Morphometric characteristics of cortical and trabecular bone in atrophic edentulous mandibles

Adaptations of the alveolar ridge after tooth loss have been well described. However, studies on the morphometric characteristics of cortical bone are rare; hence, this study of human atrophic edentulous mandibles was undertaken.

Total cortical area, porosity, and thickness, and the percentage of cortical area in the complete mandibular area as well as in an area (height, 10 mm) starting at the most caudal point of the trabecular compartment and extending in the coronal direction were determined in 185 thin ground sections of edentulous mandibles (incisor region, 49; premolar region, 76; molar region, 60; 95 from females and 90 from males; mean age, 78.2 years, SD ± 7.8 years; Caucasian donors; cause of death: cardiovascular disease). Further, mandibular height and width and degree of residual ridge resorption (RRR) were recorded.

The percentage of cortical area in the complete mandibular area increased with increasing RRR. Yet, evaluation of the 10-mm caudal portion corresponding to the basal part of the mandibular body did not confirm these changes in cortical bone. Cortical porosity and thickness decreased from the mesial to the distal region. Cortical porosity was unaffected by RRR, while cortical thickness increased, mainly at lingual aspects.

In conclusion, cortical bone remained stable in different degrees of RRR except for some modulations in the lingual aspects. Changes in the relative composition between cortical and trabecular bone are due to loss of height and total area, mainly at expense of trabecular bone area, but not to adaptations of the cortical bone.