Assessment of the Bone Mineral Content in the Mandible by Dual-Energy X-Ray Absorptiometry to Evaluate Short-Term Change.

With the objective of being able to assess response to disease or clinical treatment, the densitometry community has long sought the ability to assess short-term change in bone density. The mandible, known to have a high bone turnover, an increased vascularity, and a greater susceptibility to osteoclastic and osteoblastic activities, has long been suggested but has fallen short as a site from which to monitor an early change in the response to a treatment or a disease. The current study developed a method to assess bone density in the superimposed left and right mandibles. Examining a skull in a positioning platform showed that studies between -5.0° and +12.5° from the preferred 0° orientation generated studies that were statistically similar to studies in the preferred orientation. After establishing the distribution of bone density in the mandibles, a software was developed that would execute a search for an area of intermediate content within the body and ramus regions of the mandible; in subsequent studies of the same individual, the analysis software would place the body and ramus regions in the same location without operator dependence. Studies in a population of subjects showed that the density in the body and ramus regions varied independently and that the density in these regions was independent of age. Repeat studies with repositioning showed repeatability of 1.73% and 2.44% for the body and ramus, resulting in computed least significant change limits of 4.84% for the body and 6.83% for the ramus. Examining 45 subjects undergoing treatment for osteoporosis up to over 46 wk showed 22 (49%) subjects with an increase in 1 of the mandible sites, suggesting a benefit from treatment, whereas 12 (27%) subjects showed a decrease in both mandible sites, suggesting a poor response to treatment. We conclude that applying the methodology and allowing the software to locate and define regions of interest allow assessments of change in the bone mineral content at the mandible that will reflect early changes occurring with disease or treatment.