The rate of active tooth movement with a removable expansion appliance should not exceed 1.00 mm/month to prevent adverse effects such as root resorption, periodontal damage, and bone loss. Moving teeth too rapidly can compromise the supporting structures, leading to instability and relapse. The bone remodeling process requires sufficient time to adapt and support tooth movement safely. Controlled, gradual expansion ensures optimal biological response and maintains periodontal health. Therefore, limiting expansion to 1.00 mm per month balances effective treatment with patient safety.

Reference: Contemporary Orthodontics, 6th Edition.