Purpose: Bone quality, which is completely independent of bone mineral density (BMD), is comprised of bone architecture associated with bone cells, biological apatite, and collagen fibers. However, bone quality around implants has not been clarified since this concept has not been considered in dentistry. The aim of this study was to investigate the effect of mechanical repetitive loading on bone quality around implants in rat maxillae.

Materials and Methods: Implants were placed at 3 weeks after tooth extraction of both maxillary first molars in Wistar rats. Mechanical loading was applied via implants at twice a week for 5 weeks (20N, 5Hz, 1800 cycles). Control group did not receive mechanical loading (n=7 per each group). Euthanasia was performed at 30 minutes after the first load, and 5 weeks after the onset of mechanical loading. MicroCT, histomorphological, immunohistochemical and qPCR analyses were performed.

Results: Mechanical loading via implants significantly increased BMD but not bone mass. Osteocyte, osteoclasts and osteoblasts were significantly increased under loaded conditions in trabecular bone, but not cortical bone around implants. Mechanical loading significantly increased the production of collagen fibers in cortical and trabecular bone around implants. Especially, Type I and III collagen production was significantly upregulated in trabecular bone under loaded conditions. The preferential alignment of collagen fibers occurred in both cortical and trabecular bone around implants. Some load-related proteins were significantly distributed in bone under loaded conditions.

Discussion: Mechanical repetitive loading adopted bone quality and increased BMD, but not bone volume around implants in jaw bones. Qualitative change of bone around implants under loaded conditions may be associated with upregulated osteocyte network, and enhanced coupling of osteoblasts and osteoclasts.