Localization of impacted maxillary canine teeth: a comparison between panoramic and buccal object rule in intraoral radiography

Objectives: this study aimed to compare the efficacy of panoramic radiography and the buccal object rule in intraoral periapical radiography for localization of impacted maxillary canine teeth

Methods: a total of 20 panoramic radiographs depicting 28 displaced maxillary canines were evaluated. The ratio of the mesiodistal width of the impacted canine to the mesiodistal width of the ipsilateral central incisor was calculated and referred to as the canine-incisor index [CII]. The height of the crown of each displaced canine was classified in vertical plane relative to the adjacent incisor as apical, middle or coronal. Position of impacted maxillary canines was also determined on two periapical radiographs using the buccal object rule. Surgical exposure and direct observation of impacted teeth were later performed and served as the gold standard. The data were analyzed using SPSS and t-test

Results: there was an overlap in the CII range of the buccally [0.78-1.48] and palatally [1.15-1.75] positioned impacted canines. When considering the height factor in the middle and coronal zones, a significant difference was noted between the CII of buccally [0.78-1.1] and palatally [1.15-1.75] positioned teeth enabling determination of their buccolingual orientation [P<0.05]

Conclusion: for the impacted maxillary canines located in the middle and coronal zones [90% of cases], the CII of 1.15 and higher represents palatal impaction while the CII smaller than 1.15 represents buccal impaction

perceptibility Ccurve test applied to CCD and two methods of digitization of dental film-based radiographs

Objectives: several methods of image acquisition are accessible in dentistry. There is no overall acceptable method for image digitization so all different types of images can be comparable. The objective of this study was to compare the diagnostic accuracy of different methods of image digitization

Methods: this accuracy diagnostic test study used perceptibility curve test which first introduced by de Balder was applied. In this test a test object is used which is usually made by aluminum. Different levels of thickness and number of holes in the test object were necessary to have different levels of contrast. Images from film and CCD and digitized images by means of CCD scanners and digital camera were prepared. Nine observers assessed the images. Data collected was delivered to SPSS 13 software and for each image acquisition method; interclass correlation coefficience was computed and compared to the gold standard

Results: mean sensitivity, specifity, positive and negative like hood ratios in dependence on material thickness and the background gray value were calculated. In regions of high optical density the sensitivity for the film images was highest [0.994] following by CCD [0.905], scanner [0.889] and camera [0.821]. Difference between CCD images and scanner images was not significant. In dark regions of no dark holes the sensitivity was highest for film images [0.832] following by CCD [0.798], camera [0.714] and scanner [0.615] Difference between film and CCD images was not significant

Conclusion: the diagnostic quality of radiographic films was better than digital CCD sensors. For digitizing analog images scanners were better than digital Cameras

Accuracy of linear measurement using cone-beam computed tomography at different reconstruction angles

PURPOSE: This study was performed to evaluate the effect of changing the orientation of a reconstructed image on the accuracy of linear measurements using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Forty-two titanium pins were inserted in seven dry sheep mandibles. The length of these pins was measured using a digital caliper with readability of 0.01 mm. Mandibles were radiographed using a CBCT device. When the CBCT images were reconstructed, the orientation of slices was adjusted to parallel (i.e., 0degrees), +10degrees, +12degrees, -12degrees, and -10degrees with respect to the occlusal plane. The length of the pins was measured by three radiologists, and the accuracy of these measurements was reported using descriptive statistics and one-way analysis of variance (ANOVA); p<0.05 was considered statistically significant. RESULTS: The differences in radiographic measurements ranged from -0.64 to +0.06 at the orientation of -12degrees, -0.66 to -0.11 at -10degrees, -0.51 to +0.19 at 0degrees, -0.64 to +0.08 at +10degrees, and -0.64 to +0.1 at +12degrees. The mean absolute values of the errors were greater at negative orientations than at the parallel position or at positive orientations. The observers underestimated most of the variables by 0.5-0.1 mm (83.6%). In the second set of observations, the reproducibility at all orientations was greater than 0.9. CONCLUSION: Changing the slice orientation in the range of -12degrees to +12degrees reduced the accuracy of linear measurements obtained using CBCT. However, the error value was smaller than 0.5 mm and was, therefore, clinically acceptable.

Evaluation of the accuracy of linear and angular measurements on panoramic radiographs taken at different positions

PURPOSE: This study assessed the accuracy of linear and angular measurements on panoramic radiographs taken at different positions in vitro. MATERIALS AND METHODS: Two acrylic models were fabricated from a cast with normal occlusion. Straight and 75degrees mesially and lingually angulated pins were placed, and standardized panoramic radiographs were taken at standard position, at an 8degrees downward tilt of the occlusal plane compared to the standard position, at an 8degrees upward tilt of the anterior occlusal plane, and at a 10degrees downward tilt of the right and left sides of the model. On the radiographs, the length of the pins above (crown) and below (root) the occlusal plane, total pin length, crown-to-root ratio, and angulation of pins relative to the occlusal plane were calculated. The data were subjected to repeated measures ANOVA and LSD multiple comparisons tests. RESULTS: Significant differences were noted between the radiographic measurements and true values in different positions on both models with linear (P<0.001) and those with angulated pins (P<0.005). No statistically significant differences were observed between the angular measurements and baselines of the natural head posture at different positions for the linear and angulated pins. CONCLUSION: Angular measurements on panoramic radiographs were sufficiently accurate and changes in the position of the occlusal plane equal to or less than 10degrees had no significant effect on them. Some variations could exist in the pin positioning (head positioning), and they were tolerable while taking panoramic radiographs. Linear measurements showed the least errors in the standard position and 8degrees upward tilt of the anterior part of the occlusal plane compared to other positions.

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