Flexural Strength of 3D Printed Denture Acrylic Compared to Conventional and Milled Denture Acrylic

Introduction: Denture base acrylics have been made of ivory, wood and rubber before polymethyl methacrylate (PMMA) was utilized in the 1940's. Since PMMA is the material of choice for denture bases for esthetics and physical properties, manufacturers have attempted to create and improve PMMA with different fabrication methods. There are heat-activated and auto polymerized PMMAs as well as newer milled, injection molded and 3D printed methods. Objective: Compare the flexural strength and flexural modulus of three commercially available denture bases with a three-point bend test on ISO-standard bars. 3D printed PMMA (DentureBase Resin LP, Formlabs), Milled PMMA (Ivotion Base, Ivoclar Vivadent), and conventional heat polymerized PMMA (Lucitone 199 Hybrid, Dentsply Sirona). The null hypothesis is there is no difference in the flexural strength of the three tested materials. Methods: 30 PMMA bars split evenly in three groups by production method were fabricated in ISO-standard size of 64 x 10 x 3.3 mm. After processing, the bars were shaped, polished and measured. Samples were stored in 37-degree Celsius water for 1 week. Following completion samples were subjected to a three-point flexural test by the MTS 858 Mini Bionix II and the resulting data was used to measure flexural strength and flexural modulus. Results: Based on an analysis of variance test, it was revealed that the flexural strength of conventional (M = 72.57 MPa; SD = 7.35) and milled samples (M = 73.13 MPa; SD = 2.57) did not differ (P=0.97). However, the 3D printed samples were found to have a 30 percent higher mean flexural strength (M = 95.06 MPa; SD = 3.60) compared to conventional and milled samples, both P less than 0.001. Similarly, the calculated flexural modulus of conventional (M = 495.76; SD =75.76) and milled samples (M = 509.28; SD = 79.34) did not differ significantly, P=0.90.