Failure of a hydroxyapatite-coated endosteal dental implant: A clinical report

Abstract

B. loactive calcium phosphates have been studied as implant materials by dental and orthopedic researchers for more than 20 years. Hydroxyapatite (HA)-coated root form endosseous implants were introduced in 1984.l This calcium phosphate salt (Caic[PO&[OH]s) is applied to the roughened metallic implant surface by passing the HA powder through a high-temperature flame. The HA is ionized and converted into a plasma stream that condenses in multiple lamina onto the metallic implant surface as a partially amorphous and partially crystalline ceramic coating 40 to 100 pm thick.’ HA interacts biochemically with the collagen of the surrounding bone, which results in the deposition of bone matrix onto the coated implant3 HA has also been shown to form highly mineralized bridges of “biologic apatite”l with bone. Some authors have described HA as a ‘bioactive” material that undergoes “biointegration” (structural connection to bone) to distinguish it from “bioinert” titanium, which undergoes “adaptive osseointegration” (physical and chemical bond to bone).4-6 Others, however, have found that the electron microscopic appearance of the bone interfaces of the two materials are similar and that structural connection oftitanium to bone occurs.7-10 Research on HA biointegration demonstrated encouraging early results. In studies that extended up to 6 months, HA-coated implants exhibited greater interfacial strength and boneto-implant contact than did titanium implants.11M16 The long-term clinical success of HA, however, has become the focus of concern in recent literature. In vivo studies have revealed that, although HA-coated implants initially demonstrated better histomorphologic characteristics than did titanium surface implants, this advantage changed after 6 months and was significantly reversed