This section is dedicated to questions that don’t easily fit into any other category but that concern facial plastic surgery. For hair restoration, see Dr. Lam’s Hair Transplant Forum. http://www.drsamlamhairforum.com/
Obviously, when you say non-invasive, I assume you mean a procedure that does not require an incision of any kind. That would mean some kind of filler to widen the jawline. I also assume you mean that you are okay with the degree to which your chin sticks out, where a chin implant would usually go. If not, then the whole jaw forward and to the sides need to be widened.
First, a few things: you are only 17 years old so you are still growing so anything permanent may not be advisable per se. However, if your jaw is markedly underdeveloped then more invasive bony advancement procedures may be indicated but would have to be addressed with an oro-maxillofacial specialist. Second, you are only 17 years old so you would need a parent or guardian to consent to any treatment plans that you may have.
As far as "non-invasive" is considered, obviously, fat grafting would be a permanent solution but still would require some sedation so it is not entirely "non-invasive" even though it is entirely incisionless. I would not recommend fat grafting for several reasons. First, as mentioned, since you are 17 years old, you are still growing so fat grafting is something that I think could be a problem over time since you may have more growth in that area. Second, if you are significantly weak in the jawbone and I go in there and put a lot of fat into your jawline you will look as if you have a fat jawline. You need to replace bone deficiency with something solid and soft tissue loss with fat or other tissue. That being said in older patients who have a slightly deficient chin or slightly weak outer jawline, I do use fat grafting to correct or improve this problem that can be due to aging, weak skeletal structure, or a combination of both.
Other types of injectables that are temporary are also options like Radiesse, Restylane, etc., but remember that you are very young and these options are too expensive especially over a lifetime. I also don't think your parent/guardian would agree to this option. If you have a weaker chin and entire jawline is too small, it would be prohibitively expensive to inject the entire jawline with these products every few months so this would probably not be a great option.
As far as other types of permanent injectables other than fat, I would first offer the admonition regarding permanent fillers again in someone your age. Secondly, even though I like silicone injections for lips, nose defects, and acne scarring, it is not a great filler for large volume areas and it would also be unsafe. If you read my opinion about artefill in the "lip fullness" question, you will see where I stand on that one too for now.
Whenever you look at the jawline, you should always consider the importance of making sure that your dentition (teeth) are properly aligned and have a good bite. With a deficient jawline, you have to wonder if you have an overbite in which either your upper teeth are overgrown or your lower teeth are undergrown. This is probably why jawline work in someone your age may be something more than an injectable filler or even an implant could handle. You may need to seek orthodontic and/or orthognathic (jaw repositioning) surgery, all of course with parental supervision and guidance.
Thanks for the quick reply. My chin doesnt stick out that much, but I was thinking of having a rhinoplasty to shorten my nose and I think that would make my profile look more aligned, and I had braces for a long time so I have a good bite. As you said, because of my age there could be complications if I used some kind of filler to widen the jawline, so since I only have a slightly weak outer jawline I was wondering if there was an alternative, like exercises for the masseter that would make that muscle a bit bigger?
There are no known exercises to make one's masseter bigger per se. You can chew gum excessively etc. but I think that would be just silly. I would be careful to engage in any activity that would enlarge your masseter muscle. I really only have techniques to reduce a masseter, like Botox.