Histomorphometry of Cadaveric Implant Hydroxyapatite Coatings and Particulates

Objective: Predictions from in vitro and in vivo laboratory testing have questioned the longer-term in vivo stabilities of hydroxyapatite (HA) biomaterials. Conditions of overall properties, osseous integration and functional force transfer were also considered associated with ADA-SCDP, ASTM and ISO biomaterial standards. This study focused on outcomes from three cadaveric specimens with longevities of about 11 years each.

Methods: Custom design mandibular subperiosteal dental implants were fabricated from cast cobalt alloy (ASTM F75) with plasma sprayed HA coating on the body section. Implants were placed with solid mm size HA particulates as a bone graft. With full approvals, mandibles were harvested en bloc from human donors, fixed in buffered formalin, transferred, sectioned by Exakt® processing and imaged by Bioquant® optical microscopy (UAB-IRB X050823001).

Results: The implants were clinically functional over the 11 year periods (opinion of DM), and radiographs and gross observations showed devices in place with bone and soft tissue representing stable and functional conditions. Magnitudes from microscopic viewing and analyses showed osseous integration of residual cobalt alloy surfaces, HA coatings and HA particulates to be greater than 27, 57 and 50% bone implant contact (BIC) respectively. Anatomy, histology and histomorphometry showed longer-term retention of the coating and particulates under functional conditions.

Conclusions: Histomorphometry of three eleven-year human donor cadaveric mandibular implants showed: retained and osseous integrated HA coatings and particulates including some resorption and surface alterations; osseous integration of cobalt alloy regions; and an overall construct arrangement indicating functional force transfers through all components.

Recognition: Partial support from NIBIB-BRP Grant: RO1 EB001715-01A2 and

NIH Grant: P30-AR46031