Changes in the force-intrusion relationship of the tooth with its resting position in macaque monkeys

Abstract

Axial displacement of each test incisor relative to a screw placed in the neighbouring bone was measured by means of linear variable displacement transformers. Thrusts of 4 newtons (N) were applied axially to the tooth, either once every 30 min or as a sequence of 16 thrusts at 10 s intervals once every 30 min. For the single thrust, changes in the slope of the log displacement versus log force curves for force 0.8 – 4.0 N were correlated strongly with the change in position of the tooth within the socket. This did not occur over 30 min for the groups of 16 thrusts but, between the 1st and 16th thrusts, there was an almost constant reduction in slope. A sequence of three basic positioning mechanisms could explain this behaviour. At first, there is the simple recoil of tissues and the return of blood; in the medium term, a passive recovery of the position of the tooth after a series of loadings due to the re-polymerization of the ground substance and rebinding of the intercellular fluid; in the long term, an active positioning mechanism in which the turnover of the components of the collagen-fibre meshwork, in particular the fluid uptake, would control the position of the tooth within its socket.