Effect of Mandible Orientation on Reliability and Reproducibility of Linear Measurements Using Cone-Beam Computed Tomography

The aim of the present study was to assess the effect of mandibular inclination on accuracy of linear measurements performed on CBCT scans. In this descriptive analytical study، 12 linear dimensions between anatomical landmarks were measured on a dried human mandible. The measurements were obtained with a digital caliper three times by two observers. The mandible was scanned using a cone-beam CT (scanora 3D) with the base of mandible positioned in 5 different inclinations: horizontal، tilted downwards، tilted upwards، laterally tilted and rotated. Computer measurements of the dimensions were obtained twice by two observers، three times at each session. Then، the inclinations were corrected by the software and all the measurements were repeated. Paired T-test and Pearson correlation test were used to analyze the data. In 88. 4% of the samples، the mean computer measurements were smaller than the mean manual caliper measurements. The mean difference was 0. 01-2. 65 mm for different inclinations. The percentage error was below 10% (except for 6 cases) which is considered to be the safe margin in studies. Following correction of the inclinations، the mean absolute error exceeding 1 mm was observed in only one case and the percentage error was less than 8%. Regarding the reproducibility high inter and intra examiner correlation was observed (r>0. 9). High inter and intra examiner correlation was observed with respect to the reproducibility of the results (r>0. 9). Head orientation during CBCT scanning is not as crucial as in CT scan especially when the inclinations are corrected via software before the measurements.