Pulpitis is inflammation of the pulp chamber located in the tooth's center. There are various reasons that the center chamber may become inflamed. For example, you may have hit your tooth in the past or have decay reaching the pulp chamber. Whatever the cause is, the inflammation is a response of your body to try and heal the tooth because it senses a problem. The inflammation can create pressure in your tooth and often makes it sensitive to cold. However, for some people with pulpitis, lying down increases the pressure in the head and further increases pressure into the tooth. This pain will commonly manifest as a throbbing and aching in the tooth.
There are two degrees of pulpitis: reversible and irreversible. Reversible means the tooth may heal without treatment, and the condition will eventually disappear. Irreversible means the tooth won’t heal and need a root canal to save the tooth. A dentist can test this out for you or read this article on cold sensitivity.
In the meantime, over-the-counter ibuprofen three times a day for three days is one thing I tell some of my patients to do to reduce inflammation and pain. In addition, Ibuprofen can help reduce the possibility of reversible pulpitis progressing into irreversible. Finally, at night it is recommended to sleep with your head propped up to minimize the throbbing.