumento durante 
o ensaio de flexão rotativa, impedindo que a fratura ocorra por torção. 
As superfícies de fratura dos instrumentos analisados mostraram 
características morfológicas do tipo dúctil. Identificou-se a presença de micro 
cavidades (dimples) geralmente arredondadas que indicaram a ruptura 
causada por tensão trativa. O ensaio mecânico de flexão rotativa gera a 
indução de tensões trativas na superfície externa e tensões compressivas na 
superfície interna da região flexionada do instrumento. A repetição destas 
tensões alternadas, mesmo estando elas abaixo do limite de escoamento do 
material (regime elástico), induz a nucleação de trincas que crescem, 
coalescem e se propagam até ocorrer a fratura do instrumento por fadiga de 
baixo ciclo. Esta fratura se caracteriza pela aplicação de uma tensão elevada 
para um número baixo de ciclos (HAIKEL et al., 1999; PARASHOS & MESSER, 
2006; LOPES et al., 2010c). 
 
Considerações finais 
Para redução do número de fraturas dos instrumentos endodônticos é 
necessário que haja maior informação por parte dos fabricantes sobre a 
geometria e as propriedades mecânicas, além de um melhor acabamento 
72 
 
superficial dos instrumentos endodônticos principalmente dos classificados 
como acionados a motor. Também são fundamentais novos estudos para 
avaliar e analisar o comportamento mecânico dos instrumentos endodônticos, 
durante ensaios mecânicos de laboratório e durante o uso clínico. Além disso, 
é importante o profissional conhecer e saber usar os resultados laboratoriais na 
clínica. Os instrumentos devem ser selecionados, acionados e movimentados 
em função da anatomia do canal radicular. 
 
 
73 
 
7. CONCLUSÕES 
 
A partir dos resultados obtidos no presente estudo foi possível concluir que: 
 
1. Movimento de rotação reciprocante e contínuo: 
Os instrumentos endodônticos de NiTi mecanizados, quando acionados por 
meio do movimento de rotação reciprocante resistiram maior vida útil à fadiga 
quando comparados ao movimento de rotação contínua, independentemente 
do modelo de ensaio de flexão rotativa ser estático ou dinâmico. 
 
2. Ensaio de flexão rotativa estática e dinâmica: 
Os instrumentos endodônticos de NiTi mecanizados quando submetidos ao 
ensaio de flexão rotativa dinâmica, resistiram maior vida útil à fadiga quando 
comparados ao ensaio de flexão rotativa estático, independentemente do tipo 
de movimento rotatório, reciprocante ou contínuo. 
 
3. Análise por meio do MEV: 
A análise no MEV, independentemente, do tipo e do modelo de acionamento 
demonstrou que as superfícies fraturadas dos instrumentos endodônticos de 
NiTi mecanizados apresentaram características do tipo dúctil. Não foi 
observada deformação plástica na haste helicoidal cônica dos instrumentos 
fraturados. 
 
74 
 
Levando-se em consideração os resultados obtidos pode-se afirmar que 
na instrumentação de canais radiculares curvos, o movimento de rotação 
reciprocante no modelo dinâmico é mais seguro em relação à fratura por flexão 
rotativa (fadiga) de um instrumento endodôntico de NiTi mecanizado. 
 
 
75 
 
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	1 Cyclic fatigue Static&Dynamic.pdf
	Cyclic fatigue resistance of ProTaper Universal instruments when subjected to static and dynamic tests
	MATERIALS AND METHODS
	RESULTS
	DISCUSSION
	REFERENCES
	2 Influence of Different Manufacturing Methods.pdf
	Influenceof Different Manufacturing Methods on the Cyclic Fatigue of Rotary Nickel-Titanium Endodontic Instruments
	Materials and Methods
	Instrument Geometry (Design Features)
	Bending Resistance Tests
	Cyclic Fatigue Tests
	Static Test
	Dynamic Test
	Results
	Instrument Geometry (Design Features)
	Bending Resistance
	Cyclic Fracture
	Discussion
	Acknowledgments
	References
	7 Bending resistance Reciproc WaveOne.pdf
	Bending Resistance and Dynamic and Static Cyclic Fatigue Life of Reciproc and WaveOne Large Instruments
	Materials and Methods
	Bending Resistance Test
	Cyclic Fatigue Tests
	Static Test
	Dynamic Test
	Statistics
	Results
	Discussion
	Acknowledgments
	References
	7 Bending resistance Reciproc WaveOne.pdf
	Bending Resistance and Dynamic and Static Cyclic Fatigue Life of Reciproc and WaveOne Large Instruments
	Materials and Methods
	Bending Resistance Test
	Cyclic Fatigue Tests
	Static Test
	Dynamic Test
	Statistics
	Results
	Discussion
	Acknowledgments
	References