Infected Molar with Prior Root Canal Treatment

[JJones86]

Hi.

I just found out that I need to have my upper right back molar #2 extracted.
The tooth has an abscess and history of prior root canal treatment with crown about 15 years ago.

What causes an infection or an abscess when the tooth roots are sealed from root canal treatment and it is protected with a crown?

Thank you.

JJ

 

[Gordon]

If I could answer that one I'd be a millionaire
It's usually something like a missed root canal, a root canal with a branch that wasn't accessible to the files/disinfectant, a root canal with a "delta" system rather than a single exit for the nerve, bacteria getting in down the periodontal ligament, a leak someplace in the crown margin, lowered host response from e.g. steroid treatment...
Take your pick