EFFECT OF CA P COATING RESORPTION AND SURGICAL FIT ON THE BONE/IMPLANT INTERFACE/

The effect of coating resorption on bone apposition and attachment str ength to resorbable hydroxyapatite (HA), nonresorbable HA-coated, and uncoated rough titanium implants was evaluated in interference- and no ninterference-fit (gap of 2-3 mm) surgical models 2, 4, and 12 weeks p ostoperatively. Interference and noninterference fits showed differenc es in bone bridging. Bone apposition was circumferential around the im plants in noninterference fit. Significantly greater bone apposition w as seen to nonresorbable HA-coated implants than uncoated and resorbab le HA-coated implants at 4 and 12 weeks. Only resorbable HA coatings s howed significantly lower bone apposition for noninterference versus i nterference fit and from 4-12 weeks. At 2 weeks, strengths of bone att achment to resorbable HA-coated implants were greater than the other i mplants, and decreased to lower values (not significant) than the nonr esorbable HA-coated implants at 4 and 12 weeks. Differences in push-ou t shear strengths between interference- and noninterference-fit surgic al models were significant for uncoated implants at 4 weeks, but not f or HA-coated implants at any time period. Significant differences were seen between the three implant types only for the noninterference-fit model, where the HA-coated implants showed greater strengths than the uncoated implants (significant at 2 and 4 weeks). This study showed t hat presence of resorbable or nonresorbable HA coatings is beneficial when a gap of 2-3 mm is present between the implant and the bone. The resorbable HA-coated implants showed greatest strengths at the early t ime period. At later time periods, resorbable HA-coated implants showe d lower bone apposition and attachment strengths than nonresorbable HA coatings. However, resorbable HA-coated implants showed equivalent bo ne apposition and attachment to uncoated implants, suggesting that HA coating resorption and remodeling at the bone/implant interface can pr ovide good osteoconduction and fixation. (C) 1994 John Wiley and Sons, Inc.