Correlative experimental animal and human clinical retrieval evaluations of hydroxyapatite (HA)-coated and non-coated implants in orthopaedics and dentistry

Retrieval analyses disclosed in vivo dissociation of HA in orthopaedic acet abular components, but excellent bone ingrowth into intact HA coatings on d ental retrievals. Initial healing and the bone interface between HA-coated and non-coated implants in the posterior maxilla (Mx) and mandible (Md) was assessed in an animal model using light microscopy (LM), including confoca l (CM) and Nomarski (NM) microscopy. Seventy-two implants (36 HA-coated; 36 non-coated) were placed into jaws of six dogs; half after extraction, half after 3 months healing. Animals were euthanized 3 months postimplantation. All implants osseointegrated; however, preliminary morphometry showed high er BCL for HA-coated (51%) than non-coated implants (44%) in the Mr (p < 0. 05). BCL for HA-coated Md implants was not significantly higher (64%) than non-coated implants (62%). Bone closely apposed both implant types; however , LM suggested a more intimate association with HA coatings. Serial section s disclosed a reddish coating on the HA, possibly analogous to oral tissue proteoglycans, which was not visible with non-coated implants. This materia l was continuous with similar material coating endosteum, osteoid regions, and osteocyte (Os) lacunae close to the implant. An interdigitating canalic uli network allowed communication between interfacial Os and Os deeper with in the bone. Data suggest HA offers enhanced initial bone fixation in the M r, and that adequate bone exists for non-coated implant stability in the Md . No HA dissociation was seen with implants in the animal study, which was consistent with retrieved human HA dental implants.