1. Andrew’s Six Keys & Skeletal Pattern
Awatif, Fatin, Huda, Diyana, Fatimah, Fadhila, Aimi

2. Andrew’s Six Keys

3. 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

4. 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

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

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

7. 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

8. 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

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

10. SKELETAL PATTERN

11. Skeletal Pattern
Anterior-posterior
Vertical
Transverse

12. ANTERIOR-POSTERIOR

13. ANTERIOR-POSTERIOR
Patient has to be postured carefully with the head in a neutral horizontal position (Frankfort Plane horizontal to the floor).
Sit the patient upright in the dental chair and ask them to occlude gently on their posterior teeth.
Look at the patient in profile and identify the most concave points on the soft tissue profile of the upper and lower lips.

14. Class I Class II Class III
The most anterior part of the maxilla and mandible can be palpated in the midline through the base of the lips.
Class I Class II Class III
Class I: mandible lies 2-3 mm posterior to maxilla. (straight profile)
Class II: mandible is retrusive to the maxilla. (convex profile)
Class III: maxilla is retrusive to the mandible. (concave profile)

15. ANTERIOR-POSTERIOR
Determine the position of jaw relative to the cranial base.
Vertical imaginary line: through soft tissue nasion in the neutral head position.
Zero meridian: represent the anterior limit of the cranial base.
Assess by soft tissue A point and B point

16. ANTERIOR-POSTERIOR
Class I: A point lie 2-3 mm ahead and B point 0-2 mm behind zero meridian
Class II: B point lie more than 2mm behind zero meridian
Class III: B point lie ahead than zero meridian

17. VERTICAL

18. VERTICAL Different way to assess vertical skeletal pattern
Lower anterior face height (LAFH)
Frankfort mandibular plane angle (FMPA)

19. VERTICAL : LAFH

20. LOWER ANTERIOR FACIAL HEIGHT (LAFH)
Is used to assess vertical dimension
Ratio of the LAFH to the total face height gives an indication if the LAFH is within normal limits
Facial proportion (LAFH %)
= MxPl to Me x 100
MxPl to Me + MxPl to N
= 55% ± 2%

21. LOWER ANTERIOR FACIAL HEIGHT (LAFH)
The face can be split into thirds.
LAFH (subnasale-menton) should be approximately equal to middle face height (glabella-subnasale)

22. VERTICAL : FMPA

23. FRANKFORT MANDIBULAR PLANE ANGLE (FMPA)
It measures the relationship between LAFH and posterior face height
Normal: mandibular and frankfort lines intersect in occipital region
Increased:anterior to occipital region
Reduced:posterior to occipital region

24. TRANSVERSE RELATIONSHIP

25. TRANSVERSE RELATIONSHIP
2 components that should be assessed are :
Facial symmetry
Arch width

26. Facial Symmetry
Assessed by constructing a facial midline between soft tissue nasion and middle part of the upper lip at vermillion border
Chin should be coincident with this line
If there is assymetry, check for compensatory cant in max.occ plane
Lateral mandibular displacement can produce facial asymmetry

27. Arch Width
If maxilla is narrow, it will cause crossbite at the buccal segment if there is inadequate dentoalveolar compensation
Transverse max.discrepancy may exist due to incorrect AP positioning of max/mand.

28. References Orthodontics at glance An introduction to Orthodontics
Orthodontics. Part 2: Patient assessment and examination I; British Dental Journal 2003; 195:489–493