Lec 2.2: Andrew's 6 Keys to Normal Occlusion

Question 1

This is essential for orthodontic treatment to be considered successful.

Answer 1

Andrew’s six keys to normal occlusion

Question 2

Who identified the six keys to normal occlusion?

Answer 2

Lawrence F. Andrews

Question 3

What are the six keys to normal occlusion?

Answer 3

1. Molar occlusion
2. Crown angulation
3. Crown inclination
4. Absence of rotations
5. Tight contacts
6. Flat curve of spee

Question 4

Molar relationship should be such that the? (3)

Answer 4

• Distal surface of DMR, upper 1st permanent molar → MMR, lower 2nd molar.
• MBC of upper 1st permanent molar → groove bet. mesial & middle cusps of lower 1st permanent molar.
• MLC of upper 1st permanent molar → CF of lower 1st permanent molar.

Question 5

In normally occluded teeth, gingival portion of long axis of each crown is ______ to occlusal portion of that axis.

Answer 5

distal

Question 6

Occlusal portion of the axis is ________ to the gingival portion.

Answer 6

mesial

Question 7

Too much angulation causes a tooth to ___________?

Answer 7

Occupy more space.

Question 8

The angle between a line 90 degrees to occlusal plane and line tangent to the middle of labial or buccal surface of clinical crown.

Answer 8

Crown inclination

Question 9

Mesiodistal tip

Answer 9

Crown angulation

Question 10

Buccolingual / labiolingual torque

Answer 10

Crown inclination

Question 11

• Crown of maxillary incisors are so placed that incisal portion of labial surface is _______ to gingival portion of clinical crown.
• In all other crowns, occlusal portion of labial or buccal surface is _______ to gingival portion.

Answer 11

labial;
lingual

Question 12

• In maxillary molars, lingual crown inclination is _________ compared to cuspids + bicuspids.
• In mandibular posterior teeth, lingual inclination progressively _________.

Answer 12

slightly more pronounce;
increases

Question 13

Anterior teeth:
* Deciduous =?
* Permanent teeth =?

Answer 13

• Deciduous = more vertically oriented
• Permanent teeth = more labially inclined

Question 14

• Properly inclined teeth → ?
• Improperly inclined teeth → ?
• Too much inclination → ?

Answer 14

• proper intercuspation
• poor intercuspation
• protrusion

Question 15

Teeth should be free of?

Answer 15

Undesirable rotations

Question 16

If rotated, a molar or bicuspid occupies _____ than it would normally.

Answer 16

more space

Question 17

A rotated incisor can occupy ______ than normal.

Answer 17

less space

Question 18

Non-rotated tooth occupies _______ than a rotated tooth.

Answer 18

less space

Question 19

In absence of such abnormalities as _______.

Answer 19

Genuine tooth-size discrepancies.

Question 20

Contact points should be _____.

Answer 20

Tight

Question 21

Is a must for stability of occlusion.

Answer 21

Flat curve of spee

Question 22

Curve of Spee is measured from?

Answer 22

From most prominent cusp of lower 2nd molar to the central incisor.

(Md 2nd M → CI)

Question 23

No curve deeper than ____ is acceptable from a standpoint of stability.

Answer 23

1.5 mm