MODIFICATION OF AMINO-ACID-RESIDUES IN CARIOUS DENTIN MATRIX

The Maillard reaction between sugar and protein has been postulated as the cause for the browning and arrestment of caries lesions. This rea ction has been implicated as the cause for decreased degradability of collagen in vivo. The aim of the present study was to verify the occur rence of the reaction in vivo. Carious and sound dentin samples were t aken from extracted human teeth and analyzed for the fluorescence char acteristic of the Maillard reaction and oxidation and, by HPLC, for Ma illard products. In addition, physiological cross-links were analyzed by HPLC. Oxidation-and Maillard reaction-related fluore-scence increas ed in collagenase digests from carious dentin. Advanced Maillard produ cts (carboxymethyllysine and pentosidine) increased, whereas furosine, a marker for the initial reaction, was not observed consistently. Thi s implies no direct addition of sugars to protein, but rather the addi -tion of smaller metabolites and glycoxidation products. in addition, the physiological crosslinks hydroxylysinonorleucine and dihydroxylysi nonorleucine decreased in carious dentin. Also for hydroxylysylpyridin oline, a decrease was observed, but not consistently. In conclusion, t he caries process modifies amino acids in dentin collagen, which can l ead to increased resistance against proteolysis and ulti-mately to car ies arrestment.