Hello It depends upon the depth of the decay. If the decay is near to the nerve or bit deeper definitely cleaning of the Decay will lead to slight sensitivity while it is being done l. But in any case if you feel the sensitivity is too much you have to inform the treating dentist so that he can take adequate steps and proper treatment can be done for you. In case of deep cavity the dentist will definitely take an x-ray to check whether it is touching the nerve or far off from the nerve because the treatment would be decided accordingly.

If the decay is deep, generally it is removed and filled under the effect of anaesthesia. Post the filling, you may have sensitivity for a day or 2. If it increases or persists, you may need to get it checked as a root canal may be needed if the decay has reached the nerve.