A "boil-and-bite" is a type of dental mouthguard that can be customized for a better fit. It is made from a thermoplastic material that softens when heated in boiling water. After softening, the user bites into the material, creating an impression of their teeth. These mouthguards are commonly used for sports or to prevent teeth grinding during sleep. They provide a protective barrier for the teeth and can be more comfortable than standard, non-customized options. Popular brands include Shock Doctor and SISU, which offer various designs and thicknesses for different needs.