Hot isostatic pressing-processed hydroxyapatite-coated titanium implants: Light microscopic and scanning electron microscopy investigations

Hot isostatic pressing (HIP) was used in a new procedure to produce hydroxy apatite (HA) coatings on a commercially pure titanium (cpTi) substrate for osseous implantation. Eighteen HIP-processed HA-coated implants were placed in the inferior border of the mandibles in 2 Labrador retriever dogs and l eft submerged for 3 months. As control specimens, 12 sandblasted cpTi impla nts were placed in the same mandibles and, to compare the bone reaction, 2 additional plasma-sprayed HA-coated implants (Integral) were placed. Tissue reactions at the bony interfaces of the implants were studied in ground se ctions with the implants in situ, using ordinary, fluorescent, and polarize d light microscopy and scanning electron microscopy (SEM). The HIP-processe d HA coatings displayed an increased density in light microscopy and SEM as compared to plasma-sprayed coatings. Direct bone-implant contact was found in all 3 types of surfaces. However, the production of new bone was far mo re abundant for the HA-coated implants than for sandblasted cpTi implants. The presence of bone-forming and bone-resorbing cells indicated active bone remodeling in the interface area at 3 months after implant placement. The present results support the view that epitaxial bone growth may occur from the HA-coated implant surface. It was concluded that the increased density of the present HIP-processed HA material does not reduce the bioactive prop erties of the coatings. (Int J Oral Maxillofac Implants 1998;13:837-844).