Objectives: Finding the best voxel size for discernment of vertical bone defects with minimum patient radiation dose is a priority. This study sought to assess the effect of cone-beam computed tomography (CBCT) voxel size on the detection of vertical bone defects.
Materials and Methods: In this in vitro, experimental study, 31 vertical defects including 2 one-wall, 12 two-wall, and 17 three-wall defects were randomly created in the maxilla and mandible of four sheep skulls with the associated soft tissue using round and needle burs. Forty sound sites were considered as the control group. The CBCT scans were obtained from the skulls with 0.150 and 0.300 mm3 voxel sizes and 8 x 11 cm2 field of view (FOV). The images were randomly evaluated by two periodontists and two oral and maxillofacial radiologists, and their findings were recorded. The inter-rater observer agreement (weighted kappa), sensitivity and specificity values were calculated for each voxel size. Comparisons were made using paired t-test.
Results: The two voxel sizes had no notable difference in the detection of one-wall and two-wall defects (P>0.05). But the smaller voxel size was significantly superior for the detection of three-wall defects (P=0.001). The inter-rater observer agreement was unfavorable (kappa < 0.6) for the detection of all three defect types.
Conclusion: In general, increasing the image resolution by decreasing the voxel size increased the sensitivity and decreased the specificity of CBCT for detection of vertical bone defects, and is only recommended for detection of three-wall defects.