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operative dentistry > occlusion > Flashcards

occlusion Flashcards

1
Q

What movement of the jaw does each muscle of mastication do

A

Temporalis (T)
-Elevates and retracts the mandible
-Assists in rotation

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

Medial Pterygoid (MP)
-Elevates the mandible
-Lateral movement and protrusion

Masseter (SMA)
-Elevates and protracts the mandible
-Assists in lateral movement

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2
Q

what are the mandibular movements

A

Rotation

Translation

Lateral translation

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3
Q

Describe what the mouth is like in the resting position of the TMJ

A

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

The mouth is slightly open, up to 20mm

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4
Q

What happens with TMJ when it moves to resting position

A

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)

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5
Q

What is the terminal hinge axis

A

The imaginary horizontal axis connecting the condyles around which the. mandible performs pure rotation

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6
Q

What happens during hinge movements of the TMJ

A

Rotation of the condylar heads around an imaginary horizontal line through the rotational centers of the condyles

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7
Q

What does the facebow record

A

the relationship of the the maxilla to the terminal hinge axis of rotation of the mandible

Distance between the condyles

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

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8
Q

What heppens during translation movement of the mandible

A

Lateral pterygoid contracts

Articular disc and condyle begin to move

Travels downwards and forwards along the incline of the articular eminence, In this position a thin portion of the disc maintains the position betewen the articulating surface of the mandibular condyle and the articular eminence

May also travel laterally (laterotrusive movement)

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9
Q

What happens during the rotation movement of the mandible

A

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”

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10
Q

What is posselts envolpe

A

Describes the Extremes of mandibular movement

Border movements of the mandible in the Sagittal Plane

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11
Q

What does:

ICP
E
Pr
T
R
RCP

stand for

A

ICP = Intercuspal position

E = Edge to Edge

Pr = Protrusion

T = Maximum opening

R = Retruded Axis Position

RCP = Retruded contact position

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12
Q

What is happening in the ICP position

A

Tooth position regardless of the condylar position

The comfortable bite

Best fit of the teeth

Maximum interdigitation of the teeth

Can be called centric occlusion (CO)

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13
Q

What is happening during the E position

A

Tooth position sliding forward from the ICP

Teeth slide forward from ICP guiding on palatal surfaces of anterior teeth

Incisal edges of upper and lower incisors touch

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14
Q

What is happening during the Pr position

A

Condyle moves forwards and downwards on articular eminence

Only incisors +/- canines touch

No posterior tooth contacts

Eventually no tooth contacts

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15
Q

What is happening during the T position

A

No tooth contacts

Mouth wide open

Full translation of the condyle over the articular eminence

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16
Q

What is happening during
the R position

A

No tooth contacts

Most superior anterior position of the condylar head in the fossa

where the Terminal hinge axis is

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17
Q

What is happening during the RCP position

A

First tooth contact when the mandible is in retruded axis position

ICP is approximately 1mm anterior to RCP in 90% of the population

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18
Q

What is the returded arc of closure and where does it lie on posselts envelope

A

Retruded arc of closure is the arc of opening and closing made by the mandible whilst the condyles are rotating about the terminal hinge axis

Between R and RCP

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19
Q

What is the difference between RCP and ICP and how does the mandible move to the positions

A

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

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20
Q

What is lateral translation and what is it also known as

A

Movement resulting from contraction from one of the lateral pterygoids

Bennet movement

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21
Q

What is the bennet angle and what is it formed from

A

The path of the nonworking condyle in the horizontal plane during lateral excursion

formed by the sagittal plane and the path of the mandibular condyle during lateral movement when viewed in a horizontal plane

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22
Q

In the frontal view of posselts envelope what are the divets caused by

A

Divets are a result of canine guidance

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23
Q

What is meant by a mutually protected occlusion

A

when the mandible is moving laterally the long strong canines of the upper and lower jaw ensure that that the posterior teeth do not touch when the mandible is sliding to the side. This protects them from lateral forces

24
Q

When examining the occlusion wha are the 2 types

A

Dynamic

Static

25
Q

What equipment is good for checking occlusion

A

Millers forceps and articulating paper

26
Q

When do you mark tooth contacts

A

Before
Preparing a tooth
Removing a restoration

After
Placement of a crown
Placement of a restoration

27
Q

What is classified under static occlusion

A

Incisor Relationship

Molar relationship

Overjet/Overbite

Cross bites

Open bites

Individual tooth contacts
RCP – ICP slide (freedom in centric)

28
Q

In ICP contact what is meant by functional and non functional cusps

A

Functional Cusps

-Cusps that occlude with the opposing teeth in the intercuspal position
The lingual cusps of the upper posterior teeth and the buccal cusps of the lower posterior teeth

Non Functional Cusps

-Cusps that do not occlude with the opposing teeth in the intercuspal position
The buccal cusps of the upper posterior teeth and the lingual cusps of the lower posterior teeth

29
Q

What are the functional and non-functional casps on the mandible

A

The buccal cusps are the functional cusps with the non-functional cusps being on the lingual side

30
Q

What are the functional and non-functional casps on the axilla

A

The palatal cusps are the functional cusps on the madnible with hte buccal cusps being the non-functional

31
Q

What is the fossa on teeth and what happens during ICP

A

Depression or concavity on tooth surface

Functional cusp of a tooth contacts the fossa of the opposing tooth during ICP

32
Q

What are the ICP contacts

A

The palatal cusp of an upper molar contacts the fossa of a lower molar

The buccal cusp of a lower molar contacts the fossa of an upper molar

33
Q

What problems can arrise in static occlusion

A

Incisor relationship (Angles classification)

Overbite (The vertical overlap of the incisors)

Overjet (Relationship between the upper and lower teeth in a horizontal plane)

Crossbite (a condition where one or more teeth may be abnormally malpositioned buccal or lingually or labially with reference to opposing teeth)

Open bite (Anterior Open Bite,Lack of vertical overlap of anterior teeth when posterior teeth in full occlusion
Posterior/Lateral Open Bite
Failure of contact between the posterior teeth when the teeth are in full occlusion)

34
Q

What is dynamic occlusion

A

the contacts between the teeth when the mandible is moving

35
Q

What is canine guidance

A

When a mandible moves laterally to the working side there should only be contact between the canines

36
Q

What is meant by group function

A

When multiple teeth are in contact during lateral movement of mandible

Bilateral group function seen in toothwear

37
Q

What happens during protusion movement

A

Condyle moves forwards and downwards on articular eminence

Only incisors +/- canines touch

No posterior tooth contacts

38
Q

What is meant by occlusal interference

A

Undesirable tooth contacts that may produce mandibular deviation during closure to ICP or may hinder smooth passage to and from ICP (Schillingberg 1997)

39
Q

What types of occlusal interference is there

A

Working side

Non-worling side

protrusive

40
Q

What is working side interference

A

Occurs when there is underdesireable contact between the maxillary and mandibular posterior teeth on the same side of the arches as the direction in which the mandible has moved

If that contact is heavy enough to disocclude anterior teeth, it is interference

41
Q

What is non-working side interference

A

Occurs when there is undersireable occlusal contact between maxillary and mandibular teeth on
the side of the arches opposite the direction in which the mandible has moved in a lateral way

42
Q

What is protrusion interference

A

any posterior contact during protrusion

43
Q

Why would you want to avoid posterior contacts

A

Teeth are designed to absorb heavy forces in the direction of the long axis of the tooth

Most teeth are not designed to absorb significant lateral forces generated by occlusal interferences

Musculature gets a rest as less activity if not undesirable posterior contacts so muscles wont get any rest in occlusal interference

Occlusal trauma and undesirable tooth movement

44
Q

What are the 2 types of bruxism

A

Eccentric
The parafunctional grinding of teeth
An oral habit consisting of involuntary rhythmic or spasmodic or functional gnashing, grinding or clenching of teeth in other than chewing movements of the mandible which may lead to occlusal trauma

Centric
Clenching: The pressing and clamping of the jaws and teeth together. Frequently associated with acute nervous tension or physical effort

45
Q

What are the clinical signs of bruxism

A

Toothwear

Fractured restorations

Tooth migration

Tooth mobility (Often in absence of periodontal disease)

Muscle pain and fatigue

Headache

Earache

Pain and stiffness in the TMJ and surrounding muscles

46
Q

On a articulation cast what angles are the bennet angle and Condylar Guidance Angle set at

A

Bennet Angle set at 15

Condylar Guidance Angle set at 30

47
Q

When recording a face bow registration:

What would you do first and where

A

Mark the Anterior Reference Point

-on the patient’s right side using the Reference Plane Locator and Marker

It is the approximate position of the infraorbital foramen

48
Q

When recording a face bow registration:

What do you do with the bite fork

A

Apply bite registaryion paste but not too thickly

with bite fork arm to the right and locating notch facing up, make sure notch is at the midline

Then Firmly seat to record cusp tips of maxillary teeth and check that it is parallel with the patients’ coronal and horizontal planes

49
Q

After taking the facebow off a patient what have you recorded and what is next

A

The relationship of the maxilla to the hinge axis of rotation of the mandible

We can now mount the maxillary cast in an equivalent relationship on the articulator

50
Q

How do you mount a facebow onto a lower cast

A

An interocclusal registration can be used to mount the mandibular cast in relation to maxillary cast already mounted on the articulator using the facebow transfer

51
Q

When mounting face bow onto lower cast what are the two choices of interocclusal registration you can use

A
  1. Intercuspal Position (ICP)
    -Conformative Approach

2.Retruded Contact Position (RCP)
-Reorganised Approach

52
Q

When mounted on the cast for interocclusal registration what are the various ways to get into ICP position and why

A

No material
-Plenty of tooth contacts. ICP is obvious to technician

Wax
-ICP is not obvious to technician (make sure to not use too much should only be a thin bit with cusp tips visible, dont want increased OVD)

Paste
-ICP is not obvious to technician (make sure to not use too much should only be a thin bit with cusp tips visible, ont want increased OVD)

Record block
-Free end saddles. Casts cannot be hand articulated

53
Q

When would it be considered an unorganised approach of interocclusal registration

A

You haven’t assessed the occlusion before starting restoration(s)

You change the occlusion with your restoration(s)

You haven’t planned where your ICP will be and what the related jaw relationship is

You provide an occlusion which does not conform to the previously well tolerated one

54
Q

What is meant by conformative appraoch when doing interocclusal registration

A

the provision of restorations in harmony with the existing jaw relationships

This means that the occlusion of the new restoration is provided in such a way that the occlusal contacts of the other teeth remain unaltered

55
Q

When do you not use the conformative approach when doing interocclusal registration

A

An increase in vertical height is needed to make space for restorations

Tooth/teeth significantly out of position (ie overerupted, tilted or rotated)

A significant change in appearance is wanted
There is a history of occlusally related failure or fracture of existing restorations

56
Q

Why use reorganised approach when doing interocclusal registration

A

ICP is non-existent or no use

You need space to place restorations

RAP is a reproducible position of the mandible independent of the teeth

operative dentistry (5 decks)

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