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.
Comprehension ; Cone-Beam Computed Tomography* ; Dental Implants ; Dental Occlusion ; Dimensional Measurement Accuracy ; Mandible ; Sheep ; Titanium

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.
Dental Occlusion ; Dimensional Measurement Accuracy ; Head ; Lysergic Acid Diethylamide ; Posture ; Radiography, Panoramic