Assessment of Adhesive Protocols on the Repair Bond Strength of Vita Enamic Polymer-Infiltrated Ceramic Network Using Functional Monomer-Containing Universal Adhesives

The aim of this research was to assess the effects of different adhesive surface treatment protocols using universal adhesives on the shear bond strength (SBS) between a Vita Enamic and resin composite, as well as to analyze the associated failure modes. Eighty Vita Enamic ceramics were prepared, thermocycled, and randomly allocated into eight experimental groups following silane coupling agent pretreatment and adhesive system: Single Bond 2 (SB), silane + SB, Scotchbond Universal Plus (SBP), silane + SBP, Beautibond Xtreme (BEX), silane + BEX, Tetric N-Bond Universal (TUB), and silane + TUB. All specimens were etched with 9% hydrofluoric acid prior to adhesive application. Resin composites were bonded to the treated surfaces and subjected to SBS analysis using a universal testing device. Failure modes were performed under a stereomicroscope. Data were statistically determined using one-way ANOVA and Tukey’s post hoc test (α = 0.05). Statistically significant differences in SBS were indicated among the groups (p < 0.05). In the result, the SB (13.96 ± 2.34 MPa) and TUB (12.39 ± 2.91 MPa) groups exhibited the lowest SBS values and exclusively adhesive failure modes. Groups treated with silane and/or silane-containing universal adhesives (Sl + SB; 18.42 ± 3.11 MPa, SBP; 19.01 ± 2.62 MPa, BEX; 19.20 ± 2.96 MPa and Sl + TUB; 18.16 ± 2.82 MPa) demonstrated significantly higher SBS. The highest SBS values were achieved in the silane + SBP (24.53 ± 2.66 MPa) and silane + BEX (25.12 ± 2.74 MPa) groups, which were statistically comparable to each other and superior to all other groups. These groups also showed increased proportions of mixed and cohesive failures, indicating improved interfacial integrity. In conclusion, the SBS between Vita Enamic and the resin composite was significantly influenced by surface pretreatment and adhesive composition. Hydrofluoric acid etching combined with silane coupling agent pretreatment and silane coupling agent-containing universal adhesives provided the highest bond strength, supporting a multimodal strategy for the reliable repair of Vita Enamic restorations.