Acellular cementum plays an important role in the attachment of the periodontal ligament to the root surface. Many studies worldwide show that cementoblasts that form acellular cementum are derived from the differentiation of dental follicle cells and the epithelial-mesenchymal transition of epithelial root sheath cells. Transplantation of dental follicle cells can differentiate into periodontal fiber-like and cementum-like tissue in vivo. In vitro, both dental papilla cells and epithelial root sheath cells can induce in dental follicle cells the high expression of alkaline phosphatase. Bone sialoprotein serves as the markers of acellular cementum. Bone morphogenetic protein, Ca2+, and Wnt/β-catenin signaling pathways have also been found in the regulation of dental follicle cell differentiation. Membrane transporters associated with inorganic phosphate have a more sensitive impact on acellular cementum formation. Epithelial root sheath cells can also participate in acellular cementum through epithelial-mesenchymal transition. The differential expression pattern of D28k and distal-less homeobox-2 in dental follicle cells, epithelial root sheath cells, and cementum morphologically indicates that parts of acellular cementum may be derived from epithelial root sheath cells. Moreover, the transformation of growth factor β-snail activates the phosphatidylinositol-3-kinase/protein kinase B signaling pathway involved in the epithelial–mesenchymal transition of epithelial root sheath cells.
