Cleaning teeth with a soft toothbrush is to weak, so it’s not possible to keep the dental hygiene on the highest level. The hard or firm toothbrush may rub enamel from the tooth's surface though or make the gums raw by causing irritation.

It may lead to dental caries or to teeth oversensitivity. A medium brush is the best choice, because they clean the teeth very good and they don’t damage them.