A system may include a body having a palatal portion of a first material and a surface shaped to match a shape of a patient's palate and extending between first tooth engagement structures shaped to engage teeth on a first side of a patient's arch and second tooth engagement structures shaped to engage teeth on a second side of a patient's arch and a reinforcement structure within the palatal portion, wherein the reinforcement structure includes at least one fiber fabricated of a second material, different than the first material, and a dimension of the at least one fiber at a middle portion between respective ends of the at least one fiber is greater than a dimension of the respective ends of the at least one fiber.