Orthodontic is the describing word for work that helps teeth grow straight when they have not been growing that way — braces, wires, retainers, and the clinic around that care. We say orthodontic treatment, an orthodontic clinic, orthodontic braces. It is a doctor-and-clinic word, not a word you need at the dinner table, though plenty of families use it when a child gets braces. Though actually, the job and the field are usually named with the -s word, orthodontics; this spelling, without the s, mostly rides in front of another noun. It does not mean general dentistry, and it does not mean bone doctors, even though both of those also start with ortho- in other words.