Comparative evaluation of three different methods of surface pretreatment on the depth of adhesive resin penetration in sandwich technique - An in vitro confocal laser scanning microscopy study.

Background: Sandwich technique combines the use of resin-modified glass ionomer cement (RMGIC) and composite to reduce polymerization shrinkage and postoperative sensitivity. Effective bonding relies on adhesive penetration inside RMGIC enhanced by surface pretreatments such as acid etching and lasers ensuring improved bond strength and longevity. The present study evaluated the depth of adhesive resin penetration into RMGIC using three surface pretreatment methods in sandwich technique analyzed through confocal laser scanning microscopy (CLSM).

Materials and methods: Class I cavity preparation was done in 30 extracted maxillary premolars. RMGIC was applied and samples were categorized into three groups: Group 1 (control group, no pretreatment), Group 2 (etching was with 37% phosphoric acid for 15 s), and Group 3 (treated with erbium, chromium-doped yttrium, scandium, gallium, and garnet laser). Rhodamine B dye was mixed with adhesive resin and applied over RMGIC followed by composite restoration. Samples were sectioned buccolingually and evaluated under CLSM. Data analysis was done using analysis of variance and Tukey's post hoc tests.

Results: Statistical analysis revealed significant differences among the three groups. The laser-treated group exhibited the greatest depth of penetration compared to the acid-etched and control groups.

Conclusion: Laser pretreatment significantly enhances adhesive penetration depth compared to acid etching or control suggesting its clinical efficacy in improving bond strength in the sandwich technique.