How S-PRG Filler-containing Varnish Inhibits Degradation Of Dentin Collagen

Objectives: Dentin caries progresses in two stages. Minerals are dissolved by acid, followed by degradation of demineralized dentin matrix such as collagen. Therefore, protecting dentin collagen may be effective in inhibiting root caries. The purpose of this study was to investigate how the varnish containing surface pre-reacted glass-ionomer (S-PRG) filler inhibits degradation of dentin collagen, and subsequently, dentin demineralization.
Methods: Disk-shaped dentin specimens were obtained from human third molars. Specimens were completely demineralized by EDTA to expose the dentin collagen. These specimens were divided into four groups; 5% NaF varnish (NaF group), 0% S-PRG filler-containing varnish (0% group), 10% S-PRG filler-containing varnish (10% group), and 40% S-PRG filler-containing varnish (40% group). Each varnish was applied to specimens and immersed in distilled water for 1 day. Then, the specimens were dissolved in collagenase solution for 1 day. After centrifuging the solutions, the resultant precipitations were analyzed by SDS-PAGE to assess the enzymatic resistance. Other disk-shaped specimens, coated with acid resistant wax leaving a 3mm square window, immersed in EDTA for 3 days. After applying each varnish, specimens were immersed in a demineralizing solution (pH5.0) for 3 days. Mineral densities and lesion depth of the specimens before and after demineralization were analyzed by μCT.
Results: In SDS-PAGE analysis, the collagen after applying 10% S-PRG filler-containing varnish group was less soluble than in other two S-PRG filler varnish groups, and the amount of collagen dissolution was almost the same as that of the NaF group. In mCT analysis, the amount of mineral loss and the depth of demineralized surface after demineralization were significantly lesser in 10% and 40% group comparing with the control group.
Conclusions: 10% S-PRG filler-containing varnish was as effective as fluoride in enhancing the enzymatic resistance of human dentin.