My tooth hurts when there is pressure applied - happens for several days, then goes away and return months later. been happening for years. causes?

Fx or infection: May be fracture or recurrent infection (If upper back tooth may be from sinus problem). See your Dentist when the discomfort is active, not after it goes away.

Pressure pain: I would suggest having your dentist take a look. It could be a cavity, a fracture in the tooth, or something in the gum area, etc. Hard to say without an exam and x-rays.

Cracked tooth: The most common cause of what you're describing is a cracked tooth. There can be other causes so get it examined ASAP to get a diagnosis!

Recurrent pain: It sounds like you have a chronic infection that periodically become acute. It is not uncommon for this type of situation to wax and wane as your body tries to cope and contain it. You need to see a dentist (Endodontist) for a clinical exam, pulp test and x-ray.

See your dentist: A chronic dental abscess may produce a dull pain when pressure is applied with intermittent swelling. This abscess usually get drained through a sinus, if the sinus gets blocked it will swell up & cause pain till it burst and drain again. The dental treatment is still needed even if the pain clears - the initial source will still be there. See your dentist for diagnosis and treatment.