Bone healing capacity of titanium plasma-sprayed and hydroxylapatite-coated oral implants

The influence of surface quality, in particular surface topography and implant material, was evaluated by inserting titanium- and hydroxylapatite plasma-sprayed coated implants into the maxilla of 10 goats. Three types of plasma-spray coatings were applied to tapered, screw shaped implants; titanium plasma-spray coating (TPS), titanium plasma-spray coating with additional acid passivation (TPSA) and a bilayered coating (TPS/HA) consisting of titanium plasma-spray coating (TPS) and a hydroxylapatite part (HA). In addition, as-machined implants (TiM) were used as control. A total of 40 implants were inserted according a balanced split plot design. At the end of a 3-month healing period, it appeared that 5 implants (2 TPS, 1 TPSA, 1 TPS/HA and 1 TiM) were lost. Histological examination revealed a stronger bone response to TPS/HA coated implants. Even the TPS/HA coated implants induced bone formation on the part of the implant inserted into the sinus. No signs of delamination of the TPS coatings were visible. The HA part of the dual coating showed signs of degradation. Histomorphometrical analysis confirmed these findings. A significant difference in bone contact (P < 0.05) was measured between the TPS/HA coated implants and the other types of implants. Linear regression (r = 0.27) showed no correlation between the inscrew values at the base line and the bone contact measurements 3 months after healing. On the basis of these results, we can conclude that the chemical composition of the HA coating has a positive influence on the bone reaction. The influence of roughness is less evident.