Basic study of fluoride-releasing adhesive resin for prevention of root caries: 2. Enhancement of acid resistance of the dentin.

The human root dentin was covered with a fluoride-releasing resin (F-resin) and incubated for various periods up to 180 days in phosphate buffer. After removal of the F-resin, resistance of the dentin to decalcification by acetic acid--sodium acetate buffer was assessed by measuring both the amount of calcium dissolved during decalcification and the knoop hardness of dentin after decalcification. The acid resistance progressively increased for 90 days when assessed by measurement of calcium dissolution and for 30 days by measurement of the knoop hardness. The percent inhibition of calcium dissolution achieved by 30 days of incubation was about 90% of the maximal inhibition obtained by incubation in concentrated sodium fluoride solution (2.4 x 10(-2) M). The enhancement of acid resistance was not induced by the resin infiltrated layer of the surface dentin but by the fluoride released from the F-resin into the dentin.