Influence of build angle, printing layer thickness and aging on the flexural strength, precision, roughness and porosity analysis of a printed resin for provisional restorations.

Abstract

Evaluate the impact of printing parameters on flexural strength (σ), flexural modulus (E), precision, and surface topography characteristics of a resin used to produce provisional restorations. 450 bars for provisional restorations were printed using the SLA printing (25 × 2x2mm ISO-4049), and randomly divided into 30 groups (n = 15) according to the following factors: "printing layer thickness" (25 μm;50 μm;100 μm), "Build angle" (0°,30°,45°,60°,90°) and "thermocycling-TC" (with or without). Following printing, the samples underwent cleaning with isopropyl alcohol. Photopolymerization was performed for 15 min with an UV lamp. Subsequently, each bar was assessed using a digital caliper at 11 specific points in three dimensions for comparison with the STL file area for precision analysis. Half of the samples underwent thermocycling. All samples were submitted to the σ test. Data for σ (MPa), and (GPa) and precision (mm) were analyzed using 3 and 2-way ANOVA, respectively, and Tukey's post hoc test (5%). Micro-CT, 3D profilometry, and SEM were also performed and analyzed descriptively. The 90°/25μm_TC (63.0 ± 4.5) showed the highest σ, being only statistically similar to the 45°/25μm_TC (57.7 ± 3.1). For precision 0°/25 μm (-2.56 ± 0.04) expressed the greatest variation to the other experimental groups with a sample shrinkage of 25.6% compared to the STL file. The profilometry revealed that the 30º/25 μm group showed prominent peaks and valleys, presenting elevated roughness values with an average of Sa (28.25 μm). Moreover, it was observed that the groups with a 60° angle presented the lowest porosity values. A print layer thickness of 25 μm combined with a build angle of 90º and 45º resulted in higher σ and greater precision.