Influence of the incorporation of small-group practical seminars to a traditional lecture for the understanding of root canal morphology classification systems.

INTRODUCTION: This study aimed to assess if the incorporation of small-group practical seminars into a traditional lecture format improved the understanding and learning of the root canal classification systems in undergraduate students. MATERIALS AND METHODS: A small-group practical seminar was designed for 3rd year undergraduate students. The seminar consisted of the analysis of a guided summary of root canal morphology classifications, a participative discussion of several cases and drawing exercises of several internal anatomies based on the different classifications in templates presenting the external anatomy of different dental groups. Students were inquired about their perspectives on the different classifications and the learning strategies with an anonymous questionnaire. The knowledge acquired was assessed in an exam. The scores obtained were compared using the Mann-Whitney U-test with those obtained in the cohort of the previous year in which only the traditional lecture was delivered. RESULTS: Students' scores (mean = 7.7; SD = 2.5) were significantly higher (p = .006) than those from the previous cohort (mean = 6.9; SD = 2.3). Most students agreed that Ahmed's classification system was the most complete (98.8%) and intuitive (84%), but also the most difficult to understand (67%). All the students believed that the learning activity helped them understand the new classification system. CONCLUSION: The incorporation of small-group practical seminars into traditional lecture improved the understanding and learning of root canal configurations in undergraduate students. Students rated the classification system suggested by Ahmed et al. as the most complete and intuitive out of the three systems, but also the most difficult to learn.

Effect of exposure to root canal irrigants on the push-out bond strength of calcium silicate-based cements.

OBJECTIVES: The aim of this study was to compare the push-out bond strength (POBS) of three calcium silicate-based cements (CSBC) after exposure to saline, sodium hypochlorite (NaOCl), ethylenediaminetetraacetic acid (EDTA), and a mixture of NaOCl and etidronic acid (NaOCl+HEBP) in simulated perforation. MATERIALS AND METHODS: A total of 180 dentin slices were perforated and then filled with either Biodentine (BD), ProRoot MTA (PMTA), or Total Fill (TF). After 1 week, specimens in each group were divided into 4 subgroups (n = 15) according to the root canal irrigant (RCI) that their coronal surface was exposed to: saline, 5.25% NaOCl, 17% EDTA, or a mixture of 5.25% NaOCl and 9% HEBP (NaOCl+HEBP). A push-out test was performed, and the failure pattern was assessed. POBS data were analyzed with ANOVA and Tukey post hoc tests and the failure patterns with chi-square test. RESULTS: No differences were found when comparing the effect of RCI on the POBS of PMTA. BD showed significantly higher POBS values after exposure to NaOCl+HEBP (p < .05), and those of TF were significantly lower after exposure to EDTA (p < .05). No differences in the failure patterns were found among groups. CONCLUSION: NaOCl+HEBP had no detrimental effect on the POBS of CSBC. CLINICAL RELEVANCE: The mixture of sodium hypochlorite and etidronic acid may be considered as an alternative irrigant when treating root perforations.

Effect of exposure to etidronic acid on the bond strength of calcium silicate-based cements after 1 and 21 days: an in vitro study.

BACKGROUND: After reparation of root perforations with calcium silicate-based cements (CSBC), the surface of the material is expected to be exposed to root canal irrigants (RCI) while resuming the root canal treatment. METHODS: The aim of this study was to compare the effect of exposure to a mixture of sodium hypochlorite (NaOCl) and etidronic acid (HEBP) or other irrigants on the Push Out Bond Strength (POBS) of CSBC after two different setting times. 240 root slices 1 mm thick were obtained from single-rooted human teeth. A 1.4 mm diameter perforation was performed on each slice and filled with Biodentine (BD) or ProRoot MTA (PMTA). After 1 or 21 days they were exposed to 17% ethylenediaminetetraacetic acid, 5.25% NaOCl, a mixture of 5.25% NaOCl and 9% HEBP (NaOCl + HEBP) or saline (n = 15) and submitted to a push-out test. POBS results were analysed with ANOVA and Tukey tests. RESULTS: BD showed higher POBS than PMTA after 1 day (p < .05). After 21 days no differences were found between materials. After 1 day exposure to NaOCl + HEBP resulted in higher POBS, compared to the other irrigants (p < .05). CONCLUSION: POBS results are influenced by the cement, the setting time and the exposure to irrigants.

Cyclic fatigue resistance of K3, K3XF, and twisted file nickel-titanium files under continuous rotation or reciprocating motion.

INTRODUCTION: New designs and alloys and different motions have been introduced to increase the cyclic fatigue (CF) resistance of nickel-titanium (NiTi) files. The aim of this study was to compare the CF resistance of K3 (SybronEndo, Orange, CA), K3XF (SybronEndo), and TF (SybronEndo) files under continuous rotation and reciprocating motion. METHODS: A total of 210 files (30-tip diameter, 0.06 fixed taper), 60 K3, 60 K3XF, and 90 TF files, were divided into 7 groups (30 files each): K3-C, K3XF-C, and TF1-C were rotated at 300 rpm; TF2-C was rotated at 500 rpm; and K3-R, K3XF-R, and TF1-R were used in a reciprocating motion. CF resistance was tested in stainless steel, curved canals (60°, r = 3 mm) until fracture, and the time to fracture was recorded. The mean half-life, beta, and eta were calculated for each group and were compared with Weibull analysis. RESULTS: The probability of a longer mean life was greater under reciprocating motion for all of the files (100% for K3, 87% for K3XF, and 99% for TF). Under continuous rotation, K3XF was more resistant than K3 and TF. TF lasted significantly longer than K3. TF was more resistant to CF when rotated at 300 rpm instead of 500 rpm. Under reciprocating motion, there were no significant differences between K3XF and TF mean lives, but both were significantly longer than the K3 mean life (78% for TF and 86% for K3XF). CONCLUSIONS: Reciprocating motion and R-phase increase CF resistance.