Week 3 - Mandibular Movements

Question 1

Occlusal Stability

Answer 1

Anatomic and functional harmony caused by the balance between the elevator and depressor muscles

Question 2

At rest, where is the jaw?

Answer 2

Suspended 2-4 mm in space

Question 3

(According to this class) What are the muscles of mastication?

Answer 3

Digastric
Masseter
Temporalis
Lateral Ptrygoid

Question 4

Diagastric muscle

Answer 4

Helps open the jaw

Question 5

Masseter muscle

Answer 5

Helps close and crush

Question 6

Temporalis muscle

Answer 6

Closes the jaw

Question 7

Lateral Pterygoid muscle

Answer 7

Open and orient the jaw

Has two heads that act like oars on a boat

Question 8

Articulating disc

Answer 8

Biconcave disc in the TMJ to protect the bone from the joint

Question 9

What two bones are included in the TMJ?

Answer 9

Mandible and Temporal bone

Question 10

What direction does the jaw move during protrusion?

Answer 10

Down and forward

Question 11

Midsagittal section of the head

Answer 11

Median plane

Question 12

Transverse section of the head

Answer 12

Horizontal plane

Question 13

Coronal section of the head

Answer 13

Frontal plane

Question 14

Rotation movement of the mandible

Answer 14

Rotating around its long axis

Mandible stays in the same location

Question 15

Translational movement of the mandible

Answer 15

Leaves the former space and goes to another

In the mandible, this occurs when it moves forward

Question 16

THA (Terminal Hinge Axis or Transverse Horizontal axis)

Answer 16

Imaginary line that connects the condyles

The mandible rotates around this axis

Question 17

Working side

Answer 17

The side towards which the mandible moves during lateral movement

Question 18

Non-working side

Answer 18

The side opposite the working side

Question 19

What direction does the non-working side move during right lateral movement?

Answer 19

It moves downward, forward, and medial

Question 20

What direction does the working side move during right lateral movement?

Answer 20

Laterally

Question 21

Bennett’s Movement/Bennett’s Cone

Answer 21

The working side movement can go anywhere within a cone (called Bennett’s cone)

Question 22

Bennett’s Side Shift

Answer 22

Mandibular Lateral Rotation
During lateral movement, the jaw has to translate forward slightly, because it is up against a wall and at an angle. When it twists, it has to come forward because it can’t move the skull

Question 23

What motion does the jaw move during chewing?

Answer 23

It opens and closes in a tear-drop shape

Question 24

Ulf-Posselt’s Envelope of Motion

Answer 24

Occurs when the mouth is opening and closing

The mandible first rotates and then it translates

Question 25

Centric relation curve

Answer 25

The curve seen when the mandible first rotates

Question 26

Curve of translation

Answer 26

When the mandible translates after rotating during opening in Ulf-Posslet's envelope of motion

Question 27

Initial Point of contact

Answer 27

In 90% of the population, CO occurs with two teeth and then slide into MI In 10% of the population, they go straight into MI (CO = MI)

Question 28

What are the funcitons of Anterior Teeth?

Answer 28

``` Anterior Guidance Perform Initial acts of mastication Speech Lip Support Esthetics ```

Question 29

Anterior Guidance

Answer 29

The anterior teeth overlap, creating an angle, which help guide occlusion

Question 30

What is anterior guidance dictated by?

Answer 30

Position of the incisal edge of the mandibular anterior teeth relative to the lingual surfaces of the maxillary anterior teeth Changes in morphology of the lingual surfaces of maxillary anterior teeth Length of mandibular incisors or canines

Question 31

What are the 2 forms of anterior guidance, and which is ideal?

Answer 31

Incisal guidance | Canine guidance*

Question 32

Why is Canine guidance ideal?

Answer 32

Muscle activity is lower, leading to less fatigue

Question 33

What are the two occlusal schemes, which is ideal?

Answer 33

Anterior guidance | Group Function

Question 34

Group Funciton

Answer 34

The canines and molars are all touching at the same time | not ideal but sometimes necessary

Question 35

What are the three functions of the incisal guides on the articulator?

Answer 35

1) When anterior teeth are prepared, the angulations of the custom guide provides anterior guidance in the place of anterior teeth 2) When only posterior teeth are to be replaced, the angulation of the guide serves to estimate the buccolingual and mesiodistal cusp angles so as to avoid interference in both protrusive and on-working excursions 3) Reduce the amount of wear on the stone during excursive movements made on the articulator