Subgingival restoration on molar, is it possible?

[Mo24078]

I had a deep cavity on tooth 18 that I posted about last year on this forum,

Deep Cavity on Necrotic Molar, RCT Needed?

Hello all, I had a deep cavity on my No.18 molar on the mesial-buccal surface. Two weeks ago, my dentist removed all the decay without administering any anesthetics; he could tell just by looking at the tooth that it was necrotic and I felt no pain during the procedure. In that process of decay...

www.dentistry-forums.com

Last year, the cavity was taken out and even though the tooth was necrotic, we didn't do an RCT. Mainly due to Covid concerns and my age, we decided to hold off on that and take bi-annual X-rays to monitor the situation. Now that we're able to go back to the dentist, a recent visit showed that there is a radiolucency at the apex and the infection is draining thru the side of the tooth, there is small abscess on the buccal side of the gum, and there is also a cavity adjacent and under the big amalgam restoration that's about 4mm under the gumline. The dentist said that because this new decay is on the root of the tooth and under the gumline, it is difficult to restore and therefore suggested extraction.
I have attached the most recent periapical X-ray but it might be difficult to see the new decay. Is this 4mm subgingival restoration impossible to do? Does it definitely require a crown lengthening procedure or is there a way to do it without out that? This is my last functional tooth on the left side and I'm really hoping to save it. Thanks in advance.

 

[MattKW]

4mm subging might be possible in amalg only. Of course you also need to do the RCT to resolve the abscess. There's no need to do crown lengthening, and it might make the situation worse because you risk exposing the furcation of the roots. The only other option is to extract, and place an implant.

 

[Mo24078]

Thanks so much for your reply. I have a few follow-up questions that I would very much appreciate your opinion,

- For a subgingival amalgam restoration, do I have to look for a specialist? The dentist we saw said she wouldn't be able to do such a restoration.
- Is a subgingival restoration doomed to fail quickly because the margin is under the gumline and since it's harder to clean, bacteria will eventually get in?
- Is a crown an option her at all?

 

[MattKW]

1. A specialist is not required. Maybe your dentist is not comfortable with subging amalgs? They can be fiddly to get enough retention ("grip").
2. Yes, more likely because of the chance of decay starting again, and because the gum doesn't react well to foreign substances.
3. A crown would still be subgingival (unless you gum lengthen), and difficult to do.

I suggest the subging amalg because it is the most cost-effective solution for this bad situation. Going to the expense of crown lengthening (and crowning) may only offer a slightly better chance of success for a lot more $$$.