Impact of Salivary Contamination at Various Application Stages of an Acetone-Based Universal Adhesive on Dentin Bond Strength

This study evaluated the effect of saliva contamination at different stages of application of an acetone-based universal adhesive on dentin bond strength. Seventy-two caries-free third molars were assigned to six groups (n = 12) according to contamination step. Specimens underwent shear bond strength testing. To determine the SBS, each bonded specimen was subjected to an SBS test in a universal testing machine (Shimadzu Autograph AGS-X; Shimadzu Corp., Kyoto, Japan) equipped for operating at a crosshead speed of 1 mm/min. Data were analyzed using one-way analysis of variance (ANOVA) followed by Tamhane’s T2 test for post hoc multiple comparisons with p ˂ 0.05 as the significance level. Saliva contamination significantly affected dentin bond strength (p < 0.001). The highest bond strength was observed in the post-polymerization contamination group with adhesive reapplication (12.32 MPa), whereas the lowest values were recorded when contamination occurred after the initial adhesive application (6.37 MPa). Overall, contamination prior to polymerization resulted in reduced bond strength, while reapplication of adhesive after polymerization improved bonding performance. Within the limitations of this in vitro study, salivary contamination adversely influences the dentin bonding effectiveness of acetone-based universal adhesives, particularly when it occurs before curing. However, adhesive reapplication following post-polymerization contamination may partially compensate for this effect.