The Effect of Food Hardness on the Development of Dental Caries in Alloxan-Induced Diabetic Rats

We have previously shown that dental caries may be produced in diabetic rodent models fed with noncariogenic standard diets; however, many studies usually add large amounts of sugar to the diet to induce dental caries. Moreover, the physical properties of cariogenic diets have been reported as an important factor in the formation of caries. The aim of this study was to clarify the effect of the hardness of non-cariogenic diets on the development of dental caries in diabetic rodents. Seven-week-old female F344 rats were divided into 4 groups: intact rats fed with a standard pelletized or powdered diet and alloxan-induced diabetic rats fed with a standard pelletized or powdered diet. All of the rats were sacrificed at 52 weeks of age for morphological examinations on their dental tissue. Dental caries had developed and extended to all the molars in the diabetic rats that were fed with both the pelletized and powdered diets. Moreover, the lesion was significantly enhanced in the powdered diet group compared to that in the pelletized diet group. In conclusion, food hardness is an important factor influencing the development of dental caries in diabetic rats. 1. Introduction We recently demonstrated that diabetes directly induced dental caries in rats and mice, although a direct association between the 2 was less evident and conflicting in humans [1–4]. We demonstrated that dental caries were produced using noncariogenic diets with a low concentration of sugar in diabetic rodent models [5–7], although many studies usually add large amounts of sugar to the diet to induce dental caries [8, 9]. In addition, early studies on the production of experimental dental caries have reported the effects of physical properties of cariogenic diets with high concentrations of sugar on dental caries. These studies mainly used finely ground cariogenic diet [10–13] because it is more cariogenic compared to a coarsely ground diet in rodents. Moreover, hard and coarse foods have the ability to prevent caries [14–17]. Thus, modifying the dietary formulation may possibly enhance or reduce caries development in diabetic animals. However, no reports have investigated the effects of the physical properties of non-cariogenic standard diets on dental caries in diabetic animals. Currently, 2 types of non-cariogenic standard diet formulations (i.e., powdered and pelletized diets) are widely used in experimental rodents. In the present study, we compared the effects of these diets on the development of dental caries in a diabetic rodent model focusing on the difference in hardness between