not just dental health. Not sure if the video goes into this, but chewing broadens the physical palate during childhood development and helps develope the over all facial structure. 
Think: Pug dogs vs wolves.

Facial structure can increase the tendancy of mouth breathing. Lower oxygen intake from mouth breathing impacts i.q. 

Look at the dental profile of high carb populations, yes, but look adjacent symptoms  presented too: sleep apnea, resting heart rate, illness recovery and immune resistance, all impacted by just having a wrong face that doesn't breathe properly.