hello. Small amount of sealant escaping from the root apex is quite normal and presence of such periapical puff is an indication of complete elimination of dead tissues. if the extension is of excess limit then a surgery needed to clear that mess. can exactly comment without seeing the    x ray image.

I wish I could see your xrays...  Then i could evaluate.. Feel free to consult Laser Smile Care Centre. God bless u.

It may be due leakage from main root canals or it may be due to large area infected above the root of that teeth.ur dentist better know .follow advice.

Over extension of the root canal filling material doesn't happen usually. A small amount of over extended filling won't cause any trouble usually. There is a limit for that!!! If the infection around the root is extensive you might require a small surgery to clear them which can be decided only upon visual examination and investigations. Your treating dentist knows better of the actual scenario than us.