Association of cortical shape of the mandible on panoramic radiographs with mandibular trabecular bone structure in Japanese adults: a cone-beam CT-image analysis

Abstract

The purpose of this study was to assess the association between the cortical shape of the mandible, as detected on panoramic radiographs, and trabecular bone structure, as assessed by cone-beam computed tomography (CBCT), in Japanese adults. Panoramic radiographs and CBCT images of the mandibles of 50 subjects (18 men, 32 women), aged 45–86 years, were evaluated. An experienced oral and maxillofacial radiologist categorized the cortical shape of the mandible as detected on panoramic radiographs as normal, mildly to moderately eroded, and severely eroded cortices, respectively. All mandibles were scanned using CBCT. Four bone structure parameters of the basal portion of the mandible were calculated in three dimensions using an image-analysis system: total bone volume (mm3); cortical bone volume fraction (%); trabecular bone volume fraction (%); fractal dimension. One-way analysis of covariance with Bonferroni correction was employed to evaluate differences in the four bone parameters among the three cortical shape groups. Pearson’s correlation coefficient was calculated to examine correlations between age and cortical and trabecular bone volume fractions. Progression of cortical bone erosion was significantly associated with increased trabecular bone volume fraction (P < 0.001) and increased fractal dimension (P = 0.01). Cortical bone volume fraction decreased significantly with age (P = 0.04). However, trabecular bone volume fraction tended to increase with age (P = 0.06). The change in the trabecular bone structure of the mandible may differ from that of the general skeleton in Japanese adults.