Analysis of Flexural Strength and Brittleness of a Polyjet 3D-Printed Denture Base Polymer

This study sought to understand the effects of print orientation on a novel 3D-printing technology recently made available for the fabrication of dentures.

A total of 90 experimental samples (30 each at 0, 45, and 90 degrees) were printed using denture resin on a polyjet printer. The milled control samples (n = 10) were milled on a 5-axis dental laboratory mill from a denture base disc. 96 samples were tested for flexural strength and extension at break using a 3-point bend test on a universal testing machine. The data were analyzed using statistical software and evaluated for statistical significance using general linear models with a Dunnett test with α = 0.05.

The results showed that the flexural strength and extension at break were both affected by print orientation with the 90-degree orientation being the lowest performing group for both properties. The 0-degree and 45-degree orientations both exceeded the ISO minimum flexural strength of 65 MPa, with mean flexural strengths of 88.18 and 73.53 MPa. The 90-degree group mean was well below the standard at 28.12 MPa. The milled sample group mean was 65.18 MPa. Extension at break showed similar results with less variation in the printed groups. Mean extension at break of the milled samples group was 15.05 mm, the 0-degree was 5.99 mm, 45-degree was 4.72 mm, and 90-degree was 1.92 mm.

Flexural strength and extension at break were influenced by print orientation. A 0-degree, or horizontal, print orientation yielded the highest values for flexural strength. The milled samples had significantly higher values for extension at break, but similar values for flexural strength.