Blog

If you have ever had a filling, you have probably been warned by the dentist that you might be sensitive afterwards. Sometimes you might even be warned that you might need a root canal in the tooth… Why is that..?

When a tooth needs a filling it means that there is a bacterial infection in the tooth which is eating the tooth from the inside. Usually there is a small opening on the outside but like an iceberg the real damage occurs beneath.

That means what looks like a dark pit in a tooth can actually be a very deep decay that is close to the nerves in the tooth.

Your dentist will usually have an x-ray of the decay before doing a filling. Unfortunately this cannot show the full extent of the decay and so it is impossible to know how far it goes until the tooth is opened with a drill. The reason for this is that dentine only shows as decayed if it has lost all its mineralization and this happens late in the process.

When the tooth is opened there is a spray of air and water used to cool the drill. As the drill gets close to the nerve the air and water are sprayed on the tooth and can get into the nerve because dentine has lots of little holes (it is porous). This spray can irritate the nerve and cause sensitivity. The presence of bacteria will already have irritated the nerve and that with water spray can increase sensitivity.

Usually your dentist will seal the dentine to reduce sensitivity and place composite in layers to reduce shrinkage (Which can cause sensitivity).

Sometimes the final filling can be slightly “high” in the bite. In those cases it will be awkward to bite on and you will need to pop in for a small adjustment. The reason this can happen is that when you are numb you can’t feel things and can bite differently. Dentists use special papers to check the bite but a tiny change to your bite of less than a hair’s thickness can be enough to cause sensitivity.

If your tooth isn’t high but sensitivity becomes severe or remains a long time the nerve may be dying in the tooth. In that case it will need a root canal treatment.

Sometimes dentists will try to prevent a root canal being needed by placing a medication on the tooth near the nerve. This doesn’t always work and a root canal can be necessary even with the best dentist’s care.

If you do need a root canal treatment don’t worry. It can be performed comfortably now so you don’t need to be concerned. Do bear in mind that usually a back tooth with a root canal will be weak and usually needs to be crowned.