Fractal dimension evaluation of cone beam computed tomography in patients with bisphosphonate-associated osteonecrosis

The aim of this study was to (1) evaluate the fractal dimension (FD) in regions of the mandible on cone beam CT (CBCT) images of patients with bisphosphonate-associated osteonecrosis of the jaws (BP-ONJ) and (2) to select the most suitable region of interest (ROI) for further study on detection of bone alterations associated with bisphosphonates. CBCT images of patients with BP-ONJ were included with matched controls. Values of FD were compared between groups. Selected ROIs were: ROI-1 - below the mandibular foramen; ROI-2 - above the mandibular foramen; ROI-3 - anterior to the mental foramen; ROI-4 - above the mandibular canal. The area of bone exposure was included as ROI-5. The results were analysed using generalized estimating equations and conditional logistic regression. There were 36 patients (67% female) with a mean age of 60.7 years. The mean FDs were: ROI-1 - 1.678 for controls and 1.673 for patients (P = 0.81); ROI-2 - 1.657 for controls and 1.653 for patients (P = 0.78); ROI-3 - 1.661 for controls and 1.684 for patients (P = 0.17); and ROI-4 - 1.670 for controls and 1.698 for patients (P = 0.03). The value of the FD in the area of exposed bone was the highest (1.729). The odds of being a BP-ONJ patient vs being a control was six times as high for individuals with a higher FD score at ROI-4, although the confidence interval was quite wide owing to the small sample size. In this preliminary study, BP-ONJ patients had higher FD values than controls at regions close to the alveolar process. The results suggest that FD is a promising tool for detection of bone alterations associated with BP-ONJ.