Resumo Este estudo avaliou a resistência de união à dentina imediata e após 6 meses de adesivos universais utilizando estratégias de união convencional ou autocondicionante. Os adesivos testados foram Ambar Universal, G-Bond, Single Bond Universal, Tetric N-Bond Universal e Ybond Universal. Adesivos padrão-ouro (Scotchbond Multipurpose Plus e Clearfil SE Bond) foram os controles. Resistência de união à microtração na dentina (n=5 dentes), pH e conversão de C=C (n=3) foram avaliados. Os dados foram analisados considerando α=0,05. Todos os adesivos mostraram diferenças de pH comparados aos demais. Ybond Universal teve agressividade intermediária forte, enquanto os outros foram ultramoderados. A conversão de C=C foi diferente em quase todos adesivos. No modo convencional, em geral todos os adesivos mostraram resultados similares exceto G-Bond, que teve menor resistência de união que a maioria dos adesivos. G-Bond e Tetric-N-Bond mostraram resistências de união menores após 6 meses comparados a 24 h, enquanto os outros adesivos apresentaram estável união à dentina. No modo autocondicionante, G-Bond teve menor resistência de união que quase todos os adesivos. Após 6 meses, Ambar foi o único adesivo mostrando menor resistência de união à dentina comparado a 24 h. A maioria dos adesivos teve discreta queda na resistência de união durante o envelhecimento quando usados na estratégia autocondicionante. Os modos de falha também foram material dependentes, com um padrão geral de mais falhas adesivas e/ou pré-teste após o armazenamento. Em conclusão, o desempenho de união de adesivos universais à dentina é material dependente. Grande parte dos adesivos apresentou estável união à dentina com resultados comparáveis ao materiais padrão-ouro, particularmente quando aplicados no modo autocondicionante. Em geral, parece que o uso de adesivos universais em dentina não deve ser precedido por condicionamento com ácido fosfórico.

Abstract This study evaluated the immediate and 6-month dentin bond strength of universal adhesives used in etch-and-rinse or self-etch bonding strategies. The adhesives tested were Ambar Universal, G-Bond, Single Bond Universal, Tetric N-Bond Universal, and Ybond Universal. Gold standard adhesives (Scotchbond Multipurpose Plus and Clearfil SE Bond) were controls. Microtensile dentin bond strength (n=5 teeth), pH, and C=C conversion (n=3) were evaluated. Data were analyzed at α=0.05. All adhesives showed differences in pH. Ybond had intermediately strong aggressiveness, whereas the others were ultra-mild. The C=C conversion was different in most adhesives. In the etch-and-rinse strategy, all adhesives showed similar results generally except for G-Bond, which had lower bond strength than most adhesives. G-Bond and Tetric-N-Bond showed lower bond strengths after 6 months compared with 24 h, whereas the other adhesives had stable dentin bonds. In the self-etch strategy, G-Bond had lower bond strength than most adhesives. After 6 months, Ambar was the only adhesive showing lower dentin bond strength compared with 24 h. Most adhesives had discreet drops in bond strength during aging when used in the self-etch strategy. The failure modes were also material dependent, with a general pattern of increased adhesive and/or pre-testing failures after storage. In conclusion, the bonding performance of universal adhesives to dentin is material dependent. Most adhesives had stable dentin bonds with results comparable to the gold standard materials, particularly when applied in the self-etch mode. In general, it seems the use of universal adhesives in dentin should not be preceded by phosphoric acid etching.

Abstract Objectives: This study investigated whether increasing the concentration of acidic monomers in one-step adhesives would allow reducing their application time without interfering with the bonding ability to primary enamel and dentin. Material and methods: Experimental one-step self-etch adhesives were formulated with 5 wt% (AD5), 20 wt% (AD20), or 35 wt% (AD35) acidic monomer. The adhesives were applied using rubbing motion for 5, 10, or 20 s. Bond strengths to primary enamel and dentin were tested under shear stress. A commercial etch-and-rinse adhesive (Single Bond 2; 3M ESPE) served as reference. Scanning electron microscopy was used to observe the morphology of bonded interfaces. Data were analysed at p<0.05. Results: In enamel, AD35 had higher bond strength when rubbed for at least 10 s, while application for 5 s generated lower bond strength. In dentin, increased acidic monomer improved bonding only for 20 s rubbing time. The etch-and-rinse adhesive yielded higher bond strength to enamel and similar bonding to dentin as compared with the self-etch adhesives. The adhesive layer was thicker and more irregular for the etch-and-rinse material, with no appreciable differences among the self-etch systems. Conclusion: Overall, increasing the acidic monomer concentration only led to an increase in bond strength to enamel when the rubbing time was at least 10 s. In dentin, despite the increase in bond strength with longer rubbing times, the results favoured the experimental adhesives compared to the conventional adhesive. Reduced rubbing time of self-etch adhesives should be avoided in the clinical setup.