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Usually fistula develops due to spread of infection from periapical tissues into sinus
If fistula appears on gums after root canal treatment
,this is due to faulty diagnosis regarding teeth to be root canal treated.
An x-ray will help to evaluate fistula through inserting GP cone into interdental tissue spaces .
If necessary,adjacent teeth has to be root canal treated and abscess
has to be drained and curetted completely.
Hope this helps.
This fistula has to be tr