The relationship between masticatory function and craniofacial morphology. II A histological study in the growing rat fed a soft diet

In a previous study it was found that changed masticatory function induced by a soft physical consistency of the food caused alterations in the craniofacial morphology of the growing rat. In the present study, bone growth in the facial skeletal regions of these rats, was assessed in sutures and cortical bone by vital staining (oxytetracycline), microradiography and routine histology. Oxytetracycline was injected at day 0 of the experimental period to obtain a baseline marking, and at day 14 to enable a longitudinal description of bone growth. With these methods it was found that the overall bone apposition pattern in the viscerocranium was continuously decreased and changed to a more vertically directed pattern. Also the nasopremaxillary suture showed a more vertical orientation in the animals with the reduced function. The changed growth pattern in this study was found to be related to altered tension in the fibre system of the suture and periosteum. In addition, it was observed that obliterative osteogenesis occurred in the internasal suture (synostosis) in the group with reduced masticatory function. Thus, it seems that masticatory function may influence suture closure.