You should not be rushed into root canal therapy

Teeth with new fillings or crowns frequently are sensitive to cold and hot temperatures. This is not unusual and the discomfort is generally mild and disappears in a few weeks at most. But if it persists and is severe, it may be necessary to remove the restoration and place a temporary sedative filling or crown that provides immediate relief, though it may take weeks or months before all symptoms disappear. Then the permanent restoration can be replaced. The important point to remember is that a healthy nerve responds to both hot and cold temperatures, with the sensitivity disappearing a few seconds afterward.
The point being made is that you should not be rushed into root canal therapy without giving the nerve a chance to recuperate under a sedative material such as zinc oxide and eugenol or IRM. On the other hand, if heat is applied to the tooth and the pain intensifies, but is then relieved by swishing with cold water, nerve damage is irreversible and root canal therapy will be necessary to avoid losing the tooth.
Another cause of sensitive teeth following fillings are high spots. If the filling or crown is not carved properly to the natural contours of the tooth so that the opposing tooth hits it on closure before the other teeth come into contact, the nerve becomes irritated. You may then experience slight pain on chewing or tapping your teeth together, or the tooth may become sensitive to thermal changes. It may also loosen. This condition, called hyperocclusion, is easily corrected by returning to the dentist, who will grind down the high spot.
Occasionally, following a new amalgam filling, patients experience a tiny electrical shock whenever the jaws are opened and closed. This shock is due to a galvanic current between fillings in the upper and lower jaws as they make and break contact, especially if the tooth opposite the amalgam filling has a gold inlay or crown. The condition is almost always corrected by polishing the amalgam filling. In the USA some dentists recommend replacement of all amalgam fillings with gold to keep the same type of metal throughout the mouth. However, there is no scientific basis for avoiding dissimilar metals in the same or the opposite jaw or for replacing functional fillings.
Fillings should be smooth and carved to the contours of the natural tooth surfaces. Polishing fillings to a high luster is not necessary except in the rare occurrence of galvanic shock. Examination of fillings under an electron microscope reveals that even the most highly polished surfaces are not totally smooth. Sufficient smoothness can be obtained by burnishing amalgam fillings just after placement in the tooth. Composite fillings are more likely to require trimming and polishing to remove excess material at their margins.

Over the years amalgam fillings may darken, likewise causing a slight darkening of enamel. Amalgam fillings also become a little uneven at the edges, often forming a small crevice at the junction with the tooth surface that can be detected by a needle-tip dental explorer. At the same time, corrosion of the metal fills in the crevice and actually improves the seal of amalgam against bacterial penetration. If the seal is good enough and the explorer does not actually stick between the filling and the tooth, the filling should not be replaced. Some dentists recommend polishing amalgam periodically to smooth the edges. The procedure is called remargination. I usually do this. If the defect is slight, as described above, nothing is gained. If it is large, polishing will not solve the problem, and the filling should be replaced. For any further clarifications you can e-mail me at: bertrandstuart@gol.net.gy

(Dr. BERTRAND R. STUART D.D.S)