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It is the best question I have got in my practice and the most frequent query is how and why.
This is due to two reasons. Infected tooth with much inflammation or patient's anxious nature. So to tackle such cases it is better to prescribe antibiotics for five days then extract even if patient complaints, again it is better to give him or her tablet of Alprazolam before extraction one or two days to relieve anxiety. Moreover, before blocking the nerve, we can also give an injection of Dexamethasone which reduces inflammation.