Desensitizing ingredients in toothpaste work by either:
1. depolarizing nerve endings to reduce transmission of pain; or
2. by blocking dentinal tubules; this prevents stimuli (e.g., cold drink or air) from causing fluid flow in dentinal tubules, thereby preventing nerve pain inside the tooth from bring stimulated. Potassium nitrate is a common nerve desensitizing agent and stannous fluoride is popular agent that reduces sensitivity by occluding dentinal tubules.