Influence of implant neck design on bone formation under mechanical repetitive loading: Histomorphometric and microcomputed tomographic studies in Rabbit Tibiae

Purpose: The aim of this study was to investigate effects of implant neck design on the original concept of osseointegration and bone formation when applying mechanical repetitive loading by bone-integrated implants. Materials and Methods: Twentyeight anodized Ti-6Al-4V alloy implants with +60° or-60° grooves in the implant neck were placed in the proximal tibial metaphysis of 14 rabbits. Fourteen implants received mechanical repetitive loading along the long axis of the implant for 8 weeks at 12 weeks after implant placement. The remaining 14 implants received no loading. Histomorphometric and microcomputed tomographic analyses were then performed. Results: No effect of neck design was observed without mechanical loading, whereas osseointegration around the +60° grooves was upregulated with mechanical loading. Calculated load effects on bone structure around the implant neck with +60° grooves were larger when compared with the-60° grooves under mechanical loading. Conclusions: These findings indicate that the establishment of osseointegration and bone formation around the implant neck with +60° grooves is superior to those with-60° grooves under loaded conditions.