Mouthgard- Is this normal?

[DC Amateur Boxing]

I actually have one custom from a dentist for my son, a junior boxer. He just kept messing around with the boil/bite one and spent more time concentrating on keeping it in his mouth. One of our coaches has an extensive history in the area with 'old' pros and amateurs and gave me a local dentist that did custom pieces for $100. It was worth it!! It was very thin, but a completely different material than the boil/bites. You almost can't bite through it if you wanted. Most importantly, the fit is so snug, it take a little pressure to pull if out/off. So, now it is almost as if he doesn't have it in.

My concern was, I always though the thicker the better and I asked the dentists "How could such a small and thin item possibly protect your teeth from direct impact". He told me that the purpose of the mouth guard is to keep the teeth together and inline so that the force of any impact is actually spread across all the teeth as opposed to having it concentrated on one or a few, which can result in tooth damage. It's not so much a "wall" as it is a "brace". It's sort of the same theory as how a bed of nails works. . .

Now, that's what HE told me but here's a link that seems to back it
up. . . HEALTH: Mouth Guard Hits and Myth-es

Again, the point is although thinner, the material from the dentist-made mouthguard is better and more effective. Thicker isn't better, necessarily.