The document discusses the history and evolution of fixed orthodontic appliances, leading to the development of the pre-adjusted edgewise appliance. It describes Lawrence Andrews' research which identified six keys to optimal occlusion based on measurements of untreated dental casts. His studies found that traditional edgewise appliances did not achieve optimal occlusion in most treated cases. This led to the concept of a fully programmed pre-adjusted edgewise appliance that would incorporate his findings on natural tooth morphology and positioning.