Microbiology and treatment of
34 pág.

Microbiology and treatment of


DisciplinaOdontologia Morfofuncional do Ecossistema Bucal154 materiais1.381 seguidores
Pré-visualização21 páginas
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226
Microbiology and treatment of dental abscesses and periodontal-endodontic lesions
bacteria depends on synergism, often in combi-
nation with facultative bacteria (94, 165, 166, 214).
Table 6 summarizes studies on the experimental
abscess model using oral bacteria. Pioneering work
by Rosebury & Macdonald (135, 136, 172) and Soc-
ransky & Gibbons (186) confirmed that oral indigen-
ous bacteria were pathogenic and caused clinical in-
fection in polymicrobial mixtures.
Takazoe & Nakamura (200) found little difference
in infectivity among guinea pigs, hamsters and mice
inoculated subcutaneously with oral bacteria. Rats,
however seem to develop less severe inflammatory
reactions (102). Sundqvist et al. (193) showed in ex-
perimental infections using microbial combinations
from endodontic lesions that a species of Bacteroides
(later identified as P. endodontalis) was essential to
developing transferable abscesses.
Similarly to nonoral anaerobic combinations, the
synergistic interaction between oral anaerobic and
facultative species may cause mortality among ex-
perimental animals (143). A series of experiments
(102, 188) showed that certain strains of P. gingivalis
were more virulent than others and produced phleg-
monous abscesses and mortality among the experi-
mental animals. Inoculates of 107 or more cells have
been commonly used to obtain experimental ab-
scesses. However, a mixture of eight different strains
in inoculates of 104 cells was able to induce abscess
formation (32, 37). Using virulent strains of P. gingi-
valis, Kesavalu and co-workers (44, 52, 103\u2013107)
showed in subcutaneous experiments in mice that
dexamethasone, hydrazine, galactosamine, protease
inhibitors, protease activity and antibodies were im-
portant determinants of abscess development. P. in-
termedia, P. nigrescens, B. forsythus, Treponema spp.
and C. rectus can also participate in abscess forma-
tion that may lead to the death of the experimental
animal (77, 103, 106, 107, 201). In several studies, the
bacterial strains used to induce abscess formation
could be isolated from cardiac blood, emphasizing
the capacity of oral bacteria to invade and spread
throughout tissues. Recently, Kuriyama et al. (119\u2013
123) used a murine model to determine the viru-
lence of anaerobes other than Porphyromonas, Pre-
votella and Bacteroides spp. S. constellatus, P. micros
and F. nucleatum were lethal to mice when injected
subcutaneously in various combinations.
Experimental endodontic infections
The dental root canal and the pulp chamber can be
used as an experimental model of infection to deter-
mine the patho-etiology of endodontic lesions and
227
abscesses in or close to bony tissues (Table 7). The
model can also be used for endodontic treatment
studies (137). However, the abscess formation in the
root canal model seems to be relatively mild, and
chronic apical periodontitis usually occurs only after
experiments at durations of months or years (48).
The difference in pathological characteristics be-
tween endodontic infections and subcutaneous in-
jection or wound chamber experimental infections
may be due to the need for relatively few inoculating
cells (infection dose) or due to the minute contact
area in the apical region of the tooth between the
root canal infection and the surrounding periapical
tissues. Rodents have been used, however, for a ran-
dom exposure of dental pulps to the oral flora to
evaluate the capacity of the oral flora to cause patho-
genic changes, including abscess formation in the
periapical tissues (100, 117, 202). Fabricius and co-
workers (49, 154) exposed traumatized dental pulps
of monkeys to the oral flora. Their studies showed
that a complex microflora was associated with
radiographic and/or histological pathogenic lesions
in almost all cases and clinical abscesses or sinus
tract formation in 23% of the study teeth (154). Their
studies also demonstrated the pathogenic import-
ance of anaerobes in endodontic infections.
The rodent model cannot be used for endodontic
infections with selected strains inoculated into the
pulp chamber because of difficulty in avoiding con-
tamination due to the small tooth size; dog and mon-
key models do not experience similar contamination
problems. However, dogs are less relevant due to a
quite different and complex anatomical architecture
in the