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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:Twenty-eight 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.