CAD/CAM veneers: effect of material and thickness on color masking, bond strength and marginal fit

New CAD/CAM materials are becoming more accepted in veneer restoration. The objective is to investigate the margin integrity of CAD/CAM veneer, their color masking over dark backgrounds and shear bond strength (SBS) to resin cements. Materials and Methods: Four types of CAD/CAM materials shaded A2: Lava Ultimate (LU); IPS Empress CAD (IPS); Vita Enamic (VE); and Vitablocs Mark II (VMII) were sectioned into tiles of different thicknesses: 0.3mm, 0.5mm and 0.7mm (n=7). The color (CIE - L*a*b*) of each specimen was measured against grey background, then against each tooth-shaded background: A3, A4, B3 and C2 acrylic (Coldpac, Motloid). Color differences (ΔE) were calculated. Specimens were measured against black then white background to calculate translucency. Two-way ANOVA was used to compare the differences in ΔE among the groups (a=0.05). SBS values of 2mm thick tile specimens of the same CAD/CAM materials to resin cements, RelyX Ultimate and Varilonik Veneer, were measured using Instron Universal Testing Machine. (n=10). Statistical analysis was performed by ANOVA with Tukey-Kramer HSD multiple comparison test (a=0.05). Qualitative evaluation of margin integrity of the veneers milled from the same CAD/CAM materials in three thicknesses 0.3, 0.5 and 0.7mm were observed under the optical microscope. Results: Significant differences in masking capabilities were found among the tested material for all three thicknesses. In comparison of ΔE values of the tested materials over tooth-shaded backgrounds, specimens over shade A3 background showed the highest color masking ability. LU and VE exhibited better color masking than IPS and VMII. IPS showed significantly higher in translucency than the other groups. IPS showed the highest SBS to resin cements and LU showed lowest SBS. Materials cemented with RelyX showed significantly higher SBS values than those with Variolink. CAD/CAM milled LU and VE veneers show smoother margins when compared to IPS and VMII. Conclusion: LU and VE exhibited higher color masking, lower translucency, lower SBS values, and better margin integrity than IPS and VMI.2019-09-26T00:00:00

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