The aim of this study was to evaluate the effect of neodymium:yttrium–aluminum–garnet (Nd:YAG) laser irradiation before adhesive application on microtensile bond strength of resin composite to dentin surface. Materials and methods: in this experiment, 40 human extracted third molar teeth were chosen and the occlusal surface was cut to achieve a flat dentin surface. Groups were divided based on the adhesives (G-Premio Bond or Clearfil S3 Bond) and the presence or absence of Nd:YAG laser application. All the samples were restored with resin composite and subjected to a universal testing machine for a microtensile bond strength test. Fracture mode for each failure was analyzed under the stereomicroscope. According to the results, there was a significant difference between the two adhesives with Nd:YAG laser irradiation. The application of laser enhanced the microtensile bond strength in both adhesives. In all groups, regardless of laser application, adhesive failure was dominant between fracture patterns. It was concluded that Nd:YAG laser irradiation on dentin surface prior to adhesive application has a positive effect and significantly increases the microtensile bond strength of restoration to the tooth.

Objectives: The aim of this study was to assess the microtensile bond strength of three universal adhesives to dentin and enamel. Materials and Methods: Sixty extracted human third molar teeth were chosen and divided into six groups regarding the adhesive (G-Premio Bond, Clearfil S3 Bond or Single Bond) and tooth surface. All the applied bonding agents were universal adhesives. The teeth were polished and the adhesives were applied; then the teeth were restored with composite resin. The samples were mounted in acrylic resin and sectioned. The specimens were subjected to a universal testing machine and the microtensile bond strength was measured. The failure mode of each specimen was determined under a stereomicroscope. Data were analyzed using two-way ANOVA (α=0.05). Results: The microtensile bond strength of G-Premio Bond to enamel and dentin was 11.79±8.27 and 17.55±9.47 MPa, respectively which was not significantly different from the values in Single Bond group (15.59±10.66 and 17.19±10.09 MPa to enamel and dentin, respectively; P>0.05). However, the values for Clearfil S3 Bond were 7.11±4.23 and 7.88±8.83 MPa to enamel and dentin, respectively, which were significantly lower than the values for G-Premio Bond (P<0.05). Scanning electron microscopic (SEM) images showed that the adhesive failure was dominant in both enamel and dentin groups and in all adhesive systems. Conclusion: G-Premio Bond and Single Bond provided higher microtensile bond strength compared with Clearfil S3 Bond. Universal adhesives with their acceptable performance can be applied in self-etch mode on both enamel and dentin.