Background:Mandibular premolars are of the most difficult teeth to treat endodontically.Aims:To compare the root canal morphology of mandibular premolars between two genders in an Iranian population.Settings and Design:Totally, 230 cone-beam computed tomography images of the mandibles belonged to 115 males and 115 females were evaluated in the three spatial planes.Materials and Methods:The total number of roots and canals in the mandibular premolars was counted, and the difference between males and females were analyzed.Statistical Analysis:Data were analyzed using Chi-square test. The significance level was set as P < 0.05.Results:The majority of mandibular first and second premolars had one root (85.7% and 94.8%, respectively) and one canal (63.9% and 78.3%, respectively). The number of roots in the mandibular first premolars had statistically significant difference between two genders (P = 0.001). There was no significant difference between two genders in the number of roots (P = 0.208) and canals (P = 0.498) in the mandibular second premolars.Conclusion:According to the results of this study, the root canal morphology in the mandibular first premolars had statistically significant difference between two genders.

Aim:To compare pH changes at the cervical, middle and apical surfaces of root dentin in retreated and non- retreated teeth, after canal obturation with two different calcium hydroxide pastes.Materials and Methods:After instrumentation of 55 extracted teeth, three cavities with 0.75 mm depth and 1.5 mm in diameter were drilled at buccal root surface. The teeth were randomly divided into five groups. Canals in the first two groups were filled with either mixture of calcium hydroxide and saline solution and calcium hydroxide and 2% chlorhexidine (CHX). In the third and fourth groups canals were first obturated with gutta-percha and AH26 sealer, and then materials were removed. After 2 days canals were filled with two different calcium hydroxide pastes similar to the first and the second groups. The pH was measured in the prepared cavities at 1, 3, 7 and 14 days.Results:In the non-retreated groups, pH at the surface of the roots was significantly higher in comparison to the retreated ones (P value < 0.001). pH values were significantly higher in the non-retreated teeth filling with calcium hydroxide and saline solution (P value < 0.001).Conclusion:Regarding to the little pH changes at the surface of dentin in retreated teeth, the hydroxyl ions cannot penetrate into the dentinal tubules. Thus, to achieve higher pH at the root surface in retreated teeth, it is clinically advisable to remove more dentin from the inner walls and to use normal saline as a vehicle for calcium hydroxide rather than acidic pH materials.

Objectives: The purpose of this in vitro study was to assess the effect of root canal preparation size and taper on the amounts of glucose penetration. Material and Methods: For conducting this experimental study, eighty mandibular premolars with single straight canals were divided randomly into 2 experimental groups of 30 samples each and 2 control groups. Using K-files and the balance force technique, canals in group 1 were prepared apically to size 25 and coronally to size 2 Peesoreamer. Group 2 were instrumented apically and coronally to size 40 and size 6 Peesoreamer, respectively. Rotary instrumentation was accomplished in group 1; using size 25 and .04 tapered and in group 2, size 35 and .06 tapered Flex Master files. Canals were then obturated by lateral compaction of cold gutta-percha. Glucose penetration through root canal fillings was measured at 1, 8, 15, 22 and 30 days. Data were recorded as mmol/L and statistically analyzed with Mann-Whitney U test (P value=. 05). Results: In comparison to group 1, group 2 showed significant glucose leakage during the experimental period (P value < .0001). Also, in each experimental group, the amount of micro-leakage was significantly increased at the end of the study. Conclusions: Under the condition of this study, the amounts of micro-leakage through root canal fillings are directly related to the size and taper of root canal preparation and reducing the preparation size may lead to less micro-leakage. Key words:Dental leakage, root canal preparation, endodontics.

Background: Recurrent Herpes labialis (RHL), as a common herpes infection in healthy persons, is treated symptomatically. Melissa officinalis has antiviral effects may affect RHL. Objectives: The current double-blind randomized study aimed to compare the clinical effect of Melissa gel and 5% acyclovir cream to treat RHL. Materials and Methods:The current study was conducted on 60 healthy students of the faculty of dentistry and dormitory residents who had experienced RHL. Participants were randomly divided into group A (treated by Melissa gel) and group B (treated by 5% acyclovir cream). The subjects used the topical drugs for seven days; they were examined on the first, second, fourth and seventh days .Clinical parameters (size of lesion, pain severity, presence of erythema and healing time) were evaluated in each visit and their changes were recorded. Results: There were no significant differences between the two groups considering the changes in the size of lesions, healing time and erythema around the lesion (except on the fourth day). Pain severity alterations among the two groups showed significant differences on the second and forth days. Conclusions: Although Melissa gel effectively reduced pain severity on the second and forth days, it was not effective to treat RHL.