A growing body of clinical research examines how soft and hard toothbrush bristles differ in cleaning performance and effects on oral tissue.
“The instinct to brush harder is understandable, but the research keeps pointing in the same direction. Gentle, consistent brushing with soft bristles is more effective and less destructive.”— Rachel Zhang, Founder & Designer, Tonochi
Walk into any drugstore and the logic seems obvious: a firmer toothbrush must clean better. It is one of the most common assumptions in oral care, and one of the most persistent. But a growing body of clinical research is reaching the opposite conclusion. Soft bristles do not just match harder alternatives on plaque removal. In some cases, they outperform them.
The most striking evidence comes from a scenario where effective cleaning is especially difficult. An April 2026 study from the University of Zürich tested soft and medium bristles on teeth fitted with orthodontic brackets, where plaque hides in hard-to-reach spaces around wires and attachments. If firmer bristles had an advantage anywhere, this would be it. Instead, soft bristles achieved statistically significantly better cleaning than medium bristles, both with new brushes and after six months of simulated wear.
The pattern holds outside of orthodontics as well. An earlier study from the same university tested soft and medium bristles on regular tooth surfaces at four different brushing pressures and found no significant difference in cleaning between the two. The researchers did find one meaningful difference, however: medium bristles caused more dentin wear, particularly at higher pressures. In other words, brushing harder with a harder brush does not improve cleaning. It just increases the damage.
That damage is well documented. A systematic review of 13 clinical studies found that hard bristle toothbrushes consistently produced more gingival lesions than softer options. The review concluded that soft and extra-soft bristles are generally safe for daily use, while harder bristles carry a measurable risk of gum tissue injury over time. Both the American Dental Association and the European Federation of Periodontology now recommend soft bristles as the standard for daily brushing.
Based in San Francisco, Tonochi is an oral care firm dedicated to improving interdental health, focusing on the spaces between teeth where most oral problems begin. The company combines functional engineering and human-centered design to develop tools that are gentle on gums and enamel while effectively addressing the root causes of cavities and periodontal disease. Products are available at tonochi.com and on Amazon.