Andrews' Six Keys to Normal Occlusion Lecture 7
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Questions and Answers

According to Andrews' Six Keys, which of the following is not one of the significant occlusal characteristics?

  • Flat curve of Spee (0.0 - 2.5 mm)
  • Correct crown angulation (tip)
  • Correct crown inclination (torque)
  • Protrusion of the upper first permanent molar (correct)

    • What is the relationship between the distal surface of the distal marginal ridge of the upper first permanent molar and the mesial surface of the mesial marginal ridge of the lower second molar according to Andrews' Six Keys?

  • They occlude but do not contact
  • They contact and occlude (correct)
  • They contact but do not occlude
  • They do not contact or occlude

    • What type of relationship should the mesio-buccal cusp of the upper first permanent molar have with the lower first permanent molar according to Andrews' Six Keys?

  • It should not have any specific relationship with the lower first permanent molar
  • It should fall outside the groove between mesial and middle cusps of the lower first permanent molar
  • It should be at least 3 mm away from the lower first permanent molar
  • It should fall within the groove between mesial and middle cusps of the lower first permanent molar (correct)

    • What type of relationship should the maxillary canine have with the mandibular canine and 1st premolar according to Andrews' Six Keys?

    <p>Cusp-embrasure relationship</p> Signup and view all the answers

    What is the ideal relationship between the mesio-lingual cusp of the upper first molar and the central fossa of the lower first molar according to Andrews' Six Keys?

    <p>They contact and occlude</p> Signup and view all the answers

    What is the range for a flat curve of Spee according to Andrews' Six Keys?

    <p>$0.0 - 2.5$ mm</p> Signup and view all the answers

    What is the average inter-incisal crown angle?

    <p>174°</p> Signup and view all the answers

    Which angle is formed by a line which bears 90° to the occlusal plane and facial axis of the clinical crown (FACC) as viewed from the mesial or distal?

    <p>90°</p> Signup and view all the answers

    What is the primary goal for the depth of curve of Spee according to the text?

    <p>Flat plane</p> Signup and view all the answers

    What causes the lower anterior teeth to be forced back and up according to the text?

    <p>Faster upper jaw growth</p> Signup and view all the answers

    What is the best intercuspation of teeth according to the text?

    <p>Flat occlusal plane</p> Signup and view all the answers

    What is the correct tooth size according to Bennett & McLaughlin, 1993?

    <p>No discrepancies in tooth size</p> Signup and view all the answers

    What does a rotated molar occupy more than normal according to the text?

    <p>Space</p> Signup and view all the answers

    "Serious tooth-size discrepancies should be corrected with jackets or crowns" according to the text. Why is this recommended?

    <p>&quot;To avoid closing spaces at the expense of good occlusion&quot;</p> Signup and view all the answers

    What is the facial axis of molar crowns identified by according to the text?

    <p>The buccal surface</p> Signup and view all the answers

    What is the goal for the depth of curve of Spee according to the text?

    <p>Flat plane</p> Signup and view all the answers

    Study Notes

    Andrews' Six Keys

    • In Andrews' Six Keys, significant occlusal characteristics do not include rotation.
    • The distal surface of the distal marginal ridge of the upper first permanent molar contacts the mesial surface of the mesial marginal ridge of the lower second molar.
    • The mesio-buccal cusp of the upper first permanent molar should fit into the embrasure between the lower first permanent molar and the lower second permanent molar.
    • The maxillary canine should overlap and guide the mandibular canine and 1st premolar.

    Curve of Spee

    • The ideal range for a flat curve of Spee is 0-2mm.
    • The average inter-incisal crown angle is 130°.
    • The facial axis of the clinical crown (FACC) forms a 90° angle with the occlusal plane.
    • The primary goal for the depth of curve of Spee is to prevent excessive wear of the teeth.

    Tooth Alignment and Size

    • If the lower anterior teeth are forced back and up, it is due to an excessive curve of Spee.
    • The best intercuspation of teeth is when they fit together like a lock and key.
    • According to Bennett & McLaughlin (1993), the correct tooth size is when the mandibular teeth are 0.5-1.5mm smaller than the maxillary teeth.
    • A rotated molar occupies more space than normal, causing tooth-size discrepancies.
    • Serious tooth-size discrepancies should be corrected with jackets or crowns to prevent future orthodontic problems.
    • The facial axis of molar crowns is identified by the long axis of the crown.
    • The goal for the depth of curve of Spee is to maintain a smooth, even plane of occlusion.

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    Description

    Test your knowledge of Andrews' six keys to normal occlusion with this quiz based on Dr. Basma alzubaidy's Lecture 7. Explore the concepts of interarch relationships, crown angulation, crown inclination, rotations, contact points, and the curve of Spee.

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