Abstract
Background: This in vitro study aimed to evaluate the effect of sodium hypochlorite (NaOCl) and ethylene diamine tetraacetic acid (EDTA) as pretreatments on the resin infiltration efficacy and acid resistance of enamel white spot lesions (WSLs).
Methods: Enamel blocks prepared from the buccal surfaces of sound human premolars were placed in a demineralisation solution for 3 days to establish artificial enamel WSLs. All the blocks with WSLs were randomly divided into four groups (n = 40 per group): RI (Control): resin infiltration only. N/RI: 5.25% NaOCl pretreatment + resin infiltration; E/RI: 17% EDTA pretreatment + resin infiltration; NE/RI: combined pretreatment of 5.25% NaOCl with 17% EDTA + resin infiltration; Enamel pore exposure was measured by using SEM observation and Image J software in each group after pretreatment prior to resin infiltration (n = 8 per group). Resin penetration depth and enamel surface microhardness were assessed after resin infiltration (n = 8 per group for each test) by a confocal laser scanning microscope and a Vickers' microhardness test respectively. The remaining specimens were subjected 7 days of pH cycling after which surface enamel roughness and microhardness were assessed by an atomic force microscope and a microhardness test respectively.
Results: Compared to the control group, the enamel surface pore exposure (p = 0.007), resin penetration depth (p = 0.011) and enamel surface microhardness (p < 0.001) were all significantly increased after the pretreatment of 5.25% NaOCl alone or combined with 17% EDTA by one-way ANOVA. After pH cycling, no significant differences were found in enamel surface roughness or microhardness among the four groups (p = 0.55) by two-way ANOVA.
Conclusions: Enamel surface pretreatment of 5.25% NaOCl or combined with 17% EDTA improved the efficacy of the resin infiltration of WSLs, but might be useless in enhancing the acid resistance of resin-infiltrated WSLs.