Moso bamboo structure and application scenarios affect tuft removal force in bamboo toothbrushes

Objective Due to the anisotropic nature of bamboo, bamboo toothbrushes processed under identical conditions often exhibit quality variations. This study investigates the tuft removal force performance of toothbrushes made from bamboo with different densities and used in various application scenarios, aiming to enhance the controllability of bamboo toothbrush quality.

Method Raw bamboo was processed into toothbrushes, and the density (ρ) of each bamboo strip was recorded during manufacturing to classify the resulting toothbrushes. The tuft removal force of plastic toothbrushes and bamboo toothbrushes with varying densities was compared. Bamboo toothbrushes within the same density range were subjected to water bath treatments at different temperatures and wetting-drying cycles to simulate real-world usage conditions and evaluate durability. Additionally, tuft removal force was analyzed with respect to bamboo-green (outer) and bamboo-yellow (inner) surfaces and different hole positions on the brush head to determine optimal processing conditions. Micro-morphological characteristics of the tufting holes were examined using a digital super-depth microscope, scanning electron microscopy (SEM), and micro-computed tomography (micro-CT).

Result (1) Significant differences in tuft removal force were observed among bamboo toothbrushes made from bamboo of different densities, with removal force increasing significantly as bamboo density increased. Toothbrushes made from bamboo with density > 0.70 g/cm³ all met the national standard requirement of 15 N, while those with density > 0.75 g/cm³ outperformed conventional plastic toothbrushes in tuft removal force. (2) Durability tests on toothbrushes with 0.75 ≤ ρ < 0.80 showed that tuft removal force remained stable between 15.42 and 16.69 N after room-temperature water treatment. Even after six-day cycling tests of wetting and drying, the removal force decreased only to 15.6 N, still meeting the national standard. (3) Toothbrushes with tufts implanted on the bamboo-green surface exhibited a mean removal force of 19.55 N, higher than the 17.89 N observed on the bamboo-yellow surface. The average removal force at outer-ring hole positions (18.21 N) exceeded the overall brush head average (17.81 N), while inner-ring hole positions (17.23 N) performed below average. Variance analysis confirmed significantly superior tuft retention at peripheral hole positions (p < 0.05). (4) Microstructural analysis revealed that the natural structure of bamboo provides an excellent interfacial contact for the embedded metal bristle-holding plates.

Conclusion Bamboo toothbrushes fabricated from higher-density bamboo exhibit superior and stable tuft pulling force under daily use conditions, meeting and exceeding the performance of conventional plastic toothbrushes, thus demonstrating strong application potential. Given the differential effects of hole position and implantation surface on tuft retention, manufacturers can adopt differentiated design strategies—optimizing hole layout and selecting high-performance surfaces—to enhance the reliability and durability of bamboo toothbrushes.