Evaluation of HTR polymer as a craniomaxillofacial graft material

An experimental animal study was undertaken to evaluate the potential use of HTR polymer as a craniomaxillofacial reconstructive material. Its properties of marked hydrophilicity, a negative surface charge, and extensive porosity combined with a calcium graft coating suggested favorable osteoconductive properties. Four sites of the rabbit craniomaxillofacial skeleton were evaluated by placement of both inlay and onlay implants. Postoperative assessment at 60, 120, and 240 days consisted of histologic evaluation by tetrachrome staining of calcified sections. At 60 days, extensive osseous ingrowth into the inlay implants had occurred extending up to 2000 microns. The onlay implants, however, exhibited more limited ingrowth extending only 100 to 200 microns into the material. Over the ensuing 120- and 240-day postoperative periods, the average depth of bony ingrowth did not progress in either the inlay or onlay specimens over that observed at 60 days. Differences also were noted between the inlayed skeletal sites, with increased marrow at the recipient site resulting in increased bony ingrowth. The material appears to be biocompatible, with no evidence of infection, inflammatory reaction, or bone resorption observed around any of the implants. The implants exhibited a significant osteoconductive capability that was most manifest when implants were exposed to bleeding cortical/marrow surfaces as inlay grafts.