• Andrews described a pre-adjusted orthodontic bracket designed to control tooth movement in three dimensions, which required fewer bends introduced in to the archwire to manipulate tooth position.
  • The buccolingual crown thickness, crown angulation and crown inclination of individual teeth from 120 study models were measured, taken from patient who had never received orthodontic treatment. These values were averaged and their values incorporated in to a bracket system designed to create the six keys to occlusion.
    • Andrews produced brackets for non –extraction and extraction cases.
    • The S series were for non- extraction cases. His reasoning for this was that, in extraction cases, anti-rotation and anti-tip were to be incorporated in to the bracket design.
    • This was to eliminate the tip and rotation of the buccal surface towards the extraction site.
    • Overcompensation of the tip allows for rebound of the tooth so that  the net effect is to leave the tooth with the correct degree of tip.
    • He also recommended the use of three different set of incisor brackets, with varying degrees of torque for different clinical situations.

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