Performance of obturation techniques in anatomical irregularities located at different thirds of the root canal system.

This study aimed to compare the quality of root canal obturation (ratio of area occupied by gutta-percha (G), sealer (S), and presence of voids (V)) in different anatomical irregularities (intercanal communications, lateral irregularities, and accessory canals) located at different thirds of the root canal system of mandibular molar replicas. Sixty-seven 3D printed replicas of an accessed mandibular molar were prepared using ProGlider and ProTaper Gold rotatory systems. Three specimens were randomly selected to be used as controls and did not receive further treatment. The rest were randomly distributed in 4 experimental groups to be obturated using either cold lateral compaction (LC), continuous wave of condensation (CW), and core-carrier obturation (ThermafilPlus (TH) or GuttaCore (GC)) (n=16 per group). AHPlus® sealer was used in all groups. The three controls and a specimen from each experimental group were scanned using micro-computed tomography. The rest of the replicas were sectioned at the sites of anatomical irregularities and examined at 30× magnification. The G, S, and V ratios were calculated dividing the area occupied with each element by the total root canal area and then compared among groups using the Kruskal-Wallis test. Voids were present in all obturation techniques with ratios from 0.01 to 0.15. CW obtained a significantly higher G ratio in the irregularity located in the coronal third (0.882) than LC (0.681), TH (0.773), and GC (0.801) (p<0.05). TH and GC achieved significantly higher G ratios in those located in the apical third (p<0.05). The worst quality of obturation was observed in the loop accessory canal with all obturation techniques. Whitin the limitations of this study, it can be concluded that CW and core-carrier obturation are respectively the most effective techniques for obturating anatomical irregularities located in the coronal and the apical third.

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.

Performance of obturation techniques in anatomical irregularities located at different thirds of the root canal system

Abstract This study aimed to compare the quality of root canal obturation (ratio of area occupied by gutta-percha (G), sealer (S), and presence of voids (V)) in different anatomical irregularities (intercanal communications, lateral irregularities, and accessory canals) located at different thirds of the root canal system of mandibular molar replicas. Sixty-seven 3D printed replicas of an accessed mandibular molar were prepared using ProGlider and ProTaper Gold rotatory systems. Three specimens were randomly selected to be used as controls and did not receive further treatment. The rest were randomly distributed in 4 experimental groups to be obturated using either cold lateral compaction (LC), continuous wave of condensation (CW), and core-carrier obturation (ThermafilPlus (TH) or GuttaCore (GC)) (n=16 per group). AHPlus® sealer was used in all groups. The three controls and a specimen from each experimental group were scanned using micro-computed tomography. The rest of the replicas were sectioned at the sites of anatomical irregularities and examined at 30× magnification. The G, S, and V ratios were calculated dividing the area occupied with each element by the total root canal area and then compared among groups using the Kruskal-Wallis test. Voids were present in all obturation techniques with ratios from 0.01 to 0.15. CW obtained a significantly higher G ratio in the irregularity located in the coronal third (0.882) than LC (0.681), TH (0.773), and GC (0.801) (p<0.05). TH and GC achieved significantly higher G ratios in those located in the apical third (p<0.05). The worst quality of obturation was observed in the loop accessory canal with all obturation techniques. Whitin the limitations of this study, it can be concluded that CW and core-carrier obturation are respectively the most effective techniques for obturating anatomical irregularities located in the coronal and the apical third.

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.

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.

Influence of humidity and setting time on the push-out strength of mineral trioxide aggregate obturations.

The aim of this study is to assess how a wet environment curing affects the retention characteristics of mineral trioxide aggregate (MTA), and also to determine the time needed for curing. MTA obturations were carried out in perforated dentine slices and cured under different conditions (presence or absence of humidity and several time intervals). The obturations were then subjected to an increasing mechanical strength until they were displaced from the perforations. The push-out strength was determined as the ration of the dislodging force to the MTA-dentine contact surface. The influence of the different curing conditions on the push-out strength was then analyzed for statistical significance. Humidity significantly increased the push-out strength of MTA obturations. The effect of curing time depended on humidity: while in the absence of humidity the push-out strength did not increase after 3 days, in the presence of humidity a lengthening of the curing time up to 21 days produced a moderate increase over and above the large initial increase obtained in the first 3 days.