Comparative Evaluation of Impact and Flexural Strength of 3D Printed, CAD/CAM Milled and Heat Activated Poylmethyl Methacrylate Resins - An In-Vitro Study

Purpose: To evaluate the impact and flexural strength of 3D printed, CAD/CAM milled and heat activated polymethyl methacrylate denture base resins. Materials & methods: Sixty specimens were used in this in vitro study and divided into two main groups. Thirty specimens were used to test flexural strength and thirty specimens were used to test impact strength. For flexural strength, all the thirty specimens were divided into three subgroups- Group A, Group B and Group C. Each subgroup consists of ten specimens. Each specimen is of dimension 64 mm x 10 mm x 3.3 mm and were fabricated using 3D milling, CAD/CAM milled and conventional methods respectively. For impact strength, all the thirty specimens were divided into three subgroups- Group A, Group B and Group C. Each subgroup consists of 10 specimens. Each specimen is of dimension50 mm x 6 mm x 4 mm with 1.2mm V shaped notch along its thickness and were fabricated using 3D milling, CAD/CAM milled and conventional methods respectively. Results: For flexural strength: Flexural strength of GROUP IB (CAD/CAM milled) was higher than GROUP IA (3D printing) and GROUP IC (Heat activated). The 3D printing group (GROUP IA) exhibited higher flexural strength than heat activated group (GROUP IC). For impact strength: Impact strength of GROUP II A (3D printing) was higher than GROUP II B (CAD/CAM milled) and GROUP II C (Heat activated). The CAD/CAM milled group (GROUP II B) exhibited higher Impact strength than heat activated group (GROUP II C). Conclusion: The method of fabrication or the process of polymerisation of polymethyl methacrylate denture base resin have an effect on flexural and impact strength of the PMMA resin denture bases. All the tested specimens had flexural strength higher than the values recommended by ISO. (ISO 20795-1- 65 Mpa). Similarly, the impact strength of all the specimens had values higher than the minimum recommended by the ADA specification (ADA specification no. 12 ? 15J/m).