Tooth squeeze is a rare condition that may be experienced while scuba diving. It occurs during descent, as a trapped pocket of air in the tooth (from a cavity or filling) is squeezed by the increasing pressure. Boyle's Law tells us that as pressure on a fixed quantity of gas is increased, the volume decreases proportionally. During descent the pressure on the air spaces of the body is increasing so the diver may feel a squeeze in these areas (sinuses, ears, lungs, and the artificial air space formed by the mask). The opposite can occur during ascent and is known as "reverse squeeze"
Since this air space can't be equalized in the same fashion as the sinuses, mask and inner ears (by gently pushing in air from the lungs) the diver will not be able to continue descending due to increasing discomfort.
A dentist should be able to remedy the situation, but the best way to avoid tooth squeeze is to not have cavities. Regular dental checks can help avoid this.