Porous hydroxyapatite grafts in chronic subcrestal periodontal defects in rhesus monkeys: a histological investigation

The purpose of this investigation was to evaluate the histologic response to replamineform (porous) hydroxyapatite grafts in chronically inflamed, surgically created, periodontal pockets in Rhesus monkeys. Forty-eight subcrestal defects were surgically created in 8 Rhesus monkeys. Orthodontic wires were adapted to the base of the defects and left in place for 8 weeks. The defects were randomly assigned a treatment modality so that 8 granular porous and 8 block porous hydroxyapatite grafts were done. Eight sites were left as unoperated controls. Twenty-four contralateral sham-operated sites were treated by open curettage. Histometric measurements of the length of regenerated connective tissue attachment were recorded. Block hydroxyapatite, granular hydroxyapatite, and sham-operated sites exhibited similar amounts of regenerated connective tissue attachment, which was significantly greater than that which occurred in unoperated controls. Newly formed bone was observed within the porous channels of the hydroxyapatite grafts as well as in direct apposition on the surface of implant particles. New bone, cementum, and periodontal ligament was observed in grafted sites and in defects treated by open curettage. In some instances healing occurred by means of a long junctional epithelium. Histology confirmed that unoperated defects remained as unhealed, inflamed periodontal pockets. The results of this study suggest that porous hydroxyapatite grafts have the potential to regenerate the attachment apparatus in primates.