Effect of a hydrophobic bonding resin on the 36-month performance of a universal adhesive—a randomized clinical trial

Objectives: To evaluate if the addition of a layer of a hydrophobic bonding resin to the recommended application sequence of a universal adhesive improves the respective clinical behavior in non-carious cervical lesions (NCCLs) after 36 months. Materials and methods: Scotchbond Universal Adhesive (SBU, 3M Oral Care) was applied in NCCLs of 39 subjects using four adhesion strategies: (1) three-step ER (etch-and-rinse), (2) two-step ER, (3) two-step SE (self-etch), and (4) one-step SE. An extra layer of a hydrophobic bonding resin was applied for strategies three-step ER and two-step SE. The same composite resin (Filtek Supreme XTE, 3M Oral Care) was used for all strategies. Restorations were evaluated at baseline and 18 and 36 months using the modified United States Public Health Service (USPHS) criteria. Kruskal–Wallis, Mann–Whitney U, Friedman, and Wilcoxon non-parametric tests were computed. Results: The cumulative failure rate was 8.6%. The 36-month retention rates were 100% for both 3-ER and 2-ER, 76.0% for 2-SE, and 86.2% for 1-SE. A lower retention rate was observed for two-step SE at 36 months compared with both three-ER (p < 0.01) and two-ER (p < 0.01). Identical retention rates were measured for the two SE groups. When retention rate was compared at baseline versus 36 months for each adhesion strategy, a significant decrease was observed for 2-SE. The restorations performed with 3-ER, 2-SE, and 1-SE had a significant deterioration in marginal discoloration at the 18-month recall. Conclusions: The 36-month clinical performance of Scotchbond Universal Adhesive improved for both etch-and-rinse strategies. Clinical relevance: Phosphoric acid etching is still recommended to provide retention to composite restorations in NCCLs.