Brief Answer:
Tongue coating or infection!!

Detailed Answer:
Hello. First of all thanks for approaching Healthcaremagic for your query. Read through your query and accordingly I can say that there is nothing much to be worried in this case. Regarding the bad taste it can be due to many reasons. Due to dental cases it can be due to infection(pus)in case of decayed tooth,due to coating of the tongue,due to any other systemic medication you take.In case of sinusitis or common cold it can result in bad taste. Since you had rootcanal treatment recently it can be due to the filling material that is being dissolved into the saliva causing bad taste. It will be reduced once you put a crown over the root canal treated tooth.I also suggest you to follow these steps to reduce bad taste:

1)do brushing and flossing twice daily
2)do tongue scraping twice daily after brushing(it removes the coating on the tongue can reduce the bad taste to a greater extent)
3)do mouthwash as said by your dentist
4)do salt water gargle to reduce any infection if at all present
5)drink lots and lots of water .keep yourself hydrated
6)do inhalation for 10-15mins daily(to clear your sinus)

Follow these steps and see the difference.If it still persists after following this for 2 weeks,you have to meet ent to see for any other causes.
Regarding the symptom of root canal treated tooth, there may be pain for two to four weeks after rootcanal treatment. Also bad taste can be due to infection still persisting beneath the root.(it will heal in few weeks time after the rootcanal treatment) Its usual as the healing process beneath the tooth root is being undergone.So nothing to be worried. Just be careful not to bite with that tooth for this much time. If possible do a crown over the tooth(as suggested by you dentist).

Besides all these stay calm and happy. Happiness can be best medicine for any disease condition. Hope you are benefitted something from this reply. If you have more queries please be free to approach us.We ate always happy to help you solve your problems.Have a healthy day!!!
Dr.Rohit S Menon

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