A major disadvantage of removable orthodontic appliances is their dependence on patient compliance. These appliances must be worn consistently for the recommended duration to be effective. Inadequate wear reduces the appliance’s ability to exert continuous and controlled forces on teeth, leading to prolonged treatment times or failure to achieve desired tooth movement. Unlike fixed appliances, removable devices rely heavily on the patient's discipline, making treatment outcomes less predictable if compliance is poor. This limits their efficiency and effectiveness in complex tooth movements.

Reference: Graber's Orthodontics, 7th Edition.