Periodontal regeneration in a buccal dehiscence model in monkeys after application of enamel matrix proteins

There is increasing evidence that cells of the epithelial root sheath synthesize enamal matrix proteins and that these proteins play a fundamental role in the formation of acellular cementum, the key tissue in the development of a functional periodontium. The purpose of the present study was to explore the effect of locally applied enamel matrix and different protein fractions of the matrix on periodontal regeneration in a buccal dehiscence model in monkeys. Buccal, mucoperiosteal flaps were raised from the canine to the Ist molar on each side of the maxilla. The buccal alveolar bone plate, the exposed periodontal ligament and cementum were removed. Various preparations of porcine enamel matrix with or without vehicles were applied before the flaps were repositioned and sutured. After 8 weeks, the healing was evaluated in the light microscope, and morphometric comparisons were made. Application of homogenized enamel matrix or an acidic extract of the matrix containing the hydrophobic, low molecular weight proteins, amelogenins, resulted in an almost complete regeneration of acellular cementum, firmly attached to the dentin and with collagenous fibers extending over to newly formed alveolar bone. After application of fractions obtained by neutral EDTA extraction containing the acidic, high molecular weight proteins of the enamel matrix, very little new cementum was formed and hardly any new bone. The results of the controls in which no test substance was applied before the repositioning of the flap, were very similar to those obtained with the EDTA extracted material. Propylene glycol alginate (PGA), hydroxyethyl cellulose and dextran were tried as vehicles for the enamel matrix preparations. Only PGA in combination with the amelogenin fraction resulted in significant regeneration of the periodontal tissues.