Accuracy and reliability of craniometric measurements on lateral cephalometry and 3D measurements on CBCT scans

To compare the accuracy of craniometric measurements made on lateral cephalograms and on cone beam computed tomography (CBCT) images.

Ten fiducial markers were placed on known craniometric landmarks of 25 dry skulls with stable occlusions. CBCT scans and conventional lateral headfilms subsequently were taken of each skull. Direct craniometric measurements were compared with CBCT measurements and with cephalometric measurements using repeated measures analysis of variance (ANOVA). All measurements were repeated within a 1-month interval, and intraclass correlations were calculated.

No statistically significant difference was noted between CBCT measurements and direct craniometric measurements (mean difference, 0.1 mm). All cephalometric measurements were significantly different statistically from direct craniometric measurements (mean difference, 5 mm). Significant variations among measurements were noted. Some measurements were larger on the lateral cephalogram and some were smaller, but a pattern could be observed: midsagittal measurements were enlarged uniformly, and Co-Gn was changed only slightly; Co-A was always smaller.

CBCT craniometric measurements are accurate to a subvoxel size and potentially can be used as a quantitative orthodontic diagnostic tool. Two-dimensional cephalometric norms cannot be readily used for three-dimensional measurements because of differences in measurement accuracy between the two exams.