Composition by Casein in an Intra-oral Model The Prevention of Sub-surface Demineralization of Bovine Enamel and Change in Plaque

The ability of bovine milk phosphoprotein (casein) to be incorporated into plaque, prevent enamel sub-surface demineralization, and affect bacterial composition was determined using a modified intra-oral car-ies model. The intra-oral model consisted of a removable appliance containing a left and right pair of bovine enamel slabs placed to simulate an approximal area. Supragingival plaque was collected and impacted into the left and right inter-enamel spaces. The left side of the appliance was exposed to various sugar and salt solutions, while the right side was exposed to sugar and casein solutions. Sodium caseinate, the major fraction ot,1-casein, and a tryptic digest of tsr-casein (TD-casein) were studied. Sodium caseinate at a level of 2% w/v in a 3% sucrose-3% glucose-salt solution (pH 7.0) prevented sub-surface enamel demineralization over a ten-day period as shown by microradiography and microhardness. Two exposures of a 2% w/v sodium caseinate, oxt1-casein, or TD-casein solution (pH 7.0) per day prevented sub-surface enamel demineralization caused by six exposures of a 3% sucrose-3% glucose-salt solution per day over a ten-day period. Intact ot,-casein and tryptic peptides were shown im-munochemically to be incorporated into the inter-enamel plaque. The incorporation of casein and its breakdown in plaque did not produce a significant change in the amount or composition ofplaque bacteria. The ability of casein and tryptic peptides to prevent enamel demin-eralization was related to their incorporation into plaque, thereby increasing plaque calcium phosphate and acid-buffering capacity by the phosphoseryl, histidyl, glutamyl, and aspartyl residues and indirectly through catabolism by plaque bacteria.