Braces or other dental appliances are a potential source of mouth alcohol because they can trap and hide alcohol or food particles that could absorb and hold alcohol. If braces or dental appliances are holding even a small amount of alcohol, it could show up on the breath test and make the result much higher than it should be.
The breath test is looking for small amounts of alcohol in the breath that would indicate higher levels of alcohol in the system. Alcohol in the mouth can trick the machine into thinking that the alcohol was in the breath that came from the lungs. It is unlikely that mouth alcohol would create a false positive breath test result for someone who did not drink any alcohol at all, but if a person did have some alcohol to drink, there is a very real possibility that the breath test machine could not distinguish between the alcohol in the mouth and the alcohol in the breath. If you had braces or other dental appliances in your mouth on the day of your breath test, you might have a braces defense, especially if you had eaten and there were pieces of food caught in your braces or dental work.