Effect of layer thickness and printing orientation on the color stability and stainability of a 3D-printed resin material

Statement of problem. Although 3-dimensional (3D)eprinted resin prostheses are widely used, studies on the effects of the manufacturing parameters of 3D printing on the color stability and stainability of these prostheses are lacking. Purpose. The purpose of this in vitro study was to investigate the effects of layer thickness and printing orientation on the color stability and stainability of a 3D-printed resin. In addition, the influence of roughness and water contact angle was evaluated. Material and methods. Color changes (DE00) in tooth-colored resin specimens produced by 3D printing with 2 different layer thicknesses and 3 different printing orientations and immersed in 3 types of aging media (distilled water, coffee solution, and wine) were evaluated (n=10). The CIELab color values were measured with a spectrophotometer at baseline and different time points (1, 3, 7, 15, and 30 days). The surface roughness (Ra) of resin specimens was measured at various time points (baseline, 7, 15, and 30 days) by confocal laser scanning microscopy after immersion in coffee solution (n=15). The water contact angle was determined by using the sessile drop method (n=10). The DE00 values were analyzed by using the 3-way repeated measures ANOVA followed by the Bonferroni test and Dunnett T3 test (a=.05). Ra values were analyzed by 3-way repeated measures ANOVA (a=.05). The water contact angle data were analyzed by 2-way ANOVA (a=.05). Results. The 3-way repeated measures ANOVA showed that layer thickness, printing orientation, and storage time significantly influenced the DE00 values of the 3D-printed resin specimens in each aging medium (P<.001). The DE00 values in the 0-degree subgroups were significantly lower than those in the 45- and 90-degree subgroups (P<.05). The DE00 values in the 25-mm thick groups were significantly higher than those in the 100-mm thick groups (P<.05). The DE00 values demonstrated an increase up to 15 days in all aging media. In distilled water, the DE00 values of the specimens increased or decreased depending on the groups, whereas in the coffee solution, the values decreased after 15 days (P<.001); in red wine, the values demonstrated a continuous increase up to 30 days in all groups (P<.001). The 3-way repeated measures ANOVA showed that the Ra values did not change significantly with immersion time (P=.444). The 2-way ANOVA showed that the water contact angle was not significantly affected by layer thickness (P=.921) or printing orientation (P=.062). Conclusions. Layer thickness and printing orientation affected the color stability and stainability of the 3D-printed resin. The discoloration of the 3D-printed resin differed with time, depending on the type of aging media used.

Automated summary

This in vitro study investigated the effects of layer thickness and printing orientation on the color stability and stainability of 3D-printed resin. The results showed that layer thickness, printing orientation, and storage time significantly influenced the color changes of the resin. Water contact angle and surface roughness did not have a significant effect on stainability.