The relationship between masticatory function and craniofacial morphology. III. The eruption pattern of the incisors in the growing rat fed a soft diet

Abstract

The aim of this study was to investigate the influence of the eruption pattern of the upper incisors on the viscero-cranial morphology in rats with a reduced masticatory function. Thirty-six male rats with a mean body weight of 90 g were divided into three groups. One group received the ordinary hard pellet diet, while the second and the third group received a standardized soft diet. Furthermore, the incisors of the third group of rats were shortened regularly. The rate of eruption and attrition of the incisors was measured in all animals by means of a notch cut on every registration occasion on the distolabial gingival margin on the right incisor. At the end of the experimental period lateral cephalograms were taken, to compare the craniofacial morphology of the groups. The results indicated that variation in the consistency of the diet has an influence on the incisor eruption pattern in the rat, being lower in the soft diet group. This seemed to be an effect of altered attrition since when the reduced attrition rate was compensated for by grinding the incisors the eruption pattern resembled the normal one. The cephalometric results showed no morphological differences between the two groups which received the soft diet, although a different incisor eruption pattern was found in the two groups. In contrast, the viscerocranium, in the two soft diet groups was more orthocranially oriented and the angular process of the mandible was smaller than in the normal diet group. Consequently these craniofacial changes were independent of the incisor eruption rate and seemed to be caused by the reduced masticatory muscle function in the soft diet groups.