Measuring cortical thickness on panoramic radiographs: A validation study of the Mental Index

Objectives: To validate the Mental Index assessment obtained from panoramic radiographs. Study design: Ten dried mandibles were selected, and standardized panoramic radiographs were obtained. The specimens were then perpendicularly sectioned at the mental foramen region, and the inferior mandibular cortical thickness was recorded using a digital caliper. Measurements of panoramic radiographs were compared with the dried mandibles. Four observers carried out twice the measurements for the panoramic radiographs. Two observers performed twice the measurements of the dried mandibles. Reliability was assessed by duplicate measurements. Results: Agreement between the actual mandible measurements and the radiographic assessment was moderate for the noncorrected measurements. Agreement between anatomic and radiographic measurements improved remarkably after standard correction for magnification. Conclusions: Bone status reports based on measuring cortical thickness of the lower border of the mandible at the mental foramen based on panoramic radiographs, i.e., Mental Index, are accurate. Compensation for magnification, however, is necessary.