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Quality of Life of Implant-Supported
Overdenture and Conventional Complete
Denture in Restoring the Edentulous
Mandible: A Systematic Review
Li Zhang, MDS,* Chunxiao Lyu, DDS,* Zhenzhen Shang, DDS,* Aidi Niu, DDS,* and Xing Liang, DDS, PhD†
E
dentulism is a dentition defect that
is defined as the loss of all perma-
nent teeth in the maxilla or (and)
mandible.1 It has a serious impact on
eating, talking, facial appearance and
the quality of life (QoL). Therefore,
completely edentulous patients are
handicapped according to the World
Health Organization’s (WHO) criteria.2
Although the prevalence of edentulism
will be decreased with the improvement
of oral health care, in seniors (aged 65+),
the prevalence has still been estimated to
be 26% in the United States, 15%–78%
in Europe, and 11% in China.3
The conventional treatment for
edentulism was a complete denture.4
However, for conventional complete
denture (CCD) wearers, lack of stability
and retention of mandibular dentures,
together with residual bone resorption,
and decreased chewing ability have been
commoncomplaints.5The treatmentwith
endosseous implants has changed these
situations. This treatment significantly
improves stability, retention, and chew-
ing ability.6–8 A panel of experts reached
a consensus at a symposium held at
McGill University in 2002.9 Their state-
ment is as follows: “The evidence cur-
rently available suggests that the
restoration of the edentulous mandible
with a conventional denture is no longer
the most appropriate first choice prostho-
dontic treatment. There is now over-
whelming evidence that a two-implant
overdenture should become the first
choice of treatment for the edentulous
mandible.” Therefore, an increasing
number of researchers have investigated
the impact of implant-supported over-
dentures (IODs), such as QoL and den-
ture satisfaction.4,7,8,10
The definition of QoL, which can
be applied to most important domains
of life,11 has evolved in terms of health
by the WHO.12 QoL has been used as
an indicator to evaluate oral health,
especially in the elderly.11,13 Oral
*Graduate Student, State Key Laboratory of Oral Diseases,
National Clinical Research Center for Oral Diseases, West China
Hospital of Stomatology, Sichuan University, Chengdu, China.
†Professor, State Key Laboratory of Oral Diseases, National
Clinical Research Center for Oral Diseases, West China Hospital
of Stomatology, Sichuan University, Chengdu, China.
Reprint requests and correspondence to: Xing Liang, DDS,
PhD, State Key Laboratory of Oral Diseases, National
Clinical Research Center for Oral Diseases, West China
Hospital of Stomatology, Sichuan University, No. 14, 3rd
Section, RenMin South Road, Chengdu, Sichuan Province,
China, 610041, Phone: +86-28-85502141, Fax:
+86-28-85502407, E-mail: xingliangdent@vip.163.com
ISSN 1056-6163/17/02606-945
Implant Dentistry
Volume 26 � Number 6
Copyright © 2017 Wolters Kluwer Health, Inc. All rights
reserved.
DOI: 10.1097/ID.0000000000000668
Objective: The aim of this sys-
tematic review was to evaluate the
oral health-related quality of life
(OHRQoL) associated with an
implant-supported overdenture (IOD)
compared with a conventional com-
plete denture (CCD) in restoring the
edentulous mandible.
Methods: A literature search was
performed in the MEDLINE (through
Ovid), PubMed, and Cochrane
Library databases for articles pub-
lished between 1990 and July 2016.
The search was restricted to articles
published in English. Two reviewers
selected the articles based on the
inclusion and exclusion criteria.
Another 2 reviewers analyzed the
data.
Results: From 108 articles that
were obtained, 5 articles met the
inclusion criteria. Four studies had
a high risk of bias, and 1 study had an
unclear risk of bias. There was a sig-
nificant difference in Oral Health
Impact Profile (OHIP) scores between
pre- and post-treatment within the
groups and in posttreatment OHIP
scores between IOD and CCD
groups.
Conclusion: Regarding the eden-
tulous mandible, patients benefited
more from the IOD with 2 implants,
as determined by OHRQoL scores.
Considering the differences between
each domain of the Oral Health
Impact Profile (OHIP) questionnaire
and the lack of long-term perfor-
mance, more random control trials
with sufficient sample sizes need to be
designed to investigate long-term per-
formance after treatment. (Implant
Dent 2017;26:945–950)
Key Words: edentulism, dental
implant, satisfaction of prosthesis,
Oral Health Impact Profile
ZHANG ET AL IMPLANT DENTISTRY / VOLUME 26, NUMBER 6 2017 945
Copyright � 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
health-related quality of life (OHR-
QoL), which was introduced by Gift
and Redford,14 refers to the assessment
of an individual’s oral health and func-
tion and emotional well-being.15 The
mainmethod of investigatingOHRQoL
is a questionnaire. The validity of the
Oral Health Impact Profile (OHIP-49),
which was first used to evaluate OHR-
QoL by Slade and Spencer, has been
assessed.16 The OHIP-49 consists of
49 items that cover 7 domains: func-
tional limitation, physical pain, psycho-
logical discomfort, physical disability,
psychological disability, social disabil-
ity, and handicap. The OHIP-49 has
been used to evaluate the effectiveness
of treatment for edentulous patients in
clinical trials.4,10,17 However, as the
OHIP-49 is a long questionnaire that is
complex formost patients, and especially
for the elderly, a shorter version of it was
suggested by some researchers. The
developer of the OHIP-49 introduced
the first short version, the OHIP-14, and
found that the latter had good reliability,
validity, and precision.18 Then another
short version, named the OHIP-
EDENT, which was considered to be
more appropriate for edentulous than
the OHIP-14, was introduced by Allen
and Locker.19 The OHIP-14 and the
OHIP-EDENT have been widely used
to evaluate the OHRQoL of edentulous
patients.4,20–22
The aim of this systematic review
was to evaluate the OHRQoL of IOD,
measured by the OHIP-49, the OHIP-
14, and the OHIP-EDENT, compared
with CCD.
MATERIALS AND METHODS
This systematic review was under-
taken based on the Preferred Reporting
Items for Systematic Reviews andMeta-
Analyses (PRISMA) Guidelines.23
Search Strategy
A broad literature search was per-
formed for articles published between
1990 and July 2016 in the MEDLINE
(through Ovid), PubMed, and Cochrane
Library databases. The articles were
limited to those published in English,
and the search used the Medical Subject
Headings (MeSH). The MeSH terms
were as follows: “dental implant,”
“dental implantation,” “dental prosthesis,
implant-supported,” “denture, complete,”
“denture, overlay,” and “quality of life.”
Two reviewers (L.Z. and C.L.)
independently selected the articles first
through reading the titles and abstracts
based on the inclusion and exclusion
criteria (Table 1). If they had different
ideas about an article, a third reviewer
(X.L.) participated in a negotiation.
Then full-text documentswere obtained
from the databases mentioned above.
For those that potentially met the inclu-
sion criteria, including both the search
results and the references, full-texts
were obtained for further assessment.
Article Analysis
The literature characteristics, which
contained subjects and study design and
quantitative results, were extracted from
the original articles. The assessment of
the study design was based on the
classification of clinical epidemiology.24
The assessment of the methodological
quality of articles was undertaken by 2
reviewers (L.Z. andC.L.) independently,
based on the Cochrane collaboration’s
tool. The items were as follows: random
sequence generation, allocation conceal-
ment, blinding of participants and per-
sonnel, blinding of outcome assessors,
incomplete outcome data, and selective
reporting. If any of these items was con-
sidered to be “high risk” or “unclear
risk,” the study was assessed as “high
risk of bias” or “unclear risk of bias”correspondingly. Only when all the
items were estimated as “low risk” was
the study evaluated as “low risk of bias.”
In the case of differences, a third
reviewer was consulted.
Data Extraction
From the included articles, the re-
viewers extracted the following data:
authors, country, year of publication,
study design, sample size, follow-up
period (months), study description, type
of measurement instrument, baseline,
and posttreatment total scores. Datawere
extracted by 2 reviewers independently.
When there was disagreement, a third
reviewer provided an opinion.
RESULTS
Search Results
Of 108 articles identified from the
search, 88 were excluded after prelimi-
nary assessment through titles and ab-
stracts. After the reviewers read the
remaining 20 full-text documents, 15
studies were excluded for the following
reasons: 1 article was a systematic
review, 1 article was a review article, 2
articles did not have the total scores, 4
articles had no baseline or posttreatment
scores, 3 studies had a design that only
Table 1. Inclusion and Exclusion
Criteria
Inclusion criteria
RCT or control clinical trial (CCT)
Study for mandibular edentulism
2 implants for overdenture
OHIP used to assess OHRQoL
OHIP total scores were available
Both baseline and
posttreatment scores involved
Published in English
Exclusion criteria
Retrospective study, case report,
systematic review, and
literature review
Study contained maxillary edentulism
1 implant for overdenture or
more than 2 implants for overdenture
Other methods of measurement for
OHRQoL
OHIP total scores could not
be available
Baseline scores not reported
Implants loaded immediately
No control group: only comparing
pretreatment (CCD) with
postreatment (IOD)
This study reviewed the ones which investigated the OHRQoL,
assessed by Oral Health Impact Profile (OHIP) questionnaire,
between IOD and CCDs.
Fig. 1. Flowchart of selective progress. Five
articles met the inclusion criteria and were
thus selected for inclusion in this review ac-
cording to the PRISMA guidelines.
946 QUALITY OF LIFE OF IOD VS CCD ZHANG ET AL
Copyright � 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
converted CCD to ICD without group-
ing, 2 articles had an unclear number of
implants, 1 article was a commentary
article, and 1 article did not report both
groups’ scores. Figure 1 presents the
flowchart of the progress of selection fol-
lowing the PRISMA Guidelines.
Characteristics of Included Articles
The 5 included studies were all
random control trials (RCTs). In total,
334 participants were involved, of
which 34 participants were elders who
were older than 75 years and who
needed help for activities of life. One
study reported the outcome measured
by the OHIP-49. Three studies evalu-
ated OHRQoL using the 20-item ques-
tionnaire (OHIP-EDENT). One study
used theOHIP-14 to evaluateOHRQoL
(Table 2).
Quality of Studies Included
Risk of bias assessment (Table 3)
showed that no study had low risk of
bias, 4 studies10,25–27 had a high risk
of bias, and 1 study22 had an unclear
risk of bias.
OHRQoL of Implanted-Supported
Overdenture and Conventional
Complete Denture
Table 4 shows the included study
data, which consisted of baseline and
posttreatment scores of CCD and IOD.
Muller et al25 evaluated the outcomes
through the interaction term (time 3
treatment) between the IOD and CCD
groups. Cakir et al27 assessed the
data through pre- and post-treatment
score differences. The rest of the stud-
ies10,22,26 evaluated the group’s differ-
ences through posttreatment scores
directly. All the studies showed
that IOD had a significant effect on
improving the edentulous individuals’
QoL.
DISCUSSION
For the studies that compared the
impact on edentulous individuals’
OHRQoL of IODs versus CCDs, it
was necessary to explain the treatment
progress to the patients and ask them
whether they were willing to participate
in the trials or not; moreover, the re-
searchers would know the allocation
of the group in the course of the trials,
so a blind method was not possible, and
the risk of bias would be high. How-
ever, because of the obvious differences
between IOD and CCD, a nonblind
method was inevitable.
Table 2. Characteristics of Studies Included
Study
Study
Design
Follow-
up, mo
No. of
Participants Study Description
Outcome
Reported
Awad et al10
Canada
RCT 2 102 Evaluation of OHRQoL of IOD vs CCD (re-fabricated) for those who
had 10-y edentulous history
OHIP-49
Heydecke
et al22
Canada
RCT 6 60 Assessment of OHRQoL and general health-related quality of life
(HRQoL) of IOD vs CCD (re-fabricated) for elders, aged 65–75 y,
who had 5-y edentulous history
OHOP-
EDENT
SF-36
Muller
et al25
Switzerland
RCT 12 34 Evaluation of OHRQoL and denture satisfaction of IOD vs CCD (relined)
for elders who were older than 75 years and needed help for
activities of daily life
OHIP-
EDENT
DS-VAS
Gjengedal
et al26
Norway
RCT 24 54 Evaluation of OHRQoL and HRQoL of IOD vs CCD (relined) for those
who were younger than 76 years
OHIP-
EDENT
SF-36
Cakir et al27
Turkey
RCT 12 58 Four groups compared OHRQoL and HRQoL of implanted-supported
denture vs removable denture: Group1(IOD); Group2(implant-
supported fixed partial denture); Group3(CCD); Group4(removable
partial denture)
OHIP-14
SF-36
Some researchers re-fabricated the participants’ denture, whereas other researchers only relined the individuals’ previous denture. The researchers also investigated the patient satisfaction measured by
SF-36 or DS-VAS besides OHRQoL evaluated by OHIP.
Table 3. Risk of Bias Based on the Cochrane collaboration’s Tool
Study
Random
Sequence
Generation
(Selection Bias)
Allocation
Concealment
(Selection Bias)
Blinding of
Participants and
Personnel
(Performance Bias)
Blinding of
Outcome
Assessment
(detection bias)
Incomplete
Outcome Data
(Attrition Bias)
Selective
Reporting
(Reporting
Bias)
Award et al10 Low risk Unclear High risk High risk Low risk Low risk
Heydecke et al22 Low risk Low risk High risk Low risk Low risk Low risk
Muller et al25 Low risk Low risk High risk Unclear Low risk Low risk
Gjengedal et al26 Low risk Low risk High risk Unclear Low risk Low risk
Cakir et al27 Low risk Unclear High risk Unclear Low risk Low risk
If any of these items were considered to be “high risk” or “unclear risk,” the study would be assessed as “high risk of bias” or “unclear risk of bias” correspondingly. Only when all of the items were
estimated as “low risk” would the study be evaluated as “low risk of bias.”
ZHANG ET AL IMPLANT DENTISTRY / VOLUME 26, NUMBER 6 2017 947
Copyright � 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
When evaluating the rehabilitation
of the elders’ edentulism, several as-
pects should be considered, such as diet,
esthetics, and degree of comfort. OHR-
QoL could provide some explanations
for those problems.14 Therefore, it was
applied in the studies that compared
edentulous individuals’ OHRQoL of
IODs versus CCDs. The OHIP ques-
tionnaire was a valid tool for evaluating
OHRQoL. The studies included in this
systematic review showed that the
OHRQoL of the IOD group was better
than the CCD group (the OHIP scores
of the IOD group was lower than that of
CCD group) using different OHIP
questionnaires. This could broadly
explain that they (OHIP-49, OHIP-
EDENT, OHIP-14) had similar reliabil-
ity and validity.18,19
Although the IOD’s OHIP total
scores were lower than the CCD’s, and
therewasa significant differencebetween
the IOD group and CCD group, not all of
the scores of each domain had a signifi-
cant difference. In the study byHeydecke
et al,22 there were 3 domains that did not
show a significant difference between the
IOD group and CCD group. In the study
of Gjengedal et al,26 there were only 3
domains that had a significant difference
between the IOD group and CCD group.
Other control trials showed similar out-
comes when comparing the scores of
each domain.28,29 That might be due to
aninsufficient sample size. It also noted
that further studies should focus on those
domains in which improvement was not
obvious in the IOD group comparedwith
the CCD group.
These studies showed that the differ-
ence was significant between the CCD
group and IOD group in the short-term.
Meanwhile, 2 studies25,26 showed that the
difference after 24 months was signifi-
cant, and the difference in the interaction
term after 12 months was significant in
Muller’s study,25 with the approximate
posttreatment OHIP scores using the
same questionnaire (OHIP-EDENT).
However, there were different conclu-
sions reported by 2 systematic re-
views.30,31 Maybe these different
conclusionswerecausedby improvement
in the adaptability of the denture and (or)
the change of the oral condition and (or)
because of the cultural difference.30,32
Therefore, more longer-term RCTs with
lower risk of bias need to be designed to
solve the discrepancies.
It has been shown that IOD was
better than CCD at improving the eden-
tulous patients’ OHRQoL in the studies
included in this systematic review and in
other control trials and crossover tri-
als.29,33–35 Therefore, some researchers
have proposed that IOD should be the
first choice for rehabilitating the edentu-
lism.9,36 Another topic is the number of
implants. Some experts have stated that
IOD with 2 implants was the standard
option. Therefore, in this systematic
review, we selected the studies using
a 2-implant–supported mandibular over-
denture. However, considering the qual-
ity andmass of alveolar bone, the number
of implants varied in some studies.37,38
Some studies that evaluated an over-
denture supported by 2 or 4 implants
showed that there was no significant dif-
ference.39–42 In addition, cost must be
taken into consideration. Hence, an
overdenture supported by 2 implants
should be offered first.
CONCLUSION
For an edentulous mandible, pa-
tients benefited more from an IOD with
2 implants, as assessed by the OHR-
QoL. Considering the difference in
each domain of the Oral Health Impact
Profile (OHIP) questionnaire and the
lack of long-term performance, more
RCTs with sufficient sample sizes need
to be designed to investigate long-term
performance after treatment.
DISCLOSURE
The authors claim to have no
financial interest, either directly or
indirectly, in the products or informa-
tion listed in the article.
APPROVAL
Not required-the study did not
involve human subjects.
ROLES/CONTRIBUTIONS
BY AUTHORS
L.Zhang andC. Lyu:Designed this
study; Z. Shang and A. Niu: Searched
the literature; L. Zhang and C. Lyu:
T
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948 QUALITY OF LIFE OF IOD VS CCD ZHANG ET AL
Copyright � 2017 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Analyzed data; L. Zhang, C. Lyu, and
Z. Shang: Drafted the manuscript;
C. Lyu: Critically revised the manu-
script. All authors have read and
approved the final manuscript.
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