Influence of 3D printing parameters on surface roughness and stainability of a denture base resin: An in vitro study

Liquid crystal display (LCD) printing systems have the advantages of lower costs, higher printing speed, and the ability to use the same resins as those used in digital light processing (DLP) systems. However, the effect of the printing angles on the properties of a denture base resin printed using LCD remains unknown.

The purpose of this in vitro study was to compare printing systems DLP and LCD and printing angles (0-, 45-, and 90 degrees) on the surface roughness (Ra) and stainability (ΔE₀₀) of a 3-dimensionally (3D) printed denture base resin after immersion in coffee over time.

Disk-shaped specimens (N=72, Ø10×1.2 mm, n=12 per group) were printed using a 3D printed denture base resin (priZma 3D Bio Denture) and LCD or DLP printers at 0-, 45-, or 90 degrees. All specimens were thermocycled for 5000 cycles (5 and 55 °C). Color differences (ΔE₀₀) were calculated using the CIEDE2000 formula. Ra and ΔE₀₀ were measured before and after coffee immersion for 1 month, 3 months, 6 months, 12 months, 36 months, and 60 months. For ΔE₀₀, generalized estimating equations (GEEs) were performed and a 3-way mixed-model ANOVA was used for Ra. The post hoc Bonferroni test was performed for multiple comparisons of means (α=.05 for all analyses).

Stainability was higher for DLP ΔE₀₀ 2.86 (CI 2.52 to 3.20) than LCD ΔE₀₀ 1.95 (CI 1.61 to 2.29) (P<.001). The highest color changes (P<.001) occurred in the 3-month period of immersion in coffee: ΔE₀₀ 5.55 (CI 4.99 to 6.12) for both systems and angles. The DLP system resulted in greater color change compared with LCD in all periods except 12 and 36 months, where they were similar, regardless of the printing angle (P<.001). The most color changes occurred in the 3-month period of immersion in coffee for the specimens printed at 0- and 90 degrees (P=.007). Ra was higher for the specimens printed at 45-degrees for the DLP system (0.25 ±0.21 µm, P <.016), irrespective of the period of immersion in coffee. In addition, the Ra of both the DLP and LCD specimens printed at 45-degrees increased in the 3-month period (0.22 ±0.19 µm), remained similar until the 3-year period (0.29 ±0.21 µm), and decreased at 5 years (0.17 ±0.14 µm) (P<.005).

LCD specimens exhibited lower roughness than DLP specimens when printed at 45 degrees. The DLP system had a greater color change than the LCD system in all periods, except at 12 and 36 months when they were similar, regardless of the printing angle. The 3-month period of immersion in coffee was critical, resulting in clinically unacceptable color change values for both systems.