Tissue reaction to implanted biomaterials

Tissue reactions to the single-crystal sapphire, titanium, Co-Cr-Mo alloy, and PMMA were histologically evaluated after implantation into the subcutaneous tissue and tibia of rats. In subcutaneous tissue the reaction from early necrotic change and acute inflammation to final encapsulation by fibrous connective tissue was least pronounced around single-crystal sapphire implants. Tissue reactions of a slightly greater degree were found around titanium and Co-Cr-Mo alloy implants. The most prominent tissue reaction was observed around PMMA implants. In the tibia, single-crystal sapphire, titanium, and Co-Cr-Mo alloy implants were encapsulated by newly formed compact bone, but bone was not so evident around PMMA implants. These findings suggest that single-crystal sapphire implants have more favorable tissue compatibility than those of titanium, Co-Cr-Mo alloy, and PMMA.