The Effect of Aging by Acidic Solutions, that Simulate the Oral Conditions of Patients with Nervous Bulimia, on the Bond Strength of Repairs Influenced Using Different Bulk Fill and Nanoparticulate Composites

Purpose: This study aimed to evaluate the bond strength of aged and post-repair composites in different solutions, namely distilled water [DW]; 75% water/alcohol [WA]; and 0.02 N nitric acid [NA], which simulates the acidic conditions in the oral cavity of patients with bulimia nervosa.

Methods: We used five composites: one nanoparticulate (Z350) and four bulk fills—Filtek Bulk Fill (FBF), Filtek Bulk Fill Flow (FBFF), Surefil SDR Flow (SURE), and Opus Bulk Fill Flow (OPUS). Samples were prepared from each material and aged for 30 days. The composites underwent a surface treatment followed by repair. The repaired samples were aged for another 30 days in the same solutions used previously and subjected to the tensile test with the universal test machine. The mean values obtained for each composite were analyzed using the Shapiro-Wilk and ANOVA tests, followed by the Tukey post-test (p < 0.05).

Results: In most comparisons made among the composites, the nanoparticulate composite showed the worst bond strength values when used for repair, while the bulk fill composites showed the best results when used for repair. The highest bond strength values (MPa) were obtained with the combination of SURE/FBF-NA (8.41 ± 0.91), while the lowest values were obtained with the combination of SURE/FBFF-WA (1.57 ± 0.21).

Conclusions: Combinations of different post-repair composites were better than those of the composites alone for most of the studied groups. The DW and NA solutions did not influence adhesive strength. The WA solution reduced adhesive resistance in most studied combinations. The bulk fill composites showed higher adhesive resistance to the nanoparticulate composite for the repair of aging restorations. Aging in acidic solution affected the adhesive strength of repaired composites less than did aging in water/alcohol.