The relationship between masticatory function and craniofacial morphology: I. A cephalometric longitudinal analysis in the growing rat fed a soft diet

The influence of masticatory muscle function on the craniofacial growth pattern in the rat was studied longitudinally by means of a computerised cephalometric method. In order to induce a low functional activity, one group was fed a soft diet, while another group received a standard laboratory diet and served as a control group. The rats were in the late growing state at the start of the experiment (28-days-old) and the experimental period was 28 days. The analysis showed that a more anteriorly directed growth rotation of the viscerocranium occurred in the rats fed the soft diet compared to the rats fed the standard hard diet. Thus, the skull became increasingly more orthocranial in shape in the soft diet group. Although no difference in overall skull size could be found between the two groups an increased viscerocranial height was found in the soft diet group, which is consistent with the altered growth pattern. A decreased growth rate was also found in the gonial angle of the mandible in the soft diet group. These findings indicate that the masticatory muscle function influences not only bone remodelling in local areas, due to direct muscle action, but also the general craniofacial growth pattern.