Comparison of Tensile Bond Strength of Denture Reline Materials on Denture Bases Fabricated with CAD-CAM Technology

Purpose: The purpose of this study was to evaluate the tensile bond strength of both hard and soft denture reline materials on denture bases fabricated by 3D printing and milling CAD-CAM technology. Materials and methods: One hundred fifty denture base samples (injected, milled, printed) were fabricated (n = 30) and bonded to five different denture reline materials (COE Soft, PermaSoft, Tokuyama Rebase ii, Kooliner, ProBase Cold). Samples of each reline material were divided into five groups (n = 10), and were placed in distilled water for 24 hours prior to tension testing by a universal testing machine. Maximum tensile stress values before failure were recorded, and the failure mode was also determined. The type of failure was analyzed by a scanning electron microscope (SEM). Statistics were analyzed with one-way ANOVA and the Independent Samples t-Test (α = .05). Results: Overall, there was no statistically significant difference of tensile bond strength among the injected, milled and printed denture groups. However, the printed denture base group demonstrated significantly lower values of tensile bond strength (P < .05), with PermaSoft, Tokuyama Rebase ii and ProBase Cold groups in comparison to other denture base groups (milled and injected). The milled denture bases had the highest mean value of tensile bond strength in four out of the five denture liners tested (Coe Soft, PermaSoft, Tokuyama Rebase ii and Kooliner). There was no statistically significant difference (P < .05), between the injected, milled and printed denture bases when relined with Kooliner. When comparing the denture reline type, the lowest values were seen with the soft chairside relining materials and highest values with the hard lab reline material. As for the modes of failure, adhesive failures were observed predominantly with the printed denture base materials relined with soft chairside relining materials, while cohesive and mixed modes of failure were found in the milled and injected denture base groups. Conclusions: The printed denture bases had statistically significant lower tensile bond strength values compared with the injection and milled denture bases with the PermaSoft, Tokuyama Rebase ii and ProBase Cold denture relines, while milled denture bases demonstrated the highest values of tensile bond strength for all chairside relining groups. In addition, the soft chairside relining materials showed the lowest tensile bond strength values regardless of denture processing method with respect to the denture base type (injected, printed, and milled) compared with the hard relining materials