The most important step in preventing moistness or mould and to look after your bamboo toothbrush is to dry the bristles and the handle with a towel. This is because if you let your bamboo toothbrush soak in the cup it will not be able to dry out effectively.
Where and how you store your bamboo toothbrush is also very relevant. The bathroom is a natural damp atmosphere. Therefore consider keeping each bamboo toothbrush in separate cups or holders, in the open air to dry out. These small actions will help keep your bamboo toothbrush in top condition!