I found this out on my own as an adult after years of being unable to build a toothbrushing habit from childhood.

Brush teeth canker sores hurts to much to brush for a week forget about brushing altogether month or two later remember that i should be brushing my teeth regularly repeat

Now that i know the problem i can buy toothpaste that doesn’t actively harm me, but that doesn’t fix the 20 years of not brushing or make it easier to build that habit as an adult :/