A study of enamel bond strength to two-step self-etching system

Objectives: The purpose of this study was to evaluate the effect of prior acid etching, moisture, and omission of priming step on enamel ěSBS to two-step self-etching system.

Methods: Flat enamel surfaces were created on extracted human third molars. The surfaces were treated with one of the following procedure: Enamel surfaces were etched with phosphoric acid. Some etched surfaces were dried for 15s with oil-free compressed air and then Clearfil SE bonding resin was applied with or without Clearfil SE primer. Other etched surfaces were kept moist with cotton pellets and then bonding resin was applied with or without primer. Enamel surfaces conditioned with only self-etching primer were dried for 15s or kept moist and then bonding resin was applied. Composite resin (Filtek Z-250) was bonded to each specimen. The bonded specimens were subjected to ěSBS testing with a crosshead speed of 1 mm/min. The mean ěSBS was statistically compared using one-way ANOVA, Tukey HSD. Also the SEM analysis was performed for evaluation of the interface of enamel and composite.

Results: 1. Prior acid etching of enamel produced significantly higher bond strength than non-acid etching (P < 0.05). 2. Moisture on enamel and omission of priming step and did not significantly affect shear bond strength to two-step self-etching system (P > 0.05). 3. On prior acid etched specimens, the hybridized enamel layers with typical penetration of the resin into the demineralized zone were observed. But, on non-acid etching specimens, poorly defined resin tags and gaps were observed.

Conclusions: Under the conditions of this study, prior acid etching of enamel provided higher ěSBS values but moisture on enamel and omission of priming step did not influence ěSBS values to two-step self-etching system.