Effect of uniaxial bending methods on the flexural strength and Weibull analysis of heat-polymerized, CAD/CAM milled, and 3D-printed denture base resins.

OBJECTIVES

To compare the flexural strength and modulus of denture base resins manufactured by conventional methods, 3-dimensional (3D) printing, and computer-aided design and computer-aided manufacturing (CAD/CAM) milling using 3-point bending (3PB) and 4-point bending (4PB) methods after simulated aging.

METHODS

Ninety bars (64 ×10 ×3.3 mm) were prepared from heat-polymerized (Lucitone-199), CAD/CAM milled (G-CAM), and 3D-printed (Denturetec) denture base resins (n = 30 per material). After 10,000 thermal cycles, specimens were subjected to either 3-point bending (3PB) or 4-point bending (4PB) (n = 15 per method) to measure the flexural strength (σ and σ) and elastic modulus (E and E) using a universal testing machine. Weibull analysis was performed to evaluate the reliability (m) and characteristic strength (σ) as a function of 3PB and 4PB. Fractographic analysis was conducted using scanning electron microscopy (SEM). Data were analysed using 2-way ANOVA followed by Tukey post hoc and Student t-tests (α=.05).

RESULTS

Significant effects of material type and uniaxial bending method on flexural strength and modulus were found (P < .001). Irrespective of the flexural strength measurement approach, CAD/CAM milled resins exhibited significantly higher flexural strength in both methods (σ=125.6 ± 5.2 MPa, σ=110.5 ± 4.5 MPa) and elastic modulus (E=2400 ± 120 MPa and E=2800 ± 150 MPa) compared to 3D-printed and heat-polymerized resins. Irrespective of the denture base resin manufacturing method, σ was significantly higher than σ whereas E was significantly higher than E (P < .001). Weibull analysis exhibited highest reliability for CAD/CAM resins (m=25.24 - 43.83). Considerable microscopic differences were detected.

SIGNIFICANCE

CAD/CAM milled denture base resins exhibited superior flexural properties compared with 3D-printed and heat-polymerized resins.