Isometric muscle tension generated by masseter stimulation after prolonged alteration of the consistency of the diet fed to growing rats.

The forces developed by the masseter muscle and the diet-related changes were studied in situ. The active tetanic tension was measured indirectly by recording the forces applied to the mandible in four different predetermined interincisal distances. The highest tension developed in all the experimental groups was with an interincisal distance of 11 mm. The tetanic tension was significantly lower in rats fed a soft diet than in those fed a normal diet. This difference might be due to the smaller muscle fibres in rats with decreased functional demand. The changes in the masticatory muscles may influence the tension applied to the facial skeleton and cause the alteration in the craniofacial growth previously found in rats fed a soft diet.