Objectives: The objective of this study was to evaluate the effect of rotational speed and angle of curvature in curved root canals on the fracture of different nickel-titanium rotary instruments that is Profiles, ProTaper, and K ₃ files. Materials and Methods: Freshly extracted 180 human maxillary and mandibular molars were selected and divided into two groups of 90. Each group was then divided into three sub groups A, B, and C according to angle of curvature, Group I < 30° and Group II > 30°, which was measured by Schneider's method. Instrumentation was performed using the profile, ProTaper, and K3 (Company and in Literature name of Rotary file is K3) rotary instrument at 3 rotational speeds of 150, 250, and 350 rpm (10 molars at each rotational speed). Results: There were total of 32 instrument fractured out of 120 files. In a multivariable analysis, it was demonstrated that the rotational speed of 350 rpm fractured than those used at 150 rpm (odd's ratio [OR]: 3.6, 95% confidence interval [CI]: 1.3-10.5). An increase in the angle of curvature of the canal did not significantly increase the likelihood of fracture (OR: 1.9, 95% CI: 0.8-4.2). No significant differences were found between various designs of files used. Conclusion: Instrument fracture was associated with rotational speed and the angle of curvature.

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Aims: The purpose of this study was to evaluate the effect of saliva contamination on the micro-tensile bond strength (μTBS) of two self-etching (SE) adhesive systems (Clearfil SE Bond, Clearfil S3 Bond). Materials and Methods: Flat occlusal dentin surfaces were created on 12 extracted human third molar teeth. The two bonding systems and resin composite (Spectrum^® TPH^® 3) were bonded to the dentin under six surface conditions: Group 1: Tooth samples were randomly divided into three equal subgroups. Clearfil SE 1: This was a control group in which dentin was not contaminated with the saliva (primer/bonding/composite). Clearfil SE 2: Contaminated once (primer/bonding (cured)/saliva/rinsing/drying/primer/bonding/composite). Clearfil SE 3: The samples were contaminated 2 times (primer/bonding (cured)/saliva/rinsing/drying/primer/bonding (cured)/saliva/rinsing/drying/primer/bonding/composite). Group 2: The procedures for Group 2 were similar to Group 1 but did not contain a primer stage. Tooth samples were randomly divided into three equal subgroups (Clearfil S3 1, 2, and 3). After 24 h, the teeth were prepared for microtensile bond testing and tensile bond strength was measured (1 mm/min). The data were calculated as megapascal (MPa) and analyzed using the one-way ANOVA and Tukey's post-hoc test (P < 0.05). Results: The μTBS of the Clearfil S3 3 subgroup was statistically higher than that of the Clearfil S3 2 subgroup and Clearfil S3 1 subgroup. There were no significant statistical differences in the μTBSs between the Clearfil S3 2 subgroup and the control subgroup. There were no statistical differences in μTBSs among the Clearfil SE subgroups. Conclusion: μTBS is not affected adversely from one or two saliva contamination after the bonding procedure.

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Objective: The aim of this study was a comparative assessment of in vitro microleakage of five different new generation self-etching adhesive systems. Materials and Methods: One hundred recently extracted fresh caries-free human permanent molars were used. Teeth were randomly assigned to one of five groups (n = 20). Clearfil S ³ Bond (Group I), Xeno V (Group II), G Bond (guanine-cytosine) (Group III), Optibond All in One (Group IV) and iBond (Group V) were applied, then polymerized with light emitting diode and restored with a nanofill composite. Teeth were coated twice with acid resistant varnish and immersed in 0.5% methylene blue. Specimens were cut bucco-palatinally/lingually, with microleakage scores evaluated on a scale from 0 to 4 under a stereomicroscope and then analyzed under a scanning electron microscope. Results: The differences among the gingival and occlusal microleakage scores of the groups were statistically significant (P < 0.05) (P = 0.043, P = 0.005). Occlusal microleakage scores of Clearfil S ³ Bond and Optibond All in One were considerably lower than those of the other three groups. While the highest microleakage was observed with iBond, there was no statistical difference between the Xeno V and G Bond groups (P > 0.05). The highest gingival microleakage scores were in the iBond group; though, statistically there was no significant difference among the other groups (P > 0.05). Conclusion: The occlusal and gingival microleakage scores of self-etching adhesive systems in this study were satisfactory except for one group (Group V-iBond).

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Aim: The purpose of any restorative material is not only to restore the decayed of defective tooth and provide an effective seal between the restoration and the tooth, but also to strengthen it. Endodontic treatment removes the vital contents of the canal, leaving the tooth pulpless and resulting in teeth with calcified tissues that contain significantly less moisture than that of vital teeth. The restorative material should be as much as strong, which support the endodontically treated tooth against the occlusal forces. Thus, the present study was undertaken to evaluate different restorative technique using the polyethylene fiber in reinforcing the root-filled teeth. Materials and Methods: 50 freshly extracted maxillary premolar human teeth were taken. All teeth were divided into 2 groups, the control and experimental group), sub group I (had unrestored mesial occlusal distal [MOD] cavities), sub group II (where MOD cavities were filled with composite), sub group III (where polyethylene fiber placed occlusally on the composite restoration) and sub group IV (had polyethylene fiber inserted under the composite the restorations). The specimens were then placed into a universal testing machine. A vertical compressive force was applied at a crosshead speed of 0.5 mm/min and the force necessary to fracture. Results: Fracture resistance was significantly highest in sub group III as compared to sub group IV, sub group II and sub group I. Conclusion: This study concluded that use of polyethylene fiber inserted over or under the restoration significantly increased the fracture strength of the root canal treated teeth and when the fiber was placed on the occlusal surface of the restoration from a buccal to lingual direction significantly higher fracture resistance was observed.

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Background and Objectives: The main objective of this study was to compare and evaluate the effect of enamel preparation designs; bevel and stair step chamfer, on fracture resistance of composite resins (micro-filled and nano-filled) using incremental technique. Materials and Methods: The sample group consisted of 60 non-carious maxillary permanent central incisors. They were divided into four groups of 15 teeth each. According to the group, the teeth were prepared and restored with corresponding design and material. The teeth were subjected to compression bending test under instron testing machine then were examined under stereomicroscope. The results were subjected to statistical analysis. Results: Mean peak failure load (Newton) of among experimental groups was observed in the order; Group I (Bevel with micro-filled material) was 255.6 ± 65.0 N and Group II (bevel with nano-filled material) l was 282.1 ± 67.7 N. Group III (Stair-step chamfer with micro-filled material) was 249.8 ± 78.0 N. and Group IV (Stair-step chamfer with nano-filled material) was 283.3 ± 52.0 N. Results of the analysis of variance revealed there was no significant difference in the mean peak failure load values of the four different groups. Failure mode evaluation revealed, majority of the failures occurred as cohesive and mixed type for all the experimental groups. Adhesive type failure was observed maximum (47%) in the bevel group. Stair-step chamfer preparation showed the greatest potential for application, but also involved sacrificing less amount of tooth structure adjacent to fractured edge. Conclusion: This study concludes that both the preparations, bevel as well as stair-step chamfer are equally good to resist fracture when restored either with micro-filled or nano-filled composite resins.

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