The Effect Of Dietary Zinc Deficiency On The Development And Mineralization Of Rat Teeth

Objective:In order to understand the effect of dietary zinc deficiency on the development and mineralization of rat teeth by experiment, zinc deficiency group(ZD), zinc adequate(ZA) and pair-fed group(PF) were set during the lactation and late growth stage of rat offspring(until the root development of molar completed), various indicators were detected, and through comparing the development and mineralization conditions of rat teeth, the influences of zinc on the development and mineralization of rat teeth were explored.Methods:9 pregnant SD rats which had conceived for about 20 days and would be about to delivery were divided randomly into three groups, they were zinc deficiency group(ZD group), the zinc adequacy group(ZA group) and pair-fed group(PF group),respectively. After parturition, the ZD group was fed with low zinc fodder, which contained 8mg zinc/kg approximately. While the ZA group was fed with standard purification fodder which contained 38 mg zinc/kg approximately. The diets were given ad libitum to rat in both ZD group and ZA group. And the PF group was fed with the same fodder to the ZA group, but was pair fed to each rat in the same quantity as consumed by ZD group the previous day. All rats of three groups drunk ultra-pure water. Once the offspring were weaned, they continued on the same diets as their foster mothers who were then removed from the study. And then the offspring were killed at postnatal day 38, their mandibulars were taken. Before they were killed,their blood was taken and the serum zinc concentration of all groups was tested. First of all, the color, luster and smoothness of the mandibular incisors in all groups were observed under the natural light. And then, chose mandibular incisors of three groups to prepare the samples for measuring the microhardness of enamel and dentine. At the same time, cross-sectional and longitudinal sample of mandibular incisors were prepared and the ultrastructure of enamel and dentine were observed through SEM.Finally, HE staining was carried out on the mandible, and then the incisor germ and adjacent dentine of the first molar were observed. The data was analyzed by using SPSS 19.0 software package, P<0.05 means the difference has statistical significance.Results:1. We could see poor gloss, rough surface of mandibular incisor crowns which with darker color in ZD group by the naked eyes. While better glossy and smoother surfaces were found in the other two groups.2. Both serum zinc concentration and microhardness values of the teeth enamel and dentine in ZD group were lower than the other two groups, and the difference was statistically significant, while there was no statistically significant difference between ZA group and PF group.3. The SEM observation of enamel was that fuzzy enamel structure, irregularly arranged enamel rods with larger pore in it, and larger area of interrod substance were discovered in ZD group. While, the other two groups had clear enamel structure, their enamel rods were arranged relatively regular with no large pore in the rods. From SEM, both cross-sectional and longitudinal samples, it was observed that the dentin tubule in ZD group was distributed in disorder, was decreased in number under the same magnification and had uneven diameter. However, both ZA group and PF group had regularly distributed dentin tubule whose diameter was even, there were no obvious differences between them in these areas.4. From HE staining result, it was found that large amounts of vacuole-like structure were obviously observed in secretory ameloblast of mandibular incisor germ in ZD group and PF group, but in ZA group was not observed. The secretory ameloblast in ZD group and PF group was arranged in disorder, while it was neatly arranged in ZA group. ZD group had thinner enamel matrix and dentine than ZA group. Although the enamel matrix in PF group had the same thickness as in ZA group, the dentine was thinner than the latter. And vacuolar degeneration of odontoblast was investigated on the first molar of ZD group only, also, the predentine layer slightly broadened and interglobular dentine significantly increased in ZD group.Conclusions:1. Dietary zinc deficiency could change ameloblast morphplogy, make enamel thinner, decline mineral content, and alter enamel microstructure of rat incisor.2. Zinc deficiency of dietary could cause obstacles during dentin mineralization and changes of dentine structure of rat incisor. At the same time, it could cause odontoblast vacuolar degeneration and dentine mineralization disorder of rat molar.3. The effect of which dietary zinc deficiency on the development and mineralization of rat teeth was only associated with the lack of zinc itself, but had nothing to do with the reducing intake as a result of zinc deficiency.