Evaluation of methods for removing stains from a 3D printed resin for denture teeth

An efficient protocol for removing stains from 3-dimensionally (3D) printed artificial teeth must also preserve their surface properties.

The purpose of this in vitro study was to evaluate methods of removing stains from a 3D printed resin (Bio Crown) for artificial teeth submitted to immersion in coffee by using spectrophotometric analysis (CIEDE2000) and analyzing surface roughness with a profilometer and topography with a scanning electron microscope (SEM).

Disks (Ø10×1.2 mm) were 3D printed and stained in instant coffee simulating 1 year of consumption. Color data (L*, a*, b*) and roughness (Ra, µm) were obtained at T0 (baseline, before staining), T1 (after staining), and T2 (after each stain removal protocol, n=12). The stain removal groups used sodium perborate (SP), 0.25% sodium hypochlorite (SH), conventional polishing with brush and pumice stone + felt wheels and universal paste (CP), and polishing with 3-abrasive tip kit (AP); the control was storage in distilled water (DW). Mixed 2-way ANOVA followed by the Bonferroni test was performed to statistically analyzing data with α=.05.

Roughness increased in all groups between T1 and T2 (P<.05), except for SH. The AP (0.64 ±0.12 µm) and CP (0.52 ±0.17 µm) groups showed similar roughness and higher roughness compared with the other groups (SP 0.40 ±0.22 µm, SH 0.31 ±0.12 µm, and DW 0.34 ±0.11 µm). A significant color difference (ΔE₀₀) was observed between T0 (1.03 ±0.49) and T1 (1.36 ±0.77), (P<.001), and the color remained statistically similar between T1 and T2 (1.48 ±1.02).

No method was effective in removing coffee stains. The polishing methods resulted in greater roughness, followed by sodium perborate. The only protocol that did not increase the roughness of the 3D printed resin for artificial teeth was 0.25% sodium hypochlorite. Longer application periods of the staining removal protocols are suggested for future studies.