system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do 'adult teeth' know when to erupt?
gpt
The adult crown forms in the bone, under the primary teeth from a tooth bud. As the root structure develops it pushes the adult crown upwards which puts pressure on the roots of the primary teeth causing the roots to resorb. Eventually there is no root structure left on the primary tooth and it falls out. The roots of the adult tooth continue to develop pushing it all the way into the mouth. Not everyone gets all of their adult teeth, some get extra adult teeth, it all depends on how many tooth buds you have, and that is determined by genetics.