I've heard that ALL braces serve a medical purpose. Crooked teeth is unhealthy and can cause gum disease, difficulty proper cleaning teeth, bad breath, Tooth wear/damage, and a higher risk of injury. Therefore braces are never FULLY cosmetic. However a friend of mine says that these are just excuses to make us feel like we're not just being vain. She says that most of the time braces are cosmetic and they should be seen the same as other uneeded cosmetic procedures like a nose job or implants. I don't think that braces should be considered mostly cosmetic like plastic surgery. I do believe that crooked teeth are not as healthy. I am against the idea of braces being considered the same as cosmetic surgery. I believe all braces do have a medical purpose unlike changing the shape of a big nose.
I would like to open by saying I think braces should be considered cosmetic but not a cosmetic surgery. As someone said in the comments, surgery generally requires cutting. The points you brought up are valid but it's like washing with or without soap. Sure without soap it will look clean but it won't be. Braces are almost never necessary, especially here in the USA where there is decent dental hygiene. The US population would still be respectably healthy if braces weren't standard. The difference is have crooked healthy teeth or straight healthy teeth. Purely cosmetic. I would like to say I am for braces but I don't think they are necessary for healthy teeth.
It's true you can have healthy teeth that are not straight, but healthy straight teeth are much healthier than well taken care of crooked teeth. As i said before straightening your teeth helps the gums fit more securely around the teeth, creating the strongest defense against periodontal problems, and crowded teeth are much more difficult to floss, which can lead to plaque buildup and eventually tooth decay (since we don't get our teeth cleaned professionally everyday, straight teeth helps us clean our teeth more efficiently and completely). Can people live with some crooked teeth? yes, but if you want optimum teeth health then straight teeth are best. there is a cosmetic aspect to it, but since crooked teeth can have it's risks i still see all braces as medical. it's like a person who is slightly chubby with relatively good health. they could live a good life with no health problems, but they could start exercising and live a longer, healthier life and their choice to exercise could even eliminate possible health problems.
You're making good points but I think the problem might lie with the fact that we have slightly different definitions or notions of a cosmetic surgery. I think a cosmetic surgery is one that is not necessary for the life of the patient or the health of a part of the patient. For example, I recently had a small surgery on my kidney to correct a small defect. If I had not had the surgery I wouldn't of died but my kidney would have eventually stopped working. Thus, making it a necessary surgery. It is a similar case with braces. Yes straight teeth are healthier but as I said before they are not vital for a functioning mouth. You said cleaning crooked teeth isn't easy but not impossible. It's sort of like getting cheek implants. If you don't have them you may spend more time putting on make up to achieve a defined look but having to take more time isn't "unhealthy". Braces are not required to maintain functioning teeth thus, in my book, making it a cosmetic surgery.
My notion of a cosmetic surgery or procedure is that there has to have absolutely no real health benefits. For instance a nose job(for a big but working nose),breast/butt implants, botox, and cosmetic dental veneers have no real health benefits. They are 100% for looks. straight teeth are for both cosmetic and health reasons, so that is why I consider braces always medical. If there were no health advantages whatsoever then I would consider it cosmetic. I also realize that it is possible to clean crooked teeth completely, however in the comments someone mentions that they still could not reach certain areas with crooked teeth and they became very stained. It's funny how you brought up your story about your kidney(hope your doing fine now by the way) because I know a story of something similar but with teeth. If they didn't get their teeth straightened then they would have risked loosing their teeth. They also wouldn't have died, but they would have lost their teeth and would have to get teeth implants to crew food (which is a needed quality), thus also making braces necessary.
You said that you're notion of a cosmetic surgery is that is has no real health benefits. It is very easy to argue that any cosmetic surgery makes a person happy, and being happy has been shown to have many health benefits, physical and mental.
Let's talk about liposuction. I many ways liposuction is similar to braces. Liposuction is considered a cosmetic surgery, I assume by both of us. However, liposuction has health benefits for those who get it.
My point in all this is that braces help make your teeth healthier but do not save them from destruction. Even though they have benefits braces are cosmetic.