Evaluation of the bond strength at the resin-dentin interface using self-etching adhesive systems containing different functional monomers / Avaliação da resistência de união na interface resina-dentina usando sistemas adesivos autocondicionantes contendo diferentes monômeros funcionais

Background: Self-etching adhesive systems have attracted considerable interest in dentistry, as these materials simplify the restorative protocol and allow a less sensitive adhesive technique. The objective of the present study was to analyze in vitro the performance of self-etching adhesive systems containing different functional monomers. Materials and Methods:  The adhesives evaluated were: Clearfil SE Bond (CSE) adhesive containing 10-MDP, Optibond All-in-One (OPT) containing GPDM, Palfique Bond (PB) containing 3D-SR monomer. Immediate microtensite bond strength (mTBS) and after thermocycling were realized. Interaction between the functional monomers and dentin was characterized using thin-film X-ray diffraction (TF-XRD) and scanning electron microscopy (SEM). In the experiments were used 60 molars. Thirty molars were divided into 3 experimental conditions (n=10) according to the adhesive system; the teeth were restored and sectioned on “toothpick” specimens for mTBS. Additionally, five teeth were prepared in the form of discs and the adhesives applied without light curing on the surface for XRD analysis. For morphological evaluation in SEM, 25 teeth were treated with the respective adhesives. The mTBS data were submitted to ANOVA two factors and Tukey's test (5%).  Results: The adhesive vs. time interaction was statistically significant (p<0.001), with the CSE adhesive obtaining the highest means and being the worst performance of BP. The analysis of XRD found that the monomers interact chemically with hydroxyapatite, but with different intensities. SEM images indicate that the applied adhesives infiltrate the dentin forming resin tags in greater or lesser amounts. Conclusions: The different functional monomers have a direct impact on the effectiveness of the adhesive bond, with the 10-MDP monomer, the CSE adhesive, highlighted by the higher TBS values. The self-etching adhesive systems allow a simplification in the restorative protocol, besides a less sensitive adhesive technique and less clinical time for the procedure. Therefore, knowing its mechanical and chemical properties is important to ensure longer-lasting restorations.