intro: muscles of mastication

Question 1

What is occlusion?

Answer 1

The contact of the opposing surfaces of teeth of the two jaws.

Question 2

What is the role of TMJ in prosthodontics?

Answer 2

It relates to the movement of the condyles and the positioning of artificial teeth and occlusal morphology.

Question 3

Name the main anatomical parts of the TMJ.

Answer 3

Condyle, Glenoid Fossa, and Articular Disc.

Question 4

Why is the TMJ considered a compound joint?

Answer 4

It is composed of three or more bones, and the articular disc functions as a bone.

Question 5

What type of articulation occurs in the TMJ?

Answer 5

Ginglymoarthrodial articulation, capable of ginglymoid (rotation) and diarthroidal (translation) actions.

Question 6

What are the muscles of mastication?

Answer 6

Masseter, Temporalis, Lateral Pterygoid, and Medial Pterygoid.

Question 7

What are the associated ligaments of the TMJ?

Answer 7

Temporomandibular, Sphenomandibular, and Stylomandibular ligaments.

Question 8

Define centric relation.

Answer 8

A bone-to-bone relation between the maxilla and mandible, where the condyles are in the most superior, posterior, and medial positions.

Question 9

What is centric occlusion?

Answer 9

A tooth-to-tooth relation as the mandible closes in centric relation.

Question 10

Define maximum intercuspation.

Answer 10

The most complete interdigitation of mandibular and maxillary teeth, irrespective of condylar centricity.

Question 11

How does rotation occur in the TMJ?

Answer 11

Mandibular rotation occurs in the lower compartment between the condyle and the articular disc.

Question 12

What is the hinge axis?

Answer 12

An imaginary line connecting the rotational centers of the condyles, around which the mandible rotates for opening and closing movements.

Question 13

Describe translation in the TMJ.

Answer 13

Translation is the movement when all parts of the mandible move at the same time, occurring in the upper TMJ compartment.

Question 14

What is the movement of the condyle during mandibular opening?

Answer 14

The condyle rotates and then translates forward and downward from its centric position.

Question 15

How do condyles move during protrusive movement?

Answer 15

Condyles slide downward and forward, causing disclusion of the posterior teeth.

Question 16

What happens to the posterior teeth during protrusive movement?

Answer 16

The posterior teeth disclude as the mandible moves forward.

Question 17

What is the working side in lateral excursions?

Answer 17

The side to which the mandible moves during chewing, where the rotating condyle moves slightly downward and backward.

Question 18

What is the non-working side in lateral excursions?

Answer 18

The side opposite the working side, where the condyle translates medially, forward, and downward.

Question 19

Define Bennett movement.

Answer 19

The lateral bodily movement of the rotating condyle on the working side and the medial movement of the non-working condyle.

Question 20

What is the Bennett angle?

Answer 20

The angle formed between the midsagittal plane and the medial wall of the glenoid fossa on the non-working side (7-8 degrees).

Question 21

What is the initial side shift?

Answer 21

A medial movement of the non-working condyle during the initial 2 mm of anterior movement.

Question 22

How does progressive side shift occur?

Answer 22

After the initial side shift, there is more anterior movement with reduced medial movement.

Question 23

What is total side shift?

Answer 23

The sum of the initial and progressive side shifts.

Question 24

How do buccal cusps move during working-side lateral excursions?

Answer 24

The buccal cusps move away from their centric position along the buccal and lingual grooves of their opposing teeth.

Question 25

What are working-side interferences?

Answer 25

Contacts between the cusps of upper and lower teeth on the working side during lateral excursions.

Question 26

What is the significance of the articular disc in the TMJ?

Answer 26

It functions as a cushion between the condyle and the fossa, allowing smooth movement and distributing joint pressure.

Question 27

How does the steepness of the condylar path influence occlusion?

Answer 27

A steeper condylar path allows for longer cusps and deeper fossae, preventing protrusive interferences during mandibular movement.