vi. Oral Biology Flashcards
L40: What are the muscles of mastication?
The ‘mandibular muscles’:
- Masseter;
- Temporalis;
- Lateral Pterygoid;
- Medial Pterygoid.
L40: What is the origin, insertion and action of the masseter?
Origin: zygomatic arch
Insertion: lateral surface and angle of the mandible
Action: elevates mandible
L40: How do you examine the masseter?
- Tender in pts who have a clenching habit;
- Place one finger intra-orally and the other on the cheek;
- Is it sore, tender, inflamed?
L40: What is the origin, insertion and action of the temporalis?
Origin: floor of the temporal fossa
Insertion: coronoid process of the anterior border of ramus
Action: Elevates and retracts mandible
L40: How do you examine the temporalis?
- Tender in pts who have a clenching habit;
- Palpate its origin (can’t palpate insertion) by asking the pt to clench together;
- Is it sore, tender, inflamed?
L40: What is the origin, insertion and action of the lateral pterygoid?
Origin: from the lateral surface of the lateral pterygoid plate
Insertion: anterior border of the condyle and intra-articular disc (via two independent heads)
Function: protrudes and laterally deviates the mandible and the inferior head functions with the mandibular depressors during openings
L40: What are the insertions of each belly of the lateral pterygoid?
Inferior belly: head of the condyle;
Superior belly: intra-articular disc.
L40: What are typical symptoms of lateral pterygoid problems?
- Click on opening of mouth;
- Poor opening of mouth;
- Spasm due to exhaustion of muscle (overnight clenching).
L40: How are lateral pterygoid issues usually treated?
- Splint;
- Physiotherapy.
L40: The lateral pterygoid is not accessible to palpate so how is this examined?
- Best examines by recording the response to resisted movement (sideways);
- Palm on top of head and on mandible;
- Ask pt to move jaw sideways.
L40: What is the origin, insertion and action of the medial pterygoid?
Origin: medial surface of the lateral pterygoid plate (deep head), tuberosity of maxilla (superficial head)
Insertion: medial surface of angle of mandible
Action: elevates and assists in protrusion of the mandible
L40: Are you able to palpate/ examine the medial pterygoid?
No - due to its location and it doesn’t respond well to resistive movement tests (trismus)
L40: Following a LA injection, your pt is unable to open their mouth fully on the following day. Which muscle was hit by the LA?
Medial pterygoid
L40: When administering a LA, where should the needle contact and why?
The bone, to ensure the correct position within the pterygomandibular triangle (not the soft tissues)
L40: How many movements does the TMJ involve?
2
L40: What are the 2 movements of the TMJ?
- Rotation (initial opening);
- Translation (wider opening).
L40: What is the initial opening movement?
A hinge movement
L40: What is the secondary movement?
Translation, a sliding movement
for wider opening/ protrusive and retrusive movements
L40: Explain what happens when the mandible protrudes.
- Both condyles leave their fossae;
- Move forward along the articular eminences.
L40: Explain what happens when the mandible retrudes.
- Leave the eminences;
- Both condyles move back to their fossae;
L40: What is Posselt’s envelope?
A representation of maximum mandibular movement (from border movements of three different planes)
L40: What is the range of typical maximum biting force between molars?
200-700N (varies between teeth)
L40: What factors affect maximum biting force?
- Psychological: Fear of tooth fracture;
- Muscle mass: bigger muscles, larger forces;
- Tooth type and position: relative to TMJ, root area (PDL support).
L40: Why are greatest biting forces achieved between molars?
Closest to TMJ and muscles generating the forces, largest occlusal areas too