I would use it cold-pressed oil from seasamme seeds. Rather black seasamme because of better mineral contention ( Calcium and Magnesium ratio ).
Maybe the book Cure Tooth Decay : Heal & Prevent Cavities with nutrition ISBN 978-0-9820213-0-9 by Ramiel Nagel could give you some presentation about the regeneration of cavities and why mineral richer oil should be better.
My prejudgement of olive oil is that it is too unstable from oxidation on potential acids in saliva and this way rancid mix in mouth while OP. But this is only personal prejudgement.
So I would rather use coconut or black sesamme seed oil.
Oregano oil as it was suggested would find good idea when infcted. But when infection calms down I would emphasize the role of minerals ( macrominerals specailly the ratio betwenn Mg2++ and Ca++ ).