TOOTH ERUPTION: THE AXIAL MOVEMENT OF CONTINUOUSLY GROWING TEETH

¹ Department of Anatomy, Chicago Medical School, Chicago, Illinois

The axial movement of a continuously growing tooth is the expression of its longitudinal growth. The leading factor in this orally directed growth is the elongation of the pulp. The pulp grows in a proliferation ring at its basal end. This proliferation zone is separated from the periapical tissue by an infolding of Hertwig's epithelial sheath, the epithelial diaphragm. The pulpal growth is normally simultaneous and equal to the elongation of Hertwig's sheath.

A "hammock" ligament on which the basal end of the tooth rests acts to direct the growth of the tooth. Continuous changes in the suspensory ligament of the tooth, stimulated by the expansion of the pulp, are an integral part of the process of eruption. These changes take place in the intermediate layer of the periodontal membrane. This layer consists of a plexus of precollagenous fibers.

Schour found in hypophysectomized rats inhibition of eruption and folding of newly formed dentin. Both these findings can be explained by a specific inhibition of pulpal (mesodermal) growth, whereas epithelial growth and the induction of dentin formation are far less affected.