What does it mean if my tooth is sensitive to cold?

 There are a number of different possible answers to this question. Teeth that are bothered by drinking cold liquids or breathing cold air could be suffering from "cracked tooth syndrome, a loose filling, gingival or occlusal erosion, deep decay, or a pulpitis. If you are experiencing discomfort when dealing with cold liquids or air it's best to see your dentist so he can try to diagnose why.

When a patient comes in to a dental office with this complaint , the dentist should  interview them about when they have this symptom. (drinking cold or hot liquids or breathing cold air). Also do  they have intermittent pain on chewing food sometimes (cracked filling or cracked tooth)?

In my office, after this brief interview I have my assistant take a periapical and bitewing radiograph and I examine the tooth or teeth in question specifically  looking for signs of a crack in a tooth or filling, decay approaching the pulp and/or dentin erosion. In addition I tap gently on the tooth with the back end of my dental mirror to see whether this is causing discomfort.

Sensitivity to cold implies that the pulp of the symptomatic tooth is still vital. If the pain caused by cold doesn't linger afterwards for more than a few seconds, it is a good sign since teeth with irreversible pulpitis (tooth needs root canal) often have lingering pain after a cold challenge. 

Bitewing radiographs are quite helpful for the diagnosis of the type of proximal decay that can cause cold sensitivity and direct examination with by a dentist  can usually detect occlusal, buccal or lingual decay. Obviously if decay is noted the tooth should have all decay removed and either an interim or permanent filling placed since this can often get rid of cold sensitivity due to decay.

If a crack is noted upon examination , an excavation of the fissure is a good idea. When performing an excavation I often prepare a slot prep, two mm deep at the site of any visible occlusal crack and then examine the internal prep to see if any of this crack remains present. If so , I often place an interim filling and suggest a crown as the ultimate solution, since crowns help distribute the forces on a tooth in a way that makes propagation of the crack less likely.

Occasionally teeth with pre-existing large fillings can develop a crack that can't be detected visually since the crack is under the filling. Often I have patients bite in various positions with the wooden part of a dental Q-tip ) until they find where they are having pain. This can help isolate which tooth is causing their sensitivity . 

Sometime a dentist may recommend root canal treatment to make the patients sensitivity go away, but unless their sensitivity is prolonged or severe this approach is not the most conservative way to go since teeth sensitive to cold are invariably vital and not infected. Giving the tooth a chance to recover seems like a more sensible approach. 

As one can imagine it can be difficult to pin down why a tooth is sensitive to cold, but through careful analysis their dentist can come up with a theory as to why and can take appropriate action to lesson the sensitivity. If after a thorough exam, the cause of a patients sensitivity is still unclear, it is often best to take a "wait and see "approach in order to see if the sensitivity resolves on its own ,s tays the same or gets worse. This is certainly preferable to performing unnecessary procedures that may not help resolve the situation.