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Aim: Complex anatomy of roots requires endodontic rotary instruments that respect and follow that anatomy. The purpose of this study was to compare the shaping ability of three engine-driven nickel-titanium instruments in severely curved simulated canals. Materials and methods:Forty-eight severely curved simulated canals in resin blocks were prepared to an apical size of 25 using the following systems (n = 16 per group): ProTaper Universal (PTU), ProTaper NEXT (PTN), and WaveOne Primary (WO) (all Dentsply Maillefer, Ballaigues, Switzerland). Composite images were made from the superimposition of pre-and post-instrumentation images. The amount of resin removed by each system was measured by using a digital template and image analysis software. Shaping ability of each system was compared using different parameters: total resin removal, centering ability, canal transportation in the apical, middle and coronal third of canal. Preparation times were also recorded. The data were statistically analyzed by using analysis of variance, paired t-test, and Tukey's post hoc test.Results: Canals prepared with PTN were better centered in the apical part than those prepared with WO and PTU (p < 0.05). WO removed significantly more resin at the outer aspect of the maximum point of curvature. WO and PTU caused similar canal transportations at 7 points out of 11 measuring points. At measuring points 3, 4, and 5 WO caused more canal straightening than PTU. Instrumentation with PTU required more time than with the two other instruments (p <0.05). No preparation error or instrument separation occurred. Conclusion:In the apical part of the canals PTN obtained the best results with regard to canal transportation.Clinical Significance: All of the rotary instruments were safe in preparing severely curved canals and PTN showed better preparation of apical part of the canal.

ObjectivesThe aim of this study was to assess the influence of operator experience level on the lifespan of the WaveOne Primary file (Dentsply Maillefer, Ballaigues, Switzerland) in extracted teeth.Materials and MethodsModerately curved canals of extracted maxillary and mandibular molars were randomly distributed into 2 groups: experienced and inexperienced operators. Ten files were allocated to each group (n = 10). Each canal was prepared until the working length was reached, and the same file was used to prepare additional canals until it separated. The number of canals prepared before file separation was recorded. The fragment length of each file was measured, and the location of the fragment in the canal was determined. Data were statistically analysed using the independent 2-sample t-test.ResultsThe 2 operators prepared a total of 324 moderately curved canals of maxillary and mandibular molars. There was no significant intergroup difference in the mean number of canals prepared (p = 0.27). The average lifespan of the WaveOne Primary file was 17.1 and 15.3 canals, and the longest lifespan was 25 and 20 canals, when used by experienced and inexperienced operators, respectively. There were no statistically significant intergroup differences in separated fragment length and location.ConclusionsWithin the limitations of this study, operator experience level appears to have no effect on the lifespan of the WaveOne Primary file in preparation of moderately curved canals. Single teeth with multiple canals can be prepared safely even by a novice operator by using a single file.

Background Shaping ability of a file plays an important role during instrumentation in an endodontic treatment. This study aimed to compare the shaping ability of OneShape (OS), Hero Shaper (HS), and Revo-S (RS) instruments in simulated L-shaped canals. Methods Forty-eight simulated L-shaped canals were prepared to an apical size of 25 using OS, HS, and RS (all from Micro-Mega SA, Besançon, France), (n = 16 canals/group) systems. The amount of resin removed after each canal's preparation was measured and compared after producing a composite image made from the superimposition of pre and post-instrumented canals. Canal aberrations and the preparation time were also recorded. The data were statistically analysed by using ANOVA, Tukey, and Chi-square tests. Results One file fractured during instrumentation in the RS group. A significant difference was found at the apical end of the prepared simulated canal between the groups, with RS showing the least amount of resin removal from the inner side of the canals and HS showing the highest amount of resin removal from the outer side (P < 0.05). Regarding the total width of the canals after preparation, a significant difference was found between the groups at the apical end and the straight portion of the canals, and RS removed the least amount of resin at the straight portion of the canals (P < 0.05). No statistically significant differences were found between the different instruments regarding canal aberrations' incidence (P > 0.05). Conclusions All of the files showed a tendency to straighten the canals, whereas OS files maintained the original canal curvatures well.