Ultrastructural alterations of osteocyte morphology via loaded implants in rabbit tibiae

Osteocytes are crucial cells that control bone responses to mechanical loading. However, the effects of mechanical loading on osteocytes around dental implants are unclear. The aim of this study was to investigate whether mechanical loading via bone-integrated implants influences osteocyte number and morphology in the surrounding bone. Fourteen anodized Ti-6Al-4V alloy dental implants were placed in seven Japanese white rabbits, and implants in each rabbit were subjected to mechanical loading (50 N, 3 Hz for 1800 cycles, 2 days/week) along the implant long axis. Eight weeks after the initiation of loading, histomorphometric analysis and microcomputed tomography were performed. Scanning electron microscopy (SEM) was also performed with an acid etching technique using longitudinal and cross-sectional specimens. More bone formation around loaded implants was noted. In the implant neck, osteocytes tended to be more spherical with increased dendrite processes around loaded implants, while spindle-shaped osteocytes without increased dendrite processes were observed around unloaded implants in both longitudinal and cross-sectional images. In the bottom area, morphological changes in osteocytes were observed around loaded implants; however, dendrite processes did not differ in longitudinal or cross-sectional images, regardless of mechanical loading. These findings indicate that increased osteocyte numbers and developed dendrite processes are associated with anabolic bone responses to mechanical loading. The combination of acid etching and SEM imaging is a useful technique to assess ultrastructural osteocyte morphology around dental implants.