The effect of coffee staining and cleaning agents on the color change and surface properties of clear aligners: An in vitro study

With increasing aesthetic demands in orthodontics, clear aligners have gained widespread use. Color stability of these materials directly affects patient satisfaction. This study evaluated color changes in two clear aligner brands (Invisalign and ClearCorrect) following coffee exposure and assessed the effects of different cleaning solutions (Retainer Brite, Eludril Care, white vinegar) on color recovery. Additionally, post-cleaning color stability, translucency, and surface morphology were analyzed. A total of 96 clear aligner specimens were used in this study. Each brand was divided into six subgroups: specimens immersed in artificial saliva, specimens stained with coffee, specimens stained with coffee and subsequently cleaned with Retainer Brite, specimens stained with coffee and subsequently cleaned with Eludril Care, specimens stained with coffee and subsequently cleaned with white vinegar, and untreated specimens (control). Color changes were measured using a spectrophotometer, surface roughness was determined by atomic force microscopy (AFM), and surface topography was examined using scanning electron microscopy (SEM). According to the findings, no significant difference was found between the brands in the group immersed in artificial saliva (p = 0.881). However, in the coffee group, Invisalign aligners exhibited significantly greater color change compared to ClearCorrect aligners (p < 0.001). No significant color difference was observed in the Retainer Brite groups (p = 0.353), whereas in the Eludril Care and white vinegar groups, Invisalign aligners demonstrated greater color changes (p < 0.001, p = 0.012). For ClearCorrect aligners, no statistically significant difference was observed between the initial and post-exposure translucency values in any of the solution groups. In Invisalign aligners, a significant decrease in translucency was found only in the artificial saliva group, while no significant changes were detected in the other solution groups. When exposed to different solutions, the ClearCorrect material exhibited more pronounced surface alterations compared to Invisalign. ClearCorrect specimens showed higher surface roughness in the coffee, Eludril, and white vinegar groups, whereas no significant difference was found between the two brands in the control, saliva, and Retainer Brite groups. Keywords: Clear Aligner, Cleaning Solutions, Color Change, Surface Roughness