Immobilization of the Erupting Molar in the Syrian Hamster

¹ University of Michigan School of Dentistry, Ann Arbor, Michigan

In an attempt to understand more fully the process of tooth eruption, hamster molars in the early stages of intraoral eruption were mechanically restricted from erupting by a surgical procedure of circumferential wiring. Seventy-one second and third molars were immobilized in this manner for periods of time ranging from 2 days to 7 weeks.

No histologic changes were noted in teeth immobilized for less than 3 days, but after 4 days the root tips appeared to be distorted and bent occlusally and interradicular bone was in contact with the root bifurcation. In addition, interdental alveolar bone seemed to have continued growing occlusally, carrying the attached periodontal fibers with it and causing a greater fiber angulation than in unrestricted teeth. After 1 week of immobilization, there was evidence at the apex of a disorganized proliferation resembling osteodentin. After longer periods of restriction, this tissue appeared as a dense mass in the apical-root canal and a normal periodontal-membrane width was observed. Molars released from their restriction resumed normal root growth, and the teeth came into occlusion in 1-2 days. At the apex, the pulp and surrounding connective tissues did not exhibit any necrosis or crowding due to contained cellular proliferation. In addition, there was no evidence of vascular changes within the apical pulp or periapical tissues.

From these observations the following conclusions were drawn: (1) Roots of immobilized teeth failed to lengthen properly and contact or push against underlying bony structures; therefore root elongation may be a result of the process of eruption rather than one of the primary causes. (2) Growth of alveolar bone, which seemed to continue even when eruption was restricted, may be an important factor in eruption by creating a stress on periodontal fibers. (3) No hyperemia, vascular proliferation, or edema was observed in the apical pulp or periodontal tissues; therefore, the findings of this study do not support the theory that vascularity or vascular pressure is a significant force in eruption.

This article has been cited by other articles:

				J. P. Gorski and S. C. Marks Jr Current Concepts of the Biology of Tooth Eruption Critical Reviews in Oral Biology & Medicine, January 1, 1992; 3(3): 185 - 206. [Abstract] [Full Text] [PDF]