Abstract
Histological changes surrounding hydroxyapatite-coated shape memory alloy implants, designed blade-vent type, were examined. Implant operations were performed in the mandibular premolar and molar regions in the Japanese monkey. A fixed bridge was set between the implant head and a tooth mesial to it, and the implant was applied by occlusal loading for six months. After six-month implantation, histological structures surrounding the implant, especially the implant tissue interface, were observed by means of microradiography, light microscopy, and scanning electron microscopy. In the interface between the HAP-coating layer and newly-formed bone tissue, no connective tissue could be found, and the newly-formed bone tissue tightly adhered to the HAP-coating layer on the implant similar to ankylosis. However, connective tissue fibrous elements extending from the newly-formed bone surface invaded fine pores of the HAP-coating layer. In the no-HAP-coating portion, on the flexible implant, newly-formed bone tissue was in close connection with Ti-Ni alloy, and no interpositioning of the fibrous element could be observed. The newly-formed bone tissue was composed of an irregularly lamella-like bone parallel to the surface of Ti-Ni alloy. The margin of this newly-formed bone had a smooth line without osteoclastic bone resorption. This study demonstrated that the HAP-coated shape memory alloy implants may stimulate osteogenic activity as well as accommodate masticatory and occlusal functions and may maintain great stability and fixation in the endosseous implant operation.
