The Epithelial Sheath: Histogenesis and Function

Abstract

Epithelium is the primary formative tissue of the human tooth. Starting with the stratum germinativum, the epithelium blazes a trail through the connec-tive tissue, organizing itself and the enclosed connective tissue as it outlines the pattern for a particular tooth. It is our purpose to demonstrate that, in a broad sense, this organization of and by the epithelium takes place in 2 individual units-one of which forms the crown, the other, the root of the tooth. The second unit does not begin to function until the first has virtually completed its functioning. The familiar arrangement of the 4 epithelial layers which constitute the enamel organ serves to complete the formation of the hard tissues of the crown of the tooth up to the cervical line, or the cemento-enamel junction. The epithelial sheath serves to outline the form of the root, and further functions to organize the adjacent connective tissue for the formation of odontoblasts and root dentin. The capacity of the epithelial sheath to stimulate root dentin is not manifested until the enamel is completely formed and calcification is well on the way.