Why do you need a temporary filling?
When a cavity on a tooth is very deep, often the bacteria in that cavity will penetrate into the nerve chamber.
If we suspect that the bacteria has not penetrated too deeply into this area, we place a medicated dressing over the nerve area. This medication will cause the tooth to heal and acts as a painkiller as well. It takes a few days for the tooth to settle and the pain to subside. If all goes well the healing will be completed in 6 weeks and a permanent filling can be placed.
If, however, the nerve contains too many bacteria, the medication will not help and the patient will still experience pain. The pain could even feel worse than before the temporary filling was placed.
Why is the pain worse?
Before the filling was placed the bacteria could move freely out of the tooth. With the filling in place the bacteria builds up in and below the tooth resulting in throbbing pain. This tooth will now need to have this infected nerve removed by doing a root canal.
What happens if we do not replace the temporary filling? The filling is not strong enough to withstand the chewing forces and will eventually leak. This will cause re-infection of the nerve resulting in pain and possibly the need for a root canal.