Those who have experienced it would vouch for the fact that toothache is one of the worst pains. There could be times when the attack happens out of nowhere and you are crying for relief.
The tooth has 2 parts - the visible part called the crown and the invisible part called the root which is embedded in the jaw bone and covered by the gums.
Both the crown and the root have 3 layers from inside out. The crown has enamel, dentin, and pulp. The enamel is the mineralized part of the tooth, dentin has fine sensory dentinal tubules, and the pulp receives nerve and blood supply to the tooth through a small orifice at the end of the tooth called the apex. On the root surface, instead of enamel, there is a softer substance called cementum. The dentin and the pulp continue through the tooth, but are thinner in the root portion of the tooth.
The mouth has the largest amount of bacteria in the body. These act on the food deposits on the tooth and produce acid which leads to breakdown of the enamel. The only symptom when enamel breakdown happens is food lodgment, and it continues till treatment ensues. Once the breakdown reaches the dentin, sensitivity sets in, and most people go for treatment then. If not, the next layer is the pulp, when there is severe pain. This acute pulpitis causes pain in spurts and can be unbearable.
On the root surface, if there is periodontal disease and the gum line goes down, then cementum gets worn off (far more easily than enamel) and decay reaches the dentin and pulp (again faster than in the crown).
Whatever the case, the treatment would be the same:
The best way to avoid this is regular visits to a dentist so that decay is identified in the early stages and treated with the minimal cost and maximum natural tooth preservation.