The rate of vascularization of coralline hydroxyapatite.

Coralline hydroxyapatite (CHAP) is a porous, biocompatible bone-graft substitute manufactured by the Replamineform process. The use of this material in the experimental and clinical settings for maxillofacial onlay grafting has been recently described. This study was designed to quantitate the rate of vascularization of coralline hydroxyapatite when used in an onlay application to membranous bone in an animal model. Sixteen onlay grafts of coralline hydroxyapatite (0.5 X 0.5 X 1.0 cm Interpore 200) were placed in a subperiosteal location on the nasal dorsum of 2- to 3-kg male New Zealand white rabbits. The grafts and nasal bones were harvested en bloc at 1, 2, 3 and 4 weeks after onlay. Prior to harvest, injectable silicone visualizing agent (Microfil*) was injected by means of carotid artery cutdown. The decalcified specimens were examined on a digitizing pad to count the number of vessels appearing in the blocks of hydroxyapatite. Counting was summed and integrated by an Apple IIe microcomputer. A significant difference (p less than 0.05) was noted in both the number of vessels and the fraction of implants infiltrated by vessels between 1 and 4 weeks. The usefulness of these previously undescribed data may be in their extrapolation to onlay grafts of coralline hydroxyapatite in maxillofacial reconstruction in humans.