Tensile bond strength of soft relining materials to CAD-CAM denture base materials

This study aimed to investigate the tensile bond strength between soft relining materials and different denture base materials.

The study was conducted in accordance with ISO 23401:2023. A total of 288 rectangular specimens (10L × 10H × 20W mm) were fabricated from various denture base materials, including a heat-compression polymethylmethacrylate (PMMA), two types of milled PMAA, and three types of 3D-printed resins, with bonding using two chairside soft reline materials (Coe-Soft and Lynal). Specimens were placed in distilled water for 24 h before applying tensile force at a 5 mm/min crosshead speed. The tensile bond strength values (MPa) were calculated at maximum tensile force (N) before failure. Two-way ANOVA and post hoc multiple comparison tests were used to assess the effect of denture base and soft reline materials on the tensile bond strength (α = 0.05).

A significant difference in the tensile bond strength was found among the different types of denture base materials (p < 0.001), regardless of relining material type. Lynal-relined milled IvoBase demonstrated the highest tensile bond strength (0.5 ± 0.06 MPa), followed by Lynal-relined milled Lucitone (0.44 ± 0.03 MPa), both of which are clinically acceptable as they are equal or greater 0.44 MPa. The lowest tensile bond strength was detected in Lynal-relined 3D printed FotoDent (0.09 ± 0.02 MPa). Lynal exhibited significantly higher tensile bond strength (p < 0.05) than Coe-Soft soft reline material when bonded to PMMA bases; however, there was no significant difference between Lynal and Coe-Soft when bonded to 3D-printed base materials (p > 0.05).

The tensile bond strength between soft relining materials and denture bases is material-dependent, influenced by both the type of denture base material and the type of soft relining material used.