Effect of Enamel Matrix Derivative and Parathyroid Hormone on Bone Formation in Standardized Osseous Defects: An Experimental Study in Minipigs

Abstract

Previous experimental studies have indicated that locally administered enamel matrix derivative (EMD) and parathyroid hormone (PTH) may have a stimulatory effect on bone formation. However, it is not clear if the positive effect of EMD is related to its effect on the periodontium as a whole or directly on the bone-forming cells. In addition, it is not known if the presentation of PTH by adding the amino acid sequence Arg-Gly-Asp (RGD) is essential for its osteopromotive effect. Local delivery of a bioactive substance at the right time and in the right concentration often constitutes a major challenge. Polyethylene glycol-based hydrogel (PEG) is a degradable vehicle developed for delivery of bioactive proteins. To enhance the mechanical stability of the PEG-bioactive substance complex, an osteoconductive bone substitute material is often needed. Three standard diameter monocortical bone defects were prepared bilaterally in the mandibles of 18 Göttingen minipigs. The six defects of each animal were grafted with 1) autogenous bone chips, 2) biphasic calcium phosphate bone substitute (BCP), 3) PEG + BCP, 4) EMD + PEG + BCP, 5) PTH + PEG + BCP, or 6) PTH-RGD + PEG + BCP. A non-resorbable barrier membrane was used to cover the defects. Three groups of six animals healed for 2, 4, and 8 weeks, respectively. There was no statistically significant effect of EMD, PTH, and PTH + RGD on bone formation compared to BCP and BCP + PEG. Particulated autografts showed the highest amount of new bone formation at all observation periods. The present study fails to demonstrate any stimulatory effect of EMD, PTH, or PTH + RGD in combination with an experimental PEG hydrogel and BCP on bone formation.