The major limitation of removable appliances is their inability to control root position. These appliances primarily exert forces on the crown of the tooth, making it difficult to achieve precise root movement or torque. Effective root control typically requires fixed appliances that apply forces close to the center of resistance. Without adequate root movement, treatment outcomes may be compromised, particularly in cases requiring significant orthodontic correction. This limitation restricts the use of removable appliances to simple tooth movements rather than complex orthodontic adjustments.

Reference: Graber’s Orthodontics, 7th Edition.