Fluid pressures in the periodontal ligament of the mandibular canine tooth in dogs

Abstract

Tissue fluid pressures were monitored in the periodontal ligaments of 19 mandibular canine teeth. Resting (no load) pressures were recorded and changes in the pressure which accompanied the application and removal of forces up to 500 g. All parameters were reexamined after the animals were killed by exsanguination. The resting intraperiodontal pressure (IPP) was −1.86 ± 1.00 mmHg (mean ± 95 per cent confidence limits), markedly less than values obtained by other investigators. As these dogs were positioned with their mandibular canines at a higher elevation relative to the rest of the body than other workers have used, this may indicate that the pressure in the ligament is subject to postural variation. The resting IPP was not correlated with systemic blood pressure, and did not change significantly after exsanguination. Trauma to the ligament raised the resting IPP to −0.36 ± 1.93 mmHg. Application of load resulted in an immediate increase in pressure which decayed rapidly (halving-time less than 1 s). Removal of the load produced the inverse pattern, but with a reduced peak pressure and a longer halving-time. Trauma increased the halving-time for the decay of the load-induced pressures to the point that the pressure increases were judged to be sustained rather than transient. The pressure changes produced by the application of forces to the teeth were small compared to the loads applied, suggesting that the free fluids of the periodontal ligament make only a minor contribution to tooth support.