Effects of clear aligner cleaning agents on Streptococcus mutans biofilms and thermoplastic surface integrity: an in...

Clear aligners are increasingly used in paediatric and adolescent orthodontics, but prolonged wear and suboptimal hygiene may promote cariogenic biofilm accumulation. This study aimed to compare the antibacterial efficacy of commonly used commercial and household clear aligner cleaning agents against Streptococcus mutans biofilms and to examine their effects on aligner surface integrity. Biofilms were grown on 48 clear aligner discs; 42 (n = 7 per group across four experimental and two control groups) were used for biofilm quantification, and 6 (n = 1 per group) for SEM analysis. After biofilm formation, discs were treated with Invisalign^® Cleaning Crystals, Corega^® Proguard and Retainer tablets, Invisalign^® Aligner Cleaning Spray, or white vinegar diluted to a final acetic acid concentration of 0.5%. Viable bacteria were quantified as colony-forming units per millilitre (CFU/mL), and surface morphology was assessed by SEM. Data were analysed using the Kruskal-Wallis test followed by Dunn-Holm post hoc comparisons (p < 0.05). Commercial agents significantly reduced CFU counts compared with the negative control, whereas white vinegar did not. Median CFU values were lowest for the commercial agents (1.2-2.5 × 10³ CFU/mL), with no significant difference among them, and Invisalign^® Cleaning Crystals and Corega^® tablets were more effective than white vinegar (p ≤ 0.04). SEM corroborated the microbiological findings, showing substantial biofilm removal without apparent surface deterioration after commercial treatment. These findings support the use of commercial products in evidence-based clear aligner hygiene protocols because of their greater antibiofilm efficacy and preservation of thermoplastic surface integrity.