Teeth can become sensitive for man y reasons. Sometimes the sensitivity is an indication of a potentially serious problem. Other times, the dentally related problem may be small but effects (the sensitivity) are extremely aggravating. A tooth can become sensitive after it has been prepared (drilled) for a restoration (filling). You may have been anesthetized during the procedure, so you did not feel any discomfort when the nerve in the tooth reacted to the heat generated by the drill. The closer the drill comes to the nerve, the more likely it is to cause a sensitivity problem. The high-speed rotation of the bur in the drill generates heat, and the response of the nerve to heat is inflammation. This inflammation is felt by you as a “sensitivity”. If the decay, fracture, or drilling was not too deep, this sensitivity will decrease over time. A week to a month or two is not an unusual length of time for the sensitivity to disappear. A good sign is the continued decrease of sensitivity. However, if the occlusion (bite) is off after the restoration has been placed, the tooth may either become sensitive or may stay sensitive. Once the bite is adjusted, though, the sensitivity should disappear.
Additional reasons for single sensitivity are decay, a defective restoration, or a fractured tooth. When a tooth is decayed, temperature changes and sweets will make it sensitive. If a filling is defective or failing, leakage around the filling may cause the tooth to become sensitive. In both of these cases, the solution can be as simple as removing the decay or defective filling and placing an appropriate restoration. If the tooth is fractured, you may be sensitive to temperature changes, or when chewing food. This fracture condition may be hard to diagnose. If you think you might have this type of sensitivity, please ask for the separate handout that explains the “cracked tooth syndrome” in much greater detail.
Tooth sensitivity can also be caused by a dying nerve. The can be the result of a deep cavity. Commonly, the sensitive tooth holds an old larger filling. The nerve may have been damages during the drilling and the nerve has been dying gradually ever since. If this is the problem, the tooth will need endodontic treatment.
Two other reasons for tooth sensitivity are related. One is an inadvertent notching of the tooth surface and/or recession of the gum tissue (exposing the root surface of the tooth) caused by improper brushing: either brushing too hard, brushing with a toothbrush that is too hard, or using an improper brushing technique. This sensitivity can range from mild to extreme; the degree of sensitivity does not appear to be related to the size of the root exposure or notch. Finally, purposeful repositioning of the gum tissue during gum surgery can also lead to tooth sensitivity. While recession from brushing is slow, gum recession following gun repositioning occurs very quickly. The portion of the tooth once covered with gum and bone may now be exposed. Root sensitivity in these instances can be quite severe and immediate. It can sometimes last for months or years if not treated.
Treatment in these last instances is similar. If there is a notch is the tooth or the shape of the defect is appropriate, the defect is restored (filled in) with a bonded material. This can give immediate relief—sometimes fully. When there is no defect to be stored, the exposed and sensitive root surfaces are covered with a dentin-bonding or other material. This material is invisible and has very little thickness, so you do not notice any change in the appearance of the tooth; but it works. It may have to be reapplied after several months because the bonding material has worn away by toothbrushing.