intro: muscles of mastication Flashcards
What is occlusion?
The contact of the opposing surfaces of teeth of the two jaws.
What is the role of TMJ in prosthodontics?
It relates to the movement of the condyles and the positioning of artificial teeth and occlusal morphology.
Name the main anatomical parts of the TMJ.
Condyle, Glenoid Fossa, and Articular Disc.
Why is the TMJ considered a compound joint?
It is composed of three or more bones, and the articular disc functions as a bone.
What type of articulation occurs in the TMJ?
Ginglymoarthrodial articulation, capable of ginglymoid (rotation) and diarthroidal (translation) actions.
What are the muscles of mastication?
Masseter, Temporalis, Lateral Pterygoid, and Medial Pterygoid.
What are the associated ligaments of the TMJ?
Temporomandibular, Sphenomandibular, and Stylomandibular ligaments.
Define centric relation.
A bone-to-bone relation between the maxilla and mandible, where the condyles are in the most superior, posterior, and medial positions.
What is centric occlusion?
A tooth-to-tooth relation as the mandible closes in centric relation.
Define maximum intercuspation.
The most complete interdigitation of mandibular and maxillary teeth, irrespective of condylar centricity.
How does rotation occur in the TMJ?
Mandibular rotation occurs in the lower compartment between the condyle and the articular disc.
What is the hinge axis?
An imaginary line connecting the rotational centers of the condyles, around which the mandible rotates for opening and closing movements.
Describe translation in the TMJ.
Translation is the movement when all parts of the mandible move at the same time, occurring in the upper TMJ compartment.
What is the movement of the condyle during mandibular opening?
The condyle rotates and then translates forward and downward from its centric position.
How do condyles move during protrusive movement?
Condyles slide downward and forward, causing disclusion of the posterior teeth.
What happens to the posterior teeth during protrusive movement?
The posterior teeth disclude as the mandible moves forward.
What is the working side in lateral excursions?
The side to which the mandible moves during chewing, where the rotating condyle moves slightly downward and backward.
What is the non-working side in lateral excursions?
The side opposite the working side, where the condyle translates medially, forward, and downward.
Define Bennett movement.
The lateral bodily movement of the rotating condyle on the working side and the medial movement of the non-working condyle.
What is the Bennett angle?
The angle formed between the midsagittal plane and the medial wall of the glenoid fossa on the non-working side (7-8 degrees).
What is the initial side shift?
A medial movement of the non-working condyle during the initial 2 mm of anterior movement.
How does progressive side shift occur?
After the initial side shift, there is more anterior movement with reduced medial movement.
What is total side shift?
The sum of the initial and progressive side shifts.
How do buccal cusps move during working-side lateral excursions?
The buccal cusps move away from their centric position along the buccal and lingual grooves of their opposing teeth.
What are working-side interferences?
Contacts between the cusps of upper and lower teeth on the working side during lateral excursions.
What is the significance of the articular disc in the TMJ?
It functions as a cushion between the condyle and the fossa, allowing smooth movement and distributing joint pressure.
How does the steepness of the condylar path influence occlusion?
A steeper condylar path allows for longer cusps and deeper fossae, preventing protrusive interferences during mandibular movement.
