Resorption of the mandibular residual ridge: A micro-CT and histomorphometrical analysis

The aim of this study was to investigate whether the extent of mandibular resorption and gender is related to the bone turnover and microarchitecture of the edentulous mandible.

A mandibular bone sample was obtained at canine position from 36 edentulous participants (50% women; mean age: 65 years) during dental implant surgery. All female participants were postmenopausal. Mandibular height, duration of edentulous state and resorption pattern (Cawood classification) were recorded. Microcomputed tomography was used to determine bone mineral density, bone volume fraction, trabecular connectivity density, trabecular number, trabecular thickness and trabecular separation. Histomorphometric analysis was used to assess bone turnover: osteoid area and surface were measured as a parameter for bone formation and osteoclast numbers were determined as a parameter for bone resorption. Correlations between micro-CT, histomorphometrical parameters and clinical data were analysed with correlation coefficients and parametric and non-parametric tests.

Lower mandibular height was strongly associated with higher bone mineral density in trabecular bone. Women showed higher osteoclast numbers in trabecular bone than men. In trabecular bone of women, bone volume was significantly related to osteoclast numbers, osteoid surface and osteoid area.

The higher trabecular bone mineral density found in the edentulous mandible could either indicate a restructuring process of the resorbed mandible or suggests that the inferior region of the mandible is more highly mineralised. In women, higher bone turnover is associated with lower bone volume, suggesting an effect of postmenopausal oestrogen deficiency on bone turnover in the edentulous mandible.