Comparison of alloplastic implants for facial bones by scintigraphy and histology: an experimental study

Reconstruction of bone defects and contour irregularities in the craniofaci al region is difficult and often requires complex solutions. This study inv estigated the tissue response, vascularization and bone ingrowth, in hydrox yapatite, porous polyethylene and silicone elastomer when used as bone graf t substitutes. 24 albino rabbits (8 rabbits for each implant) were used in this investigation. Hydroxyapatite 500 particles, silicone rubber and porou s high-density polyethylene were placed in the cavities formed with a drill in the rabbit frontal bones. As a part of a prospective study the vascular ization rates of all implant materials were analyzed 10 days and 2 months a fter surgery using (99m)Technetium-MDP (Methylene diphosphonate) scintigrap hy of the skull. The scintigraphic studies were performed 2 hours after int ravenous injection of 4 mCi (148 MBq) Tc-99m-MDP. The frontal bone was exci sed on the 10th and 60th days. All tissue specimens were placed first in 10 % formalin and then in 10% nitric acid solution for decalcification. The va scularization, connective tissue ingrowth, foreign body reaction and bone r egeneration around the implant were evaluated. Results of this study sugges ted that hydroxyapatite and porous polyethylene were stabilized in bone whi le as expected silicone was mobile, also hydroxyapatite implants are vascul arized better and are more biocompatible than porous polyethylene.