Re: sensitivity from composites/crows

First, on composites. When placed in molars, the prep is coated with a two part liquid that seals the dentin tubules and allows the composite to adhere. The composite material is placed in increments (layers) and cured in between since the curing light (blue light) can only harden the material to a certain depth. Understand that all composite material shrinks upon curing and can cause micro-fissures between it and the tooth structure that over time 'leaks' and can cause sensitivity from cold, sweets, ect. Composites are estimated to last only 5-7 years before needing replacement. Also, molars that are heavily (over) filled several times over the years, leave the tooth susceptible to fractures that cause sensitivity. If a tooth becomes sensitive to cold AND biting pressure, the fracture has entered deep enough that the parts of the fracture are flexing and the tooth should be crowned to hold the parts together. It sounds like you have micro-leakage around the composites and the only way I know to help is to have them replaced. More drilling on the teeth causes more fracture potential and if the cold sensitivity does not bother too much, leave well enough alone.

Second, on crowns. The previous post that stated that a sensitive tooth means a healthy nerve is correct. When the tooth is prepped for crown, the margin of the crown should be knife-edged to fit against the tooth near the gumline with no ledges protuding that can 'catch' floss or allow plaque to accumulate underneath causing decay on the root surface. However, even with good technique from the dentist in drilling, good margin adaptation from the lab tech who makes the crown and good dental cement material to seal, there is still some possibility of leakage under the crown margin of fluid from saliva and foods. Again, if not that bothersome, leave alone.

Third, on root sensitivity. Many people experience receeding gums from gum disease or over-agressive brushing with abrasive paste that overtime strips the tissue away from the root leaving it exposed. The root surface is not covered by enamel and the tubules or rods in the tooth (think of it like a crystal with tiny rods) send cold directly to the pulp (nerve).

Fourth, on occlusion (bite). After dental work, a person may experience cold sensitivity due to the fillings/crowns changing the bite or being too 'high'. Even a paper thickness change in occlusion can cause the tooth to be over-sensitive because 500 pounds per square inch of force can traumatize the tooth and the nerve or ligaments supporting the tooth become inflammed.

Return to the dentist and have him/her check your bite and adjust if neccesary. There is a fluoride varnish called Duraphat or Duraflor that can be placed on the exposed root surfaces that seals the tubules and can last for many weeks/months if you are not opposed to fluoride. Continued check-ups every 6 months allows the dentist to check margins of crowns and fillings for marginal decay and teeth for fractures.