How long is too long for a root canal to be filled. ?

Post root canal: You really need to have a permanent restoration as soon as possible after your root canal is completed. Prior to that you would have a temporary filling in your tooth. You could risk breaking the tooth or having it get contaminated. So please get it filled ASAP!

Root canal: If the root canal has a temporary filling, research has shown that some of the temporary material can leak in less than 3 weeks. If your dentist put a permanent restoration in then the root canal won't leak, but you tooth is at risk to vertical root fracture which means that it could fracture and not be able to be fixed, requiring extraction. This happens a lot, Rule of thumb is get a crown ASAP.

No time frame: Root canal teeth become brittle after treatment. There's probably a fairly large defect, too (that's why you needed root canal therapy in the first place). Get a crown to protect the tooth. Place a large filling and risk vertical fracture, loss of the tooth, and increased cost in replacing the tooth. All the best....

As Soon As Possible: If not filled, the temporary coronal seal of the restoration can be disrupted in time and could result in coronal leakage or tooth fracture. See your dentist ASAP to complete the treatment.