Desensitizing toothpaste contains ingredients to help prevent or reduce tooth sensitivity. Many have potassium nitrate, which numbs the nerve in the tooth to prevent tooth pain, for example.
Another ingredient is stannous fluoride, which blocks the tubule holes in the tooth that lead to the nerve, stopping pain in its tracks. Many desensitizing kinds of toothpaste also have fewer ingredients than regular toothpaste, so there are fewer irritants reaching the tooth’s nerve.