[Mobility of premolars under load in partially edentulous dentition]

The mobility of the upper and lower premolars under load was investigated in relation to the interproximal contact and occlusal facets. The mobility was measured on ten subjects with the molars missing in the bucco-lingual and mesio-distal direction, using a non-contact sensor system, when a 500 gram load was applied in the horizontal direction, during hard biting in intercuspation and biting of foods. The ratio of the tooth movement in the bucco-lingual direction to the mesio-distal direction was larger in the upper premolars than in the lower ones. As the total mobility increased, the tooth movement was larger on the buccal side than on the lingual side of the upper jaw, on the lingual side than on the buccal side of the lower jaw, and on the mesial side than on the distal side of both jaws. The direction of the movement did not coincide with the direction of the load, due to the horizontal rotation. When biting, the first premolars showed a mesial movement and the second premolars showed a more distal movement than the first premolars. A correlation between the direction of the tooth movement during hard biting and that of the facets was observed.