Adhesive evaluation of three types of resilient denture liners bonded to heat-polymerized, autopolymerized, or CAD-CAM acrylic resin denture bases

Levels of bond strength between different types of resilient denture liner materials bonded to different denture base acrylic resins, CAD-CAM acrylic resins in particular, have not been well reported. The purpose of this in vitro study was to measure the tensile bond strength and durability of various combinations of 3 different resilient denture liners bonded to 3 different poly(methyl methacrylate) denture base materials. The tensile bond strength of 3 resilient denture liners, namely Ufi Gel SC, Silagum-Comfort, and Vertex Soft, combined with heat-polymerized (Vertex Rapid Simplified), autopolymerized (Vertex Self-Curing), and computer-aided design and computer-aided manufacturing (CAD-CAM) (IvoBase CAD) denture base resins were tested by using a universal testing machine (total N=138). Half of the specimens were thermocycled between 5°C and 55°C for 1500 cycles before testing. After testing, modes of failure and interface surfaces were examined using light microscopy and scanning electron microscopy, respectively. Thermogravimetric analysis was carried out to analyze the differences in content between the 3 different denture base acrylic resins. The mean tensile bond strength values ranged from 0.36 ±0.1 MPa to 1.51 ±0.46 MPa. CAD-CAM denture base materials showed the lowest range of bond strength when coupled to resilient denture liners (0.36 to 0.42 MPa). No statistically significant differences (P=.74) were found in bond strength between the thermocycled (0.71 ±0.23 MPa) and non-thermocycled groups (0.74 ±0.21 MPa). Silicone-based resilient denture liners exhibited the highest tensile strength with each type of denture resin. All 3 types of failure modes (adhesive, cohesive, and mixed modes) were observed. Silicone-based resilient denture liners produced the highest tensile bond strength to all denture bases tested. Resilient denture liners bonded to CAD-CAM denture bases produced the weakest tensile bond strengths. Thermocycling did not produce statistically significant differences in tensile bond strength of the resilient denture liners to the denture base resins.