Andrew’s Six Keys The six keys to normal occlusion, serve as a goal Can be used to evaluate why good class I occlusion failed to be achieved at the end of treatment They are: Correct molar relationship Correct crown angulation Correct crown inclination No rotations No spaces Flat occlusal plane

Andrews’Six Keys- Correct Molar Relationship The MB cusp of upper first molar occludes with the groove between the MB and middle buccal cusp of lower first molar DB cusp of upper first molar contacts the MB cusp of lower second molar

Andrews’Six Keys - Correct Crown Angulation All tooth crowns are angulated mesially

Andrews’Six Keys - Correct Crown Inclination Incisors are inclined towards the buccal or labial surface Buccal segment teeth are inclined lingually

Andrews’Six Keys - No Rotation None of the teeth should be rotated to achieve normal occlusion Rotated molars and premolars occupy more space Rotated incisors occupy less space Rotated canines adversely affect aesthetics and may lead to occlusal interferences

Andrews’Six Keys - No spacing ( tight proximal contact) If there is no anomalies in the shape of the teeth or intermaxillary discrepancies in the mesiodistal tooth size, the contact points should be next to each other in normal occlusion

Andrews’Six Keys – Flat Occlusal Plane The mandibular curve of spee should not be deeper than 1.5 mm