Jaw separation and maximum incising force.

A gnathodynamometer was constructed to study the effect of varying the degree of jaw opening on the maximum incising forces in 20 human subjects. The incising force was greatest when the gap (distance) between the incisal edges of maxillary and mandibular incisors was 17 +/- 3 mm. We suggest that with further refinement, the measurement of the optimum distance could be used to determine the occlusal vertical dimension. The IEMG was monitored simultaneously with the incising-force measurements. No relationship was found between the maximum incising force and the IEMG at different openings of the jaws.