The Effect of Bite Registration on the Reproducibility of Parallel Periapical Radiographs Obtained with Two Month Intervals

Statement of Problem: Digital Subtraction Radiography (DSR) needs reproducible alignment between the x-ray source, the object, and the film for obtaining identical projections of the same anatomic region.Purpose: The aim of this study was to evaluate the effect of bite registrations (placed on individual bite blocks) on the reproducibility of parallel periapical radiographs,obtained every 2 months, in patients undergoing periodontal surgery for furcationinvolvement.Materials and Methods: Ninety eight parallel periapical radiographs were used in this study. The radiographs were taken with individual bite-blocks attached to the beamguiding device. In order to individualize the bite blocks, bite registrations were fabricated using silicon impression material, and were placed on the individual bite blocks. All radiographs in each series were processed under similar conditions and were digitized with the flatbed scanner fitted with a transparency adaptor (hp Scanjet 7400) at 300 dpi resolution. Reproducibility of this method for obtaining similar parallel periapical radiographs was assessed by measuring the horizontal and vertical distances between two selected unchanged reference points on each radiograph and comparing them in each series. Reliability of measurements was analyzed using the one wayrandom model intraclass correlation coefficient for average of raters.Results: For both measurements (Horizontal and Vertical) statistically significant reliability was found between three repeated radiographs with two month intervals in 16 patients, as well as 5 repeated radiographs with two month intervals in 10 patients (P<0.001).Conclusion: The result of this study shows that bite registration on individual bite blocks is enough for obtaining identical parallel periapical radiographs

A Comparison of the Effectiveness of Chloroform in Dissolving Dissolving Resilon and Gutta-Percha

Objective: Application of chemical solvents especially in roblematic canals is usually a part of the retreatment process.This study was performed to compare the solubility of Gutta-Percha and Resilon in chloroform and to find the effect of sample thickness as well asthe time of shaking on their solubility.Materials and Methods: Specific weight of Resilon and gutta-percha was placed in a sample tube and after adding 1.0 ml of chloroform at 37ºC, the tubes were capped and shaked for 1, 3 and 5 minutes. The amount of non dissolved material was determined by reweighting of each sample and the percent of solubility was assessed according to the exact weight loss of the samples. The procedure was repeated three times for a given thickness and time of shaking. The difference in the solubility of Gutta-Percha and Resilon aswell as the effect of sample thickness and time of shaking on solubility were assessed by repeated measurement ANOVA (p<0.05).Results: Resilon has significantly higher solubility than Gutta-Percha in chloroform (p<0.05). Resilon as well as Gutta-Percha Solubility are increased significantly over the time .The amount of solubility is not affected by sample thickness.Conclusion: Comparison of Resilon and Gutta-Percha solubility in chloroform shows that one of the advantages for Resilon could be the chance for using possible safer organic solvents during retreatment

Efficacy of Panoramic Mandibular Index in Diagnosing Osteoporosis in Women

Objective: In this study, the usefulness of Panoramic Mandibular Index (PMI) on panoramic radiographs in diagnosis of osteoporosis was evaluated and its correlation with bone mineral density (BMD) of the neck of femur and spine was determined.Materials and Methods: In this cross-sectional study, 140 patients (all females) were categorized as either normal, osteopenic or osteoporotic according to the WHO classification in relation to their spinal and femoral BMD determined by dual energy X-ray absorptiometry.Regarding menstruation, they were also divided into menopausal, nonmenopausal,or oophorectomized groups. Panoramic radiographs were taken from all the women in the study. PMI was calculated. The data were analyzed using Kruskal-Wallis,Mann-Whitney, and Pearson tests.Results: Specificity and sensitivity of PMI in differentiating normal and osteopenic/osteoporotic cases were 88% and 44%, respectively. The mean PMI of nonmenopausal women was significantly different from those of menopausal and oophorectomized ones. There was a weak correlation between PMI and spinal BMD (r=0.23,P<0.05) and a moderate negative one between age and mean PMI (r=-0.45, P<0.0001).Conclusion: Dental panoramic radiographs can be used in clinical practice to assist identifying individuals with low bone mass