Changes in periodontal pulsation in relation to increasing loads on rat molars and to blood pressure

Pulsation originating from the vascular system of the periodontal ligament (PDL) is apparently synchronized with the heartbeat. As periodontal pulsation causes pulsatile tooth vibration, it might be possible to evaluate it indirectly by measuring tooth vibration. Periodontal pulsation has been found to be dependent on blood flow and blood pressure in the PDL. Heavy orthodontic force is known to reduce blood flow and decrease the amplitude of the pulsation. The purpose now was to examine (1) the magnitude of the experimental orthodontic force that will impair PDL blood flow; and (2) the differences in the amplitude of pulsation between normal and hypertensive animals. The experiments were performed on 10 Wistar, 10 Dahl S and 10 Dahl R rats. Hypertension was induced in Dahl S rats. The head and maxilla of anaesthetized animals were immobilized. Mesial tipping forces of different loads (0.098–0.882 N) were applied to a molar and periodontal pulsation was measured with a highly sensitive laser displacement meter. The periodontal pulsation at each load resembled a blood-volume pulse wave. Its amplitude began to decrease at a load of 0.588 N in Wistar and Dahl R rats, and at 0.784 N in Dahl S rats. The group with induced hypertension had a significantly larger amplitude than the other two groups when 0.588 N was applied. These results suggest that: (1) periodontal pulsation can indicate a PDL overload; and (2) that systemic blood pressure affects the amplitude of periodontal pulsation during loading.