Evaluation of apical transportation and apical root sealing in root canals prepared with mtwo rotary system with and without apical enlargement ­ an in vitro study

The aim of this study was to evaluate apical transportation and apical root canal sealing after root canal filling in human teeth prepared with MTwo® Rotary System with and without apical foramen enlargement. Twenty mandibular premolars were divided into two groups (n=10). Group 1 had root canals prepared 1mm beyond the apical foramen. Group 2 had root canals prepared 1mm below the root canal length. After chemo-mechanical preparation, samples were submitted to scanning electronic microscopy. Apical foramen images had 75x magnification at standardized positions, allowing measurements from the apical foramen area before and after root canal preparation, and after root canal filling. Apical foramen shape and apical transportation, as well as its level of circumferential filling after root canal preparation were accessed using the Image Subtraction System. Scanning electronic microscopy analysis demonstrated that samples of Group 1 showed larger foraminal diameter than samples of Group 2 (p<0.05). Apical foramen transportation was statistically different between Groups 1 and 2 (p=0.0108). Furthermore, the apical foramen sealing also differed statistically between groups 1 and 2 (p=0.0007) and 100% of samples of Group 1 showed apical root canal sealing. Apical root canal sealing was more effective when the root canal was prepared with apical foramen enlargement, even when the apical transportation was detected.

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.