A force is defined as a push or pull exerted on an object that tends to alter its state of rest or motion. In orthodontics, this force is transmitted through the bracket-archwire system to the tooth, which then transmits it to the PDL and alveolar bone. The PDL acts as a viscoelastic medium that cushions and distributes the applied stress, initiating a cascade of cellular reactions leading to bone remodeling.Forces are characterized by magnitude, direction, point of application, and line of action. The magnitude determines how much stress is applied to the tooth; the direction determines the...