Tooth sensitivity after a filling
There can be multiple reasons for tooth sensitivity after a filling. The first and most likely one is that after the anesthesia wears off, your teeth might feel sensitive due to the fact that your mouth was numb for a while and as the feeling in your mouth slowly comes back, it may take time to adjust to the sensation. Tooth sensitivity after any procedure may be normal as it takes time for the mouth to heal. It is the same idea as getting any medical procedure done, it takes time to heal.
Another reason for tooth sensitivity that is less to do with healing may be that the filling material was built over too high, where it needs to be shaved down to fit in line with your other teeth. In this case, the solution is to see the dentist and get the filling shaved down and leveled out.
Tooth sensitivity after whitening
Tooth sensitivity after whitening your teeth, or even when using a whitening toothpaste, is completely normal. Teeth whitening and products with teeth whitening agents contain hydrogen peroxide or carbamide peroxide, both of which break down layers on your teeth in order to ‘clean’ and whiten. When this happens, the layers that are left exposed will obviously be left vulnerable for a while which is what causes teeth sensitivity.
Tooth sensitivity in day-to-day life
Tooth sensitivity in day-to-day life can be cause by a multitude of reasons:
brushing or flossing with too much enthusiasm; brushing with too much pressure can actually overtime break off protective layers on your teeth, exposing microscopic hollow tubes or canals that lead to your dental nerves.
acidic foods; lemon (yes, that includes lemon water), kiwi, pickles, sour candies, tomato sauce, soft drinks/soda water etc. If your canals are exposed, then eating acidic foods
excessive plaque; aka not brushing or flossing enough! It is important to keep up with your dental hygiene and tooth sensitivity is a very easy tell-tale sign of not doing so.