Measuring mandibular ridge reduction on oblique cephalometric radiographs.

The aim of this study was to test the accuracy of a setup for measuring alveolar ridge reduction of totally edentulous mandibles and of mandibles with abutment teeth for overdentures, on oblique lateral cephalometric radiographs. For that purpose, a cephalostat was modified so that the patient's head--in particular the mandible--could be fixed in a reproducible manner. Four radiographs were used for measuring all parts of the mandible. To assess the accuracy of the method, two randomly chosen parts of the mandible of 20 patients were X-rayed twice. The radiographs were traced independently by two observers and the height of the mandible was measured along a line drawn perpendicularly to the tangent of the lower border of the mandible on these X-rays. The method appeared to be simple, less time-consuming, and accurate. The average standard deviation of the measurements of the height of the mandible was 0.15 millimetres. When measuring ridge reduction, the standard deviation was 0.21 millimetres.