Effect of enamel priming for resin infiltration on subsequent composite bonding

Resin infiltration is a micro-invasive treatment option to manage enamel opacities, arresting lesion progression and improving esthetics. As restorative interventions may be required during or after infiltration treatment, this study evaluated the bond strength of composite resin to infiltrated bovine enamel, focusing on the effect of enamel priming.

Bovine sound incisors (n = 120) were used and demineralized lesions were created in half of the specimens. Prior to resin infiltration (Icon, DMG, Hamburg, Germany), the etched enamel surface was dried with either Icon Dry or Icon Prime (DMG), the later containing 10-Methacryloyloxydecyl dihydrogen phosphate (10-MDP). A resin composite (Ecosite Elements, DMG) was placed without any adhesive and half of the specimens in each group underwent ageing using thermocycling (5°C/55°C, 5000 cycles); the other half served as non-aged controls. Notched-edge shear bond strength (SBS) was measured after storage of the specimens in water at 37°C for 24 h. A three-way ANOVA (α = 0.05) was used to analyze the effects of enamel priming (Icon Dry/Icon Prime), enamel type (sound/demineralized) and aging condition (aged/non-aged). Failure mode analysis was performed by SEM.

Enamel priming with Icon Prime significantly increased SBS compared to Icon Dry (p = 0.012). No significant main effects were observed for enamel type (p = 0.671) or aging condition (p = 0.794). Adhesive failure predominated at the enamel-infiltrant interface; no interfacial degradation was observed after thermocycling in Icon Prime-pretreated specimens.

Bond strength between composite resin and infiltrated enamel can be clinically sufficient without an adhesive if the oxygen inhibition layer is preserved, enabling simplified workflows. Long-term bond durability depends on the aging resistance of the infiltrant layer itself, making enamel priming a key determinant.