Maybe it’s an economic curse. Wealthy people tend to have good teeth. Sure, here and there a cavity. But the bulk of the market for new teeth is probably poor.
Only because they tend to have much more aggressive parents about teeth health, going to the dentist, etc. it has nothing to do with being rich, even the lowest 10% in income can afford toothpaste and a toothbrush which you can probably get for free. The problem is that it's low on the list of priorities.