Growth of the craniofacial bone is a complex biological phenomenon induced by highly coordinated interaction between genetic and environmental factors. The purpose of this study was to confirm whether the environmental factors, namely powdered diet and extraction of all upper molars, have an influence on the cranium and mandibular bone size, bone volume, mineral bone density, widths between left and right condyles and gonions, and intra-arch widths at the first and third molars in rat mandibles.Ten 5-week-old male Wister rats were fed on powdered diet after extraction of all upper molars (experimental group=5 rats) and pellet diet without extraction of molars (control group=5 rats) for 20 weeks. At 20 weeks of age, the animals were examined by Microcomputer tomography. The mean values of the measurements in the two groups were compared.There was no significant difference between the groups in the cranial sizes. The vertical lengths were significantly shorter in the experiment group than the control group while no significant difference was observed in the mandibular horizontal lengths and widths at the left and right condyles and gonions. The mandibular volume and bone mineral density in the experimental group were significantly lower than that of the control group. The intraarch width at the lower third molars was also significantly shorter in the experimental group than the control group.

The purpose of the present study was to determine whether different consistency of diet and malocclusion induced by the extraction of molar teeth on the masticatory organs modulated gastric acid secretion, gastric emptying and intestinal transit in young and elder rats. Male Wistar rats (young, 5 weeks; elder, 1.5 years) were used in this experiment, and were divided into 2 groups. Group one (G1) was maintained with solid diet, Group two (G2) with mud diet. Further, the mandibular molar teeth of G2 were extracted. The experimental period was 10 weeks. The effect of aging and malocclusion on the parameters of gastric secretion was examined using pylorus-ligated rats. The gastric emptying rate (GER) and small intestinal transit rate was determined in rats by evans blue from the stomach and charcoal from the small intestinal, respectively. In pylorus-ligated rats, Young-G2 rat of gastric juice volume, acid output and pepsin secretion remarkably showed significant decrease in comparison with Young-G1 group, but there was not significant difference between Elder-G1 and Elder-G2. GER of Young-G2 rat group was 44.2±7.9%, significantly lower than that of Young-G1 rat group (61.6±8.8%, P<0.01), but Elder-G1 rat group were not significantly different than those of rats of Elder-G2 group. In small intestinal transit rates of charcoal meals, G1 and G2 of young were 73.3±9.1 and 55.1±8.6%, respectively, and Elder groups were 61.7±9.8 and 52.6±7.7%, suggesting an insignificant effect on diet. These results suggest that the diet and malocclusion, induced by extraction of mandibular molar teeth of young rat groups, may have a great influence compared to elder rat groups. that neurogenesis in the adult hippocampus was restrained by aging and soft-diet feeding. In the hard-diet mice, the number of BrdU-positive cells in the dentate gyrus was fewer in 6 month old mice than 3 month old mice at any survival period investigated 2). Mavropoulos 3) have demonstrated that alteration of food consistency in young growing rats induced a lower mandibular alveolar bone, mineral density and decreased trabecular bone volume and thickness caused by a reduction of masticatory