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The effects of Nd:YAG laser irradiations at different power settings on several oral pathogens were evaluated. A total of 252 dentin samples were divided into seven groups consisting of 36 dentin specimens each. In each group, 9 of the 36 specimens were used as controls, thereby including a control in every group. The remaining 27 specimens were divided into three subgroups consisting of nine specimens according to different Nd:YAG laser settings (1.5, 1.8, and 2 W). Each group was inoculated on the nonpulpal side with one of the following microorganisms: Candida glabrata, Candida tropicalis, Candida krusei, Candida sake, Candida lusitaniae, Candida kefyr, and Rhodotorula mucilaginosa. The following irradiation procedure was used: the specimens were irradiated on the bacteria-free side (the side consisting of the pulpal wall) using contact mode under the constant scanning movement of the optical fiber at an angle of 10°. One lasing cycle consisted of four irradiation cycles of 10 s each, with 15-s intervals in between each irradiation cycle. The remainder of the controls and the lased specimens of each group were prepared for the microbiological investigation. After incubation for 24 h at 37 °C, the colonies were counted, and the total number of surviving microorganisms was statistically assessed. Microorganisms irradiated with Nd:YAG laser at power settings 2 W, 15 pps did not survive. Although there was a significant reduction of microorganisms at 1.5 and 1.8 W, when comparing Nd:YAG laser irradiation with the control group, sterilization did not occur.

The purposes of this study were to evaluate the ability of a group of third-year dental students without any endodontic clinical experience to use the ProTaper Instruments (Dentsply Maillefer) to decrease the amount of straightening of curved canals on human molar teeth and to determine the incidence of instrument fractures and instrumentation time. Thirty-one undergraduate dental students in Turkey received a training session. The students prepared a total of 144 root canals in human mandibular or maxillary molar teeth with ProTaper. Fifty-six teeth were excluded due to unreadable image, misinformation, or straight or severe curve. Using pre- and post-preparation digital radiographs, the straightening of curved root canals was investigated. Loss of working length and incidence of fracture were also noted. A total of eighty-eight curved root canals were selected. Mesiobuccal or mesiolingual roots with curvatures of between 20° and 43° as assessed by Schneider's method and working length of between 15 mm and 22.5 mm were included in the study. The means of the curved root canals before and after the instrumentation were 29.5° ± 6° and 27° ± 6.3°, respectively. The means of the working length before and after the instrumentation were 19 mm ± 2.1 mm and 18.3 mm ± 1.9 mm, respectively. A statistically significant difference between straightening of curved root canals and loss of working length was found between before and after instrumentation (p<0.000). The mean straightening of curved root canals and loss of working length after preparation with the size F1 ProTaper file were 2.5 mm ± 3.6 mm and 0.7 mm ± 0.6 mm, respectively. Only two F1 ProTaper instruments fractured at the apical level. The study concluded that rotary instruments performed adequately with inexperienced operators who received a brief structured training session.

Objective: The objective of this study was to evaluate whether the changes in the design of the ProTaper canal instruments contribute to the shaping ability of the instrument in terms of the morphology of curved canals measured by the cross-sectional area using the Bramante method., Study Design: Ten extracted human mandibular molars with root canal curvatures between 25 degrees and 41 degrees were used. Ten mesiobuccal canals were instrumented with ProTaper and 10 mesiolingual canals were instrumented with ProTaper Universal rotary instruments. Pre- and postoperative sections were obtained from the coronal, middle, and apical portions and analyzed. Statistical analysis was performed using the Student t test (P < .05)., Results: No statistically significant difference was observed in terms of amount of dentin removed, transportation, variation of canal shape factor or change in working length, and working time (P > .05). Only one instrument fracture (F2 in the ProTaper group) and 2 instrument deformations (S1 and F3 in ProTaper and ProTaper Universal, respectively) were noted., Conclusion: Within the limitations of this study, the modifications on ProTaper instruments were found to not create any discrepancy on the shaping abilities of instruments and the evaluated other factors. In addition, both rotary nickel-titanium instruments prepared a well-shaped root canal with minimal canal transportation.

The aim of this study was to compare the amount of apical extrusion during manual instrumentation and engine-driven rotary instrumentation in teeth with disrupted apical constriction. Fifty-two teeth were divided into two groups comprising 26 teeth each. Teeth in each group were further divided into two sub-groups, the apices of which were enlarged approximately to a diameter of 0.2 mm and 0.4 mm. One group was instrumented using standardized technique with K-files and the other with ProFile .04 Taper Series 29, while irrigating with sodium hypochlorite. Glass vial model was modified for collection of extruded debris and irrigant as well as to integrate an electronic apex locator to the experimental assemble. The statistical analysis using Student's t test revealed no significant difference between instrumentation with K-files and ProFile .04 taper files (p > 0.05). There was a tendency with both techniques to extrude apically more material as the diameter of the apical patency increased.

This study evaluates the amount of remaining tooth structure and possibility of producing lateral perforation following the use of different diameters of parallel-sided Parapost drills in groups of different canal curvatures (0 degrees-15 degrees, 16 degrees-25 degrees, 26 degrees <) in distal canals of first and second mandibular molar teeth. After enlargement of root canals using the crown-down pressureless technique, Parapost drills #1, #2, and #3 were used in the different canal groups for the preparation of a post space. Standardized digital radiographs were taken before the post space preparation and after each Parapost drill application. Four horizontal lines (a, b, c, and d) were drawn at equal distances on these images, starting from the pulp chamber floor moving apically at 2 mm increments. There were no significant differences between the different curvature groups at the a, b, c, and d levels for the critical level of the remaining tooth structure (multiple comparison test; p>0.05). However, in considering root perforation, both at the inner and outer side of the roots, there were statistically significant differences at "c" and "d" levels in group 3 (#3 drill) without taking into account the root curvature (ANOVA; p< 0.5). None of the specimens showed strip perforation.