Bone regenerative response following bone augmentation using hydroxyapatite with and without growth factors

Abstract

The purpose of this study was to determine whether adding transforming growth factor-13 (TGF-13) which is known to promote osteogenesis or 15 amino acid polypeptide obtained from collagen type I (P-15) which is known to enhance DNA synthesis in cultured fibroblasts, would enhance the osseoint~gr.ation- of porous anorganic bovine bone block (HA-block) to mandibular bone surface. Total of 45 rabbits were divided into three equal groups. The buccal side of the mandible in ea.ch anesthetized animal was surgically exposed,. decorticated and 10 x 5 x 4 mm. HA (Group I), HA+ TGF-13 (Group II) or HA + P-15 (Group III) blocks. were affixed to .host bone using two, titanium screws. Animals were sacrificed, 1 wk, 4 wks and 8 wks after surgery. A core of the implant· and underlying host bone was used to determin.e osteocalcin using Western and Slot blot analyses before perfusing the animals with 4% forma}in. The contralateral sides were only decorticated and served as sham controls. The interface between the HAblock and the ho.st bone showed a signifi.cantly higher (P<0~05) number of mesenchymal cells in the HA + TGF--P. and HA + P-15 one week group when c.ompared. to HA-alone. This numb.er of mesenchymal ·cells declined significantly .by the 4th and 8th weeks. The proliferating cell nuclear antigen (PCNA) index using immunohistochemistry als.o showed a significant increase in the one week groups and· then also declined. Alkaline phosphatase, osteocalcin, bone volume, and new bone formation were all significantly increased by the 4th and 8th weeks and were significantly higher in the HA + TGF-13 and HA + P-15 at 4 wks after surgery. In addition, the macropores of the lower halves of all blocks were filled with new bo.ne. The den~ity of the newly formed bone was comparable to the control bone. These res.ults indicate that anorganic :bovine bQne blocks are osteoconductive and their pores permit growth of new bone. The adding of TGF-P or P-15 enhanced all parameters of osteogenesis at the mandibular bone surface.