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In vivo pilot study on toothbrush filament end-rounding and surface integrity using 360° microscopy
Summary
A six-month in vivo study found that polyamide toothbrush filaments showed accelerating degradation — acceptably rounded tips dropped from 64% to 29% after 360 brushing cycles — with surface residues potentially originating from manufacturing microplastic contamination. This is directly relevant to microplastic research as it quantifies toothbrush filament wear as a daily oral microplastic exposure route and highlights the need to rinse new brushes before use.
This pilot study investigates the morphological changes and end-rounding quality of polyamide 6.12 (PA 6.12) toothbrush filaments over six months of regular use. Ten adult participants (N=10) used standardized manual toothbrushes twice a day, and filament tips were sampled at four intervals: baseline, 90, 180, and 360 brushing cycles. Using 360° rotational microscopy, the study assessed filament geometry and surface residues. Results showed a decline in acceptably rounded filaments decreased from 64% at baseline to 29% after 360 cycles, whereas surface residues decreased significantly from 87% in the unused state to 17% and 18% after 180 and 360 brushing cycles. Rotational analysis revealed asymmetrical wear and angle dependent damage, often missed by static imaging. These findings suggest that residues on new toothbrushes may originate from manufacturing processes or micro-plastic contamination, highlighting the importance of rinsing new brushes before use. The study demonstrates that longitudinal in vivo evaluation with 360° microscopy enables precise assessment of surface residues and tip rounding quality under real-world brushing conditions.