Mandibular Movements

Question 1

___ is the dental specialty that deals with restoring missing oral and para-oral structures.

Answer 1

Prosthodontics

Question 2

___ ___ involves restoring teeth by non-removable artificial substitutes.

Answer 2

Fixed prosthodontics

Question 3

The complex 3-dimensional mandibular movement can be broken down into two basic components, ___ and ___.

Answer 3

rotation; translation

Question 4

In the sagittal plane, the mandible is capable of ___ and ___.

Answer 4

rotation; translation

Question 5

Rotation occurs around the ___ ___ ___ or ___ ___ ___ (THA), which is an imaginary line connecting the centers of the two condyles.

Answer 5

terminal hinge axis; transverses horizontal axis

Question 6

In the sagittal plane, the rotational movement is limited to about __-__ mm of incisal separation before the mandible begins to translate.

Answer 6

20-25

Question 7

T/F. Mandibular movement around the sagittal axis occurs when one condyle moves superiorly while the other remains in the terminal hinge position.

Answer 7

False. One condyle moves INFERIORLY. This inferior displacement of the condyle is limited naturally by the ligaments and musculature of the TMJ.

Question 8

What types of motions are produced by horizontal axis rotation?

Answer 8

opening and closing

Question 9

In the horizontal plane, the whole mandible can make a straight ___ movement.

Answer 9

protrusive

Question 10

In lateral movement of the mandible, the non-working condyle travels ___ and
___. The working condyle exhibits slight ___ translation (Bennett movement). This may be slightly forward or slightly backward.

Answer 10

forward; medial; lateral

Question 11

In a straight protrusive movement, both condyles will move ___ as they slide along the eminencies

Answer 11

downward

Question 12

Explain lateral movements in frontal plane of the non-working and working condyles.

Answer 12

In lateral movements, the non-working condyle will move downward and medial. The working condyle, however, will rotate and move lateral and upward or lateral and downward.

Question 13

Ulf Posselt described this range of movement in the ___ planes of orientation using a starting reference point between the two mandibular ___ ___. This range of movement is also referred to as the “__ __ __.”

Answer 13

three; central incisors; envelope of motion

Question 14

Pure rotational opening can occur until the anterior teeth are __-__ mm apart.

Answer 14

20-25

Question 15

T/F. Pure rotational opening occurs with translation of the condyles.

Answer 15

False. The mandible can be lowered (mouth opening) in a pure rotational movement without translation of the condyles.

Question 16

What happens during the second rotational movement during opening?

Answer 16

The condyle is translated down to the articular eminence when the mouth rotates open to its maximum limit.

Question 17

During the second stage of opening, the condyles move ___ and ___ while the anterior portion of the mandible moves ___ and ___.

Answer 17

anteriorly; inferiorly; posteriorly; inferiorly

Question 18

T/F. The second stage of opening involves rotation and translation.

Answer 18

True

Question 19

What is the maximum opening range?

Answer 19

50 to 60mm when measured between the incisal edges of the maxillary and mandibular teeth

Question 20

If the mandible is manipulated upward on the centric relation arc of closure until tooth contact occurs, the mandible is now said to be in ___ ___.

Answer 20

centric occlusion (CO)

Question 21

What muscle is involved in the closure of the mandible?

Answer 21

inferior lateral pterygoids (which keep the condyles positioned anteriorly)

Question 22

T/F. Superior contact movements are determined by the characteristics of the occluding surfaces of the teeth.

Answer 22

True.

Question 23

In approximately __% of the population, this contact occurs between only one or two maxillary and mandibular teeth

Answer 23

90

Question 24

Contacting surfaces are located on the ___ inclines of the mandibular tooth (teeth) and the ___ inclines of the maxillary tooth (teeth).

Answer 24

distal; mesial

Question 25

Forces applied to the teeth when the condyles are in centric relation (CR) will create a superoanterior shift of the mandible to the ___ ___.

Answer 25

intercuspal position (maximal intercuspation)

Question 26

The slide between CO and MI is referred to as “__ __.”

Answer 26

centric slide

Question 27

In intercuspal position or at MI, the opposing anterior teeth are in contact. When the mandible is protruded from MI, contact between the ___ edges of the mandibular anterior teeth and the ___ inclines of the maxillary anterior teeth results in an anterorinferior (opening) movement of the mandible.

Answer 27

incisal; lingual

Question 28

The mandible has to open as the mandibular anterior teeth
ride down along the lingual concavity of the maxillary anterior teeth until they
reach an __-to-__ (__-to-__) position.

Answer 28

end-to-end; edge-to-edge

Question 29

What dictates the path of the mandible as it continues to move forward and clear the anterior teeth?

Answer 29

the posterior teeth

Question 30

If from the maximum open position the patient is instructed to close, what path will the mandible trace?

Answer 30

the path of the habitual arc of closure

Question 31

T/F. The physiologic rest position of the mandible lies on the habitual arc of closure.

Answer 31

True.

Question 32

What is the position that the mandible assumes when all muscles are at a state of equal relaxation?

Answer 32

physiologic rest position

Question 33

Define the vertical dimension of occlusion (VDO) and vertical dimension at rest (VDR)

Answer 33

It is the distance between two arbitrary reference points on each side of the maxillary and mandibular teeth when the teeth are separated by the interocclusal rest distance or space. This distance at physiologic rest position

Question 34

What are the four muscles of mastication? What muscle is an accessory muscle?

Answer 34

masseter, temporalis, lateral and medial pterygoid muscles

digastric

Question 35

Explain the Bennett’s side shift.

Answer 35

Because the condyles are oblong and not spherical, the center will shift and will take the condyle slightly out of the cone of Bennett.

This causes a mandibular lateral translation

Question 36

what are the functions of anterior teeth?

Answer 36

anterior guidance, perform initial acts of mastication, speech, lip support, esthetics

Question 37

which types of bites have no anterior guidance?

Answer 37

class III (end to end), class III, anterior open bite

Question 38

Anterior guidance includes what two subcategories?

Answer 38

incisal guidance and canine guidance

Question 39

What are the two types of occlusal schemes?

Answer 39

anterior guidance and group function

Question 40

what factors determine the anterior guidance?

Answer 40

the lingual concavities of the maxillary anterior teeth as well as the vertical and horizontal overlap of maxillary and mandibular anterior teeth.

Question 41

If the relationship of the maxillary and mandibular canines determines the lateral jaw movement, the term ___ ___ is used in reference to the path during lateral movement.

Answer 41

canine guidance

Question 42

What serves to guide the diclusion of posterior teeth?

Answer 42

The inclination of the articular eminence of the TMJ and the morphology of the lingual surfaces of anterior teeth

Question 43

what are the three posterior determinants of mandibular movements?

Answer 43

1. inclination of articular eminence
2. medial wall of glenoid fossa
3. intercondylar distance

Question 44

What are the two anterior determinants of mandibular movements?

Answer 44

1. horizontal overlap of anterior teeth

2. vertical overlap of anterior teeth

Question 45

what are the other determinants of mandibular movements?

Answer 45

1. occlusal plane
2. curve of spee
3. neuromuscular response

Question 46

Anterior guidance is dictated by the position of the ___ edge of the mandibular anterior teeth relative to the ___ surfaces of the maxillary anterior teeth.

Answer 46

incisal; lingual

Question 47

Anterior guidance is dictated by changes in morphology of the ___ surfaces of maxillary anterior teeth.

Answer 47

lingual

Question 48

Anterior guidance is dictated by the length of mandibular ___ or ___

Answer 48

incisors or canines

Question 49

For incisal guidance, immediate disclusion of posterior teeth takes place on mandibular ___.

Answer 49

protrusion

Question 50

For canine guidance, immediate disclusion of posterior teeth takes place as soon as the ___ movement begins.

Answer 50

lateral

Question 51

What function occurs when the mandibular buccal working cusps travel downward, forward, and lateral in contact with the lingual inclines of the maxillary buccal cusps, simultaneously with the canines?

Answer 51

group function

Question 52

One use of the incisal guide table is to ___ an existing guidance prior to preparing teeth.

Answer 52

record

Question 53

Another use of the insical guide table is to ___ wax patterns, which may be abraded during movements of the articulator

Answer 53

protect

Question 54

T/F. 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 interferences in both protrusive and non-working excursions.

Answer 54

True