A medium or hard, firm-bristled toothbrush is the best for both teeth and gums. Organic bristles, as opposed to nylon or other synthetic material, tend to become too soft, and wear out very quickly. As they also take a long time to dry out they also have a tendency to harbour bacteria. This is one of those occasions when 'artificial' appears to be preferred over 'natural'. It is also important to change your toothbrush regularly, as frayed bristles are not effective for plaque removal.
Sodium fluoride is the ingredient.
They contain cetylperidium chloride. Desensitising tooth-pastes are available for treating sensitive teeth. They contain formalin, formaldehyde or strontium chloride. Mouth Washes Mouth-washes were originally used for bad breath. They contained a deodorant.