Effect of an additional bonding resin on the five years performance of a universal adhesive: a randomized clinical trial

Objectives: To evaluate the effect of the application of an additional hydrophobic bonding resin on the clinical performance of a universal adhesive applied in etch-and-rinse (ER) or self-etch adhesive (SE) strategy in non-carious cervical lesions (NCCLs) after 5 years. Materials and MethodsScotchbond Universal Adhesive (3M Oral Care) was applied in 134 NCCLs of 39 subjects using different adhesive approaches: 3-step ER (3-ER), 2-step ER (2-ER), 2-step SE (2-SE), and 1-step SE (1-SE). An extra layer of a hydrophobic bonding resin was applied for groups 3-ER and 2-SE. All lesions were restored with Filtek Supreme XTE resin composite (3M Oral Care). Restorations were evaluated at baseline and at 5 years using the modified USPHS criteria. Mann-Whitney U and Wilcoxon tests were performed, and the survival rates (retention/fracture) were analyzed using Kaplan-Meier and Log-rank tests (p < 0.05). ResultsThe recall rate was 66.7% at 5 years. The cumulative survival rate was 96.9% for 3-ER, 96.8% for 2-ER, 71.4% for 2-SE and 81.3% for 1-SE strategies. Log-rank-test was statistically significant (p = 0.006). Retention rates were 100% for both ER groups, 75% for 2-SE and 81.3% for 1-SE. At 5 years, 2- and 1-SE approaches showed similar retention rates, but lower than those for 3- and 2-ER. A significant decrease in retention rate was detected for 2-SE (p = 0.007) and 1-SE (p = 0.014) groups between baseline and 5 years. All groups, except 2-ER, showed an increase in marginal discoloration. This parameter was statistically significant difference between 2-ER and 1-SE (p = 0.004). ConclusionsThe addition of a hydrophobic bonding resin to the recommended application sequence of Scotchbond Universal Adhesive did not improve its clinical performance in NCCLs after 5 years. Higher retention rates were found when this adhesive was applied in ER mode.Trial registrationThis manuscript is a 5-year follow-up of a randomized clinical trial that started in 2012 when there was no strong recommendation for registration in clinicaltrials.gov. The results after 36 months of clinical service were previously published in this journal.