Aim: This study aimed to compare the fracture resistance of root canal treated (RCT) teeth restored with different types of resin composite restorations.Methods: A total of 40 freshly extracted human intact mature permanent maxillary premolars were selected and randomly assigned into 4 groups (n = 10 each); the EXF group in which teeth were RCT and restored with a fiber-reinforced bulk-fill flowable composite (Ever-X flow) and covered with a nanofilled resin composite (Filtek Z 350), the RBF group in which teeth restored with polyethelene fibers (Ribbond) with a bulk-fill flowable composite (Filtek bulk-fill flow) covered with the same nanofilled composite, the FBF group in which teeth restored with a bulk-fill flowable composite without fiber reinforcement (Filtek bulk-fill flow) also covered with the same nanofilled composite and the control group in which teeth remained intact without any preparation. All teeth were subjected to a thermo-mechanical cycling after which a static fracture test was performed using the universal testing machine to record the load at failure. Results:The significantly higher mean value of fracture resistance was recorded in the control group than other experimental groups (P < .05). The EXF group showed the highest and followed by RBF group, and the lowest mean value was found in FBF group (P < .05). Conclusion:Within the limitation of the present study, either short fiber-reinforced composite and polyethylene fiber-reinforced composite may have superior resistance to fracture and could reinforce RCT teeth compared to nanofilled composite without fiber reinforcement.

Aim: To evaluate the efficacy of different kinematics in removal of root canal filling materials.Methodology: A total of 60 human freshly extracted mature permanent maxillary central incisors were selected. Access cavities were prepared and the teeth were cleaned and shaped then obturated. Teeth were randomly divided into three groups according to removal technique (manual H-file, ProTaper NEXT file and Reciproc file), then split longitudinally and photographed. The images were transferred to a computer, and total canal space and the remaining filling material were quantified. The ratio of the remaining filling material to the total root canal space was computed with the aid of AutoCAD software. The mean percentages of the remaining filling material and removal time were analysed using the Kruskal-Wallis, Friedman's test and one-way ANOVA test. Results:The mean percentage of the remaining filling material was significantly higher in group I than both II and III, While there is no statistically significant difference between group II and III. Regarding comparison between the root levels, the apical level showed the statistically significantly highest mean percentage of remaining endodontic filling material, followed by the middle and the coronal levels. The time required to remove filling material was significantly shorter in group III followed by II and I. Conclusion:Total elimination of root canal filling is a challenge especially in the apical part. No statistically significant difference was found between the two kinematics regarding the efficiency in removing obturation materials, while reciprocation was faster than rotation in removal time.

Objective To evaluate the success rate of retrieving separated instrument, the root canal volume changes using cone-beam computed tomography and the retrieval time using Ruddle's technique, Terauchi file retrieval kit (TFRK) and Endo Rescue kit. Methods Sixty human mandibular first molars were selected, and a 4-mm portion of #25/.04 rotary files were separated in the middle third of moderately curved mesio-buccal canals. Teeth were randomly assigned into three groups (n=20): R group, in which separated files were retrieved according to Ruddle's technique; T group, in which separated files were retrieved using TFRK and E group, in which separated files were retrieved using Endo Rescue kit. Values were analyzed using IBM SPSS. Results presented as mean±standard deviation and 95% confidence interval for the root canal volume and time and frequency (%) for success rate. Comparisons of differences in time, canal volume and success rate between groups were assessed. Results Retrieval was successful in R and T groups (70% and 80% respectively) without any significant difference between them (p=0.715), while E group hadn’t any successful samples (0.0%) with significant difference compared to R and T groups (p<0.001, p<0.001). E group showed the highest increase in canal volume followed by R group, while T group exhibited the lowest increase in canal volume. There was no significant difference in the mean retrieval time between R and T groups (p=0.815). Conclusion TFRK provides a more conservative way for retrieval of separated instrument from the middle third of moderately curved canals.

Root canal preparation is one of the most important steps in endodontic treatment (1,2) . An old endodontist saying, "What is removed from the root canal may be more important than what is placed inside it" (3) . Although many advancements have been madein endodontics in the last years, the complicated root canal anatomy still adversely affects root canal preparation (4) . The apical third is the most difficult to be cleaned and shaped because of the ever-increasing complexity of the anatomy (5) .