I try to compare it with the absence of the wax.
I have played the clarinet and flute in braces for four years without waxing or problems.
You just have to put it on top of the metal. You can separate the dimensions you need. The heat on your finger will help it shape the right position.
The wax can be used at any time. Especially if there's a place that really irritate your mouth.
You should use a new thing every time...
I never bought... My orthodontist provided it.
