Related Experiment Video
Updated: Mar 15, 2026
Impact of Fabrication Techniques and Polishing Procedures on Surface Roughness of Denture Base Resins
Published on: January 17, 2025
Effect of cleaning protocols on optical properties of thermoformed and direct 3D-printed clear aligners: An in vitro
Tuğba Haliloğlu Özkan1, Elif Nadide Akay Polat1, Can Sever2
1Department of Orthodontics, Faculty of Dentistry, İstanbul Medeniyet University, İstanbul, Turkey.
Objective:
The aim of this study was to compare the effects of five commonly used cleaning protocols on the optical properties of thermoformed and direct 3D-printed clear aligners (CAs).
Material And Methods:
A total of 100 unused aligners (25 per brand: Invisalign®, ClearCorrect™, Smartee® [thermoformed], and 4D Aligner™ [direct 3D-printed]) were randomly assigned to five cleaning groups: (1) water rinse, (2) brushing, (3) brushing with toothpaste, (4) cleaning tablet solution, and (5) mild colourless soapy water. Each protocol was applied once daily for 7days. Colour and translucency parameters were measured using a spectrophotometer at baseline (T1), after 48hours of cleaning (T2), and after 7days of repeated daily cleaning (T3). Colour difference (ΔE) and translucency difference (ΔTP) were then calculated for the T1-T2 and T1-T3 intervals. Data were analysed using two-way ANOVA to assess the effects of aligner brand, cleaning protocol, and their interaction on ΔE and ΔTP.
Results:
Invisalign® and ClearCorrect™ aligners showed significantly lower colour change than Smartee® and 4D Aligner™ at T2 and T3 (P<0.001), with Smartee® exhibiting the highest discoloration over time. Water rinsing and brushing alone resulted in significantly smaller ΔE and ΔTP compared with cleaning tablet solutions and mild liquid soap (P<0.01-0.001). Notably, the magnitude of these differences depended on the aligner brand, as certain cleaning protocols caused pronounced ΔE and ΔTP in Smartee® and 4D Aligner™ but had more limited effects on Invisalign® and ClearCorrect™ (P<0.001).
Conclusions:
Colour stability of CAs appears to depend not only on the cleaning method but also on the interaction between aligner brand and cleaning protocol, highlighting the importance of considering material-specific factors when providing cleaning advice.
