Physical Danger
You’ll have the same physical danger that dentists have, but on a smaller scale. Dental procedures tend to take more time and are more invasive than orthodontics. Once you put the brackets, bands, and ligatures on, you’re really only replacing wires and tightening...for the most part.
Still, any time you put your hands in someone’s mouth, you need to wear gloves and be aware of things like hepatitis, HIV, and other blood-related diseases.
You’re also working on kids, and kids get sick...a lot. Better stock up on Emergen-C, wear a mask, and use lots and lots of hand sanitizer.