Objectives: The aim of the present study was to compare the effect of enamel pre-treatment with: 37% phosphoric acid-etching or self-etching adhesive and Er:YAG Laser (2940nm) on shear bond strength, microleakage and penetration depth of a fluoride-releasing resin-based pit and fissure sealant applied to sound premolars.

Methods: Seventy-two sound premolars were randomly allocated into 3 groups according to enamel pretreatment protocol. The experimental groups included: Group I: 37% phosphoric acid-etching, Group II: self-etching adhesive, Group III: Er:YAG Laser treatment. Each group was divided into two subgroups (A: shear bond strength, B: microleakage and penetration depth). Shear bond strength test was performed using Universal testing machine. Microleakage and penetration depth were tested after thermocycling (500×, 5-55°C, dwell time: 30s) and dye penetration method. Samples were assessed under Stereo-microscope with a magnification of ×40. One-way ANOVA followed by Tukey's post hoc test was used to analyze data.
Results: Shear bond strength and microleakage results showed that there was statistically significant difference among different groups while penetration depth results showed there was no statistically significant difference among all groups.
Conclusions: Conventional acid etching was the best pretreatment method prior to resin-based fissure sealants in terms of bond strength and microleakage.