NiTi loss on the dentinal walls and instrument deformation during root canal preparation.

The purpose of this study was to quantify the presence of nickel (Ni) and titanium (Ti) on dentin walls of prepared root canals using Endosequence (ES) and Wave One (WO) systems, the deformation, and fracture of these instruments. Thirty extracted human premolar teeth were selected and prepared with WO, ES, and manually (control group-CG). Each instrument was used in four root canals. The root canals were irrigated with 2.5% sodium hypochlorite solution. After preparation, roots were sectioned longitudinally and the apical third was analyzed by scanning electron microscopy with X-ray microanalysis (SEM-EDS). The percentage of Ni and Ti found on dentin walls was compared using Kruskal-Wallis test and post hoc Dunn. The instruments deformation and fracture was evaluate by SEM before and after use. Spiral distortion, fractures, and surface wear were compared using Mann-Whitney test. The level of significance was set at 5%. Ni and Ti were found on the dentin walls of the apical root canal for ES and WO systems (p > .05). No distortion in the spirals and no instrument fracture were observed. Regarding to surface wear, most of the instruments scored as moderate wear (p > .05). This study concluded the WO and ES presented Ni and Ti loss. In addition, the preparation of four root canals did not caused irreversible deformation in WO and ES instruments.

Effect of calcium hydroxide on the bond strength of two bioactive cements and SEM evaluation of failure patterns.

The aim of this study was to assess the effect of calcium hydroxide on bond strength of two bioactive cements. One-mm thick longitudinal slabs of root dentin were obtained from freshly extracted human monorradicular teeth (n = 60). Simulated root perforations (1 mm in diameter) were prepared in radicular dentin. Thereafter, the specimens were randomly divided into two groups (n = 30), according to the repair material: MTA (n = 30) and Biodentine (BD) (n = 30). Next, the specimens in each group were further randomly divided into 4 equal subgroups (n = 15) according to the prior use of Ca(OH)2: MTA/Ca(OH)2 and BD/Ca(OH)2 groups: perforations were filled with calcium hydroxide [Ca(OH)2] and after 7 days, it was removed, and MTA and BD groups: calcium hydroxide dressing were not used. Push-out test was performed at a crosshead speed of 1 mm/min. Bond strength values were compared statistically using Kruskal-Wallis test and Dunn's post-test at a significance level of 5%. The failure analysis was performed using a stereoscopic and classified as adhesive, cohesive and mixed. The push-out bond strength of MTA and BD was not affected by the prior use of Ca(OH)2 (p > 0.05). BD yielded higher push-out bond strength values compared with those of MTA, regardless of the use of Ca(OH)2 (p < 0.05). Mixed failures were predominant in all groups. Ca(OH)2 placement for perforations sealing does not alter the bond strength of MTA and BD to the root dentin. BD presented higher bond strength values than MTA. SCANNING 38:240-244, 2016. © 2015 Wiley Periodicals, Inc.