Evaluation of the success of current adhesive systems in bonding to caries affected dentin

Objective: To evaluate the long-term bonding success of sound and caries-affected dentin using universal adhesives by microtensile bond strength test, electron microscopy (SEM) and confocal laser scanning microscopy (CSLM) images to be taken from resin-dentin interfaces. Material and Method: In this in vitro study, a total of 120 sound and decayed human molar teeth were extracted using a manual excavator until soft caries lesions reached a hard dentin layer, and a flat surface was created by reducing the dentin level with a precision cutting device. With the Vickers microhardness test, the surface microhardness was determined by applying a 25 g load for 15 seconds, and the sound and caries-affected dentin samples were divided into 3 subgroups (sound dentin-SD, caries-affected superficial dentin-D1 and caries-affected deep dentin-D2). Dentin samples were divided into 4 subgroups for each group and adhesive systems were applied; Group 1: Peak Universal Bond (Ultradent)+self-etch mod, Group 2: Peak Universal Bond (Ultradent)+etch and rinse mode, Group 3: G-Premio Bond (GC)+self-etch mode, Group 4: G -Premio Bond (GC) )+etch and rinse mod. A nanohybrid universal resin composite structure was prepared on the samples. Hourglass shaped slabs kept in 37 C0 distilled water were cut off at 1 mm/min head speed in a universal test device for microtensile bond strength (μTBS) test after 24 hours and 1 year, and the fracture types were evaluated with a stereomicroscope at 25x magnification, with a SEM and CSLM of the resin-dentin interfaces. One-way analysis of variance (One-way ANOVA), Scheffe multiple comparison test and independent t-test were used for statistical analysis, and the level of significance was determined as p≤ 0.05. Results: After 24 hours, the highest bond strength value was recorded in the SD group at PUB-SE (36.80 MPa), the lowest value in the D1 group at G-PB SE (17.60 MPa). After 1 year, the highest bond strength value was recorded in the SD group at G-PB SE (30.38 MPa), the lowest value in the D1 group at PUB SE (16.67 MPa). Conclusion: It was observed that the bond strength of universal adhesives to caries-affected dentin was significantly lower compared to sound dentin, a significant difference was observed between different modes of application, and the Vickers test was an effective method to distinguish between sound and caries-affected dentin. Key words: caries-affected dentin, microhardness, universal adhesive, microtensile bond strength, confocal laser microscopy.