The long-term effects of hard alloplastic implants when put on bone.

The resorption of bone beneath 4 alloplastic materials has been studied for periods up to 18 months in rabbit skulls. When the effects of pressure were negated, there was no significant difference in bone resorption attributable to placement above or below the periosteum. Dacron backing or polyurethane backing were associated with more inflammation and greater bone reaction than were plain silicone or stainless steel. The changes noted at 18 months were essentially the same as those noted at 6 months.