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Root canal retreatment - how much tooth?



Nov 6, 2022
London, England
Hi, me again.

I had a root canal probably 12 years ago now, never crowned (always seemed odd to me) which means it's see some wear and tear including me clenching it and I think that's how the new decay got in.

How much tooth would you need to be able to do a retreatment? I have two cusps on the edge on of the filling and after that it's a mishmash of tooth and amalgam. I want to save the tooth but I don't want to chuck £££ if it's not gonna be possible.
Any chance of a photo? Otherwise it's pure guesswork.
@Gordon apologies not my best as it's my first molar and I have a small mouth.

If tooth cusps are bottom left and right, top right is filling where there is no tooth edge. Looks a bit gross as I tried at one point to fill it with temp filling.


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OK, looks like it might be a 50/50 one. The main thing will be how far down below the gum level the defect extends, there's no easy way to work that out in advance if it's a close call, x-rays are helpful but not in the marginal ones :)
The issues are:
1) You can't get an adequate seal during RCT so it's likely to fail
2) Margin of the subsequent crown/filling being too far into the gum to get a good seal, so likely to fail due to decay or gum disease.