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 & Aims: The aim of this study was to evaluate the accuracy of Cone-BEAM Computerized Tomography (CBCT) linear measurements in dry mandibles by comparing them with direct measurements.Methods: Two human dry mandibles were used in this study. Thirteen sites were selected on each mandible. Specimens were scanned by CBCT and linear measurements were made using Planmeca Romexis 2.3.0.R software. Mandibles were cut into sections at marked locations and the same distances were measured by a digital caliper. Differences between two methods were assessed using paired t- test.Results: The mean differences for bone height, bone width and the crest-canal distance between CBCT and digital caliper measurements were -0.47±1 mm, -0.14±0.78 mm and 0.00±0.76 mm respectively. The differences were only, significant for bone height measurements (P<0.05). There was a high carreltion between the result of CBCT and gold standard.Conclusion: The results of this in-vitro study on mandible indicate that, although there is a statistically significant difference for bone height measurements between the two methods, the difference is not significant in clinical applications. Thus, CBCT was shown to be a useful technique for preoperative dental implant planning.

In this paper, an alternative approach in operational modal analysis is presented, utilizing image processing technique and transmissibility functions. Imaging sensors do not impose additional mass on the structure due to their non-contact nature, while transmissibility functions, independent of excitation type, can directly extract mode shapes. The innovation of this research lies in combining these two techniques to record dynamic responses and identify modal properties. To capture the temporal response history from video signals, the block-matching method with sub-pixel accuracy was employed. Validation was conducted by recording the response of the tip of a cantilevered steel BEAM subjected to impact excitation, using a high-speed camera and a laser vibrometer, simultaneously. The RMSE plots in the time domain and the PSD in the frequency domain indicate high accuracy of this method. Using this approach, the displacement time histories of various points on the structure were extracted from the video signals, and the modal properties, including natural frequencies, damping ratios, and mode shapes, were identified using the transmissibility matrix method. The results obtained from the proposed method were compared with the stochastic subspace identification (SSI) method and analytical solutions. The findings reveal the accuracy of the modal identification approach introduced in this article. The highest relative error in estimating the natural frequencies of the first and second modes, compared to the values from the laser method, are 0.19% and 0.13%, respectively, and in comparison to the analytical values, they are 0.34% and 1.5%, respectively.

Vibration analysis of vessels conveying blood flow embedded in viscous fluid is studied based on the modified strain gradient theory. The viscoelastic vessels are simulated as a non-classical EulerBernoulli BEAM theory. Employing Hamilton’ s principle, the governing equations for size-dependent vessels are derived. The Galerkin method is used in order to transform the resulting equations into general eigenvalue equations. The effects of the blood flow profile and its modification factors, red blood cells (RBCs) and hematocrit are considered in the blood flow. Besides, the influences of the constitutional material gradient scale, blood flow, internal pressure, structural damping coefficient, viscous fluid substrate and various boundary conditions on the natural frequencies and critical buckling velocities are studied. It is revealed that as the hematocrit, fluid viscosity of substrate, internal pressure and mass ratio increase, the natural frequencies and critical buckling velocities decrease. Furthermore, the results indicated that the strain gradient theory predicts the highest natural frequencies and critical buckling velocities among others. The results are compared with those available in the literature and good agreement has been observed.

Background and purpose: BEAM shaper is a type of applicator used in conjunction with the intraoperative electron radiotherapy. This study aimed at quantitative evaluation of the photon contamination of this applicator using Monte Carlo simulation.Materials and methods: In this experimental study, at first the head of LIAC accelerator was simulated along with the BEAM shaper applicator using MCNPX Monte Carlo code. Validity of the simulated model was evaluated by comparing the percentage depth dose curves obtained by Monte Carlo simulation and practical dosimetry. Finally, the photon contamination at different clinical field sizes and electron energies was quantitatively determined.Results: The results showed that by increase in field size, the photon contamination of the BEAM shaper applicator was considerably decreased. Furthermore, increment of electron energy could increase the photon contamination.Conclusion: Increasing the photon contamination at the phantom surface by increment of electron energy and decrement of field size can be attributed to increasing the probability of electron interaction with the steel blades of the BEAM shaper and production of bremsstrahlung radiation at higher energies. Due to the photon contamination, employing the BEAM shaper applicator can increase the surface dose.

Background and Aim: BEAM shaper applicator is one of the dedicated applicators for intraoperative electron radiotherapy which is usually employed for large tumors irradiation. Due to the high weight and lack of possibility of direct placement on the patient’ s body, a considerable air gap exists between the applicator and patient. Therefore, determination of the effective position of electron source (SSDeff) is absolutely necessary to correct the applicator output for air gap effect and accurate delivery of the prescribed dose to the patient. The aim of this study was to determine the SSDeff for all square fields of BEAM shaper applicator at different electron energies using Monte Carlo (MC) simulation. Materials and Methods: At first, the head of LIAC accelerator and BEAM shaper applicator were simulated by MCNPX MC code and then, the validity of the simulated model was evaluated through comparing the calculated percentage depth dose (PDD) curves at different field sizes and energies with the corresponding practiacal values. After verifying the simulated model, the SSDeff was determined for different field sizes and electron energies using inverse square law (ISL) method. Results: The results showed that the SSDeff is a function of electron energy and radiation field size. Dependency of SSDeff on field size variations was much more than that on the alterations in the electron energy. Generally, increase in the field size or electron energy led to increase in SSDeff. Conclusion: The determined SSDeff values for the electron BEAM of the BEAM shaper applicator in our study, can be used to correct the electron BEAM output for clinical purposes.

Introduction: The inferior alveolar canal is an important anatomical structure in the field of dentistry implants and cone BEAM computed tomography (CBCT) is an important diagnostic technique. The aim of this study was to evaluate the prevalence of anatomical variations of the mandibular canal observed in CBCT images. Materials & Methods: In this descriptive-analytic study 384 inferior alveolar canals were evaluated in 192 patients, who were referred to the radiology department of Isfahan Azad University in 1396 for a cone-BEAM computed tomography. Radiographs were performed to assess the frequency of different left and right mandibular canal segregations by sex in terms of upper and lower position, baccolingual position, shape of the general canal. The frequency and different types of existing mandibular plug canals were also evaluated. Data were analyzed by Chi Square, independent T Test, paired t-test. (p value < 0. 05). Results: The mandibular canal was 2. 1% of the lower position, 11. 9% of the upper position and 86% of the middle position. Statistically significant differences were observed between the frequency distributions of canal positions and gender (p value = 0. 004). The prevalence of Bifid mandibular canals was 14. 8%. There was no significant relationship between the shape of the general channel path and gender. There was no significant difference between the mean distance between the mandibular canal and the buccal cortex in both Molar and Ramus with the sex of the subjects and the side of the canal (p value < 0. 05). Conclusion: The highest frequency of mandibular canal in most subjects was on the right in the intermediate position. The mean distance between mandibular canal and buccal cortex in Ramos and Molars area on both right and left sides was not significantly different between men and women.

Introduction & Objective: The mental foramen is a part of lower jaw which has neurovascular bundles and also is important in biology. 3D imaging of this area by cone BEAM computed tomography (CBCT) before surgery can prevent some problems. This study aims to evaluate the anatomic position and geometrical shape of the mental foramen by CBCT images.Materials & Methods: In this research, the CBCT images (by NewTom and Planmeca promax 3D set) of 85 patients referred to dentistry school clinic or other clinics in Hamadan city were studied. These patients did not have their first and second premolar teeth extracted in both right and left sides. The geometrical shape of mental foramen, the canal angle connecting to mental foramen compared to the buccal plate of lower jaw, distance from the lower border of mental foramen to the lower border of lower jaw, position of mental foramen relating to the root of adjacent tooth and the incidence of accessory mental foramen were studied.Results: The means of canal angle connecting to mental foramen in the right side in men and women were 123.3 and 130.1 and in the left side were 123.8 and 133.7, respectively. The mean distance from the lower border of mental foramen to the lower border of lower jaw in the right side in men and women were: 12.4 and 13.3 mm and in the left side were: 12.7 and 13.6 mm, respectively. Also, there is a meaningful statistical relation between gender and the angle of canal of mental foramen, regarding to the buccal plate in both sides.Conclusion: Regarding to the variations in the position and shape of mental foramen and the angle connecting to the mental foramen related to the buccal plate and accessory mental foramen, investigation of CBCT images before placement of implants is necessary.