Comparison of repair properties of denture base materials fabricated for CAD/CAM technique to conventional denture base material

The aim of this study is to evaluate the mechanical properties of repaired polymethyl methacrylate (PMMA) based denture base materials fabricated for CAD/CAM technique and to compare them with conventional heat-polymerized PMMA denture base material. A total of 288 specimens (65x10x2.5 mm) were prepared from CAD/CAM blocks obtained from three different manufacturers and heat-polymerized acrylic resin. To simulate denture fracture and repair process, a 2 mm repair gap and 45°margin design was prepared. The specimens were repaired with autopolymerizing and visible light cured acrylic resin. Microwave energy, keeping in hot water and hydroflask curing were applied as an additional polymerization cycle to the samples repaired. The mechanical properties of the repair were evaluated with the three-point bending test. Data were statistically evaluated by 2-way analysis of variance for prosthetic base material and repair material (p≤0.05). The mechanical properties of the denture base materials of CAD/CAM technique were found to be significantly higher than heat-polymerized group (p≤0.05). The mechanical values of all groups repaired with by visible light cured acrylic resin were significantly lower than the values of the groups repaired with autopolymerizing resin treated with additional polymerization cycle (p≤0.05). As well-known with heat-polymerized denture base materials, mechanical properties of denture base materials fabricated with the CAD/CAM technique repaired with autopolymerizing acrylic resin can be recovered at a rate of 50-70%. Additional polymerization cycles positively affected the mechanical properties. Repair with visible light cured acrylic resin is not recommended because of poor mechanical properties for conventional and CAD/CAM denture base materials.