Introduction: Different techniques have been proposed to help achieving apical patency during endodontic treatment and Retreatment. The objective of this in vitro study was to compare reestablishment of apical patency in teeth previously subjected to root canal treatment using manual and reciprocating instruments. Methods and Materials: A total of 40 single-rooted extracted human mandibular incisors were selected and prepared using the Hero 642 sequence to 45/0. 02 and obturated using Tagger’ s hybrid technique to 1 mm short of the apex. Teeth were divided into two groups according to the type of instrument used to regain patency: group 1, hand K-files and group 2, reciprocating WaveOne Primary files (25/0. 08). Fisher’ s exact test was used in the statistical analysis. Result: In group1, apical patency was regained in 9 of the 20 teeth tested (46%), compared to 20 teeth (100%) in group 2. The difference between the groups was significant (P<0. 0001). Conclusion: Our study shows that reciprocating instrumentation is more successful in regaining apical patency in single-rooted, previously treated teeth.

Introduction: Advantages of endodontic treatments over tooth extraction have increased the demands for these treatments. Success rate of these treatments is generally lower than the primary root canal therapies. Recently, single visit treatments have gained more popularity. But, the influence of completing Retreatment in a single appointment on success of the treatment is still a controversy. The aim of this study was evaluating the most common causes offailures and determining the success rate of completing Retreatments in single appointment.Materials and Methods: Hundred and twenty four patients who had single appointment Retreatment within past 4 years in postgraduate ward of Shaheed Beheshti Dental School were selected and clinical and radiographic examinations were carried out. The data were analyzed by SPSS using Chi-square and Exact Fisher tests.Results: Success rate and uncertain cases were shown to be 50.7% and 34.2%, respectively and failure rate was 15.1 %. Presence of periradicular lesion or history Of swelling prior to Retreatment had significant effect on the success of single visit retreatrnents (p<0.001). Another important finding of the study was that the success rate of Retreatments was significantly higher in cases, referred for restorative purposes compared with retreatrnents for nonrestorative purposes (p<0.001).Conclusion: The overall success rate of single appointment Retreatments is up to 84.9% which is considerably higher in cases referred for restorative purposes. So based on the results of this study single appointment Retreatment of symptom less teeth is recommended.

Introduction: The aim of the present ex vivo research was to compare the remaining filling material and the volumes of dentine removed after Retreatment of curved canals with two rotary systems naming ProTaper Universal Retreatment and Mani NRT-GPR using micro-computed tomography (micro-CT). Methods and Material: Forty mandibular molars containing two completely separated canals, with curvature angle of 25-35° and a curvature radius <10 mm were prepared to the Mtwo instrument 35/0. 04 and filled with warm gutta-percha and AH-Plus sealer. The teeth were randomly divided into 2 groups (n=20), according to the Retreatment system evaluated: ProTaper Universal Retreatment (PR group) or Mani NRT-GPR (MR group). Retreatment was considered complete when the working length was reached and when smooth dentinal walls were observed, with no evidence of filling material adhered to instruments or in the irrigating solution. Preoperative and postoperative micro-CT images were obtained with an isotropic voxel size of 11. 88 μ m to observe the volume of residual filling material in the canals and dentine removed after Retreatment. Statistical analysis was performed by Student’ s t-test (P<0. 05). Results: The mean percentage of remaining filling material was 12. 96% for PR group and 24. 26% for MR group (P=0. 0056). The percentage of dentin removal was greater in the PR group (5. 02%) than MR group (1. 36%) (P=0. 0028). Both systems failed to completely remove the filling material from the canals. Conclusion: ProTaper Universal Retreatment system was more effective than Mani NRT-GPR system regarding removal of root filling material and also removed significantly more dentine after Retreatment of curved mesial root canals of mandibular molars.

Introduction: Pharmacotherapy with analgesics and non-steroidal anti- inflammatory drugs has been traditionally used to relief post- operative pain of endodontic treatments. However, due to the side effects reported for these drugs, some efforts have been made to decrease the post- operative pain of the endodontic treatments through laser irradiation. The present study aimed to evaluate the effects of low level laser therapy (LLLT) on the reduction of pain after root canal Retreatment.Methods: In this clinical trial, 61 patients requiring endodontic Retreatments in posterior teeth were selected. A single visit endodontic Retreatment was performed. After biomechanical preparation, low level laser was irradiated to the buccal and lingual mucosa overlying the apices of the target tooth in the experimental group. In the control group patients received placebo laser to eliminate the probable psychological effects of laser. Laser irradiation was done with a single dose of 808 nm wavelength (Whitening Lase II- Laser DMC, Samsung, Korea) with 100 mW power, and dose of 70 J/cm2 for 80 seconds. Pain severity was recorded before, immediately after and 4, 8, 12, 24 and 48 hours after the treatment by visual analogue scale (VAS). The pain scores were statistically analyzed by chi- square test between 2 groups. The effects of different variables on the post-operative pain experience were also studied by means of Logistic regression. Results: Pain scores decreased significantly through time until 48 hours after treatment. No significant differences were observed between the 2 modalities regarding pain scores at any time. According to regression analysis, pain severity scores were lower in the laser-irradiated specimens than control groups (OR=5.69); however, this difference was not statistically significant. Consumption of analgesics after the treatment had significant effect in decreasing post-operative pain experience (OR=56) while factors of age, gender, laser irradiation, pre- treatment pain scores and education level did not.Conclusion: Low level laser irradiation had limited effects to decrease pain associated with the endodontic Retreatments in the first and second molars; however, more studies are required to assess the effects of different parameters of low level laser in this regard.

Mandibular premolars have earned a reputation for having aberrant anatomy. The occurrence of three canals with three separate foramina in mandibular premolars is very rare. If predictable treatment of a three rooted mandibular premolar is planned, precise knowledge of clinical and radiographic anatomy is absolutely necessary. These teeth may also require special shaping and obturating techniques. This article reports and discusses the treatment recommendations for an unusual occurrence of three canals with three separate foramina in a second mandibular premolar.