Abstract: Disclosed is a dental appliance composed of a thermo-plastic polymer with low compressibility, high toughness, and high tensile strength, with a low softening point. The appliance has perforations that enable it to be easily custom-fitted by the user or a health professional. The appliance begins as a generally U-shaped, unformed dental tray that is significantly thinner than existing dental appliances. Once fitted, the dental appliance provides superior protection against damage to the enamel of the teeth and abrasion of the teeth due to bruxism or other mechanism leading to biomechanical wear of dental surfaces. The perforations facilitate the custom-fitting process by allowing the user to suck air through the perforations, thus applying a negative pressure between the material and the teeth while the material is still soft and pliable.