TOOTH SUSPENSION. A COMPARATIVE STUDY OF THE PARADENTAL TISSUES OF MAN AND OF THE GUINEA PIG

¹ Departments of Pathology, Medical School and Operative Dentistry, Dental School, Harvard University, Boston, Mass.

1. The teeth of man and of rodents are so designed that the functional stresses of occlusion are absorbed and dissipated chiefly in the incisal part of the paradentium. The apical part of the paradentium is subjected to relatively minute forces. 2. The first force of occlusion is exerted as hydraulic pressure on the walls of the alveolus. 3. Escape of fluid by means of vascular channels communicating with the bone marrow spaces allows a gradual extension of the periodontal fibers by which the full force of occlusion is ultimately transmitted as tension to the alveolar bone. 4. Further efficiency in the absorption of occlusal forces is secured by the spiral form of the teeth themselves and the resiliency of the dentin of which they are composed. 5. The cross-sectional form of the tooth root is efficiently designed to resist forces tending to flatten the arc of longitudinal curvature of the tooth. This form also offers efficiently shaped surfaces for the transmission of pressures on the labial and mesial sides, while furnishing maximum surface for attachment of the periodontal fibers on the lingual and distal sides. 6. Enamel formation in rodents is carried on in the protected environment of the apical region. A number of modifications of tooth form and of periodontal structures contribute to the maintenance of such an environment.