I went my entire childhood and into early 20s before a new (to me) hygienist explained that most tooth decay is essentially an integral of PH level. The accumulation of how acidic your mouth is and for how long. They also explained that avoiding acidic foods and drinks is not enough, because bacteria that feeds on sugar produces an acidic byproduct. I adjusted my behavior based on that (consume way less sugar, and when having anything sugary or acidic, have it with hot water/tea/coffee) and my dental visits changed entirely since then.