TEMPOROMANDIBULAR JOINT

Question 1

Ligaments of the TMJ

Answer 1

1. Lateral TMJ (late phase biomechanics)
2. Sphenomandibular
3. Stylomandibular

Question 2

TMJ articular disc regions attachments:

Answer 2

• Posterior
• Intermediate
• Anterior

Question 3

Posterior region of the TMJ articular disc attaches to the following:

Answer 3

• Collagen rich inferior retrodiscal lamina
• Elastin rich superior retrodiscal lamina

Question 4

Anterior region of the TMJ disc attaches to the following:

Answer 4

• Tendon of the superior head of the lateral pterygoid muscle
• Temporal bone anterior to articular eminence

Question 5

Masseter muscle:

Answer 5

• Origin: inferior zygomatic bone and arch
• Insertion: external surface of the mandible between the angle and coronoid process
• Action: bilaterally elevates and protrudes the mandible unilaterally ipsilateral lateral excursion
• Innervation: mandibular nerve, branch of CN V – trigeminal nerve

Question 6

Temporalis muscle

Answer 6

• Origin: temporal fossa
• Insertion: coronoid process and ramus of the mandible
• Action: bilaterally elevates and protrudes the mandible; unilaterally ipsilateral lateral excursion
• Innervation: mandibular nerve, branch of CN V – trigeminal nerve

Question 7

Medial pterygoid:

Answer 7

• Origin: lateral pterygoid plate
• Insertion: internal surface of the mandible between the angle and mandibular foramen (anterior to ramus)
• Action: bilaterally elevates and protrudes the mandible; unilaterally contralateral lateral excursion
• Innervation: mandibular nerve, branch of CN V – trigeminal nerve

Question 8

Lateral pterygoid (superior head):

Answer 8

• Origin: greater wing
• Insertion: medial capsule, TMJ, disc, and pterygoid fossa
• Action: bilaterally eccentrically controls the disc during closing; unilaterally contralateral lateral excursion
• Innervation: mandibular nerve, branch of CN V – trigeminal nerve)

Question 9

Lateral pterygoid (inferior head):

Answer 9

• Origin: lateral pterygoid plate
• Insertion: pterygoid fossa and neck of mandible
• Action: bilaterally DEPRESSES and protrudes the mandible; unilaterally contralateral lateral excursion
• Innervation: mandibular nerve branch of CN V Trigeminal

Question 10

what three muscles close the mouth (elevation of the mandible)

Answer 10

1. Masseter
2. Temporalis
3. Medial pterygoid

Question 11

what two muscles open the mouth (depression of madible)

Answer 11

1. Lateral pterygoid (inf head)
2. Suprahyoid

Question 12

3 lateral excursion muscles

Answer 12

• Medial pterygoid
• Lateral pterygoid (Inf and superior heads)
• All contralateral excursion

Question 13

protrusion muscles

Answer 13

lateral pterygoid (inferior and superior heads)

Question 14

retrusion muscles

Answer 14

temporalis

Question 15

What are the secondary muscles of mastication?

Answer 15

• infrahyoids
• suprahyoids

Question 16

In the adult the mouth can be opened an average of_____ as measured between the incisal edges of the upper and lower front teeth

Answer 16

50 mm

Question 17

Maximal opening of the mouth typically occurs during actions such as…

Answer 17

yawning and singing

Question 18

The interincisal opening is typically large enough to fit ______ adult “knuckles” (proximal interphalangeal joints)

Answer 18

three

Question 19

Functional movement (depression) for eating is about ___ mm or ____ knuckles

Answer 19

18 mm

one knuckle

Question 20

The early phase of depression of the mandible, constituting the first 35% to 50% of the range of motion, involves primarily ______ of the mandible relative to the cranium.

Answer 20

rotation

the condyle rolls posteriorly

Question 21

The late phase of opening the mouth consists of the final 50% to 65% of the total range of motion. This phase is marked by a gradual transition from primary rotation to primary ​

Answer 21

translation.

The transition can be readily appreciated by palpating the condyle of the mandible during the full opening of the mouth.

During the translation the condyle and disc slide together in a forward and inferior direction against the slope of the articular eminence

Question 22

The early phase of elevation of the mandible involves primarily ______ of the mandible relative to the cranium.

Answer 22

translation

in a posterior and superior direction

Question 23

The late phase of closing (elevation) the mouth is marked by a

Answer 23

rotation

condyle roll anteriorly

Question 24

protrusion normal ROM

Answer 24

3 mm

Question 25

Protrusion arthrokinematics

Answer 25

* Condyle and disc **translate** anteriorly without significant rotation * Mandible slides slightly downward during protrusion and upward during retrusion * Extremely important for full opening

Question 26

Pain dominant vs. Stiff dominant

Answer 26

* pain dominant = no mobs * stiff dominant = mobs

Question 27

lateral excursion normal ROM

Answer 27

11 mm each way

Question 28

lateral excursion arthrokinematics

Answer 28

* Side to side translation of the condyle and disc in the fossa * could be a good exam for finding hyper-mobility

Question 29

branches of the trigeminal nerve

Answer 29

* Opthalamic * Maxillary * Mandibular: proprioceptive fibers TMJ

Question 30

there is a crossing between the **trigeminal nerve** and **C1 to C4 cervical nerve roots**

Answer 30

Trigemino-cervical nucleus

Question 31

many patient with TMJ pain have headaches, why?

Answer 31

* Trigemino-cervical nucleus * C1-C4 spinal nerves: Afferent pain fibers from C1-C4 have projections through the spinal nucleus of the trigeminal nerve as it coordinates sensation from the opthalamic, maxillary and mandibular portions * Consequently, suboccipital compression of C1-C4 nerves can present as TMD symptoms in the head and face.

Question 32

what is extremely important for full opening of the mandible?

Answer 32

protrusion

Question 33

Categorizing TMJ Disorders: (all have pain in and around the TMJ, altered mandibular mechanics/motions, +/- joint noises)

Answer 33

* **Osteoarthritis:** crepitus * **Capsulitis/ligaments:** loss of motion all directions * **Internal Derangement:** * Functional dislocation of the disc anteriorly with reduction **(clicks present)** * Functional dislocation without reduction (clicks not present, limitation of motion to rotation, no translation, motion limited to 25mm opening * **Psychological:** * Up-regulation of central nervous system, trigeminal nucleus * Those with TMJ tend to be over-reactive to their environment * Anxiety, depression, anger, fear all tend to increase with chronicity and may contribute to increased pain

Question 34

TMJ disorders differential diagnosis

Answer 34

* Vascular: migraine or cluster headaches * Intra-cranial disorder: weight loss, ataxia, weakness, fever, etc * Neuropathies: trigeminal neuralgia * Ear or sinus disorders

Question 35

resting position of the TMJ

Answer 35

with tongue resting on the palate and mouth slightly open

Question 36

Intraoral lateral pterygoid palpation

Answer 36

upper vestibule

Question 37

intraoral medial pterygoid palapation

Answer 37

bottom lingual aspect of the teeth

Question 38

Internal Derangement Disc Dysfunction: ## Footnote **Stage I**

Answer 38

disc slightly anterior, inconsistent click, mild or no pain

Question 39

Internal Derangement Disc Dysfunction: ## Footnote **Stage II**

Answer 39

* disc anterior reciprocal click * painful

Question 40

Internal Derangement Disc Dysfunction: ## Footnote **Stage III**

Answer 40

reciprocal click, now later during opening and earlier during closing, **most painful stage**

Question 41

Internal Derangement Disc Dysfunction: ## Footnote **Stage IV**

Answer 41

click rare, disc no longer relocates, stays anterior, **pain rare**

Question 42

# TMJ Is there a **C-shaped**^? or an **S-shaped**^? deviation to movement?

Answer 42

* **C-shaped**: hypomobility on side of direction * **S-shaped:** motor control problem