Influence of Universal Adhesives With or Without Silane Compared to One-Step and Two-Step Silane Agents on Bond Strength to Lithium Disilicate

Objective: To evaluate the microshear bond strength (μSBS) to lithium disilicate achieved with universal adhesives (with and without silane) compared with one-step and two-step silanes, immediately (IM) and after thermocycling (TC). Chemical interaction (CI) was also assessed. Material and Methods: Lithium disilicate blocks were randomly assigned to nine groups (n = 10) according to surface treatment (silane-free [ALB; AllBond Universal] and silane-containing [AMU; Ambar Universal APS Plus, SBU; Scotchbond Universal Plus] universal adhesives, one-step [PPR; Porcelain Primer, PRO; Prosil, CPR; Ceramic Primer], or two-step silanes [BIS; Bis-Silane, EXP; experimental silane, SIL; Silano Mais]). After hydrofluoric acid etching, treatments were applied and resin cement cylinders bonded. μSBS was measured after 24 h or 10,000 thermocycles. CI was analyzed by micro-Raman spectroscopy. Data were evaluated using two-way ANOVA and Bonferroni tests (α = 0.05). Results: Surface treatment, evaluation time, and their interaction significantly influenced μSBS (p < 0.001). IM, two-step silanes, PPR, and AMU showed higher μSBS, whereas the silane-free universal adhesive demonstrated lower values. After TC, SIL, BIS, PPR, and AMU maintained higher μSBS. Raman analysis demonstrated comparable CI for AMU and SBU compared with one- and two-step silanes. Conclusions: Bond strength was influenced by pretreatment strategy and aging. Two-step silanes were more consistent, although selected simplified systems achieved comparable performance. Clinical Significance: Two-step silanes remain the most predictable option; however, certain silane-containing universal adhesives and specific one-step silanes may offer simplified alternatives when durability limitations are considered.