2. 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

3. 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

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

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

6. 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

7. 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

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