Effects of obesity on the rat incisor enamel and dentine thickness, as well as on the hemimandible shape over generations

Abstract

Obesity has several effects on the general body metabolism. However, little is known about the impact of obesity on the growth and shape of mineralized tissues like mandibles and teeth, as well as if it effects are passed down from generation to next. Therefore, in this study, we aimed to evaluate, over nine generations using the consanguineous mating (inbreeding), the effect of the obesity condition produced by the reduction in the number of rats per litter during the lactation period on the hemimandible shape, dentine, and enamel of the rat incisor. Litters were reduced to two males and two females after birth, and were consanguinity mated in adulthood for nine generations. For all evaluations performed in this investigation, only males were used. The control group was formed by a non-consanguineous litter containing eight males. The parameters evaluated were food consumption, body weight, Lee Index, and bone density of the hemimandible bone. Incisor enamel and dentine thickness were also evaluated. The hemimandible shape was evaluated using geometric morphometry. The results show a significant and progressive increase in food intake, Lee Index, body weight, hemimandible weight, and enamel thickness, and a decrease in dentine thickness. The linear measurements of the length of the ramus ascending hemimandibular segment were found to be shorter, while its height was increased. In contrast, the geometric morphometry shows that the general hemimandible shape changed over the consanguineous obesity generations. We conclude that over generations, obesity increases and maintains the parameters evaluated with significant changes in hemimandible shape as well as in the dimensions of enamel and dentine of incisors, suggesting that enamel and dentine could be used as phenotype biomarkers to detect changes in tooth and craniofacial development related to obesity effects.