My dad was a dentist and I've never had a cavity. TBH any fluoride is fine, so other preventative care should take priority. The idea being that with proper technique, and barring other health conditions like dairy allergies, nobody should experience tooth decay. This is anecdotal, but ranked from highest to lowest (top 3-5 especially!), I'd say:
* Brush teeth morning and night with any name brand fluoride toothpaste, replacing toothbrush often like every 6 months
* Use a floss pick morning and night, and preferably on any gum pockets after meals, since cavities form where the tartar is, where the food sits, which can be revealed by using disclosing tablets periodically
* Use a water pick morning and night
* Get fluoride treatments from the dentist every 6 months until adulthood, after that is too late except as maintenance, but continue that schedule for checkups
* Sleep with mouth closed at night using nasal strips and optionally taping mouth in an x-shape to not stretch philtrum, because dry mouth causes gum disease
* Avoid sugar and foods like potato chips which stick to roots and cause tartar, or brush afterwards
* Drink milk until adulthood and continue until intolerant, also eat leafy green vegetables and other high-calcium foods
* Eat whole fresh firm foods which develop the jaw and teeth, especially in youth while still growing
* Exercise, especially weights and athletic movements that exercise the face and jaw to promote development and encourage blood flow
* Work on head/neck posture and sit upright in chair while working, since mouth breathing is caused by poor posture that narrows the throat's air supply, which causes dry mouth which leads to bad breath and tooth decay
* Don't smoke and avoid excessive alcohol
* Consider orthodontic treatment if bite is off, since once enamel is worn, it takes too long to redeposit before the tooth wears to the point of failure, but get multiple opinions and avoid all extractive dental work and/or headgear, since orofacial myofunctional exercises accomplish the same thing and can have better long-term results