The Effects on Dentin of Proteolytic and Acidogenic Bacteria Isolated from the Carious Lesion

Abstract

The effect of oral lactobacilli, actinomycetes, cocci, proteolytic bacteria, and proteolytic enzymes on intact dentin was detd. by weight loss and by reaction of the organic matrix with diazonium salts. The latter reaction directly indicates accessible tyrosine and histidine and indirectly indicates dipeptide linkages accessible to lytic enzymes. The results showed that acidogenic bacteria from dentinal caries decalcified intact dentin in vitro and rendered its organic matrix reactive with diazonium salts and lytic enzymes. Acidogenic bacteria did not lyse such an accessible organic matrix; proteolytic bacteria were able to do so, but produced only minimal changes in intact dentin. Proteolytic bacteria did not lyse naturally carious dentin as readily as they lysed acid decalcified dentin. Actinomycetes from dentinal caries produced discoloration in noncarious dentin similar to that seen in dentin of old or arrested caries. Pepsin-acid mixtures produced variable changes in the organic matrix of dentin that correspond somewhat to the action of oral acidogenic microorganisms. Trypsin had an action on dentin similar to that caused by proteolytic bacteria.