occlusion and restorative dentistry 1

Question 1

define occlusion

Answer 1

how the teeth meet

Question 2

what is the TMJ

Answer 2

The TMJ is the joint between the condylar head of the mandible and the mandibular fossa of the temporal bone
TMJ is a synovial, condylar and hinge-type joint

Question 3

what are the different parts of the TMJ

Answer 3

• Cranial base
• Mandible
• Muscles of mastication
• Innervation
• Vascular supply
• Articular disc

Question 4

what are the superior and inferior articular cavities lined by

Answer 4

The superior and inferior articular cavities are lined by separate superior and inferior synovial membranes

Question 5

what is the capsule

Answer 5

The capsule is a fibrous membrane that surrounds the joint and attaches to the articular eminence, the articular disc and the neck of the mandibular condyle

Question 6

what is the articular disc

Answer 6

The articular disc is a fibrous extension of the capsule that runs between the two articular surfaces of the TMJ

Question 7

what does the articular disc articulate with

Answer 7

The disc articulates with the mandibular fossa of the temporal bone above and the condyle of the mandible below

Question 8

how is the disc attached to the condyle

Answer 8

The disc is also attached to the condyle medially and laterally by the collateral ligaments

Question 9

what does the anterior disc attach to

Answer 9

The anterior disc attaches to the joint capsule and the superior head of the lateral pterygoid muscle

Question 10

what does the posterior disc attach to

Answer 10

The posterior portion attaches to the mandibular fossa and is referred to as retro-discal tissue

Question 11

what is the retro-discal tissue like

Answer 11

Unlike the disc itself the retro-discal tissue is vascular and highly innervated and is a major contributor in the pain of TMD

Question 12

what muscle groups are involved in the mandibular movement

Answer 12

• Muscles of Mastication

• Suprahyoid Muscles
	○ Elevate the hyoid bone or depress the mandible
	○ Suprahyoids are the:
		§ Digastric
		§ Geniohyoid 
			□ These 2 depress the mandible and elevates the hyoid
		§ Stylohyoid 
			□ Initiates swallowing by pulling the hyoid bone posterior superior
		§ Mylohyoid muscles  Elevates the hyoid bone and the floor of the mouth

Question 13

what mandibular movement does the muscles of mastication cause

Answer 13

Involved in depression, elevation and lateral movements of the mandible

Question 14

what are the suprahyoid muscles

Answer 14

§ Digastric
§ Geniohyoid 
	□ These 2 depress the mandible and elevates the hyoid
§ Stylohyoid 
§ Mylohyoid muscles

Question 15

how does the stylohyoid muscle iniates swallowing

Answer 15

Initiates swallowing by pulling the hyoid bone posterior superior

Question 16

what does the mylohyoid muscle do

Answer 16

Elevates the hyoid bone and the floor of the mouth

Question 17

what mandibular movement does the suprahyoid muscles cause

Answer 17

Elevate the hyoid bone or depress the mandible

Question 18

what is the function of the temporalis

Answer 18

Elevates and retracts the mandible
Assists in rotation

Elevates the mandible closing the mouth and also retracts the mandible pulling the jaw posteriorly

Question 19

where is the temporalis muscle found

Answer 19

Originates from the temporal fossa and condenses into a tendon which inserts onto the coronoid process of the mandible

Question 20

what are the functions of the lateral pterygoid muscle

Answer 20

Positions disc in closing (superior - SLP)
Protrudes and depresses mandible and causes lateral movement (inferior - ILP)

Unilateral action produces a side to side or lateral movement of the jaw

Question 21

where does the superior head originate from

Answer 21

Superior head originates from the greater wing of the sphenoid

Question 22

where does the inferior head originate from

Answer 22

Inferior head originates from the lateral pterygoid plate of the sphenoid

Question 23

where do the 2 heads of the lateral pterygoid muscle converge

Answer 23

The 2 heads converge into a tendon which attaches at the neck of the mandible

Question 24

what are the functions of the medial pterygoid muscle

Answer 24

Elevates the mandible

Lateral movement and protrusion

Question 25

where does the superficial head of the medial pterygoid muscle originate from

Answer 25

The superficial head originates from the maxillary tuberosity and the pyramidal process of the palatine bone

Question 26

where does the deep head of the medial pterygoid muscle originate from

Answer 26

The deep head originates from the medial aspect of the lateral pterygoid plate of the sphenoid bone

Question 27

where do the heads of the medial pterygoid muscle attach to

Answer 27

Both heads attach to the ramus of the mandible near the angle of the mandible

Question 28

what are the functions of the masseter muscle

Answer 28

Elevates and protracts the mandible | Assists in lateral movement

Question 29

where do the superficial and deep parts of the masseter muscle originate from

Answer 29

Superficial part originates from the maxillary process of the zygomatic bone The deep part originates from the zygomatic arch of the temporal bone

Question 30

what does the masseter muscle attach to

Answer 30

Both parts attach to the ramus of the mandible

Question 31

what are the 2 major types of mandibular movement in terms of occlusion

Answer 31

- rotation | - translocation (lateral translation)

Question 32

what is rotation movement

Answer 32

* Small amount of mouth opening (up to 20mm) * Condyle and disc remains within the articular fossa * No downwards or forwards movement * Also known as "hinge movement"

Question 33

what is the rest position of the TMJ

Answer 33

The resting position of the TMJ is with the mouth slightly open, lips together and the teeth not in contact ○ Resting vertical dimension ○ The space between the teeth is the free-way space

Question 34

what can be measured when the patients clench their teeth in a closed-pack position ie teeth are closely clenched

Answer 34

Occlusal vertical dimension

Question 35

what happens when the mouth is opened just a small amount (20mm)

Answer 35

When the mouth is opened just a small amount (20mm) the condyle hinges within the articular fossa There is no downwards or forwards movement ~ no protrusion

Question 36

what are hinge movements

Answer 36

Rotation of the condylar heads around an imaginary horizontal line through the rotational centres of the condyles The imaginary line is termed the terminal hinge axis

Question 37

what does a facebow record

Answer 37

Terminal hinge axis | Distance between the condyles

Question 38

what is a facebow

Answer 38

It allows a maxillary cast to be placed in an equivalent relationship on the articulator

Question 39

what does using a facebow allow for

Answer 39

a facebow is a caliper like instrument that records the relationship of the maxilla to the terminal hinge axis of rotation of the mandible

Question 40

what is translation

Answer 40

* Lateral pterygoid contracts * Articular disc and condyle begin to move * Travels downwards and forwards along the incline of the articular eminence * May also travel laterally (laterotrusive movement)

Question 41

what does posselts envelope show

Answer 41

Extremes of mandibular movement | Border movements of the mandible in the Sagittal Plane

Question 42

what are the different points on posselts envelope

Answer 42

``` ICP = Intercuspal Position E = Edge to Edge Pr = Protrusion T = maximum opening R = Retruded Axis Position RCP = Retruded Contact Position ```

Question 43

what is ICP

Answer 43

Intercuspal Postion (ICP) • Tooth position regardless of the condylar position • The comfortable bite • Best fit of teeth = maximum interdigitation of the teeth

Question 44

what else can ICP be called

Answer 44

• Can be called centric occlusion (CO)

Question 45

what is edge to edge

Answer 45

* Tooth position * Teeth slide forward from ICP guiding on palatal surfaces of anterior teeth * Incisal edges of upper and lower incisors touch

Question 46

what is protrusion

Answer 46

* Condylar moves forwards and downwards on articular eminence * Only incisors + / - canines touch * No posterior tooth contacts * Eventually no tooth contacts

Question 47

what is maximum opening

Answer 47

* No tooth contacts * Mouth wide open * Full translation of the condyle over the articular eminence

Question 48

what is the retruded axis position

Answer 48

* No tooth contacts * Most superior anterior position of the condylar head in the fossa * Terminal hinge axis

Question 49

what is the retruded contact position

Answer 49

* First tooth contact when the mandible is in retruded axis position * ICP is approximately 1mm anterior to RCP in 90% of the population

Question 50

what is the relation of the ICP to the RCP

Answer 50

ICP is approximately 1mm anterior to RCP in 90% of the population RCP and ICP not coincident so the mandible slides forward to achieve ICP

Question 51

what is lateral translation

Answer 51

When the lateral pterygoid muscle on one side contracts the mandible moves to the opposite side The bony wall of the glenoid fossa stops the working side condyle moving any further to the right the side the mandible moves towards is the working side the side the mandible is moving away from is the non-working side eg When the mandible is moving to the right, the left condyle moves forward and inward Whilst the condyle on the right will shift slightly in a lateroposterior direction (or rotate on a vertical axis)

Question 52

what is lateral translation of the mandible known as

Answer 52

This slight lateral translation of the mandible is known as the Bennet movement (bodily shift of the mandible at the working side)

Question 53

what is the bennet angle

Answer 53

The path of the non-working condyle in the horizontal plane during lateral excursion The Bennet angle is the angle formed by the Sagittal plane and the path of the mandibular condyle during lateral movement when viewed in a horizontal plane

Question 54

what is the frontal plane

Answer 54

• ICP is maximum intercuspation • PP is the physiological rest position with no tooth contacts • Divets are a result of canine guidance ○ When the mandible is moving laterally the long strong canines of the upper and lower jaw ensure that the posterior teeth do not touch when the mandible is sliding to the side ○ This protects them from lateral forces and gives rise to the term a mutually protected occlusion