Use of Reparative Agents Topical Fluoride Activated by CO₂ Laser and Curodont™ Repair and NR-5™ on Vickers Hardness and Micro-Shear Bond Strength of Eroded Enamel to Composite Restoration

Aim: This study aims to assess the impact of various reparative remineralizing agents, specifically topical fluoride (TF) and a combination of a carbon dioxide laser (CO2 laser) with TF, as well as regenerative agents such as Curodont™ Repair and NR-5™, on two key factors—the micro-Vickers hardness (VH) of eroded enamel and the micro-shear bond strength (µSBS) of composite restoration. Materials and Methods: A total of 50 single-rooted premolars with intact enamel were sectioned mesiodistally into two halves, making a sample size of 100 specimens. All of the samples were then exposed to Coca-ColaTM for 2 min each day over 1 month to induce erosion on the enamel surface. The specimens were then embedded in acrylic cold-cure resin facing a flat surface upward. The samples were then arbitrarily divided into five groups based on the remineralizing and regenerative agents used, as follows (n = 20): Group 1: No remineralizing agent, Group 2: Curodont™ Repair, Group 3: NR-5™, Group 4: TF, and Group 5: CO2 laser + TF. The VH of the pretreated enamel surfaces was analyzed and µSBS testing and failure mode of composite restoration were performed using a universal testing machine (UTM) and stereomicroscope. ANOVA and Tukey’s post hoc were performed for data analysis. Results: In Group 3, the (NR-5™)-treated teeth exhibited the highest VH values and µSBS. In Group 1, the (No remineralizing agent)-treated specimens displayed the lowest VH and the lowest µSBS. An intergroup comparison analysis unveiled that Group 3, Group 4 (TF), and Group 5 (CO2 laser + TF) presented comparable outcomes of microhardness and bond strength. The Group 2 (Curodont™ Repair) samples exhibited no significant difference in VH and µSBS, as compared to Group 1. Conclusions: The use of a combination of NR-5™ technology and a CO2 laser in conjunction with TF has been shown to significantly augment the natural mineralization process. This enhancement results in increased microhardness and an improved bond strength in the treated enamel