There was a little girl in the news when I was pregnant and teaching fifth grade. She was from a school near Seattle, where I live. Anyway, she made the news because she did some research and presented it to her school principal. She argued, and won, the right for the kids in her school to chew gum as a teaching aid. She found that it helped them concentrate and helped them score better on tests. The kids were allowed to chew gum so long as they followed the rules. I tried it with my fifth graders but they kept breaking the rules. I know that chewing gum helped me focus and study when I was in college. My students, however, kept dropping it on the floor, chewing it impolitely, and chewing huge quantities of it. So my problem is not the act of chewing gum. I just don't want to see your gum while you chew and I want it put in the trash when you are done.
I chew gum occasionally between meals when I cannot clean my teeth. My dentist recommended that when I was a kid and I have never had a plaque problem or a cavity problem. But, I only chew sugar free for a few minutes.
I tell my 2 year old she cannot have gum until she can brush all her teeth clean twice a day, every day. And, she has to be able to control herself to never swallow it.