Considering the annual organ dose limits, the eye lens dose limit is the main factor determining the frequency of system application.

It can be concluded that the effective shielding area is an important parameter in thyroid gland dose reduction. Lead frontal collars with large effective shielding areas (>~300 cm but not necessarily very large) are appropriate for an optimized thyroid gland dose reduction particularly for the critical patients in dental panoramic imaging. Regardless of the shape and thickness, using the Pb-equivalent shields is not justifiable in dental panoramic imaging.

Background: Gonial and Frankfurt mandibular plane angles are two of the most important measurements required for orthodontic treatment and orthognathic surgery. Currently, lateral cephalograms are used for the determination of Go and FMA angles; however, in this method, measuring individual gonial angles becomes difficult due to the superimposed images of anatomical structures in a lateral cephalogram. Objectives: The aim of the present study is to check the possible application of panoramic radiograph to determine gonial and Frankfurt mandibular plane angles. Material and Methods: A total of 90 panoramic and 90 cephalometric radiographs were obtained retrospectively from patients who attended our orthodontic clinic. The mean age of the patients was 18.9±5.9 years. Gonial and Frankfurt mandibular angles were determined on both lateral cephalograms and OPGs and the patients were divided into three groups of horizontal, normal, and vertical growers. Pearson's correlation coefficient was used for data evaluation. Results: Pearson's correlation coefficient showed that there were significant correlations between the means of Gonial and Frankfurt mandibular plane angles determined by OPG and Lateral cephalograms. (p<0.01) Conclusion: Panoramic radiograph can be reliably used to determine of gonial and Frankfurt mandibular angle and thus reduce the need for obtaining further cephalometric images from patients.

ARTICLE INFOBackground and Aim: Mental nerve injury is one of the challenges of implant surgeries in the anterior mandibular region, which leads to complications such as paresthesia of the lip and chin. The present study aimed to evaluate the prevalence of the Inferior Alveolar Nerve's (IAN) anterior loop and mandibular incisive canal by use of CBCT. Methods and Materials:In this descriptive study, 200 high resolution CBCT images of the patients referring to a private oral and maxillofacial radiology center were evaluated. The images were obtained by NewTom Giano unit and were measured in NNT viewer software. Reconstructed panoramic-like images were prepared, and upon the detection of the anterior loop, cross sectional slices were made and dimensions of the anterior loop were calculated by counting the cross sections. In addition, the maximum diameter of the incisive canal was measured, and the location of this diameter was determined on the cross sections relative to dental roots. Data were analyzed by Chi-Square test. Results: In the 200 evaluated subjects, the prevalence of the anterior loop, with the minimum length of 3mm, was estimated to be 19% and the prevalence of the incisive canal was valued to be 87.5%. No significant correlation was detected between the presence of the anterior loop and age, gender, dental status and side of the jaw. Also, no significant association was detected between the presence of the incisive canal and age, gender and dental status (p=0.597,p=0.492,p=0.643) respectively. The maximum diameter of the incisive canal was 5.3 mm which was located between the first and second premolars. Conclusion: Considering the results, it seems that evaluation and measurement of the length of the IAN's anterior loop and the diameter of the incisive nerve by CBCT are necessary steps to prevent nerve injuries during surgical procedures in the anterior mandibular region.

Introduction Formation of oronasal fistula is a common complication after surgical closure of cleft lip and palate (CLP). This study aimed to compare the maxillary sinus volume in 9-12-year-old CLP patients with and without an oronasal fistula who had undergone surgical closure of the cleft at 1 year of age, using cone-beam computed tomography (CBCT). Methodology This descriptive, cross-sectional, analytical study was conducted on CBCT scans of 50 patients with unilateral CLP who were between 9-12 years and had undergone surgical closure of the cleft at 1 year of age in two groups with and without an oronasal fistula (n=50). The patients were selected among those presenting to a private orthodontic office between 2001-2009 and already had CBCT scans taken for orthodontic treatment. The 3D CBCT scans were reconstructed with Mimics software, and the volume of the maxillary sinuses was measured on the images. Data were compared using t-test. Results The maxillary sinus volume was significantly smaller in patients with oronasal fistula compared with those without it (9510.7±492 mm3 vs. 10278.2±512 mm3, P<0.000). The maxillary sinus of the affected side was smaller than that of the unaffected side in both groups of patients with and without an oronasal fistula (P<0.05). Conclusion IImmature patients with unilateral CLP and oronasal fistula have a smaller maxillary sinus than unilateral CLP patients without an oronasal fistula, and may be at higher risk of respiratory infections.

Background and Aim: Considering the significance of the detection of proximal caries and the limited information available on the diagnostic value of digital radiography after the use of enhancement filters, this in-vitro study sought to compare the diagnostic value of digital radiography with and without the use of the edge enhancement (EE) filter in the detection of proximal enamel caries in premolars. Materials and Methods: This in-vitro study was conducted on 80 extracted intact human premolars. Every two teeth were mounted in a single block using putty impression material and every two blocks were placed in articulation. Digital bitewing radiographs were taken and saved twice, once in their original form and once after the application of the EE filter. Afterwards, a cavity was prepared on the proximal surface of one of the teeth (chosen randomly) in each block using a bur and then, the tooth was put back in the block. Digital bitewing radiographs were taken again with the same exposure settings. The 80 final images were printed on radiographic films and were evaluated by three oral and maxillofacial radiologists. The results were compared with the gold standard (the cavities formed by a bur). The data were statistically analyzed by Chi-square test. Results: The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy were 75%, 87.5%, 85.7%, 77.7% and 81.2%, respectively in the original digital radiographs and 80%, 95%, 94.1%, 82.6% and 87.5%, respectively in the enhanced images. The difference between the two groups was not statistically significant (P=0.7, P=0.3, P=0.3, P=0.7, P=0.3). Conclusion: Application of the EE filter does not improve the diagnostic accuracy of radiographs in the detection of proximal enamel caries.

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