Fogorvosi szemle, 2007 (100. évfolyam, 1-6. szám)
2007-10-01 / 5. szám
221 FOGORVOSI SZEMLE ■ 100. évf. 5. sz. 2007. in the defects treated with enamel matrix derivative; whereas in the untreated control defects only a reparative, cellular cementum developed [1], On the basis of these findings the enamel matrix derivative (EMD) from the tooth pouches of not erupted teeth from young pigs were isolated, purified and lyophylisated. Since EMD are an extreme hydrophobic substance, they were brought by means of a propylene glycol alginate (PGA) carrier into soluble form before their use in regenerative periodontal therapy [5]. A recent study has identified enamel matrix proteins and proteolytic enzymes present in EMD and compared them with those extracted from developing porcine enamel itself [6]. The results have shown that while developing enamel contained amelogenins, albumin, amelin, and enamelin, EMD contained only amelogenins. Thus, at the time being it may be assumed that the main component of EMD are amelogenins [4-6]. A technique or a material must, however, fulfil the following criteria in order to be classified as “regeneration-promoting” [7]: • In vitro studies, which confirm the action mechanism. • Controlled histological animal studies, which demonstrate formation of new root cementum, periodontal ligament and alveolar bone. • Human biopsies, which show formation of root cementum, periodontal ligament and alveolar bone on a plaque-infected root surface. • Controlled clinical studies, which prove a gain of clinical attachment and radiological new bone formation. In the following overview, the existing evidence regarding the clinical use of EMD is provided. In vitro studies Several in vitro investigations were carried out to study the mechanism of EMD on the periodontal ligament and gingival fibroblast and on bone cells [8-40], Thus, in a series of laboratory studies the migration, attaching, proliferation, biosynthetic activity of PDL cells and formation of mineralized nodules following the application of EMD were examined. To determine the possible presence of existing polypeptide factors immunoassays were performed [5, 8]. The results have shown that: a) under in vitro conditions EMD promotes the proliferation of periodontal ligament (PDL) fibroblasts, but not that of epithelial cells, b) the total protein synthesis of the PDL fibroblasts increases, and c) the formation of mineralized nodules by PDL fibroblasts is promoted. PDL fibroblasts treated with EMD displayed an increased intracellular cAMP concentration and autocrine releasing of TGF-ß1, IL-6 and PDGF AB in comparison to the control group (without addition of EMD) [12], Although the epithelial cells showed an increased release of cAMP and PDGF AB following the additional application of EMD, their proliferation and growth rate was inhibited [10, 12]. It was concluded that EMD simultaneously promotes the growth of mesenchymal cells by inhibiting epithelial cells and, in the same time, it promotes the release of autocrine growth factors from PDL fibroblasts [12]. Similar findings were also reported by Okubo et al. [13] who demonstrated that EMD has no appreciable effect on osteoblastic differentiation although it stimulates cell growth and IGF-1 andTGF-ß1 production in PDL cells. Palioto et al. [14] have evaluated the effect of EMD, IGF-1, and the combination of these two factors on the proliferation, adhesion, migration, and expression of type I collagen in PDL fibroblasts. The results have indicated that the proliferation of PDL fibroblasts was significantly stimulated by EMD and EMD plus IGF-1 in a dose- and time-dependent manner whereas these factors did not affect adhesion, migration, or expression of type I collagen of these cells. Other data indicate that EMD may contain additional mitogenic factors such as TGF ß and BMP-like growth factors that stimulate fibroblastic proliferation and contribute to the induction of biomineralization during periodontal regeneration [15-18]. Keila et al. [19] have investigated the effects of EMD on rat bone marrow stromal cells (BMSC) and on gingival fibroblasts (GF). EMD increased the osteogenic capacity of bone marrow and mineralized nodule formation. The presence of EMD in the initial stages (first 48 hrs) of the culture was crucial for this effect. In contrast, EMD did not induce osteoblastic differentiation of GF but increased up to two-fold both their number and the amount of matrix produced. In further investigations it was shown that the attaching growth and metabolic rate of PDL fibroblasts increased significantly when EMD was added in cell cultures, and that EMD may convert the differentiation pathway of a pluripotent C2C12 mesenchymal cells into osteoblast and/or chondroblast lineage [8-10, 12, 20]. PDL fibroblasts showed a significantly increased alkaline phosphatase activity following the application of EMD and it enhanced human PDL fibroblast proliferation [21,22]. In the presence of EMD, human PDL fibroblasts showed some morphological changes that made them more similar to cementoblasts than to fibroblasts, suggesting a process of cellular differentiation [22], A recent study examined the influence of EMD on the viability, proliferation, and attachment of periodontal fibroblasts to diseased root surfaces [23], PDL cell proliferation appeared to be ameliorated following exposure to EMD and the SEM analysis suggested that cellular attachment to diseased dentin was enhanced following EMD application. Further investigations have demonstrated that EMD significantly increased the mRNA synthesis of the matrix proteins - versican, byglycan and decorin - and led to an increased hyaluronan synthesis in the gingival and PDL fibroblasts [9]. It was also suggested that integrins are involved in the interaction of PDL and gingival fibroblasts with EMD [24], However, it has to be emphasized that in most studies EMD had a stronger effect on the PDL fibroblasts than on
