theres a 'disease' that affects a very big percetange of people
if children and teens have mouth breathing, that deforms their jaws and teeth in more or less degree while growing
mouth breathing is unnatural, is caused by ambient factors, your nose is designed to work perfectly
2 dentists told me most cases of mouth breathing are caused by milk and cheese
i think is logical, because mouth breathing is caused by ambient factors, so it must be because of the food
also milk is a weird food, you are stealing cow's milk, the milk is for their babies
why would an adult from a different specie drink their milk
heres an article about it
https://pubmed.ncbi.nlm.nih.gov/20129889