Histological investigation of the tissue response to hydroxyapatite used as an implant material in periodontal treatment.

Patients with severe periodontitis and who had one or more teeth with infrabony pockets were treated by periodontal surgery with implantation of hydroxyapatite particles into the bone defects at the time of surgery. Subsequently, in three patients it was found necessary to extract a tooth for reasons not related to the previous periodontal treatment. Specimens that included the local soft tissues and crestal bone attached to the teeth were obtained at 22, 40 and 80 weeks after placement of the implant. They were decalcified and stained with haematoxylin and eosin and examined under light microscopy. The healing response was found to vary between specimens, and between sites within the same specimen. The early stage of healing showed the implant particles surrounded by collagen. Subsequently, varying degrees of resorption of the periphery of the particles was seen, and at some sites bone deposition was observed. These different healing responses were found to be progressing concurrently at sites in close proximity. Further work is needed to confirm the histological findings described in the paper.