Abstract
OBJECTIVE:The purpose of this study was to evaluate the distribution of microorganisms in the root canal system (RCS) and periapical lesions of dogs' teeth after rotary instrumentation and placement of different calcium hydroxide [Ca(OHy-based intracanal dressings.MATERIALS AND METHODS:Chronic periapical lesions were experimentally induced in 80 premolar roots of four dogs. Instrumentation was undertaken using the ProFile rotary system and irrigation with 5.25% sodium hypochlorite. The following Ca(OH)2-based pastes were applied for 21 days: group 1 - Calen (n=18); group 2 - Calen+CPMC (n=20); group 3 - Ca(OH2 p.a. + anaesthetic solution (n=16) and group 4 - Ca(OH2 p.a.+ 2% chlorhexidine digluconate (n=18). Eight root canals without endodontic treatment constituted the control group. Histological sections were obtained and stained with Brown & Brenn staining technique to evaluate the presence of microorganisms in the main root canal, ramifications of the apical delta and secondary canals, apical cementoplasts, dentinal tubules, areas of cemental resorption and periapical lesions. The results were analyzed statistically by the Mann-Whitney U test (p<0.05).RESULTS:The control group showed the highest prevalence of microorganisms in all sites evaluated. Gram-positive cocci, bacilli and filaments were the most frequent morphotypes. Similar microbial distribution patterns in the RCS and areas of cementum resorption were observed in all groups (p>0.05). The percentage of RCS sites containing microorganisms in groups 1, 2, 3, 4 and control were: 67.6%, 62.5%, 78.2%, 62.0% and 87.6%, respectively.CONCLUSION:In conclusion, the histomicrobiological analysis showed that the rotary instrumentation and the different calcium hydroxide pastes employed did not effectively eliminate the infection from the RCS and periapical lesions. However, several bacteria seen in the histological sections were probably dead or were inactivated by the biomechanical preparation and calcium hydroxide-based intracanal dressing.
Highlights
After pulp necrosis the pulp cavity becomes progressively colonized by the microorganisms that inhabit the oral environment and interconnected systems[36]
Similar histomicrobiological patterns were seen between the control group and the experimental groups with respect to: ramifications of the delta, cementoplasts, main root canal, dentinal tubules and cement resorption (p>0.05)
The periapical lesions of the group filled with Ca(OH) /anaesthetic showed histomicrobiological aspects similar to that of the control group (p>0.05), while among the other groups a significant reduction was noted (p
Summary
After pulp necrosis the pulp cavity becomes progressively colonized by the microorganisms that inhabit the oral environment and interconnected systems[36]. Control of the root canal system infection, one of the main goals of the endodontic treatment, consists of attaining a significant reduction in the number of viable microorganisms by elimination or inactivation[1,3,4,9,10,32,34,38,40,41]. Biomechanical preparation is phase of endodontic treatment with the greatest impact on the intracanal microbiota[3,4,21,34,37]. Residual microorganisms shall be eliminated or inactivated because they might recolonize the root canals after biomechanical preparation[3,4,29,30,32] and even after obturation[10,17,25,26,41]
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