The tooth is an amazing sensory organ. The outside of the tooth, the enamel, is the hardest tissue in the human body. The enamel surrounds another layer of the tooth called the dentin. The pulp contains blood vessels, nerve fibres and other connective tissue. The entire tooth lies suspended in the bone by the periodontal ligament.
The nerve supply to the pulp and the periodontal ligament gives the tooth its “life“. The sensation of hot , cold and the ability to sense on biting into hard objects is because of the nerve supply to the tooth. Each tooth in the mouth gets its nerve supply from the nerve endings of the main nerve. Further, the teeth in the upper jaw and that in the lower jaw are supplied by different branches of the main nerve. The teeth in the upper jaw or the maxilla is supplied by the maxillary nerve ( a branch of the fifth cranial nerve-the trigeminal nerve ). The teeth in the lower jaw or the mandible is supplied by the mandibular nerve ( a branch of the fifth cranial nerve-the trigeminal nerve ).
Any infection in the tooth like an untreated decay or an untreated gum disease triggers a signal to the brain. This in turn causes the sensation of pain. If the tooth is not treated at this point, destruction of the soft tissues further leads to the infection spreading to the bone. The damage at this stage may be irreversible leading to the loss of the tooth.