Assessment of the inferior mandibular canal's position by cone-beam computed tomography

Objectives: it is important to know the exact location and anatomic variety of inferior alveolar nerve canal for different procedures of mandibular surgeries. The aim of the present study was to evaluate inferior mandibular canal's anatomic position by Cone-beam Computed Tomography [CBCT]

Methods: in a cross sectional study, CBCT were taken and assessed from 130 patients [260 semi-arch] referring to the radiologic department of Shahid Beheshti Dental Faculty. Three points including 1cm before mental foramen [point A], under second molar's furcation [point B] and 1cm after mandibular foramen on the inferior alveolar canal [point C] were chosen. The canal diameter, length and the distance between the canal and inferior border of mandible were measured. SPSS version 19 software used for data analysis. T and variance tests evaluated the role of age, gender, and canal length and jaw side

Results: mean age of patients was 43.73+/-13.25. Canal length, 61.71 +/- 4.95 ml and canal diameter was 2.94 +/- 0.58 mm. The distance between the canal and the inferior border of mandible was 9.47 +/- 2.23 mm. There was a significant difference in gender and age for all parameters. The distance between the canal and the inferior border in C point and at mental foramen in cases with short and long canal length showed a significant difference. [p?0.012] None of the variables showed significant difference between right and left sides

Conclusion: the anatomic position of mandibular canal is related to gender and canal length, and independent to age and side

Effect of slice thickness on the accuracy of linear measurements made on cone beam computed tomography images [in vitro]

Objective: cone beam computed tomography [CBCT] is applied for the imaging of the maxillofacial and dental structures, particularly for surgical treatments and dental implants. The aim of this study was to assess the effect of slice thickness on the accuracy of CBCT linear measurements

Methods: in this diagnostic accuracy study, forty-two titanium pins with the same dimensions were inserted into seven dry sheep mandibles. The length of the pins before the insertion was carefully measured by a digital caliper, [0.01mm accuracy]. Imaging of the mandible performed using CBCT New Tom VGi. After image reconstruction by NNT Viewer, linear measurements were made on cross-sectional slices [thicknesses of 0.125, 0.5, 1 and 2mm] by three radiologists. The accuracy of measurements assessed using descriptive indices and compared between different slice thicknesses by repeated measures ANOVA

Results: repeated measures ANOVA showed a significant difference between different slice thicknesses [P=0.024]. According to the least significant difference [LSD] test, the difference in absolute errors was significant in all thicknesses [P=0.024]. Measurements at 0.125 mm thickness were significantly different from others, with a higher error rate [mean absolute error=0.17]. Measurements at 0.5mm thickness showed a significant difference with those at 0.125 and 2mm [mean absolute error=0.15]. Measurements at 2mm thickness were significantly different from those at 0.125 mm thickness [mean absolute error=0.13].The average error rate was lower in 2mm thickness and the measurements were more accurate

Conclusion: a statistically significant difference was seam between CBCT measurements and actual sizes in different slice thicknesses. The differences were below 1mm, and clinically acceptable

Prevalence of taurodontism of permanent molars in dental school of Shahid Beheshti university from 2000 to 2006

Objective: Taurodontism is a dental anomaly characterized by elongation of root body and apical displacement of the pulp chamber floor associated with shortening of roots and their narrowing at the cementoenamel junction [CEJ]. Due to having a dilated apical one-third, these teeth may cause complications during extraction, locating canal orifices and instrumentation. This study aimed to assess the prevalence of taurodontism of permanent molars in a small Iranian population

Methods: This retrospective descriptive study was conducted on 1,100 dental records of patients that were randomly selected among 5,672 records available in the archives of School of Dentistry, Shahid Beheshti University of Medical Sciences from 2000 to 2010 that met the inclusion and exclusion criteria. Teeth with extensive restorations or carious lesions were excluded. One observer evaluated all the radiographs and the teeth were classified based on the presence or absence of taurodontism. All positive cases were re-evaluated by two examiners and accurate measurements were made using a caliper according to Shifman and Chanannel criteria

Results: A total of 1,184 radiographs were evaluated; of which 447 [47.7%] belonged to males and 737 [62.3%] belonged to females. A total of 5,532 first and second molars of both jaws were evaluated in these radiographs. There were 1,310 [23.7%] maxillary first molars, 987 [17.8%] mandibular first molars, 1,731 [31.3%] maxillary second molars and 1,504 [27.7%] mandibular second molars. Overall, 293 teeth had taurodontism; of which, 179 belonged to females and 114 belonged to males

Conclusion: The prevalence of taurodontism in the understudy population was 6.41%. It appears that taurodontism is not as rare as it is thought to be

Capability of senior dental students in detecting the presence and diagnosing the depth of proximal caries on a bitewing radiograph

Accurate and early detection of a carious lesioncan prevent its further extension. Therefore, capability to accurately diagnose carious lesions is a must-have qualification for dental graduates. The purpose of this study was to evaluate the ability of senior dental students of a dental university in detecting the presence and diagnosing the depth of proximal caries on a bitewing radiograph. The present study was a diagnostic assessment and a total of 100 bitewing radiographs of optimal quality were randomly selected from patients' files. Radiographs were separately observed by 30 senior dental students and 5 university professors from Shahid Beheshti School of Dentistry [in order to determine the gold standard] under similar conditions. The observers were asked to detect presence of carious lesions and diagnose its depth according to the set criteria and mark in the questionnaire. If 3 university professors unanimously agreed on presence or absence of caries, this opinion would be chosen as the gold standard of the study. In order to obtain reliability, radiographs were once again observed and evaluated one month later by the same 5 university professors and 11 students. Data were analyzed using SPSS software and Kappa values were analyzed and compared with t-test. The mean Kappa value for 2 times observation was 0.777 +/- 0.065 among professors and 0.664 +/- 0.131 among students. According to Fleiss, this rate was excellent for 3 professors and 3 students. Diagnostic sensitivity, specificity, positive predictive value and negative predictive value of students in caries detection were 78.22%, 82.14%, 79.68% and 80.81%, respectively. Diagnostic capability of students in differentiating carious lesions from healthy tissue was optimal and their reliability was not significantly different from the gold standard. Students were mostly able to detect the presence of carious lesions but there was an under-estimation about the depth of caries