Dentin Demineralization under Varnish Containing Multi-ion Releasing Filler

Objectives: To compare the anti-demineralization effects on dentin of a varnish containing surface reaction-type prereacted glass-ionomer (S-PRG) filler as a multi-ion releasing filler and one containing 1.0%NaF which release equivalent amounts of fluoride.
Methods: Specimens (n=18, bovine root dentin) were divided into three groups of six; 1) Control (CONT; no coating), 2) NaF Varnish (FV; 1% NaF + 40% silica filler, Shofu, Japan), 3) PRG Varnish (PV; 40% S-PRG filler, Shofu, Japan). Experimental surface on each specimen was prepared and coated according to group. They were then immersed in 6 ml of deionized water (37°C, 3d) after which the varnish was rubbed off with a cotton swab. Acid-resistant varnish was applied, exposing a 1×3 mm window, then the specimens were immersed in 8% methylcellulose gel demineralization system (1.5mM CaCl2, 0.9mM KH2PO4, 50mM acetic acid, pH5.0, 37°C, 1w). Then 300 µm-thick sections were cut from each specimen perpendicular to the experimental surface, and mineral profiles, integrated mineral loss (IML: vol%×µm) of lesions, mineral density of surface and lesion body (vol%) were obtained by transverse microradiography and dedicated software.
Results: The average mineral profile, surface mineral density of FV and PV were over 30%. That of the lesion body of FV was almost 14%, and that of PV was 18%. PV showed significantly lower integrated mineral loss (2,523±121) than CONT (3,200±184) (ANOVA, Games-Howell’s, p<0.05), however, there was no significant difference between Cont and FV (2,817±149). S-PRG filler contained in PRG varnish released several ions providing buffering and anti-demineralization activity. Once those ions had penetrated into the root dentin, the anti-demineralization effect remained.
Conclusions: PRG varnish contributes to maintain an anti-demineralization effect under the dentin surface even after the varnish containing S-PRG has been removed.