This is a before and after using hydroxyapatite toothpaste.
However, the best prevention is proper diet and
nasal breathing.
If I had a cavity forming, this is exactly what I’d do to stop and reverse it:
Diet
I'd center my diet around grass fed beef, pastured eggs, and raw dairy.
I’d limit/eliminate carbs and acidic foods and drinks. No snacking.
Optional: I’d consider taking a vitamin D, K2, and magnesium supplement
Breathing
I’d ensure I'm only nasal breathing and that my mouth is always closed, both during the day and at night.
Brushing
I’d brush in the morning and before bed (+floss) with hydroxyapatite toothpaste.