Titanium-reinforced polytetrafluoroethylene membrane combined with inorganic polyphosphate induces exophytic bone formation in rabbit calvaria

The purpose of this study was to examine if the application of titanium-reinforced expanded polytetrafluoroethylene(TR-ePTFE) membrane combined with bovine bone mineral(BBM) soaked in inorganic polyphosphate promotes exophytic bone formation in rabbit calvaria. For this purpose, a total of 8 rabbits were used, and rectangular decorticated calvaria sites were created using a round carbide bur. In the control group, rectangular parallelepiped-shaped TR-ePTFE membranes (RPTPMs) were filled with BBM soaked in saline and placed on the decorticated sites and fixed with metal pins. In the experimental groups, RPTPMs were filled with BBM soaked in 4%, 8% and 16% inorganic polyphosphate prior to fixing with metal pins. Animals were sacrificed at 4 and 8 weeks after surgery, and new bone formation was assessed by histomorphometric as well as statistical analysis. The results indicated that at 8 weeks, all the experimental groups demonstrated exophytic bone formation. At 8 weeks, the 8% polyphosphate group revealed the most new bone formation (p<0.05). On the basis of these findings, we conclude that inorganic polyphosphate has a promoting effect on bone regeneration, possibly by enhancing osteoinductivity of the decorticated wound area and osteoconductivity of the carrier material, but not much as we expected.