The minimum force required to retard and redirect maxillary growth is 300-400 gm/side because this range provides sufficient pressure to influence sutural growth and remodeling without causing tissue damage or patient discomfort. Forces below this threshold (<100-200 gm) are generally inadequate to produce significant orthopedic changes, while higher forces (>500 gm) risk adverse effects such as root resorption or soft tissue irritation. Applying a consistent force of 300-400 gm per side optimizes the balance between efficacy and safety in maxillary orthopedic treatments, ensuring effective growth modification.

Reference: Graber Orthodontics, 6th Edition.