Variable ratios of lactate and malate dehydrogenase-like enzyme activities and LDH isoenzyme distribution in the odontoblast-predentine region of intact and carious human teeth.

Abstract

Coronal odontoblast-predentine tissue was collected from intact teeth and from teeth with various types of occlusal caries. Lactate (LDH) and malate (MDH) dehydrogenase-like activities in the non-sedimentable (20,200 g), saline-soluble tissue extracts were measured. The calculated LDH/MDH ratio was higher (p < 0.050) in teeth with initial dentine caries (0.81) than in intact teeth (0.67). However, the ratios remained below 1.0 in all types of the tissues analyzed, suggesting a predominantly aerobic metabolism in the odontoblast-predentine region. In the enamel and in the initial dentine caries groups as well as in the group of teeth restored with amalgam, both the LDH and MDH values remained near to the level of intact teeth. The further development of the various lesion was associated with a gradual decrease in the dehydrogenase-like activities. This decrease became significant in recurrent carious lesions. The observation reassured the previously presented concept that a significant depression of several metabolic events occurs in the area of severe injury. Electrophoresis of odontoblast-predentine extracts revealed three anodally migrating LDH isoenzymes. Among these, LDH₂ and LDH₃ were the most prominent, both with intact and carious samples. This was thought to give further evidence of the aerobic pattern of metabolism suggested to predominate in the area.