Accuracy of using different voxel sizes to detect osseous defects in mandibular condyle

Introduction
Clinical evaluation of temporomandibular disorders alone is insufficient and should be supported with radiological imaging modalities. Cone-beam computed tomography (CBCT) is the ideal method for evaluating bony components of temporomandibular joint.

Objectives
The aim of this study was to present the ability of different voxel sizes in identifying osseous defects of mandibular condyle using CBCT images.

Material and methods
The study sample consisted of nine dry human skulls (12 temporomandibular joints), containing fabricated osseous defects of different sizes (0, 0.8, 1, and 1.6 mm). The joints were imaged using five imaging protocols (0.400, 0.200, 0.150, 0.100, and 0.075 mm3). Evaluation of the fabricated defects was carried out by two different observers, who noted presence or absence of a defect. Kappa coefficients were calculated to assess the intraobserver and interobserver agreement for each setting. Sensitivity, specificity, accuracy, and positive and negative predictive values were used to compare the observers’ performance according to the gold standard and different defect diameters. Statistical significance was set at p < 0.05.

Results
The best results for both observers in comparison with the gold standard were achieved at a voxel size of 0.075 mm3. The sensitivity, specificity, and accuracy generally increased with decreasing voxel size. Positive and negative predictive values increased with decreasing voxel size and increasing defect size.

Conclusions
Obtaining CBCT scans with voxel sizes of 0.100 or 0.075 mm3 should be considered for the evaluation of osseous defects of mandibular condyle. A voxel size of 0.100 mm3 may be preferable due to lower patient’s irradiation dose.