A Lip Protector is a device that covers your braces brackets to protect the insides of your lips and cheeks. When your brackets are covered, it prevents the inside of your mouth from becoming irritated. There are many different types of Lip Protectors. Some fit over only the front of your brackets, some fit over all sides of your brackets, and some cover individual brackets. If you play a brass or wind instrument, your dentist or orthodontist can custom-make a lip protector to help your embouchure.
Your orthodontist may have lip protectors to give you, or you can buy them online.