The effect on intrusive tooth mobility of surgically removing the cervical periodontal ligament in monkeys (Macaca fascicularis).

The intrusive mobility of 10 teeth was recorded at half-hourly intervals under 4N loads following reflection of the gingiva in 2 animals. After 3 h, the periodontal ligament surrounding the coronal area of the root was removed with a steel bur to a depth of 4 to 5 mm; loadings were then continued. For 5 teeth, little or no change in mobility occurred. Displacement increased in the other teeth which could be accounted for by tilting, the teeth not being vertical. The residual healthy ligament seemed to withstand the small vertical loads as though the periodontium was intact, whereas cutting the ligament, mesially and distally in a previous experiment, but not removing it, substantially weakened the supporting mechanisms.