EFFECT OF LACTIC-ACID AND PROTEOLYTIC-ENZYMES ON THE RELEASE OF ORGANIC MATRIX COMPONENTS FROM HUMAN ROOT DENTIN

The mechanisms of organic matrix breakdown in the root caries process are not well understood. Therefore, the combined and separate effects of lactic acid and Dentin proteins proteolytic enzymes on the degradat ion of human dentin collagen, glycoproteins, Glycoproteins proteoglyca ns and phosphoproteins were investigated in the present study. Dentin powder was pretreated with lactic acid (pH 4.0), distilled and deioniz ed (dd) Phosphoproteins water (pH 7.0) and EDTA/guanidine HCl (pH 7.4) for 24 h. Pellets of acid- or dd water-pretreated dentin powder were washed, dried, and then treated with trypsin, bacterial or mammalian t issue collagenase, or control buffer for 3 h. The released dentin prot eins were analyzed by reducing sodium dodecyl sulfate-polyacrylamide g el electrophoresis and immunoblotting to identify degraded type I coll agen, proteoglycans, glycoproteins and phosphoproteins. All water and acid pretreatment and enzyme treatment groups demonstrated two collage n fragment bands with molecular weights at approximately 79 kD. Furthe r studies showed that the 79 kD, proteins from acid-pretreated dentin collagen were degraded by tissue collagenase, suggesting that endogeno us collagenase may be involved in the degradation of root dentin colla gen. Dentin proteoglycans were detectable in all the treatment groups by protein slot blotting. Relatively few distinct glycoproteins and pr oteoglycans, and no phosphoproteins were detected by immunoblotting. R esults from this study suggest that both acids and proteolytic enzymes from either host or microbial origin are important in the degradation of human dentin matrix and the mechanisms involved in the release of various noncollagenous proteins may be different.