title: Theoretical considerations of headgear therapy: a literature review. 1. Mechanical principles.
mesh_terms: D001696:Biomechanical Phenomena; D005115:Extraoral Traction Appliances; D006801:Humans; D008962:Models, Theoretical; D009967:Orthodontic Appliances; D009968:Orthodontic Appliances, Removable; D012399:Rotation; D014087:Tooth Movement Techniques