Can household ultrasonic cleaners enhance the stain removal efficacy of chemical agents on orthodontic aligners?

OBJECTIVES: This study aimed to evaluate the effectiveness of household ultrasonic cleaning with/without peroxide-based and peroxide-free cleaning methods for stain removal on polyurethane aligner material. METHODS: Seventy-two polyurethane aligner specimens (Invisalign, Align Technology Inc.) were stained for seven days in a standardized coffee solution and randomly assigned to six cleaning protocols (n = 12/group): peroxide-free cleaner (Invisalign Cleaning Crystals [ICC], Align Technology Inc., San Jose, CA, USA) or peroxide-based cleaner (Corega Proguard [CP], Stafford-Miller Limited, Waterford, Ireland), each applied without, 5, or 10 min of household ultrasonic assistance (Shantou Huan Te Tong Intelligent Technology Co., Guangdong, China; Serial No: 20240001) at 50 kHz. Color was measured at baseline (t0), after staining (t1), and after ultrasonuc cleaning (t2) using a spectrophotometer (VITA Easyshade Compact; VITA Zahnfabrik, Bad Säckingen, Germany). The CIEDE2000 formula was used to calculate color changes (ΔE00), specifically evaluating staining (ΔEt0-t1), net color change ((ΔEt0-t2), and cleaning efficacy (ΔEt1-t2). Data were analyzed using Repeated Measures and two-way ANOVA, followed by Bonferroni adjustment (significant at p < 0.017). RESULTS: All specimens showed comparable discoloration after staining (p > 0.05). Cleaning efficacy (ΔEt1–t2) did not differ between cleaning agents, ultrasonic durations, or their interaction (p > 0.05). Net color change (ΔEt0–t2) differed between agents (p = 0.018), with ICC exhibiting lower residual discoloration than CP. Although a significant agent-ultrasonic interaction was detected (p = 0.043), Bonferroni-adjusted post-hoc comparisons did not reveal any statistically significant pairwise differences between individual cleaning protocols. CONCLUSIONS: Household ultrasonic cleaning did not improve the stain-removal efficacy of either cleaning agent. Color recovery was primarily influenced by the chemical formulation of the cleaner rather than ultrasonic assistance.