Effects of lactate dehydrogenase on fissure caries in rats.

The effect of supplementing the diet or drinking water with lactate dehydrogenase (LDH) on the formation of caries lesions in rats was investigated. Addition of LDH [20 and 5 mg/kg in the high-sucrose (65%) diet, 2 and 1 U/ml in the drinking water (LDH-specific activity 735 U/mg solid)] resulted in significant reductions (p less than 0.01) in the number and severity of caries lesions when the enzyme was administered to rats for 4 or 7 days, although no significant differences were found after 14 or 21 days. No differences were observed between effects of addition to water or diet. Fissure caries failed to develop when rats were fed a low sucrose diet (5%) containing LDH (20 mg/kg diet), whereas 50% of the animals in the control group developed lesions. The findings indicate that LDH may play an important role in delaying the onset of caries lesion formation in rats, and that the protection observed may be inversely related to the intensity of the cariogenic challenge.