Introduction: This study evaluated the removal of the filling material during endodontic retreatment considering the presence of cracks and the dentin age. Methods and Materials: A total of 20 freshly extracted single-rooted teeth were categorized into the following two groups according to the age of the patients: Group Young (Y; aged 18-30 years) and Group Old (O; aged )60 years). Each tooth specimen was scanned by microcomputed tomography (micro-CT) subsequently after endodontic retreatment with the Reciproc instruments (REC). The images were analyzed for differences in the volume of dentin cracks and the presence of the filling material in the middle and apical thirds of the teeth among the groups, according to the dentin age. Results: The micro-CT images showed that after retreatment, there were more cracks in the old root dentin than those in the young root dentin, although the difference was not statistically significant (P>0. 05). The greatest reduction in the filling material was achieved when the old root dentin with cracks was retreated when compared with that of the young root dentin with cracks, but the difference was not statistically significant (P>0. 05). Conclusion: The dentinal age and the presence of cracks were not found to be relevant factors for the removal of the filling material.

Background: Multislice computed tomography (CT) angiography is a robust imaging method for noninvasive assessment of coronary artery diseases، which is associated with high radiation dose. Having knowledge of the various parameters used to estimate the dose plays an important role in increasing the understanding of dose delivered to patients and help operators and technologist to reduce the dose. In this research، the amounts of Weighted Computed Tomography Dose Index (CTDIW) for coronary CT angiography exams were measured in Isfahan city, IranMethods: To calculate the dose، an ionization chamber (Piranha، X-ray Analyzer، RTI Electronics and Sweden) and acrylic body phantom were used. Common conditions of coronary CT angiography used in two centers were applied for this project. Finally, CTDIW of all the scans were calculated using the related formulation.Findings: The amount of mean CTDIW for calcium score exams in Sina and Alzahra hospitals were 0.468±0.190 and 2.354±0.610 mGy, respectively (P = 0.007); and for coronary CT angiography scans in Sina and Alzahra hospitals were 6.221±1.290 and 5.299±0.840 mGy, respectively (P=0.860).Conclusion: CTDIW for the calcium score was significantly different in the two centers، but there was not significant difference in the two centers for coronary CT angiography scans. In this study، the amount of CTDIW was much lower than the measured in other centers. Since scan parameters have an important effect on the dose value، training and precision of technologist result in dose reduction and patient radiation protection.

Background and Objective: The aim of this study was to evaluate the diagnostic ability of CBCT to detect external root resorption.Subjects and Methods: External root resorption defects of different sizes and in different locations were simulated in 60 human mandibular incisors. Cavities simulating root resorption defects of small size (0.3´0.6 mm), medium (1.2´0.6 mm) and large (1.8´0.9 mm) were drilled in the cervical, medial and apical thirds of buccal surfaces. The teeth were divided in random groups and mounted in the mixture of acryle and dryed skull sheep powder. CBCT scan was used to evaluate external root resorption in 180 root thirds by two blinded observer. Statistical analysis was done with Kappa test.Results: Sensitivity of CBCT to detect external root resorption was 89% and the specificity was 99 %.The most defects that was detected were on the medial root thirds and the lowest defects that were detected were on the apical root. The percentage of small defects detection was 80%.Conclusion: CBCT technique is a very good method to evaluate external root resorption with high sensitivity and excellent specificity. It can detect the defects as small as 0.3mm.

Background: Paranasal sinus disease is one of the most common problems of patients that refer to ENT centers. Adding to clinical examination, imaging plays an important role in diagnosis and treatment. Also the imaging of paranasal sinuses is necessary before surgery. Although computed tomography is the modality of choice for these areas, it has some disadvantages which the most important one is its high patient's dose. The aim of this study is the comparison between cone beam volumetric tomography and conventional computed tomography computed tomography, in evaluation of these areas.Methods: In this descriptive-analytic study Coronal computed tomography imaged and cone beam volumetric tomography images were performed for40 patients referred to ENT department of Amir Aelam Hospital in Tehran, Iran. Computed tomography images were observed by general radiologist and cone beam volumetric tomography images by Maxillofacial radiologist and their results' were recorded. Also ENT surgeon recorded her observations during surgery. Data were analyzed using Mc Nemar test with Kappa and weighted Kappa agreement coefficient.Results: No statistical difference was shown between the efficacy of computed tomography and cone beam volumetric tomography in evaluation of paranasal sinuses (p>0.05).Conclusion: As there was not any difference between conventional computed tomography and cone beam volumetric tomography in the assessment of paranasal sinuses and additional advantages of the later, cone beam volumetric tomography is suggested for paranasal sinus imaging before surgery.

Background and Aim: For certain surgical procedures (e.g. placement of implants), an accurate localization of the mandibular canal is of utmost importance to avoid injuries to the neurovascular bundle. The aim of the present study was to evaluate, the accuracy of spiral tomography for the localization of the mandibular canal.Material and Methods: By means of the cranex tome multifunctional unit (orion corporation Sordex, Finland), tomographic slices were taken at 4 different locations in each posterior mandible segments (distal to the mental foramen). The mandibles were then sectioned at these 4 sites with a specialize designed drill. The following 4 measurements were preformed both on the tomograms (A, B, C and D) and the bone sections (A’, B’, C’ and D’) at the 4 sites.Results: We found an average mean difference of 0.02 mm with a standard deviation of 0.33 mm. The reported data showed that %95.2 of cases are in ±0.5 mm and %98.4 of cases are in ±1 mm (overestimate and underestimate).Conclusion: Spiral tomography using the cranex tome multifunctional x-ray unit provides accurate information and sufficient detail for preoperative planning of implant in the posterior mandible.