4/10: Determinants of Occlusal Morphology

Question 1

What are the factors that determine the patterns of mandibular movements?

Answer 1

The TMJ’s and the anterior teeth

Question 2

Where should the posterior teeth pass to maintain harmony?

Answer 2

Pass close to but NOT contact the opposing teeth during mandibular movement

Question 3

What are structures that control mandibular movement?

Answer 3

• structures that influence the movement of the posterior portion of the mandible (TMJs)
• structures that influence the movement of the anterior portion of the mandible (anterior teeth)

Question 4

What are posterior controlling factors (condylar guidance)?

Answer 4

• the angle at which the condyle moves away from a horizontal reference plan
• the condylar guidance

Question 5

What is the condylar guidance angle?

Answer 5

The angle at which the condyle moves away from a horizontal reference plane

Question 6

What is the condylar guidance angle considered to be?

Answer 6

A “fixed factor”, since in the healthy patient it is unalterable

Question 7

What determines how the anterior portion of the mandible moves?

Answer 7

Anterior teeth

Question 8

What happens as the mandible protrudes or moves laterally?

Answer 8

The incisal edges of the mandibular anterior teeth occlude with the lingual surfaces of the maxillary anterior teeth

Question 9

What determines the amount of vertical movement of the mandible?

Answer 9

The steepness of the lingual surfaces

Question 10

What kind of factor is anterior guidance considered to be?

Answer 10

Variable rather than a fixed factor

Question 11

How can anterior guidance be altered?

Answer 11

By pathologic conditions (caries, wear, etc), or dental procedures

Question 12

What must be in harmony during all mandibular eccentric movements?

Answer 12

The morphologic characteristics of each posterior tooth with its opposing tooth or teeth

Question 13

What is the morphology of the teeth influenced by?

Answer 13

The pathway it travels across its opposing tooth or teeth

Question 14

What are components of mandibular movements?

Answer 14

Vertical component (supero-inferior movement)
Horizontal component (antero-posterior movement)

Question 15

What is the vertical component a function of?

Answer 15

Superio-inferior movement

Question 16

Where do we want posterior teeth to pass close to in the vertical component?

Answer 16

Close to but not contact opposing teeth during mandibular movement (occlusal harmony)

Question 17

The length of the cusp and the distance it extends into the depth of an opposing fossa depends on?

Answer 17

1. Anterior controlling factor of mandibular movement
2. Posterior controlling factor of mandibular movement
3. The nearness of the cusp to those controlling factors

Question 18

What do vertical determinants control?

Answer 18

The function of the superior-inferior movement (cusp height, fossae depth)

Question 19

What do horizontal determinants influence?

Answer 19

The direction of grooves and ridges on the occlusal surfaces, and the placement of the cusps in the horizontal plane

Question 20

What are vertical determinant factors?

Answer 20

Height of cusps
Depths of fossae

Condylar guidance (posterior controlling factor)
Anterior guidance (anterior controlling factor)
Nearness of the cusp to the controlling factor
Plane of occlusion
Curve of spee

Question 21

What are posterior controlling factors?

Answer 21

Fixed factors
Condylar guidance
The two TMJs

Question 22

What happens to the condyle when the mandible is protruded?

Answer 22

The condyle descends along the articular eminence

Question 23

What is condylar guidance?

Answer 23

The angle at which the condyle moves away from the horizontal reference plane

Question 24

What happens to the condylar guidance angle when the mandible makes a lateral movement?

Answer 24

Greater than when the mandible makes a protrusive movement

Question 25

The steeper the eminence the...

Answer 25

The more the condyle must move inferiorly There is greater vertical movement It allows for steeper posterior cusps

Question 26

What are anterior controlling factors?

Answer 26

Anterior teeth Anterior guidance

Question 27

What do anterior teeth determine?

Answer 27

How the anterior portion of the mandible moves

Question 28

What is anterior guidance altered by?

Answer 28

Restorations Orthodontics Extractions Caries habits Tooth wear

Question 29

Anterior guidance is a ________ rather than a _______ factor

Answer 29

Variable; fixed

Question 30

What is the anterior guidance angle?

Answer 30

The angle formed by the intersection of the horizontal plane and the disclusive pathway of the anterior teeth

Question 31

What is the anterior guidance angle influenced by?

Answer 31

Vertical overlap (VO) Horizontal overlap (HO)

Question 32

What does VO overlap do to the anterior guidance angle?

Answer 32

Increases the anterior guidance angle

Question 33

What does HO overlap do to the anterior guidance angle?

Answer 33

Decreases the anterior guidance angle

Question 34

What does increased anterior guidance angle do?

Answer 34

More vertical component Allows for steeper posterior cusps

Question 35

What happens when a tooth is nearer to the TMJ?

Answer 35

The more the joint anatomy will influence its eccentric movement and the less the anterior teeth influence its movement

Question 36

What are other factors that influence cusp height?

Answer 36

Plane of occlusion Curve of spee Mandibular lateral translation movement

Question 37

What is the plane of occlusion?

Answer 37

An imaginary surface that touches the incisal edges of the incisors and cusp tips of the occluding surfaces of the posterior teeth

Question 38

What happens to the posterior cusps as the plane of occlusion becomes more parallel to the angle of eminence?

Answer 38

Posterior cusp tips must be made shorter

Question 39

Where does the curve of spee go?

Answer 39

Anteroposterior

Question 40

Where does the curve of spee extend?

Answer 40

From the tip of the mandibular canine along the buccal cusp tips of the mandibular posterior teeth

Question 41

What is curvature described in?

Answer 41

Terms of length of radius of the curve

Question 42

What happens to the curve with a short radius?

Answer 42

More acute than with a longer radius

Question 43

The flatter the plane of occlusion, the ________ the cusp height

Answer 43

Greater

Question 44

What is the radius of the curve of spee?

Answer 44

Short radius

Question 45

Describe the short radius of the curve of spee

Answer 45

the ANGLE at which the mandibular teeth move away from the maxillary teeth WILL BE LESS THAN WITH A LONG RADIUS, therefore the CUSPS will need to be SHORTER

Question 46

What happens if the plane of occlusion is rotated more anterior?

Answer 46

- more teeth anterior to perpendicular line - taller cusps

Question 47

What happens if the plane of occlusion is rotated more posterior?

Answer 47

- more teeth posterior to perpendicular reference line - shorter cusps

Question 48

What is bennett movement?

Answer 48

Effect of mandibular translation movement on cusp height

Question 49

What kind of movement is mandibular lateral translation?

Answer 49

Bodily sideshift of the mandible during lateral movements

Question 50

What does inward movement depend on?

Answer 50

- morphology of the medial wall of the fossa on the orbiting side - inner portion of the TM ligament attached to the lateral pole of the rotating condyle

Question 51

Is the temporomandibular ligament tight?

Answer 51

Yes, very - not common

Question 52

What kind of movement occurs around the rotating condyle?

Answer 52

Pure arcing movement

Question 53

Describe the translation of the mandible in the temporomandibular ligament?

Answer 53

No lateral translation of the mandible

Question 54

The more medial the medial wall is from the condyle, the _____________________________

Answer 54

More lateral translation movement

Question 55

What is lateral translation movement described in?

Answer 55

- amount - timing -direction

Question 56

The greater the amount of lateral translation, the ___________________________ the cusps must be

Answer 56

Shorter

Question 57

Describe the movement of the rotating condyle

Answer 57

May move in a combination of movements - laterosuperior - lateroinferioposterior etc

Question 58

What does laterosuperior movement require?

Answer 58

Shorter posterior cusps

Question 59

What does inferior movement allow?

Answer 59

Taller cusps

Question 60

What has the greatest influence on occlusal morphology?

Answer 60

Lateral translation timing

Question 61

How can translation movement occur?

Answer 61

Early late

Question 62

What is early translation called?

Answer 62

Immediate lateral translation (or immediate sideshift)

Question 63

What is late lateral translation called?

Answer 63

Progressive lateral translation (or progressive sideshift)

Question 64

When is immediate lateral translation seen?

Answer 64

Before the condyle begins to translate from the fofsa

Question 65

The more the immediate movement, the ________ the cusps must be

Answer 65

Shorter

Question 66

Graph of vertical determinants of occlusal morphology

Answer 66