Reliability and applicability of 3D measurements of posterior teeth

Background: Due to the lack of studies, we evaluated the validity and reliability of multirooted tooth measurements derived from cone-beam computed tomography (CBCT) and periapical (PA) radiography. Methods: CBCT scans and PA radiographs were obtained from 16 patients (30 and 18 maxillary molars and premolars, respectively, were evaluated). The CBCT scans were taken at 0.4 mmvoxel size. Using X, Y, and Z coordinates, the cusp tips and root apices were used to calculate two tooth lengths and two root lengths of the premolars, and three tooth lengths and three root lengths of the molars. PA radiographs were taken from the same patients at the same time. The same tooth and root lengths were measured. Results: There were no systematic differences between replicates. Systematic errors ranged from 0.001 to 0.119 mm (premolars) and from 0.001 to 0.052 mm (molars). Only buccal premolar root lengths, as measured on the PA radiographs, and buccal molar root lengths, as measured on the CBCT images, showed statistically significant differences (P < 0.05). Random method errors ranged from 0.11 to 0.22 mm with CBCT and from 0.06 to 0.14 mm with PA radiography. PA radiography significantly underestimated root length and overestimated molar tooth length. Conclusions: Although both methods are reliable, greater random errors were associated with the CBCT than with PA measurements. PA radiography underestimated buccal lengths and overestimated lingual tooth lengths of the premolars and molars, respectively. (C) 2014 World Federation of Orthodontists.