When people hear that they have a cavity, they are often surprised because it doesn't hurt. The truth is that cavities do not always cause pain, and there is a simple explanation for this. The Decay Process Explained A tooth that is in the early stages of decay does not necessarily hurt. The enamel is the hardest portion of the tooth and does not contain any nerve endings, so decay in this area does not cause pain. The next layer is the "dentin." Dentin isn't as hard as enamel, but it also does not contain any nerve endings. Therefore, decay that reaches the dentin doesn't cause pain either. When Pain Begins The pain begins when untreated decay reaches the tooth's pulp. At this point, you may experience pain when you bite into your food and/or ingest hot or cold food or beverages. It may even be very painful when you are not eating or drinking. Sometimes, untreated decay infects the nerve and causes an abscess to develop, and this is what causes throbbing pain. Once you have reached this point, it will be too late for your dentist to treat the cavity with a simple filling. Root canal therapy will be required to remove the infected soft pulp of your tooth.