THE RESORPTION OF BONE-IMPLANTED CORALS VARIES WITH POROSITY BUT ALSOWITH THE HOST-REACTION

Three different exoskeletons of coral species Porites astreoides (P), Montastrea annularis (M), and Dichocoenia stokesi (D) were implanted f or 2-20 weeks in rabbits. At 2, 4, 8, or 20 weeks, the exoskeletons pr esented variations in their resorptions depending on the species. To u nderstand the variations in the decreasing speed of the implants despi te their similar chemical composition, a study of the surface and arch itecture of the coral was carried out using scanning electronic micros copy, porosity was evaluated, and growth and differentiation of osteog enic cells cultured in vitro were observed for more than 1 month. At t he cellular level, the surface of the implants was identical. Three-di mensional structures of the implants were variable, but the porosity v alues [P = 42.7%, M = 40.7%, and D = 17.4%] could not completely accou nt for the differences in the resorbing process of the species. Standa rd histologic studies performed at 2, 4, 8, and 20 weeks after implant ation produced the same pattern with P or M, showing aspects of rapid resorption; however, with D there were images resembling those of a fo reign-body reaction. It seems that when resorption is not quick enough , a foreign body reaction develops which further slows down the proces s. This work focuses on the importance of porosity when using coral as bone substitute. (C) 1995 John Wiley and Sons, Inc.