Does he want braces? Does he need braces for other reasons than cosmetic? It will make a big difference. No experience as a teen, but I had braces as an adult to correct a severe and worsening bite problem (ironically, my teeth looked fine, but they only touched on the very back molars), and yes, I have ADHD and SPD, (and no, SPD doesn’t go away as an adult). The process was very painful, and every brace adjustment required several visits because as the teeth shift you need to ensure they touch properly, and I was extremely sensitive to even the smallest imperfection. Having food stuck on the braces bugged me a lot (I refused to eat rice for years after that). To fix that, I had to brush after every food I put in my mouth, and I have a severe gag reflex with brushing — and I also despise the taste of practically every toothpaste. Then there was the flossing through the braces. Let’s just say it was more pleasant not to eat, and in the pictures of that time I looked like I will break in half if you breathe on me. Did the braces help? Oh yes! But I had strong motivation to put up with all that.
And after it’s all over, you need a retainer and you need to wear it if you don’t want it all to go to waste. (And while I had braces, my coworkers which had braces as teens showed me the teeth that went back into position because they refused to wear their retainer). And that’s where the ADHD kicks in. You need to remember where you put it. You need to remember to wear it every night. You need to remember to take it to travel. I threw it in the garbage twice by accident and had to dig for it. You need to wash it every day or it will really stink. You need to get these tablets to dissolve scale, and use them occasionally.
So yes, it is an unpleasant process :p But as with everything ADHD, motivation can go a really long way. If the motivation is not there, I don’t know that I recommend it. I can see the parent point of view on this one, being a parent myself (and knowing how unbelievably expensive and inconvenient the process is as an adult!). But as an ADHD and SPD person, this was very, very hard.