Whatever it is, I personally would do nothing about it. Karies can revert. Or "harden" so it does not matter/hurt.
Your teeths look good.

Just take care you get all nutrients, add liver/organs if you are not eating them,
cut back on sugar/acid. Include wild edibles like Lindenleaves, Nettles.. they have good amount of nutrients too. Do not need much of them though!
All will be good.

Inger