Background and Aim: Preparation of tooth structure by laser systems produces a surface with different characteristics. Therefore, selecting an appropriate bonding system is necessary to achieve the maximum bond strength. The aim of this study was to compare the bond strength of Adper Single Bond 2 adhesive and Single Bond Universal to dentin prepared by bur or laser. Materials and Methods: In this experimental study, 48 third molars were collected. The enamel was abraded by wet grinding to achieve flat surfaces of dentin. Samples were divided into 4 groups. Group 1: bur preparation + Single Bond Universal adhesive, Group 2: bur preparation + Adper Single Bond 2, Group 3: Er:YAG laser preparation + Single Bond Universal adhesive and Group 4: Er:YAG laser + Adper Single Bond 2. Nanocomposites were bonded to the samples. The shear bond strength was measured. Failure mode was evaluated under a stereomicroscope. Data were analyzed using twoway ANOVA. The level of significance was considered as 0.05. Results: The shear bond strength of the laser group was significantly lower than that of bur group (P<0.001). No significant difference was observed in shear bond strength regarding the type of adhesive used (P>0.05). The failure mode in all groups was mainly mixed. Conclusion: Preparation of dentin by Er: YAG laser decreased the bond strength in comparison to diamond bur preparation. The type of adhesive did not affect the bond strength, regardless of the preparation method.

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Background and Aim: Fractured metal-ceramic restorations may be repaired with composite in some cases to postpone the fabrication of a new restoration. Knowledge about the bond strength can help predict the success rate of this treatment modality. The aim of this study was to assess the effect of two types of mechanical surface treatment of metal along with the use of different adhesive systems on bond strength of composite to a non-precious metal alloy. Materials and Methods: In this in vitro experimental study, 110 metal discs were fabricated of nickel chromium alloy and were randomly divided into two groups of surface preparation with sandblasting (S) and bur (B). In each group, the samples were divided into five subgroups based on the adhesive system and composite resin used: Group NC: Z350 composite without application of adhesive; group AC: Alloy primer/Clearfil AP-X; group ZA: Z-Prime Plus/Aelite; group MT: Monobond Plus/Tetric N Ceram; group AZ: Adper Single Bond Plus/Z250. In the positive control group (PC), metal discs were covered with feldspathic porcelain. All samples were then subjected to 1000 thermal cycles and shear bond strength was measured. Data were analyzed using one-way ANOVA, two-way ANOVA and Tukey's HSD test (P<0.05). Results: The interaction effect of type of surface treatment and type of adhesive system on bond strength was significant (P<0.05). The highest bond strength (148.7 MPa) was noted in group PC and the lowest bond strength (2.78 MPa) was noted in group B+NC. The bond strength was 13.72 MPa in group S+AZ, 10.84 MPa in group B+AZ and 12.72 MPa in group S+ZA, which did not have a significant difference with the bond strength of group PC. Conclusion: Type of surface preparation and adhesive affect the bond strength. Surface preparation by sandblasting or bur combined with the use of Adper Single Bond Plus and also combination of Z-Prime Plus adhesive and sandblasting yielded the highest bond strength value.