Dental and facial dev.

Dentists and orthodontists recognize chronic mouth breathing as a significant contributor to poor oral hygiene and orthodontic problems. 

To study the relationship between mouth breathing and craniofacial growth plugs were inserted to monkey’s noses to force them to mouth-breathe :  the primate on the right had his nose plugged, and you can see the change in the face shape (which we also see in humans). You can also see how it affects jaw development

—”Children whose mouth breathing is untreated may develop long, narrow faces, narrow mouths, high palatal vaults, dental malocclusion, gummy smiles, and many other unattractive facial features, such as skeletal Class II or Class III facial profiles.

—These children do not sleep well at night due to obstructed airways; this lack of sleep can adversely affect their growth and academic performance.

—Many of these children are misdiagnosed with attention deficit disorder (ADD) and hyperactivity”

“if mouth breathing is treated early, its negative effect on facial and dental development and the medical and social problems associated with it can be reduced or averted.”