Abstract
INTRODUCTION: Changes in the physical properties of manual toothbrush bristles are key indicators of toothbrush effectiveness. While wide-head-type manual toothbrushes have recently gained popularity in Japan, limited research has examined how their bristle properties change over time. This study aimed to investigate time-dependent changes in the overall and individual tuft bristle characteristics of wide-head-type toothbrushes, compared with conventional compact-head-type toothbrushes. METHODS: Sixteen participants from Hiroshima University were initially enrolled. After excluding three individuals who withdrew for personal reasons, 13 participants completed the study. Toothbrushes were collected at baseline (T0), after one month (T1), and after two months (T2), with new toothbrushes provided at each time point. In total, 18 wide-head-type and 21 compact-head-type toothbrushes were analyzed. Seven tuft locations were assessed in the wide-head type, and eight in the compact-head type. Bristle splaying and abrasion were measured using a digital microscope and scanning electron microscopy (SEM). For overall bristle splaying, 864 tufts in total were assessed for the wide-head type (48 tufts per toothbrush) and 357 tufts in total for the compact-head type (17 tufts per toothbrush). For individual tuft bristle splaying and abrasion, 126 tufts in total were analyzed for the wide-head type (seven tufts per toothbrush) and 168 tufts for the compact-head type (eight tufts per toothbrush). RESULTS: No significant changes were observed in overall bristle splaying over the two-month period for the wide-head-type toothbrush. The wide-head-type toothbrush had fewer spread tufts than the compact-head-type. During the study period, the total abrasion score per tuft was significantly lower for the wide-head-type toothbrush than for the compact-head-type. Additionally, significant bristle splaying and abrasion were observed only in the rightmost middle region tuft of the wide-head type. CONCLUSIONS: Wide-head-type toothbrushes were less susceptible to tuft splaying and abrasion. The number of spread tufts influenced overall brush deformation. Variations in tuft location may differentially affect the rate of bristle wear.