This document discusses the deleterious effects of orthodontic force, including mobility and pain, effects on the pulp, root structure, and alveolar bone height. Mobility and pain are related to the magnitude of force applied - light forces minimize these issues. Heavy forces can cause pulp damage and undermining resorption leading to mobility. Root resorption is common with orthodontic treatment but is usually clinically insignificant, though heavy prolonged forces can cause permanent loss of root structure. Crestal bone loss of 0.5-1mm occurs with orthodontic tooth movement.