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Andrew’s Six Keys & Skeletal Pattern

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

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Andrew’s Six Keys & Skeletal Pattern

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

  2. Andrew’s Six Keys

  3. 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 Andrew’s Six Keys

  4. 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 Molar Relationship

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

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

  7. 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 Rotation

  8. 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 - No spacing ( tight proximal contact)

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

  10. SKELETAL PATTERN

  11. Anterior-posterior • Vertical • Transverse Skeletal Pattern

  12. ANTERIOR-POSTERIOR

  13. 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. ANTERIOR-POSTERIOR

  14. The most anterior part of the maxilla and mandible can be palpated in the midline through the base of the lips. • 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) Class I Class II Class III

  15. 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 ANTERIOR-POSTERIOR

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

  19. VERTICAL : LAFH

  20. 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% LOWER ANTERIOR FACIAL HEIGHT (LAFH)

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

  22. VERTICAL : FMPA

  23. 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 FRANKFORT MANDIBULAR PLANE ANGLE (FMPA)

  24. TRANSVERSE RELATIONSHIP

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

  26. 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 Facial Symmetry

  27. 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. Arch Width

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

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