Changes in axial mobility of undisturbed teeth and following sustained intrusive forces in adult monkeys (Macaca fascicularis).
The axial mobility and changes in rest position were studied over 3-h periods. No loads were applied to 10 teeth. All displayed reduction in mobility; eight became extruded. Other teeth were displaced into their sockets to a sustained level by a screw for 3 h. Mobility decreased for those teeth which were intruded a distance equivalent to less than 800 mN force, but increased following greater intrusion. It is argued that vascular changes played no part; it is more likely that aggregation of proteoglycans occurred in the periodontal ground substance when there was little or no displacement of the tooth. Displacement would have generated tension in the collagen fibres of the periodontal ligament, leading to smaller proteoglycan molecules being formed and a consequent increase in mobility.