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"nBackground and Aims: Accurate bone measurements are essential for determining the optimal size and length of proposed implants. The radiologist should be aware of the head position effects on image dimensions in each imaging technique. The purpose of this study was to evaluate the effect of mandibular plane angle on image dimensions in linear tomography."nMaterials and Methods: In this in vitro study, the vertical dimensions of linear tomograms taken from 3 dry mandibles in different posteroantenior or mediolateral tilts were compared with actual condition. In order to evaluate the effects of head position in linear tomography, 16 series of images while mandibular plane angle was tilted with 5, 10, 15 and 20 degrees in anterior, posterior, medial, or lateral angulations as well as a series of standard images without any tilt in mandibular position were taken. Vertical distances between the alveolar crest and the superior border of the inferior alveolar canal were measured in posterior mandible and the vertical distances between the alveolar crest and inferior rim were measured in anterior mandible in 12 sites of tomograms. Each bone was then sectioned through the places marked with a radiopaque object. The radiographic values were compared with the real conditions. Repeat measure ANOVA was used to analyze the data."nResults: The findings of this study showed that there was significant statistical difference between standard position and 15º posteroanterior tilt (P

"nBackground and Aim: Accurate bone measurements are essential to determine the optimal size and length of dental implants. The magnification factor of radiographic images may vary with the imaging technique used. The purpose of this study was to compare the accuracy of linear tomography and panoramic radiography in vertical measurements, as well as the accuracy of linear tomography in mandibular width estimation. "nMaterials and Methods: In this test evaluation study, the vertical distances between the crest and the superior border of the inferior alveolar canal, marked with a metal ball, was measured by linear tomography and panoramic radiography in 23 sites of four dry mandible bones. Also the mandibular width was measured at the same sites. Then, the bones were sectioned through the marked spots and the radiographic measurements were compared with actual values. "nResults: The vertical magnification factor in tomograms and panoramic radiographs was 1.79 (SD=0.17) and 1.69 (SD=0.23), respectively. The horizontal magnification of tomograms was 1.47 (SD=0.17). A significant correlation was found between the linear tomographic and actual values, regarding vertical dimensions (p

Statement of Problem: One of the major goals, in most dental researches, is to measure bone destruction or deposition due to the progression or regression of disease. Failure of human eyes to detect minor radiographic density changes resulted in more accurate methods such as optical densitometry and direct or indirect digital densitometry."nPurpose: The aim of this study was to determine the accuracy of a newly proposed method of indirect digital densitometry using modified Photoshop software."nMaterials and Methods: Radiographs from 37 samples of urografin solution with three concentrations (12.5%, 25% and 37.5%) were taken on dental radiographic films no.2 and digitized by a scanner. A region with 800*800 pixels was cropped from each image and compressed with the Joint Photographic Experts Group (JPEG) compression algorithm and saved. These new images were then put into registration with new algorithm using MATLAB software version 6.1. This algorithm assigned each image and average pixel value (between 0 and 255). The association between concentration and calculated values for each image was tested with regression analysis and the meaning fullness of differences between calculated values was also analysis by ANOVA test. Tukey HSD and Alpha Krunbach were used whenever needs."nResults: Regression analysis revealed significant correlation between concentration and calculated average pixel value (r=0.883). The differences between average of pixels value for different concentration was significant (P=0.0001). Pixel values showed a good intra- sample and intra-group repeatability (Alpha Krunbach: a=99.96%, a=99.68%)."nConclusion: This method due to its high accuracy, easy usage and densitometer independency can be considered as a suitable alternative for conventional densitometry methods.

Statement of Problem: Computer Sciences, in radiology, like other fields, is of high importance. It should"nalso be noted that the accuracy of the technique and work conditions affects the radiographs information"nconsiderably. There for, in order to get more accurate diagnostic information, it seems necessary to investigate"ndifferent digitized radiographic techniques and to compare them with the conventional technique."nPurpose: The aim of this study was to compare the accuracy of conventional and digitized radiographic"nimages by three digitization techniques in proximal caries detection."nMaterial and Methods: In this research study, sixty extracted human canines, premolars and molars were"nmounted in blocks and imaged on E-Kodak film, similar to bitewing radiographs. Ten bitewing radiographs"nwere then scanned at 600 d.p.i with flat bed scanner and a digital camera, then digitized at 300 d.p.i with"nanother digital camera. The digitized images were displayed randomly on a high-resolution monitor. Six"nobservers assessed the caries status of 120 proximal surfaces by conventional and digitized images. The"nobserver's scores were compared with the results of the macroscopic examination. Reliability of each"ntechnique was calculated. Data were analyzed using chi-square and ANOVA tests."nResults: No significant differences were detected between different techniques in intact proximal surfaces and"nenamel caries diagnosis. However, digital techniques were more sensitive in dentin caries detection (P

Background and purpose. Coronavirus (COVID-19) is a contagious disease causing severe acute respiratory syndrome which had a catastrophic effect on the world population and resulted in more than 2.9 million deaths worldwide. Epidemiological investigations have recently announced blood type has an association with the incidence of COVID-19 infection. Consequently, research in this regard can be effective in determining a person's susceptibility to a viral infection. Therefore, we investigated the relationship between blood types and the risk of COVID-19 in patients admitted to Khorshid laboratory, Tehran, Iran. Materials and methods. From January to March 2020, 50 nasal and throat swapb samples of patients' secretions were obtained from patients who were admitted to Khorshid laboratory. They were confirmed to have COVID-19 virus RNA and real-time polymerase chain reaction (PCR)-ABI, and their blood type was determined simultaneously. After collecting data to determine the relationship between COVID-19 infection and blood type, a confidence interval of 90 % was considered using SPSS 16. Results. The mean age of the patients was measured at 38.4±6.3 years. According to PCR results, 100 % of the subjects with COVID-19 showed blood type A. In addition, the ratio of blood type A to the percentage of reference type O was higher ( P =0.009). Conclusion. There was a significant relationship between ABO blood type and susceptibility to COVID-19. As the current study suggests, those with blood type A are at a higher COVID-19 infection risk than those with blood type O., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2024 The Authors.)

Background: Prediction of skeletal growth is necessary for growth modification and surgical orthodontic treatments and is usually done by assessing skeletal maturity indicators in hand-wrist radiographs. The use of growth stages of cervical vertebrae in lateral cephalograms has been suggested to avoid overexposure., Objectives: This study seeks to assess the degree of agreement between hand-wrist and cervical vertebrae maturation stages for skeletal age determination and prediction of the peak growth spurt (PGS)., Patients and Methods: This cross-sectional study was conducted with 67 boys and 66 girls between 8 and 18 years of age, divided into 11 age groups; 266 hand-wrist radiographs and lateral cephalograms were obtained and analyzed. Hand-wrist maturation stages were evaluated according to the Grave and Brown, Bjork system (stages 1 - 9). The cervical vertebral maturation stage (CVMS) was determined on lateral cephalograms based on a system described by Baccetti et al. (CVMS 1-5). To apply the Cohen's kappa index, the stages of growth were reduced to 5 intervals (A - E) to relate the 5 CVMS to the 9 stages of Bjork hand-wrist analysis., Results: In all age groups, the skeletal maturity stages of the hand and wrist bones and the cervical vertebrae of the girls were ahead of the boys. Cohen's kappa test revealed a low level of agreement between the two methods [Kappa (95% CI) = 0.312 (0.290 - 0.377)]; concordance was slightly higher in males (K = 0.33 for males versus 0.27 for females). Evaluation of concordance coefficients between the stages determined by the two methods indicated the highest concordance in 8- and 9-year-olds and the lowest in 12- and 14-year-olds. The level of agreement between the two methods was only acceptable in 8- and 9-year-olds of both genders and 10-year-old boys. The level of agreement between the two methods in other age groups was not acceptable., Conclusion: The level of agreement between the two methods was low; thus, they cannot be used alternatively to estimate patients' skeletal age or to predict the PGS. This may be due to the effect of different maturation levels (influenced by the environment, ethnicity, and gender) on the agreement between methods for skeletal age determination.

Introduction: The aim of this in vitro study was to compare the efficacy of ProTaper retreatment (ProTaper R) and Mtwo retreatment (Mtwo R) files in removing gutta-percha and GuttaFlow from endodontically treated straight root canals., Methods and Materials: The root canals of 60 human mandibular single-rooted premolars were prepared and randomly divided into two groups (n=30). In groups A and B the root canals were obturated using lateral condensation of gutta-percha plus AH 26 and GuttaFlow, respectively. The canal orifices were temporarily sealed and the roots were incubated for 3 months at 37(º)C and 100% humidity. Primary cone-beam computed tomography (CBCT) images were taken after incubation period. The specimens in each group were randomly divided into two subgroups (n=15). ProTaper R files (D1, D2, and D3) were used in groups A1 and B1 while Mtwo R files (25/0.05 and 15/0.05) were used in groups A2 and B2. The time required to extirpate the root filling was also recorded. After retreatment, another CBCT scan was taken at the same position. The volume of remaining filling materials inside the canals was calculated before and after retreatment. The data was analyzed using the two-way ANOVA and independent t-test., Results: The remaining filling materials in the canals treated with ProTaper were less than Mtwo. The remaining volume of GuttaFlow was less than gutta-percha regardless of the system applied. Mtwo R files removed root fillings faster than ProTaper R., Conclusion: ProTaper R removed filling material more efficiently compared to Mtwo R which required less time to remove root filling material.