Formation of intermediate cementum. III: 3H-tryptophan and 3H-proline uptake into the epithelial root sheath of Hertwig in vitro

Abstract

The intermediate cementum is a narrow, mineralized tissue between the cementum and dentin. Recent studies have shown that this tissue is mineralized by the epithelial root sheath in a way similar to the mineralization of the innermost layer of aprismatic enamel. In the present investigation uptake of proline and tryptophan into the epithelial root sheath was studied with autoradiography. Tryptophan is an amino acid that is incorporated into enamel matrix but not into collagen. Tryptophan uptake was significant in the whole epithelial root sheath, but not into the odontoblasts or predentin. Proline was incorporated into the predentin while the root sheath was unlabeled. This indicated that the matrix of the intermediate cementum was formed by the epithelial root sheath of Hertwig, and that this matrix was a noncollagenous matrix possibly of the same nature as enamel matrix.