Effect of reciprocating instrumentation on chlorhexidine substantivity on human dentin: chemical analysis followed by confocal laser microscopy

The present research analyzed the reciprocating instrumentation associated to chlorhexidine (CHX) substantivity as its correlation with E. faecalis viability in ex vivo root canals. Eighty extracted single-rooted human teeth were used, being 40 to high-performance liquid chromatography (HPLC) and 40 to confocal laser scanning microscopy (CLSM). In both, teeth were decoronated and the cervical third was prepared. In the CLSM analysis, the root canals were inoculated with E. faecalis for 14 days. Samples were divided into 4 groups (n=10) according to instrumentation technique: no instrumentation and irrigation with distilled water (control); manual instrumentation (K-File); rotary instrumentation (ProTaper Next); and reciprocating instrumentation (Reciproc R25). Two percent chlorhexidine was applied as irrigating substance in experimental groups. Longitudinal grooves resulted in 2 halves root and 20 proof bodies in each group. Samples were divided by chance in two groups (n=10) and the outcomes were evaluated after two days and one week. The retained chlorhexidine and live cells after instrumentation techniques in each evaluation time was measured by HPLC and CLSM, respectively. Specific analysis was applied for experimental tests (p≤0.05). Both rotary as well as reciprocating techniques significantly reduced the amount of chlorhexidine on dentin in all observation periods (p<0.05). After evaluation times, all experimental groups presented lower live cells compared to control, but without statistically difference. Intragroup comparisons in times of evaluation showed no differences in instrumentation techniques, in chlorhexidine retention and number of live cells (p>0.05). Reciprocating instrumentation does not interfere on chlorhexidine substantivity.

Influence of ultrasonic activation in association with different final irrigants on intracanal smear layer removal

Aim: To evaluate the influence of ultrasonic activation (US) with different irrigant regimens in smearlayer removal. Methods: One hundred bovine incisors were instrumented and divided into tengroups (n=10) according to final irrigation protocols: distilled water (DW); DW+US; 17% EDTA;QMix; 10% citric acid; 37% phosphoric acid; 17% EDTA+US; QMix+US; 10% citric acid+US; 37%phosphoric acid+US. The samples were then submitted to scanning electron microscopy where ascore system was used to evaluate the images and effectiveness of proposed treatments. The datawere statistically analyzed by Kruskal-Wallis and Mann-Whitney U tests for intergroup comparisonsas well as the Wilcoxon and Friedman tests for intragroup comparisons at 5% significance level.Results: In the cervical third, groups 17% EDTA, QMix, 10% citric acid, 17% EDTA+US, QMix+USand 10% citric acid+US were more effective in smear layer removal (p<0.05); in the middle third,groups 17% EDTA+US and QMix+US were more effective in smear layer removal (p<0.05); in theapical third, groups 17% EDTA,17% EDTA+US and QMix+US were more effective in smear layerremoval (p<0.05). Conclusions: US can aid 17% EDTA and QMix in smear layer removal at themiddle third and QMix at the apical third, contributing to the cleaning of root canal system.