Aim:Bone around dental implants constitutively receives occlusal force via implants. However, the influence of mechanical stimulation such as bite force on bone around implants remains unclear. The aim of this study was to investigate the effect of mechanical loads on bone-related cells around implants in rat maxillae.
Methods:9-week-old female rats were used. Both maxillary first molars were extracted and threaded-implant was placed at 4 weeks post-extraction. At 3weeks post-implant placement, mechanical repetitive load (3Hz, 1800 cycles, twice a week) was applied for 2- and 5-weeks on randomly selected implants. The remaining implants did not receive any loads (n=7/group). Micro computed tomography was carried out to analyze bone mass and bone mineral density (BMD). Histomorphometric and immunohistochemical analyses were performed to detect bone-related-cells and collagen contents inside the thread of implants.
Results:The number of osteoblasts and osteocytes were decreased in a time-dependent manner, irrespective of mechanical loads. On the other hand, application of mechanical loads for 5 weeks significantly increased BMD and type I collagen around implants with no alteration of bone mass when compared under non-loaded conditions. This load application significantly increased the number of osteocytes and osteoblasts, but not osteoclasts when compared under non-loaded conditions. Moreover, application of mechanical loads for 2 weeks significantly increased the number of osteoblasts and osteoclasts inside the thread as compared under non-loaded conditions.
Conclusion:Mechanical repetitive loads via implants affect osteocyte network, collagen content and bone remodeling. Conversely, non-loaded conditions reduce the number of bone-related cells around implants. Number change of bone-related cells may contribute to the increase in BMD, but not bone mass. Our findings suggest that bone around dental implants constitutively changes bone quality, but not bone quantity under loaded conditions.