Antimicrobial effects of four different probiotic compositions and delivery forms on clear aligner biofilm: A...

To evaluate the short-term antimicrobial effects of consumer probiotic formulations on bacterial load and biofilm accumulation on clear orthodontic aligners using a randomized four-period crossover design.

Twenty Invisalign users completed four 7-day intervention periods separated by 14-day washouts. Interventions comprised: (1) probiotic gummy (Bonatona; Bacillus coagulans, 1.5 × 10⁹ CFU/dose), (2) probiotic rinse (Perfora; proprietary multi-strain blend, 1.5 × 10⁹ CFU/10 mL), (3) probiotic capsule (HealthKart; multi-strain, 3.0 × 10¹⁰ CFU/dose), and (4) probiotic drink (Yakult Original; Lacticaseibacillus paracasei Shirota, ∼6.5 × 10⁹ CFU/65 mL). Products were used as labelled; Labelled strains included Bacillus coagulans, Lacticaseibacillus paracasei Shirota, and proprietary multi-strain Lactobacillus/Bifidobacterium blends (10⁹-10¹⁰ CFU/dose). No independent verification of strain identity or viability was undertaken. After each period, 5-mm discs from standardized aligner sites were analysed for total viable counts (CFU/mL) and for biofilm matrix (EPS) and viability using confocal laser scanning microscopy (CLSM) with Concanavalin A staining. Primary analysis used linear mixed-effects models with treatment, period, and sequence as fixed effects and subject as a random intercept. Least-squares means (95 % CI) and Bonferroni-adjusted contrasts are reported. Trial registered at CTRI/2024/08/072820.

All four probiotic delivery forms produced significant reductions in total viable counts and EPS fluorescence compared with pre-intervention controls (P < 0.001). CFU reductions ranged from 0.62-1.06 log₁₀ (mean reduction 3.8-4.3 × 10³ CFU/mL), with the probiotic drink showing the largest decrease (LS-mean difference vs. baseline = 1.055 log₁₀ CFU; 95% CI: 0.93-1.18; P < 0.001). Similar reductions were observed in CLSM fluorescence (mean differences 93-145 AU; all P < 0.001).

Short-term use of consumer probiotics delivered as a drink, rinse, gummy, or capsule, demonstrated statistically significant antimicrobial reductions in aligner biofilm. The probiotic drink yielded the greatest effect. Given the short intervention duration and label-only verification of probiotic content, these findings should be interpreted as preliminary. Larger, species-resolved studies with longer follow-up and comparison against routine mechanical cleaning are needed before clinical recommendations can be established.