Effect of different remineralization agents on microhardness and shear bond strength of enamel

EFFECT OF DIFFERENT REMINERALIZATION AGENTS ON MICROHARDNESS AND SHEAR BOND STRENGTH OF ENAMEL Objective: This study aimed to investigate the effects of remineralization agents on enamel surface microhardness (VHN) and shear bond strength (SBS). Method: In the study, 105 human premolar teeth were used. Each tooth was sectioned buccolingually into two pieces and the buccal pieces were covered with nail polish leaving a 3x3 mm area open. The samples were randomly divided into five groups (n=21). Group 1, consisting of sound enamel, served as the positive control. Artificial caries lesions were induced in all other groups by immersing the samples in 0.5% citric acid twice daily for 30 minutes over three days. Group 2, comprising demineralized enamel, served as the negative control. The samples in Group 3 (CCP-ACPF paste; MI Paste Plus®, GC, Leuven, Belgium), Group 4 (5% NaF varnish; Profloroid Varnish, Voco, Cuxhaven, Germany), and Group 5 (NovaMin toothpaste; Sensodyne Repair & Protect®, GlaxoSmithKline, Brentford, Middlesex, UK) underwent the respective remineralization treatments for one week, following the manufacturer's instructions. One sample from each group was analyzed using SEM to evaluate surface morphology. After measuring the VHN of the samples using a Vickers hardness tester (Duramin, Struers, Germany), a 3x3x2 mm universal composite resin was applied to the enamel surface. Then, the SBS of the samples was tested using a universal testing machine (Autograph AGS X; Shimatsu Corp, Kyoto, Japan) at a crosshead speed of 0.5 mm/min. Failure types were examined using a stereomicroscope. The data were statistically analyzed using SPSS software (α=0.05). Results: The VHN (202.61±15.77) and SBS (11.81±3.69) were the lowest in group 2. In all remineralization groups, VHN and SBS were significantly higher than in group 2 (p<0.05), but lower than in group 1. There wasn't significant difference in SBS among remineralization groups. Adhesive failure was significantly higher in group 2 compared to the other groups (p<0.05). Conclusions: It was concluded that remineralization agents are effective in increasing the microhardness of demineralized enamel and significantly affect the bond strength and failure modes of composite resins to enamel. Keywords: Demineralization, Remineralization, CPP-ACPF, NaF, NovaMin, Shear Bond Strength, Microhardness