Six Keys to Normal Occlusion

Question 1

what are the six keys of normal occlusion

Answer 1

• molar relation
• crown angulation
• crown inclination
• rotations
• contact points
• occlusal plane

Question 2

what is a key I molar relationship

Answer 2

• the distal marginal ridge of the maxillary first molar occludes on the mesial marginal ridge of the mandibular second molar
• the ML cusp of the maxillary first molar must occlude on the central fossa of the mandibular first molar

Question 3

in key I molar relation if the maxillary and mandibular molars are in a normal relation the canines and premolars:

Answer 3

enjoy an embrasure relationship buccally and a cusp fossa relationship lingually

Question 4

describe the key II crown angulation

Answer 4

the gingival portion of the long axis of each tooth is distal to the incisal portion

Question 5

in key II crown angulation what determines the amount of M-D space they consume

Answer 5

the degree of tip of the incisors

Question 6

what does it mean if you have a positive number for crown angulation

Answer 6

distal tip of the crown

Question 7

what does it mean if you have a negative reading for crown angulation

Answer 7

mesial tip of the crown

Question 8

crown angulation is measured in relation to:

Answer 8

the incisal edge

Question 9

what is the normal crown angulation

Answer 9

around 5 degrees

Question 10

what is another term for crown angulation

Answer 10

tipping

Question 11

what is another name for crown inclination

Answer 11

torque

Question 12

angulation is in the ____ direction

Answer 12

MD

Question 13

inclination is in a ____ direction

Answer 13

BL

Question 14

what does a positive number for crown inclination mean

Answer 14

the gingiva is lingual to the incisal edge

Question 15

what teeth have negative crown inclination numbers? positive?

Answer 15

• negative: posterior
• positive: anterior

Question 16

why do we need to place proper torque

Answer 16

if you do everything will fall into place for molar relationships, overbite, overjet, and cusp embrasure occlusion

Question 17

what is the crown inclination for maxillary posterior teeth

Answer 17

continuous

Question 18

what is the crown inclination for mandibular posterior teeth

Answer 18

progressively increased from canines through second molars

Question 19

what is another term for the relationship between inclination and angulation

Answer 19

the wagon wheel effect

Question 20

what is the relationship between inclination and angulation

Answer 20

for every 4 degrees of lingual root torque, there is one degree of mesial root tip

Question 21

a rotated molar occupies ____ MD space

Answer 21

more

Question 22

a rotated anterior tooth occupies _____ MD space

Answer 22

less

Question 23

a normal anterior tooth occupies ______ MD space than a molar

Answer 23

more

Question 24

in the absence of genuine tooth size discrepancies, ideal occlusions should have:

Answer 24

tight contacts

Question 25

what occlusal plane should be a treatment goal

Answer 25

a flat

Question 26

why do we want a flat occlusal plane

Answer 26

intercuspation of teeth is best when the occlusal plane is flat

Question 27

why do we want to get rid of the curve of spee

Answer 27

• can produce damaging force to PDL
• easier to move teeth on a flat plane- mechanical purposes