Protein content and amino-acid content of consolidated carious lesions in human enamel and of experimental lesions in bovine enamel exposed to the human mouth.

Consolidation is a natural defence reaction that results in arrest of enamel caries. Experimental consolidated lesions (ECL) were compared with naturally-consolidated lesions (NCL): ECL were obtained by exposing pre-softened, bovine-enamel slabs to the oral environment in 3 subjects for 2 h, 24 h or 7 days, and NCL were sampled from extracted human teeth with white or yellow spots of arrested caries. Protein content of ECL from 2 subjects were similar to each other and to that of NCL throughout the experimental period. The ECL of the other subject showed a gradual increase in protein content with significantly higher values at day 7. The predominant amino acids in ECL were glutamic acid, proline and alanine, and in NCL, glutamic acid, glycine and alanine. The amino-acid composition of the 7-day ECL was closer to that of NCL than were that of the 2 and 24 h ECL. Intra-oral ageing caused significant reductions in proline and glycine and pronounced increases in aspartic acid, threonine, alanine and leucine. Thus the adsorbed or incorporated organic material in the ECL changed from having components dissimilar to NCL to ones similar to NCL. This intra-oral model might be useful for studies of the organic material incorporated into enamel during the process of consolidation.