<prompt> The six keys to normal occlusion were given by:Lawrence F. A.AngleLischerMoyer  <response>: ANDREWS SIX KEYS TO NORMAL OCCLUSIONLawrence F Andrews studied 120 casts of non-orthodontic patients with normal occlusion for four years 1960-1964. He identified 6 key characteristics.He was of the opinion, that for normal occlusion to exist these six characteristics had to be present. According to Andrews, the 6 keys to normal occlusion contributed individually and collectively to the total scheme of occlusion and, were therefore essential for an orthodontic treatment to be considered successful.Ref: Textbook of orthodontics Gurkeerat Singh 2nd ed page no 59 