BONDING TO ENAMEL USING A UNIVERSAL ADHESIVE

Interventions: restorative procedure All the patients selected for this study received dental prophylaxis with a suspension of pumice and water in a rubber cup and signed an informed consent form two weeks before the restorative procedures.

The degree of sclerotic dentin from the NCCLs was measured according to the criteria described by Swift and others. The cavity dimensions in millimeters (height, width, and depth), the geometry of the cavity (evaluated by profile photograph and labeled at \<45o, 45o-90o, 90o\<135o, and >135o), the presence of an antagonist, and the presence of attrition facets were observed and recorded. Pre-operative sensitivity was also evaluated by applying air for 10 s from a dental syringe placed 2 cm from the tooth surface and with an explorer. These features were recorded to allow comparison of the baseline features of the dentin cavities among experimental groups.

To calibrate the restorative procedure, the study director placed one restoration of each group to identify all steps involved in the application technique. Then, the two operators, who were resident dentists with more than five years of clinical experience in operative dentistry, placed four restorations, one of each group, under the supervision of the study director in a clinical setting. The restoration failures were shown to the operators prior to starting the study. At this point, the operators were considered calibrated to perform the restorative procedures.

The operators restored all teeth. All participants received four restorations, one of each experimental group in different lesions previously selected according to the inclusion criteria.

Before restorative procedures, the operators anesthetized the teeth with a 3% mepivacaine solution (Mepisv, Nova DFL, Rio de Janeiro, RJ, Brazil) and cleaned all lesions with pumice and water in a rubber cup, followed by rinsing and drying. Then, shade selection was made using a shade guide.

Cleaning of all lesions with pumice and water in a rubber cup was carried out, followed by rinsing and drying. Using a shade-selection guide, the proper shade of the composite was determined. Following the ADA guidelines, the operators did not prepare any additional retention or bevel.

The NCCLs received the multimode adhesive system applied in different modes: 1-step self-etch approach (SE), selective enamel etching (SEE), 1-step self-etch applied for double time in the enamel (SE2X), 1-step self-etch approach with additional layer (SE1+) was applied as described below. The compositions, more details regarding the adhesion strategies used and batch numbers are described in Table 2.

The adhesives were light-cured with a LED light-curing unit (1,000 mW/cm2) (Radii-cal), according to the manufacturer's instructions (Table 2). Opallis (FGM) composite resin was used in 2 to 3 increments, each one being light-cured (Radii-cal) for 30 s. The restorations were finished immediately with fine #2200 diamond burs (KG Sorensen). Polishing was performed with rubber points (Astropol, Ivoclar Vivadent, Liechtenstein).