Oral treatment devices formed from wax-based compositions that are thermally stable when formed into a three-dimensional shape to a temperature of at least 45° C. and plastically deformable at room temperature (25° C.). The wax-based compositions include a wax fraction homogeneously blended with a polymer fraction. The wax fraction includes at least one wax. The polymer fraction includes at least one polymer selected such that, when the wax and polymer are homogeneously blended together, they yield a wax-based composition having the desired properties of thermal stability and plastic deformability. Oral treatment devices are dimensionally stable to a temperature of at least 40° C. without external support and can be plastically deformed in a user's mouth to become at least partially customized to the size and shape of user's unique dentition and/or an appliance in a user's mouth.