Effect of repair and thermal cycling on the flexural strength of denture base materials fabricated from different methods

Objective: The aim of this study was to evaluate the flexural strength of the denture base materials produced by different methods after repair and was to evaluate effect of thermal aging. Materials and Methods: A total of 120 specimens were fabricated by conventional, CAD/CAM milled, and 3D-printed denture base materials for this in vitro study. Specimens were divided into four groups; non-repaired groups (N), repaired groups (R), non-repaired-aged groups (N-aged), and repaired-aged (R-aged) groups. In N groups, specimens were stored in the water bath for 24 h before the flexural strength test. In N-aged groups, samples were subjected to thermal aging for 5000 cycles, then tested. For repaired R groups, samples were repaired with auto-polymerized acrylic resin and storage in the water bath for 24 h then tested. For the R-aged groups, samples were repaired with auto-polymerized acrylic resin, aged for 5000 cycles, then tested. Specimens were performed a three-point loading test using a universal testing machine. Data were analyzed using Wilcoxon and Kruskal-Wallis tests. Results: When the groups were compared with each other, the difference between all groups was found to be statistically significant (p<0,05). Regardless of the thermal cycling process, in N groups, the highest flexural strength was recorded in N-CAD group (92,53±6,52 MPa), the lowest flexural strength was recorded in N-3D group (33,72±2,74 MPa). Regardless of the thermal cycling process, in R groups, the highest flexural strength was recorded in R-C groups (31,80±5,86 MPa) and the lowest flexural strength was recorded in R-3D groups (8,37±1,20 MPa). Thermal cycling and repair process showed a decreasing effect on flexural strength in all groups. Conclusions: The ideal flexural strength among denture base materials was found in CAD/CAM milled denture base materials.