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Introduction: In the present study a method to investigate light and radiation field congruence utilizing an amorphous silicon electronic portal imaging device (EPID) was developed. An alternative method for routine dynamic multi-leaf collimator (DMLC) quality assurance (QA) using EPID was also described. Materials and Methods: This study employed an amorphous silicon (aSi) EPID, the associated EPI software and a diamond-shaped template. The collimator jaws of the linac (Elekta iViewGT) were aligned such that the light field fell directly on the corners of the diamond. A radiation detection algorithm within the EPI software determined the extent of the radiation field. The light and radiation field congruence was evaluated by comparing the vertices of the diamond reference structure to the detected radiation field. In addition, the digital jaw settings were recorded and later compared to the light field detected on Kodak x-omat films and EPIs. In this study an alternative method for routine dynamic multi-leaf collimator (DMLC) quality assurance (QA) using (EPID) was described. This QA was done by producing a pattern of five 0.5-cm bands 5-cm apart and performing a visual spot-check for dose peak location, dose peak values, interband distance and band gaps measured at Full Width at Half-Maximum (FWHM) of the test pattern for this QA experiment. An aSi EPID and films are used for the DMLC QA to test the practicality and efficacy of EPID vis film. Results: Light radiation field congruence tests with films and EPIs were comparable, yielding a difference of less than 1.2 mm, well within the allowed 2-mm tolerance. A disparity was observed in the magnitude of the detected light field. The X and Y dimensions of the light field measured with film differed by less than or equal to 1.6 mm from the digital collimator settings, whereas the values extracted from the EPIs differed by up to 1.8 mm. The FWHM of the multi-leaf collimator (MLC) obtained by the EPID is 6.34 mm, which is slightly higher than the 6.18 mm for the film. The lowest dose at the valley is significantly lower for the EPID than for the film. The dose peak value of the EPID is found to be 97.9 with standard deviation of ±1.59 and the dose peak value of film is found to be 96.5 with standard deviation of ±2.41, respectively. Film and EPID track the distance between peaks with a mean of 49.8 and 49.53 mm and standard deviation of ±0.3 and ±1.02 mm, respectively. EPID is able to track the location of individual dose peaks for all the leaf pairs consistently to a standard deviation of ±0.12 to ±0.47 mm, slightly better than that of ±1.00 to ±1.26 mm for the film. Conclusion: EPIs were found to be a quick and reliable alternative to film for qualitative and relative analyses. Also EPID is as good as the film in resolving the band pattern of the DMLC test field. Although the resolution of the EPID is lower than that of the film, it is high enough to faithfully reproduce the band pattern without significant distortion. Since EPID images can be acquired, analyzed an...

Objective: The objective of this study was to evaluate, in vitro, the influence of two concentrations of carbamide peroxide bleaching agents with and without topical desensitizing gels on enamel microhardness, roughness, and shear bond strength to orthodontic metal brackets. Methods: One hundred and sixty-eight (168) human extracted premolars for orthodontic purpose were obtained and randomly divided into seven groups (n =24): Group 1, control group (Neither bleaching nor desensitizing); Group 2, bleached with 22% carbamide peroxide; Group 3, bleached with 22% carbamide peroxide followed by Minerals desensitizing gel; Group 4, bleached with 22% carbamide peroxide followed by ''D.M. Sense'' desensitizing gel; Group 5, bleached with 35% carbamide peroxide; Group 6, bleached with 35% carbamide peroxide followed by Minerals desensitizing gel; Group 7, bleached with 35% carbamide peroxide followed by ''D.M. Sense'' desensitizing gel. Microhardness test and roughness measurements were carried on specimens immediately after finishing of treatment, using Vickers Diamond Microhardness Tester and Roughness Analyzer respectively. Only specimens for brackets shear bond strength (SBS) were stored for 7 days in distilled water after treatments and before testing. Shear bond strength were tested using Instron Universal Testing Machine Results: Statistical significant differences were found between groups. Groups that received bleaching treatments only, showed greater deterioration in all tested properties than, groups received desensitizing treatments after bleaching treatment. Conclusion: Application of desensitizing agent after in-home bleaching is highly recommended to minimize deleterious effects of bleaching agents.

Maxillary canines are the most commonly impacted teeth, second only to third molars. Maxillary canine impaction occurs in approximately 2% of the population and is twice as common in females as in males. Approximately one-third of impacted maxillary canines are located labially and two-thirds are located palatally. Lateral incisor demonstrates an important role in the etiology of palatally impacted canines. So, the objective of this study is to compare the difference in the shape of lateral incisor (crown-to-root angulation) adjacent to palatally and labially impacted canine using conventional 2D and 3D radiographs. Sample of this study consisted of 60 patients (32 females and 28 males) with a mean age of 13.94 years. For each subject, two sets of radiographs (panoramic and CBCT scan) had been obtained. These patients were divided into 2 groups: The first group consisted of 35 patients with palatally impacted maxillary canines; the second group consisted of 25 patients with labially impacted maxillary canines. The control group (third group) consisted of normally erupted maxillary canines (25 subjects). Crown to root angulations of lateral incisors were measured. t test for independent samples was used to assess the crown-root angulation of lateral incisors. The results revealed that There was

Objective: The present study aimed to evaluate nasal septal deviation and palatal vault depth in subjects with unilaterally buccally and palatally impacted canine using cone beam computed tomography (CBCT). Subjects and Methods: CBCT scans of 60 subjects were divided into 3 groups of 20 each, control group (no impaction), labial group (group with unilaterally labially maxillary impacted canine) and palatal group (group with unilaterally palatally maxillary impacted canine). Palatal depth and nasal septum deviation were measured and compared among the studied groups. Results: Deviated nasal septum was found in 10% of control group, 60% in palatally impacted maxillary canine group and the highest ratio (80%) was found in labially impacted maxillary canine group. Nasal septum deviation was significantly greater in the impaction groups compared with the control group, but there was no significant difference between labially and palatally impacted groups. Conclusion: maxillary canine impaction can be expected when nasal septum is deviated