Effect of Staining and Cleaning Agents on the Colour Stability and Surface Roughness of Clear Aligners

This study aimed to evaluate the effects of various staining and cleaning agents on the colour stability and surface roughness of Invisalign aligners (Align Technology).

240 aligners were assigned to five staining groups (coffee, black tea, cola, red wine and distilled water). They were immersed daily for 15 min over 3 times per day. Each group was divided into six cleaning subgroups (Corexyl, Cleaning Crystals, Corega ProGuard, Corega, Toothpaste and distilled water). After 7 days, colour change and surface roughness were assessed from multiple regions using a spectrophotometer and profilometer. Regional measurements from the same aligner were averaged to obtain one representative value per aligner. Robust Two-Way ANOVA tested the effects of staining and cleaning agents.

Staining agents significantly affected colour change (p < 0.001). Coffee caused the greatest discoloration, followed by tea and wine, while cola showed the lowest staining potential. All staining agents induced perceptible colour changes (∆E₀₀ > 1.8). Cleaning agents also significantly influenced colour change (p = 0.001). Corexyl and Crystals achieved significantly lower ∆E₀₀ values than toothpaste and distilled water. For surface roughness, only staining agents showed a significant effect (p = 0.001); cleaning agents and staining × cleaning interaction were not significant. Tea and wine produced significant Ra increases compared with distilled water.

Aligner discoloration differed according to beverage type, with coffee, tea and wine producing greater changes than cola. Corexyl and Cleaning Crystals showed comparatively favourable colour stability, whereas surface roughness changes were mainly related to staining agents. These findings highlight the multifactorial nature of aligner aesthetic changes.