Effect of different universal adhesive application protocols on shear bond strength of bulk fill composite to resin modified glass ionomer

Abstract Aim To evaluate the shear bond strength (SBS) of bulk fill composite to resin modified glass ionomer cement (RMGIC) after different universal adhesive application protocols. Patients and methods Thirty RMGIC (Ionoseal) discs are prepared using split Teflon mold with central holes 5 mm in diameter and 2 mm in height that were randomly divided according to different universal adhesive application protocols into three equal groups (10 each) as fallow: group I: Bulk fill composite was immediately placed without any treatment over RMGIC using another split Teflon mold with central holes 3 mm in diameter and 2 mm in height. Group II: Bulk fill composite was placed on RMGIC after treating of RMGIC discs with universal adhesive (Futurabond U). Group III: Bulk fill composite was placed on RMGIC after treating of RMGIC discs with 35% phosphoric acid and Futurabond U. Samples were thermocycled for 5000 cycles. SBS was measured using universal testing machine and the nature of the fracture was determined using stereomicroscope. Data was collected and analyzed statistically at a significance level of P less than 0.05. Results The highest mean SBS was recorded in group III followed by group II, while the lowest SBS was in group I. Samples in group I showed statistical significant differences versus both group II and III with P value 0.021 and less than 0.001, respectively, while there is no statistically significant difference when comparing SBS values of group II versus group III with P value 0.227. All the tested samples revealed only mixed failure mode. Conclusions Using universal adhesive system in sandwich technique provide a reliable bond between RMGIC and bulk fill composite than without any adhesive treatment. Using universal adhesive in total-etch mode improve the bond strength between the tested material but without significant effect compared to self-etch mode.