Purpose: To analyze the accuracy of two computer-aided navigation techniques to guide the performance of endodontic access cavities compared with the conventional access procedure. Materials and Methods: A total of 30 single-rooted anterior teeth were selected, which were randomly distributed into three study groups: Group A—guided performance of endodontic access cavities through computer-aided static navigation system (n = 10) (SN); Group B—guided performance of endodontic access cavities through computer-aided dynamic navigation system (n = 10) (DN); and Group C—manual (freehand) performance of endodontic access cavities (n = 10) (MN). The endodontic access cavities of the SN group were performed with a stereolithography template designed on 3D implant planning software, based on preoperative cone-beam computed tomography (CBCT) and a 3D extraoral surface scan, and endodontic access cavities of the DN group were planned and performed by the dynamic navigation system. After endodontic access cavities were performed, a second CBCT was done, and the degree of accuracy between the planned and performed endodontic access cavities was analyzed using therapeutic planning software and Student’s t-test. Results: Paired t-test revealed no statistically significant differences between SN and DN at the coronal (p = 0.6542), apical (p = 0.9144), or angular (p = 0.0724) level; however, statistically significant differences were observed between the two computer-aided navigation techniques and the MN group at the coronal (p < 0.0001), apical (p < 0.0001), and angular (p < 0.0001) level. Conclusion: Both computer-aided static and dynamic navigation procedures allowed accurate performance of endodontic access cavities.

Purpose: To analyze the influence of the pecking motion frequency on the cyclic fatigue resistance of endodontic rotary files. Material and Methods: Sixty PlexV 25.06 endodontic rotary files were selected and distributed into three groups: 30 movements/min (n = 20), 60 movements/min (n = 20), and 120 movements/min (n = 20). A dynamic cyclic fatigue device was designed using Computer Aided Design/ Computer Aided Engineering (CAD/CAE) technology and manufactured by 3D impressions to simulate the pecking motion performed by an operator. Failures of the endodontic rotary files were detected by a Light-Emitting Diode (LED)/Light-Dependent Resistor (LDR) system controlled by an Arduino-Driver complex and management software. Endodontic rotary files were tested on an artificial root canal manufactured by wire electrical discharge machining (EDM), with similar dimensions to those of the instrument under examination. Endodontic rotary files were used following the manufacturer’s recommendations. The results were analyzed by ANOVA and Weibull statistics. Results: All pairwise comparisons revealed statistically significant differences in all three variables, except for the difference in the number of cycles between the groups with 60 and 120 movements/min (p = 0.298). The scale distribution parameter of Weibull statistics showed statistically significant differences in all three variables, except for the differences in the number of cycles between groups with 30 and 60 movements/min (p = 0.0722). No statistically significant differences in the three variables were observed for the shape distribution parameter. Conclusion: A low frequency of pecking motion is recommended to reduce the risk of failure of endodontic rotary files associated with cyclic fatigue.

Background: The aim of this study was to analyze the effects of the time of use (TU) and sterilization cycles (SC) of endodontic reciprocating files on cyclic fatigue resistance. Methods: One-hundred-and-twenty (120) Procodile NiTi endodontic reciprocating instruments were selected at random and distributed into the following study groups: A: 0 sterilization cycles/0s time of use (n = 10); B: 0/60 (n = 10); C: 0/120 (n = 10); D: 1/0 (n = 10); E: 1/60 (n = 10); F: 1/120 (n = 10); G: 5/0 (n = 10); H: 5/60 (n = 10); I: 5/120 (n = 10); J: 10/0 (n = 10); K: 10/60 (n = 10); and L: 10/120 (n = 10). A dynamic cyclic fatigue device was designed using computer-aided design/computer-aided engineering (CAD/CAE) technology and created with a 3D printer to simulate the pecking motion performed by the clinician. Failure of the endodontic rotary instrument was detected by a light-emitting diode-light-dependent resistor (LED-LDR) system controlled by an Arduino driver complex and management software. The results were analyzed using the ANOVA test. Results: All pairwise comparisons presented statistically significant differences between the time to failure, number of cycles to failure and number of cycles of in-and-out movement for the time of use study groups (p < 0.001), but not in the number of sterilization cycles (p > 0.05). Conclusions: The time of use of NiTi endodontic reciprocating files negatively affects dynamic cyclic fatigue resistance. Dynamic cyclic resistance is not affected by the number of sterilization cycles.

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S15 Objectives To compare the 6-month clinical performance of a "universal" adhesive in non-carious Class V lesions using four different adhesive strategies. Materials and Methods 21 patients participated in this study, in which 70 Class V restorations were placed. The restorations were randomly assigned into four experimental groups according to different adhesive strategies of Scotchbond Universal Adhesive (SBU, 3M ESPE): A. 3-step etch-andrinse: 34% phosphoric acid (PA, Scotchbond Universal Etchant, 3M ESPE) and application of SBU followed by one coat of the non-solvated bonding resin Scotchbond MultiPurpose Adhesive (SBMPA, 3M ESPE); B. 2-step etch-and-rinse: 34% PA followed by SBU; C. 2-step selfetch: SBU followed by one coat of SBMPA; D. 1-step self-etch: SBU alone. All restorations were evaluated at baseline and after 6 months by two blind observers using the USPHS criteria. Statistical analysis was performed with the non-parametrical tests Kruskal-Wallis, Mann Whitney U and Wilcoxon (p<0.05). Results Only one restoration from the group 1-step/SBU was lost at six months. Marginal adaptation was the only criterion for which statistically worse scores were measured after 6 months (p<0.01). Significantly more bravo scores were detected when SBU was used following a self-etch strategy. The restorations performed with SBU as 1-step self-etch adhesive exhibited a significantly deterioration of the marginal adaptation after 6 months. Conclusions Restorations performed with SBU under a self-etch strategy showed worse marginal adaptation after 6 months of clinical use compared to those with SBU under an etch-and-rinse strategy. The addition of a nonsolvated hydrophobic coating (SBMPA) did not influence the clinical performance.