Prevalence of middle mesial canal in mandibular first molars using cone-beam computed tomography technique.

BACKGROUND: The purpose of this study was to evaluate the prevalence of middle mesial canal in mandibular first molars using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: In this descriptive study, a total of 768 radiographs of mandibular first molars, 384 for males and 384 for females, taken at a private radiology center in Isfahan, were assessed for the presence of middle mesial canal based on the gender of the patients. All samples had been prepared by one CBCT machine. The images were evaluated by endodontists and radiologists. Then, the morphology of first molar mesial root canals was assessed by Vertucci classification, and the obtained results were analyzed by SPSS software using a Chi-square test. The comparison was considered statistically significant at P < 0.05. RESULTS: Twenty-four samples (3.13%) had a middle mesial canal. The prevalence rates of the middle mesial canal in the females and males were found to be 9 and 15 (2.35% vs. 3.92%), respectively, indicating no statistically significant difference (P = 0.21). Of 24 teeth with middle mesial canal, 17 samples (70.8%) were of Type XII and 7 samples (29.2%) were of Type VIII. There was no statistically significant difference between genders with regard to the prevalence of different types of middle mesial canals (P = 0.19). CONCLUSION: The prevalence of the middle mesial canal was rather low in this study, and it is necessary to detect additional canals in the patients under root canal treatment.

The effect of voxel size on the measurement of mandibular thickness in cone-beam computed tomography.

BACKGROUND: Cone-beam computed tomography (CBCT) is a new imaging technology that has been widely used in implantology, oral and maxillofacial surgery and orthodontics. This method provides 3-D images that are composed of voxel, which is the smallest image unit, and determines image resolution. Smaller voxel is associated with the higher resolution and also greater radiation exposure. This study was aimed to find out the effect of voxel size on the measurement of mandibular thickness. MATERIALS AND METHODS: Using voxel sizes of 0.30 mm and 0.15 mm, two CBCT protocols (protocol 1: Field of view (FOV) of 15 cm, 85 kVp, 42 mAs, 0.15 mm voxel, 14 s scan time; protocol 2: FOV of 15 cm, 85 kVp, 10 mAs, 0.30 mm voxel, 14 s scan time) were carried out on 16 dry human mandibles with permanent dentition. Mandibular thickness was measured at seven different sites (midline region, bilateral canine regions, bilateral mental foramen regions and bilateral molar regions). Analysis of variance was used for analysis of data using the Statistical Package for the Social Sciences version 20 (SPSS Inc., Chicago, IL, USA). P < 0.05 considered to be statistically significant. RESULTS: No statistically significant differences were found between different protocols regarding the mandibular thickness (P > 0.05). CONCLUSION: Considering the insignificant differences of the mandibular thickness measurements using different voxel sizes, it would be more reasonable to use 0.30 mm voxel size instead of 0.15 mm voxel size to avoid unnecessary radiation exposure.

Using cone beam computed tomography to detect the relationship between the periodontal bone loss and mucosal thickening of the maxillary sinus.

BACKGROUND: Maxillary sinuses are covered by a 1 mm thick mucous membrane that when this membrane becomes inflamed, the thickness may increase 10-15 times. The common causes of odontogenic sinusitis are dental abscesses and periodontal disease. Computed tomography (CT) is considered the gold standard for sinus diagnosis. Recently, cone beam computed tomography (CBCT) has been introduced for dental and maxillofacial imaging, which has several advantages over traditional CT, including lower radiation dose and chairside process. This study aims to find the association between mucosal thickening (MT) of the sinus and periodontal bone loss (PBL) and pulpoperiapical condition. MATERIALS AND METHODS: A total of 180 CBCT images were reviewed. PBL was assessed in six points under each sinus at the mesial and distal sides of the upper second premolar and first and second molars by measuring the distance from the alveolar crest to the point 2 mm under the cemento-enamel junction (CEJ). The MT was assessed at six points in the floor of the sinus precisely over the mentioned points. To assess the possible role of pulpoperiapical condition on the sinus MT, the existing teeth were classified into five groups due to the probable effect of each condition on the pulp and peri-apex. The statistical association between MT of sinus and PBL and pulpoperiapical condition was assessed using SPSS software (SPSS Inc., version 16.0, Chicago, IL, USA) and bivariate correlation and binary linear regression statistical tests (P < 0.05). RESULTS: MT was observed in 39.4% of patients (mean = 4.68 ± 5.25 mm). PBL was seen in 33% of the patients (mean = 1.87 ± 1.63 mm). Linear regression test showed that there is an association between both PBL and pulpoperiapical condition and MT, but the effect of PBL was about 4 times stronger. CONCLUSION: This study showed that MT of the maxillary sinus was common among patients with PBL and MT of the maxillary sinus was significantly associated with PBL.

Comparing the range of µ and ß angles in 6-17-year-old children of Isfahan with normal occlusion.

BACKGROUND: Linear and angular measurements such as A point, nasion, B point (ANB) angle and Wits appraisal index are not accurate enough to evaluate sagittal relationship of the jaws. The aim of this study was to evaluate and compare the range of µ and ß angles in 6-17-year-old children of Isfahan, having normal occlusion. MATERIALS AND METHODS: This was an analytical descriptive study. For this study, 235 cephalometric radiographs of patients who didn't receive orthodontics treatments and based on 13 indexes had normal occlusion, were selected. After tracing of cephalograms, ANB angle, Wits appraisal index, µ angle (resulted from the intersection of AB line and perpendicular line from point A to mandibular plane) and ß angle (resulted from the intersection of AB line and perpendicular line from point A on CB line) were measured. Data was analyzed by t-test, ANOVA and Pierson-Spearman correlation coefficient (P < 0.05). RESULTS: Mean value of µ and ß angles were 17.34 ± 3.47 and 31.7 ± 3.31 and ranged from 8-27 to 21.5-39 respectively. According to t-test, there was a significant difference between two sex groups for µ angle (P = 0.02); however, it was not significant for ß angle. According to Spearman correlation coefficient, there was no significant difference between age and µ angle; however, ß angle was directly and significantly related to age (r = 0.435). There was significant and reverse relationship between µ and ß angles with ANB angle and Wits appraisal index. CONCLUSION: µ and ß angles are reliable and can be used to evaluate the anterior-posterior relationship of the jaws.