Effect of occlusal morphology on the accuracy of bite force measurements using thin film transducers

Occlusal transducer foils using piezoelectricity or pressure-dependent electric resistance are potential candidates for a measurement system for both absolute levels and changes in bite force. This preliminary in vitro study evaluated the possible usefulness of such transducer foils in the assessment of occlusal forces in centric occlusion.

Piezoelectric force transducer foils 33 microm thick were placed between pairs of teeth with the dentition in centric occlusion. Occlusal forces were recorded in five patients, who were instructed to bite as hard as possible for about 1 second. Acrylic resin casts of each pair of antagonistic teeth were aligned with the help of interocclusal records. The casts were mounted in a jig, where a defined load could be applied. The ratio of applied force and measured sensor signal permitted a set of calibration factors.

A correction factor for each pair of teeth helped determine the ratio by which measured occlusal force exceeded actual tooth load. Differences in occlusal morphology gave rise to a wide span of correction factors (1.01 to 2.80). Steep cusp angles resulted in a wedge action that gave rise to a strong increase in occlusal forces, which were about twice as high as actual tooth load, with wide variation.

This method of bite force measurement eliminated the influence of occlusal morphology by individual correction for each pair of opposing teeth. To measure the absolute load of antagonistic teeth with thin film transducer foils, one must take into account individual occlusal morphology. Forces measured with the films are a function of both actual tooth load and occlusal morphology.