Healing of periodontal defects treated with enamel matrix proteins and root surface conditioning--an experimental study in dogs.

Application of enamel matrix proteins has been introduced as an alternative method for periodontal regenerative therapy. It is claimed that this approach provides periodontal regeneration by a biological approach, i.e. creating a matrix on the root surfaces that promotes cementum, periodontal ligament (PDL) and alveolar bone regeneration, thus mimicking the events occurring during tooth development. Although there have been numerous in vitro and in vivo studies demonstrating periodontal regeneration, acellular cementum formation and clinical outcomes via enamel matrix proteins usage, their effects on the healing pattern of soft and hard periodontal tissues are not well-established and compared with root conditioning alone. In the present study, the effects of Emdogain (Biora, Malmö, Sweden), an enamel matrix derivative mainly composed of enamel matrix proteins (test), on periodontal wound healing were evaluated and compared with root surface conditioning (performed with 36% orthophosphoric acid) alone (control) histopathologically and histomorphometrically by means of the soft and hard tissue profile of periodontium. An experimental periodontitis model performed at premolar teeth of four dogs were used in the study and the healing pattern of periodontal tissues was evaluated at days 7, 14, 21, 28 (one dog at each day), respectively. At day 7, soft tissue attachment evaluated by means of connective tissue and/or epithelial attachment to the root surfaces revealed higher connective tissue attachment rate in the test group and the amount of new connective tissue proliferation in the test group was significantly greater than the control group (p<0.01). New bone formation by osteoconduction initiated at day 14 in the test and control group. At day 21, the orientation of supra-alveolar and PDL fibers established, and new cementum formation observed in both groups. At day 28, although regenerated cementum was cellular in all of the roots in the control samples, an acellular type of cementum (1.32+/-0.83 mm in length and 3.16+/-0.23 microm in width) was also noted in six roots of test samples with an inconsistent distribution on the root surfaces. The amount of new cementum was significantly higher in the test group than the control group samples (p<0.01). The width of the cellular cementum in the control group was more than the cellular cementum in the test group, but the difference was not statistically significant (p>0.05). A firm attachment of acellular cementum to the root dentin with functional organization of its collagen fibers was noted, and, the accumulation and organization of cellular cementum in the control group was more irregular than the cellular cementum formed in the test group. The amount of new bone was 2.41+/-0.75 mm in the test and 1.09+/-0.46 mm in the control group at day 28. The rate of bone maturation (the number of osteons) was found higher in the test group (10.75+/-0.85) than the control group (5.50+/-0.86). Under the limitations of the study, our results reveal that when compared with root surface conditioning, enamel matrix proteins have more capacity for stimulating periodontal regeneration via their positive effects on root surfaces, i.e. inhibition of gingival epithelium down growth and stimulation of connective tissue proliferation and attachment to the root surfaces during wound healing. An acellular type of cementum regeneration and new alveolar bone formation by an accelerated osteoconductive mechanism are also achieved with application of enamel matrix proteins.