著者

加藤 剛士

出版者

北海道大学

巻号頁・発行日

2014-03-25

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Modern people tends to have soft food . Therefore experimentalstudies have been performed to examine unfavorable influences to growth ofmasticatory muscles and craniofacial bone induced by such a dietary habits.The aim of the present study was to clarify the effects of soft diet on thetemporomandibular joint (TMJ) in growing rats using thehistomorphometrical and immunohistochemical methods. Twenty-four maleWistar rats were weaned at age 21 days and were divided into control andexperimental groups. Control rats were fed a solid food and experimentalones fed a liquid food from 1 to 8 weeks. After injection with5-bromo-2’-deoxyuridine (BrdU), the animals were perfused with 4%paraformaldehyde solution and the whole heads were removed. Serialcoronal sections of TMJ were stained with Haematoxylin and Eosin or withBrdU-immunohistochemistry. Three dimensions and the thickness ofcartilage layer of the TMJ were measured using histological sections, andcell proliferation in the TMJ was examined using immunostained sections.The height and width of the zygomatic process of mandibular fossa inexperimental group were smaller than in control group after 4 weeks. Thewidth and length of the condyle of experimental animals were also smallerthan those of controls after 4 weeks. In the mandibular fossa, articular zone(AZ) and hypertrophic zone (HZ) at 4 weeks and AZ and intermediate zone(IZ) at 8 weeks in the experimental groups were thinner than in the control.All zones at 4 weeks and AZ at 8 weeks of the condyle in the experimentalgroup were also thinner. The labeling indices of BrdU in IZ of themandibular fossa and of the condyle in the experimantal groups were lowerthan in the controls at 4 weeks and at 1 and 4 weeks, respectively. Thesefindings suggest that the soft food-intake inhibits the growth of the TMJ ofrats, due to low proliferative activity of cells in IZ.