Influence of differences in the hardness and calcium content of diets on the growth of craniofacial bone in rats

Objective:  To examine the effects of a soft diet and a low-calcium diet on the craniofacial growth and bone architectures of the maxilla and mandible. Materials and Methods:  Male rats (n  =  20, 3 weeks old) were divided into four groups. Ten rats were given a normal-calcium diet, and the other rats were given a low-calcium diet. Each group was then divided into two subgroups, which were fed a hard or a soft diet. After 4 weeks, craniofacial growth and architecture in maxillary and mandibular bone were analyzed using cephalometry, micro-computed tomography, and histopathology. Results:  The low-calcium diet had no effect on serum calcium levels. The low-calcium diet had the greatest effect on craniofacial bone growth, while the soft diet affected the growth of several bone sites that are attached to the masseter muscle. A low-calcium diet resulted in the deterioration of the connectivity of the trabeculae in the furcation region of the maxillary and mandibular first molar, while a soft diet resulted in the diffuse disappearance of trabeculae in the central part of the furcation regions. In the midpalatal suture, a low-calcium diet resulted in inhibition of cartilaginous ossification, although the midpalatal suture had a normal cartilaginous structure. A soft diet resulted in narrower cartilage cell layers in the midpalatal suture. Conclusions:  We demonstrated that a low-calcium diet and a soft diet resulted in a deterioration of bone structures in both the maxilla and in the mandible; however, the mechanisms underlying these effects differed between diets.