Effect of maxillary edentulousness on mandibular residual ridges.

Bone mineral density (BMD) was measured in five different regions of the mandible of 77 postmenopausal women. These women were also classified according to the remaining, clinically determined alveolar height in the edentulous distal regions of the mandible. The duration of edentulousness in the maxilla and in the mandible was determined anamnestically. All subjects were edentulous in the maxilla, and 42 were also edentulous in the mandible. The other 35 women had teeth only in region d35-d45. This study shows that after extraction of the last teeth in the mandible, the BMD of the cortical bone is not lowered, but that the BMD of the trabecular portion is lowered more by mechanical stress caused by the remaining natural teeth than by maxillary dentures. This feature becomes apparent when duration of edentulousness in the maxilla is compared with the BMD values of different regions in the mandible.