Diabetes and salivary gland dysfunction are major factors that induce dental caries in
experimental animals, but there are no reports analyzing the association of dental caries
and salivary glands in an animal model of diabetes mellitus (DM). To clarify the initial
development of dental caries and preceding salivary gland disorder, we performed a
histopathological analysis on teeth and salivary glands in diabetic Wistar rats 7 weeks
after alloxan treatment (DM group) in comparison with nondiabetic rats (Non-DM group) and
functional analysis on saliva secretion during the experimental period.
Pilocarpine-induced salivary fluid secretion in diabetic rats gradually decreased with
continuous hyperglycemia from immediately after alloxan treatment to the time of autopsy.
Histopathologically, Oil Red O-positive lipid droplets accumulated in the acinar cells of
the parotid gland. No tooth was stereoscopically defined as having dental caries in any of
the rats in either group; however, the external appearance remarkably changed owing to
occlusal wear in almost all molars in the DM group. The initial lesions of dental caries,
appearing as micro-defects in dentin with bacterial colonization on the molar surface,
were identified using histopathological analysis, and the incidence in the DM group was
more than twice that in the Non-DM group. In conclusion, hyperglycemia simultaneously
induces initial caries development and enhances spontaneous occlusal wear in molar teeth
of Wistar rats 7 weeks after alloxan treatment. The parotid gland dysfunction caused by
hyperglycemia may be mostly involved in the pathogenesis of occlusal wear as well as in
dental caries in this diabetic model.