Occlusion Flashcards
1
Q
Parafunctional movement that results in excessive tooth grinding and jaw clenching outside of masticatory function is known as what?
A
Bruxism
2
Q
What is the Bennett Angle?
A
The angle created in the sagittal plane of the non-working condyle during lateral movement. General values is 15 degrees
3
Q
What would be the clinical signs of an Angle’s Class II Div II?
A
Maxillary anterior teeth are retroclined and a deep overbite exists
4
Q
What would be the clinical signs of an Angle’s Class II Div I?
A
Maxillary anterior teeth are proclined and a large overjet
is present.
5
Q
What is condylar guidance?
A
The horizontal path followed by the condyle when it is travelling the glenoid fossa during mandibular opening
6
Q
Where are dentally relevant proprioceptors found?
A
PDL
Muscles of mastication
TMJ
7
Q
What is cuspid protected occlusion?
A
If biting in max intercuspation, the teeth are guided laterally/protrusive from canines, provides disocclusion posteriorly
8
Q
Is wear Pathological?
A
Not really since everyone has it
9
Q
Should you do an Occlusal Equilibration?
A
No, it’s against MI to grind down cups to “ideal occlusion”
10
Q
When is OVD first established?
A
During eruption of primary dentition
11
Q
What is the role of diastemas in mixed dentition?
A
Space Maintenance: to make space for permanent arch to develop
12
Q
What changes during very gradual tooth wear through life course?
A
Increased OVD via continual eruption
13
Q
What happens during very rapid tooth wear?
A
Overruption can not compensate at same rate, so a decrease of OVD
14
Q
What adaptive features occur with reduced cusp height in tooth wear
A
Alteration in mastication patterns
Remodelling of TMJ
15
Q
Early eruption of secondary dentition can result in what sort of problems?
A
Likelihood to erupt forward, creating crowding and rotation
16
Q
When does group function take place?
A
When canine guidance is gradually removed through wear of the canines, the 1st/2nd pre-molars come into lateral excursion
17
Q
How does interproximal tooth wear occur?
A
Due to high occlusal load
18
Q
What is the main limitations of a plane line articulator?
A
Simple hinge device that takes the average geometry that may not be suitable particularly for ethnic variation.
Also can’t take into account lateral movement
19
Q
What does the facebow record?
A
Relationship of Maxillary Arch to the TMJ and Cranial Base
20
Q
What is the importance of taking the bite record using a semi-adjustible articulator?
A
Gives the relationship between the Mx + Mn in maximum interdigitation.
The Mandibular arch can then be poured and placed against the bite record
21
Q
What are 4 possible errors that can happen when taking a facebow record?
A
- Not getting an even reading of the condyles
- Bitefork can move after patient bites down
- Facebow readings are bumped after reading - hang the facebow up
- Weight of model against bitefork moves the reading
22
Q
The combined readings of the facebow and bitefork give you what?
A
The angle of the maxillary arch in relation to the superior aspect of the maxilla itself (cranial base)
23
Q
Why don’t we use fully adjustable articulators?
A
They are complicated AF
24
Q
What does a protrusive (incisal edge-to-edge) bite record tell you?
A
- The angle of the articular eminence
- Condyle has moved down the eminence
- Posterior Teeth have discluded: this is important in designing an appliance that can fit
25
Doing a canine-to-canine bite (lateral) record will give you what?
The bennett angle
26
When planning to build a partial denture for a partially edentulous patient what sort of record needs to be take?
Centric Relation record as it is not longer corresponding Centric Occlusion
27
What are 7 indications for a nightguard?
1. Protection from Attrition
2. Protection from Cusp Fracture (particularly from Amalgams, Ceramic crowns)
3. Protection from Enamel Flaking
4. Protection for new restorative Work (from Bruxer)
5. Protection against sports trauma
6. Relief of Pain from TMD
7. For remineralisation products (eg Tooth Mousse)
28
What is the purpose of pouring a duplicate cast when making a nightguard?
For the dentist and lab technician to be able to check the final product as the survey cast would have been modified to accommodate undercuts
29
What are the 2 types of coverage that are possible with a nightguard?
Full Occlusal Coverage
| Anterior Coverage
30
What are the 3 textures possible with a nightguard?
Hard
Soft
Bilaminar
31
When constructing a nightguard, what 2 situations need to be tested to ensure bilateral disclusion?
1. Protrusive incisal-to-incisal bite
| 2. Maximum lateral mandibular movement
32
What is a ramp design for a nightguard?
Anterior portion of occlusion is higher, so that in eccentric occlusion there is disclusion in the posteriors
33
What is a flat design for a nightguard?
All teeth are in contact at the same time
34
Why might wearing a nightguard with just anterior coverage in the long term be a bad idea?
1. High loading on anteriors
2. Potential for orthodontic intrusion
3. Posterior eruption
35
Not taking a bite record when during the first appointment for a nightguard will result in what during the second appointment?
The dentist spending a lot of time adjusting the nightguard with an acrylic bur because it doesn't fit and is correctly in occlusion
36
What 3 things need to be checked on the 2nd mouthguard appointment
Place in the mouth and check:
1. Fit
2. Thickness
3. Occlusion - Centric and Posterior Disclusion
37
What is interference on a mouthguard?
When there is contact on the posteriors when the mouthguard is fitted on the following scenarios:
1. Contact on non-working side during canine guidance (lateral movement)
2. Contact during protrusive guidance
38
How do you take a secondary impression?
1. Take a primary impression
2. Pour a cast
3. Then construct a special tray that fits around the cast
4. Take a secondary impression using the special tray
Result is more accurate as the special tray minimises alginate distortion
39
How is the thickness of the nightguard determined on a plane-line articulator?
Wax thickness determines nightguard thickness
40
How is the thickness of the nightguard determined on a semi-adjustable articulator?
The dentist determines the thickness by adjust the incisal pin
41
If you were to design a masticatory system, what 6 features would be ideal? (EXAM ALERT)
1. High Speed Movement
2. Minimal Friction
3. Congruency (matching shapes of fossa + condyle for function)
4. Stability in Centric Occlusion
5. Minimal Loading
6. Pressure Compensation
42
T/F: The movement path on mouth opening is sagittal in nature?
False
43
At the end of rotation, where is the posterior thick zone located in relation to the condyle?
12 O Clock
44
At the end of rotation, where is the anterior thick zone located in relation to the condyle?
9 O Clock
45
What is the role of the Temporomandibular Ligament (TML) in mastication?
These discal ligaments provide posterior restraint to prevent the disc from slipping backwards
46
What is the role of the retrodiscal tissue in mastication?
Prevents the “piston” suction effect to allow for highly efficient motion and return on closing
47
T/F: The Articular disc capsule is vascular in nature
False, it is reliant on synovial fluid for nutrition
48
T/F: The Articular disc is made up of fibrocartilage
False, unlike other joints it is made up of fibrous tissue
49
What are the main muscles used to enter into centric occlusion?
Masseter
| Temporalis
50
T/F: The Superior Lateral Pterygoid Muscle is activated to stabilise during jaw closing
True: the superior head exerts forward traction on articular disk during closure, thus impedes return on disc to normal position. This helps to stabilise jaw closing
51
T/F: The Superior Lateral Pterygoid Muscle is deactivated on jaw opening
True
52
Describe the motion of the articular disc during translation
Articular Disc simultaneously
1) Rolls backwards onto the head of the condyle
2) Moves anteriorly along the articular eminence
53
T/F Discal ligaments are a common source of TMD pathology
False, it is one of the last tissues to degenerate. Most likely sources will be holes + fibrosis of the articular disc
54
Which direction does the condyle bend on clenching and which muscles assists to provide this motion?
Masseter pushes out laterally which bends the condyle laterally as well
55
T/F: The aetiology of TMD is the condyle pushing into auriculotemporal nerve causing pain
False, this was Costen's theory in the 1930s but is now disproven
56
T/F: The majority of patients complaining of head / neck pain will be primarily muscular and skeletal in nature?
False, the majority will have transmission problems of peripheral nerves > spinal nerves but referring into the head/neck
57
What are the 7 main symptoms of TMD?
```
Jaw and face pain
Temporal headaches
Referred Ear Symptoms
Limited Opening
TMJ Clicking
Crepitus
Locking
```
58
Why is there a larger percentage of women who experience TMD?
Transmission of pain is heavily mediated by estrogen. Epidemiology of TMD is equal between sexes before 12, but higher in women after puberty
59
T/F: Trigeminal Neuralgia is a form of TMD
False - TMD only pertains to musculoskeletal disorders of the masticatory system
60
T/F: The Articular Eminence is present at birth?
False, it develops during adolescence
61
T/F: The maximum opening of the mouth in a child is the same as an adult
True, without the articular eminence, there is less restriction on range of motion, so the max opening will be similar (4.5cm) despite the jaw being smaller
62
Developmentally, when does the superior head of the Lateral Pterygoid muscle connect to the condyle
At adulthood
63
What key developmental features have occurred with the TMJ at adulthood?
1) Developed Articular Eminence
2) Disc has moved forward
3) Development of retrodiscal tissue
4) Superior head of the Lateral Pterygoid muscle becomes a muscle connected to the condyle
64
Embryologically at Week 9, there is condensed fibrous tissue that appears adjacent to the condyle. What does this become?
The Articular Disc
65
What is the role of Meckel's cartilage?
It is an embryological blueprint for the development of jaw and musculature
66
T/F: At birth, there is no articular eminence
True. The articular eminence develops in adolescence and its absence allows for same 4.5cm max opening in children as in adults.
67
T/F: The Retrodiscal tissue exists at birth
False
68
What allows for remodelling and repair in the condyle
The Proliferative layer of mesenchymal cells. This typically exists to allow regeneration until around 50 years of age
69
What is the main role of the deep head of masseter?
Primary works as a stabiliser muscle to prevent excessive protrusion and keep the jaw in place during physical activity
70
T/F: The Masseter is involved in gross brute force that is easily fatigued
True
71
When will the digastric muscle aid in depressing the mandible?
When the hyoid bone is held in place by the infrahyoid muscles
72
What reflexes are the digastric muscle involved with?
Unloading reflex: when hard food in occlusion breaks
Guarding reflex: Digastric is activated at 10% even when individual is subconsciously aware that the food type is not stable even before hard closing (situational awareness)
73
T/F: Most people are bilateral chewers
False
74
T/F: The movement arc of the non-working condyle is longer than the working side
True
75
T/F: The movement of the non-working side will on closing will finish in a more retruded position
False
76
What occurs when the teeth comes into contact during mastication
Trigger for swallow reflex
77
T/F: During the opening phase both depressors and elevator muscles are both partially engaged
True
78
Why does the movement of the condyle on the working side not completely linear with the articular eminence?
To accommodate the size of the food bolus on the working side
79
What sort of click would be indicative of a Eminence Click?
Unilateral click on wide opening
80
What sort of click would be indicative of Deviation in Form?
Click that occurs during the middle 1/3 of both opening and closing
81
What sort of click would be indicative of Anterior Disc Displacement
Click occuring twice during motion
1. Anywhere on opening: depends when the disc jumps back onto contact with condyle
2. Click occurs again in intercuspal at end of close - when the condyle falls off the disc
82
T/F: Diurnal Parafunction is always caused by stress
False
Clenching can occur for reasons other than stress
1) Exercise
2) Deep Concentration
3) Relaxing
4) Conditioned actions
83
What are the 3 main categories of TMD Parafunction?
1) Day/Night Function
2) Non Functional activities - finger nail biting, thumbsucking
3) Masticatory Muscle Activity
84
What sort of myogenous dysfunction symptoms would be evident for nocturnal bruxing?
Sore masticatory muscles on waking
85
What sort of myogenous dysfunction symptoms would be evident for diurnal bruxing?
Sore masticatory muscles in the afternoon
86
What are the 2 main forms of Arthrogenous Dysfunction in TMD?
1) Inflammation (Synovitis/Capsulitis)
| 2) Abnormal loading resulting in deviation in form (Thinning of condyle and perforation of articular disc)
87
What are 3 reasons disc displacement occur?
1. Natural Anatomical Variation: Loose TML, slope of eminence
2. Macro/Microtrauma
3. Increased friction
88
T/F Disc Displacement with reduction will result in limited mouth opening
False, With reduction is when the condyle can regain contact over the articular disc which has been displaced anteriorly.
89
T/F: Clicking occurs during Disc Displacement with reduction
True, the click occurs when the condyle and articular disc come back into contact
90
What are the 3 types of muscle in the body?
Cardiac
Smooth
Skeletal
91
What is isotonic muscle contraction?
When tension is applied via force/weight and the muscle changes in length, resulting in joint movement
92
What is isometric muscle contraction?
When tension is applied but the muscle does not change in length
93
T/F: During mastication both isometric and isotonic movements are applied
True
- Isotonic occur when teeth are in contact
- Isometric results in jaw opening/closing
94
What is Tetanic Contraction?
Sustained muscle contraction when motor nerve that innervates muscles emits action potentials at a high rate. This is results in a muscle twitch.
95
What is muscle fatigue?
Fatigue: the decrease in tetanic force under specified rates of stimulation.
When muscle movement is applied repeatedly, the ability for that muscle to repeatedly work at the same rate decreases and plateaus
96
What happens to muscle fibres when an action potential is generated?
1. Neuromuscular Junction is the synapse between motor axon and muscle fibres
2. Action Potential travelling down the motor axon results in vesicles of acetylcholine (Ach) to be released from the presynaptic endings of the motor axon
3. Ach diffuses across the synaptic clefts to receptors located on the membrane of the muscle fibres
4. Stimulation of receptors by Ach increases permeability of Sodium ions
5. Creates a Depolarisation of muscle cell membrane and Action Potential is initiated in the muscle fibre
6. Action Potential releases calcium in the sarcoplasmic reticulum, allowing the formation of the cross bridge between the actin + myosin fibres via the exposure of the troponin filaments and muscle contraction occurs. ATP is required to “recock” the cross-bridge in anticipation of the new contraction stroke
97
What are the origin + insertion of the deep fibres of the temporalis?
Origin: Medial Wall of Temporal Fossa / Superior Temporal Line
Insertion: Coronoid Process
98
What are the origin + insertion of the superficial fibres of the temporalis?
Origin: Temporal Fascia
Insertion: Coronoid Notch as the Tendon of Temporalis
99
What is the action of the temporalis?
Elevates
Retrudes
Aids in lateral
100
What provides motor innervation to the Temporalis muscle?
Trigeminal >
Mandibular >
Anterior + Posterior Deep Temporal Branches
101
What are the origin + insertion of the deep head of the medial pterygoid?
Origin: Medial Surface of the lateral pterygoid plate
Insertion: Medial Surface of the ramus
102
What are the origin + insertion of the superficial head of the medial pterygoid?
Origin: Maxillary Tuberosity / Pyramidal Process of the palatine bone
Insertion: Inner aspect of the angle of the mandible
103
What is the action of the medial pterygoid?
- Closes Jaw
| - Parallels masseter muscle
104
What provides motor innervation to the medial pterygoid muscle?
Trigeminal >
Mandibular >
Medial Pterygoid Branch
105
What are the origin + insertion of the upper head of the lateral pterygoid?
Origin: Greater wing of sphenoid bone
Insertion: Anterior part of Articular Disc
TMJ Capsule
106
What are the origin + insertion of the lower head of the lateral pterygoid?
Origin: Lateral Surface of Lateral Pterygoid Plate
Insertion: Pterygoid Fovea on the neck of Condyle
107
What is the action of the lateral pterygoid?
Open Jaw
- Lateral Excursion
- Protrusion of Mandible
- Active on Grinding: provides stability on centric
108
What provides motor innervation to the lateral pterygoid muscle?
Trigeminal >
Mandibular >
Lateral Pterygoid Branch
109
What are the origin + insertion of the superficial head of the masseter?
Origin: Zygomatic Bone
- Inferior Border of the anterior ⅔
Insertion: Angle of the Mandible
110
What are the origin + insertion of the deep head of the masseter?
Origin: Zygomatic Process of Temporal Bone
- Medial Border
- Inferior Border of Posterior ⅓
Insertion: Ramus + Coronoid Process
111
What is the action of the masseter?
Elevates
Retrudes
Aids in Lateral
112
What provides motor innervation to the masseter muscle?
Trigeminal >
Mandibular >
Masseteric Branch
113
What are the 2 actions of the digastric muscle?
If hyoid bone is held in place (Open mouth) Elevates Jaw
Some Retrusion
Some Lateral
If mouth is closed, contraction lifts the hyoid bone for swallowing
114
What innervates the digastric muscle?
Anterior Belly: Mandibular Nerve
Posterior Belly: Facial Nerve
115
What is the origin and insertion point of the anterior belly of digastric?
Origin: Digastric Fossa of Mandible
Insertion: Tendon of Hyoid Bone
116
What is the origin and insertion point of the posterior belly of digastric?
Origin: Tendon of Hyoid Bone
Insertion: Digastric Notch on inner aspect of the mastoid process
117
What is the origin and insertion point of the anterior belly of digastric?
Origin: Outer Surfaces of the Alveolar Processes of Maxilla and Mandible
Insertion: External Oblique Ridge
118
What is the action of buccinator?
Pulls back the angle of the mouth, pushing food to the posterior occlusal surfaces to assist mastication
119
What provides motor innervation to the buccinator muscle?
Facial Nerve >
| Buccal Branch
120
What provides sensory innervation to the buccinator muscle?
Trigeminal > Mandibular >
| L Buccal
121
How are growth and development different from each other?
Growth: increase in size or number
Development: physical and physiological increase in complexity and degree of organisation of tissues
122
How is variability in growth measured?
Deviation from normal (mean) for height and weight on a standard growth chart. Plotting individuals above and below the norm shows where they sit in regards to central tendency.
123
Why is timing of growth important?
To know whether an individual has commenced/finished growth spurt early/late when compared to the mean.
124
On Scammon's curve, why would lymphoid tissues peak around 10 years of age?
Lymphoid tissues more active during childhood to aid immune response against primary infections in early life.
125
On Scammon's curve, why is neural development the fastest during early infants to toddler years?
Development of neural networks to allow for motor skills (walking, handling objects), speech and cognitive behavioural development
126
Which form of cranial growth gives the best data to aid research in growth and development?
A. Craniometry
B. Anthropometry
C. Cephalometric Radiology
D. Three-Dimensional Imaging
D. Three-Dimensional Imaging
- Allows for 3D spatial measurements
- Can be taken cross sectionally or prospectively
- Can account for hard and soft tissue
127
What is hyperplasia?
Increase in number of cells
128
What is Hypertrophy?
Increase in size of cells
129
What is appositional growth?
Growth of new tissue at the periphery of existing structures. Common in hard tissue structures such as a bone and teeth
130
What is interstitial growth?
Grown of tissue via increase in size by hyperplasia or hypertrophy within the interior of a part or structure that is already formed. Can only occur in non rigid tissues including cartilage. Eg chondrocytes growing new cartilage
131
What is the main difference between endochondral and membranous ossification
Endochondral ossification involves the growth of cartilage matrix that is eventually calcified
Intramembranous ossification involves mesenchymal cells that differentiate into osteoblasts that forms a bone matrix and remodelling into compact bone
132
A Synchondrosis is comprised primarily of what tissue?
Hyaline Cartilage
133
What growth method occurs for the maxilla?
Intramembranous Ossification - apposition of bone at the sutures between the maxilla, cranium + cranium base, followed by surface remodelling
134
Overall what direction of growth in the maxilla?
Downwards and Outwards via surface remodelling around the sutures
135
What growth method occurs for the mandible?
- Endochondral growth via cartilage model for the ramus at TMJ with surface remodelling
- Intramembranous growth: Body of mandible via periosteal apposition on the posterior surface
136
What direction is the growth of the mandible
Visibly, the jaw appears to be moving downwards and forwards, but the intramembranous growth is occuring superiorly and posteriorly
137
Endochondral Ossification occurs mainly in which type of bones?
Long Bones
138
The skull mainly grows via what mechanism?
Intramembranous Ossification
Intramembranous ossification is the growth of bone by mineralisation of matrix that is secreted by osteoblasts. It typically growths to form “ice cream sandwich” plates of compact bone in areas such as the skull. The growth mechanisms occur by the following means:
1) Development of ossification centre from mesenchymal cells
2) Osteoid Bone Matrix forms
3) Woven Bone + Periosteum Form
4) Bony Collar of compact bone formed
139
According to Angle, what is defined as normal molar occlusion
MB cusp of upper 6 lined up with MB groove of lower six
140
According to Angle, what is defined as class 1 malocclusion?
Normal occlusion with crowding
141
According to Angle, what is defined as class 2 malocclusion?
MB cusp of upper 6 is anteriorly placed to the MB groove of the lower 6
142
According to Angle, what is defined as class 3 malocclusion?
MB cusp of upper 6 is posteriorly placed to the MB groove of the lower 6
143
What is Class 2 Div 1 Malocclusion?
MB cusp of upper 6 is anteriorly placed to the MB groove of the lower 6
Div 1 maxillary anterior teeth are proclined and a large overjet is present
144
What is Class 2 Div 2 Malocclusion?
MB cusp of upper 6 is anteriorly placed to the MB groove of the lower 6
Div 2 maxillary anterior teeth are retroclined and a deep overbite exists
145
What is the Molar's Canine relationship
Mesial incline of upper canine contacts the distal incline of the lower canine
146
What are disadvantages to Molar's classifications
1. Doesn’t tell us the relationship from the coronal plane e.g. midline,
2. If reference teeth are missing then it is hard to categorise/classify
3. Classifying all occlusion and malocclusion into 4 categories is oversimplistic
147
What is Anterior guidance ?
Movement of anterior teeth during jaw protrusion and lateral movements that aids posterior disclusion. In the movement, lower anterior teeth slide against the palatal surfaces of the upper anterior teeth which results in a guiding of the occlusal molar surfaces into disclusion. (This is to prevent off-centre force on the posteriors to which they are not well equipped against.)
148
What is th interincisal angle and what is the average range?
The angle made by the intersection of the long axis of the maxillary central incisor with the mandibular central incisor.
Statistically, a normal angle is about 130-135°
149
What does Articulating Paper capture?
1. Extent of contacts during movement
| 2. Static placement of occlusal contacts during articulation
150
What are the 3 types of articulators that can be used?
Plane Line
Semi-Adjustable
Fully Adjustable
151
What are the 3 directions involved with Axial Alignment?
Mesial / Distal (side to side)
Facio / Lingual (forward / backwards)
Extrusion (vertical - over/under eruption)
152
What is the significance of the articular eminence to condylar movement?
It is the track the condyle moves along during mandibular movement
153
What is the Balancing Side?
The side of the mandible which moves towards the median line in lateral excursion
154
What is the bennett angle?
The angle created in the sagittal plane of the non-working condyle during lateral movement. General values is 30 degrees
155
What ranges of motion can be incorporated in a border movement diagram
```
Edge to Edge
Maximum Protruded Contact
Retruded
Rest Position
Maximal Hinge Opening
Maximal Opening
Intercuspal Position
Maximum Lateral Excursion
```
156
What is bruxism?
Parafunctional movement that results in excessive tooth grinding and jaw clenching outside of masticatory function.
157
What are buccal segments?
Premolars and Molars - used when referred to as a group (any teeth that have buccal rather than labial surfaces)
158
What is canine guidance?
During lateral excursion of the mandible, the canines come into contact and guide the posterior to disclude. Overtime Canine Guidance is lost due to wear and this becomes group function.
159
What is Centric Relation?
The most superior and retruded relation of the Md to the Mx when the condyles are in the most posterior unstrained position in the glenoid fossae from which lateral movement can be made at any given degree of jaw separation.
This can correlate with intercuspal position, unless the patient has experienced significant tooth wear, erosion etc. that change the contact positions of the teeth.
160
Where are the 5 centric stops found?
1. Lingual cusps of maxillary posterior teeth
2. Buccal cusps of mandibular posterior teeth
3. Central pits and marginal ridges
4. Incisal edges of lower anterior teeth
5. Lingual sides of upper anterior teeth
161
What are the 3 phases of the chewing cycle?
1. Opening Phase
2. Closing Phase
3. Intercuspal Phase
162
Opening Phase of the chewing cycle has 2 phases, what are these in order?
1. Slow Opening
| 2. Fast Opening
163
Closing Phase of the chewing cycle has 2 phases. What are these are what sort of contraction is occurring?
Beginning: elevators show isotonic contraction
End: transition to isometric contraction
164
What is Condylar guidance?
The horizontal path followed by the condyle when it is travelling the glenoid fossa during mandibular opening.
165
What is Condylar Inclination
The angle of inclination of the condylar guidance to an accepted horizontal plane. Typical value is 30 degrees
166
What is cuspal interference?
Tooth contacts that prematurely interferes with normal mandibular closing path to centric occlusion
Need to check there are no interference after placing a restoration
167
What is edge-to-edge contact?
When the incisal edges of the upper and lower incisors are in contact.
168
What is the envelope of motion?
All possible movements of the mandible on an individual using the lower central incisors as a guide. These can be charted into a 3D shape known as the Envelope of Motion
169
What does the Facebow record?
A device that relates the maxillary arch to the intercondylar axis and the point orbitale. These measures can be translated to an articulator
170
What is freeway space?
Distance between the Rest Position and the Intercuspal Position.
Typically 2-4mm.
Interruption of freeway space will rapidly lead to TMD (inability to relax jaw muscles)
171
What is group function?
Simultaneous contact between multiple teeth on the working side during functional movement of the mandible. This is to distribute occlusal forces more evenly amongst the teeth.
172
What are guiding cusps?
When in occlusion the buccal cusps of Mx teeth / lingual cusps of Mn teeth have contact on the occlusal surfaces only
173
What is the intercondylar distance?
Distance between both condyles, measured from the centre of each condyle.
Radiographs or Facebow record can be used to obtain this measurement.
174
What is the term used to indicate when teeth are in maximal contact?
Intercuspal Occlusion
175
How are intercuspal position and intercuspal occlusion different?
Both are when the teeth are in maximum contact
Intercuspal Position = position of the mandible
Intercuspal Occlusion = the contacts in max contact
176
Interocclusal distance (IOD) is also known as what?
Freeway Space
177
Leeway Space is defined as what?
The difference in space between:
Primary C-E Teeth &
Permanent 3-5 Teeth
This space accommodates eruption of permanent teeth in a growing jaw
178
What is long centric?
When centric relation and centric occlusion are not the same, long centric is the freedom of movement for the jaw to move from centric relation to central occlusion. This is important in maintaining when constructing new dentures.
179
What is maximum hinge opening?
Largest opening of the jaws involving only rotation of condyle in the glenoid fossa. It does not involve translatory movement.
Average max hinge opening is 3cm
180
What is Myofascial pain dysfunction syndrome (MPD)?
MPD describes muscle pain that is believed to be of fascial origin. The exact mechanism of pathology is unknown.
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What is the neutral zone?
The space in the oral cavity where the vector forces exerted by the tongue muscle is equal to the opposing forces exerted laterally by the buccinator muscles (cheeks) and anteriorly by the orbicularis oris muscle (lips).
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What is Occlusal Vertical Dimension (OVD)?
OVD Is the facial measurement distance measured when the occluding rims or teeth are in contact. Measurement is typically taken from the nose to the chin
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What is overjet?
The horizontal distance between the upper incisors ahead of the lower incisors. Normal range is 2-3mm
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What is overbite?
Measurement of the vertical overlap between upper and lower incisors. Measured as a percentage
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What is rest position?
The position of the jaw when the muscles of mastication are in a relaxed state and maintained by the sustained contraction of the temporalis muscle. This is usually slightly off from intercuspal position.
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What is Rest vertical dimension (RVD)
Is the measurement between the chin and the nose when the patient is in the rest position.
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What is retruded hinge axis?
The axis on which the condyle moves (rotates) in when the mouth is opening and the condyle movement is purely rotational
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What is Retruded Relation?
The guided occlusal relationship occurring at the most retruded position of the condyles in the join cavities. A position that may be more retruded than the centric relation position
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What is a scissor bite?
When the maxillary posterior teeth occlude entirely on the buccal aspect of the mandibular posteriors.
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What is the working side?
The movement of jaw towards a particular direction away from the median during lateral excursion. If moving right laterally, the working side is on the right
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What is Parafunction?
Behaviours that have no functional purpose
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What are some consequences of oral parafunctional habits?
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Excessive Tooth Wear
Tooth Fracture
Severe Malocclusion
Degenerative Joint Conditions
Muscular Hypertrophy
Muscle Contraction Headache
Myofacial Pain
Muscular Pain
Joint Pain
TMJ Disc Derangement
Flattening/Wear of condylar articulating surfaces (Clicking)
Periodontal Tissue Injury
Alveolar Bone Loss
Destruction of prosthetics / restorative dentistry
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What are first signs of nocturnal bruxism in the mouth?
In normal occlusion: usually Flattening of Canine Cusp Tips occurs first
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What is the grinding pattern of nocturnal bruxism?
Intense Rhythmic Grinding patterns + Periods of sustained forceful clenching
- Can occur throughout the night - up to 90 minute intervals for 5 minutes per episode
- Found through all stages of sleep
- Mostly in Stage 2 sleep
- Bruxism during REM sleep is often indicative of worse symptoms
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How could we differentiate between nocturnal and diurnal bruxism?
1. Ask patient if they are aware of any repetitive behaviours (diurnal)
2. Determine patient occupation (divers, musicians)
3. Is the pain on waking (then nocturnal)
4. Pattern of wear - unilateral could identify external objects (diurnal) rather than opposing teeth
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What are some causes of diurnal bruxism?
1. Strenuous Physical Activity
2. Leaning on mandible (phone, reading, driving)
3. Occupation (divers, musicians)
4. Superstitious Behaviours (pen biting)
5. Non-verbal communication (clenching when angry/stressed)
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How can nocturnal bruxism be diagnosed?
1. Dental Exam: Active Cusp Tip wear, muscle/joint pain, fatigue, when stiffness is identified (morning/evening), muscular hypertrophy
2. Provocation Test: lateral excursion of mandible to align facets with pain/stiffness locations
3. Pain Relief Test with analgesics
4. Sleep Tests
5. Grind Tests
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What are causes of nocturnal bruxism?
1. Psychosocial: heightened stress, life factors
2. Drug Use (Meth)
3. Medications (Anti-Psychotics)
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What are some unique features of the TMJ that differentiate it from other synovial joints?
1) Only joint system with a rigid end point of closure
2) Bilateral movement due to contralateral joint
3) Complex articulation
4) Hybrid Hinge + Sliding Socket (rotate/translate)
5) Only joint that can “dislocated” internally without external forces acting upon it
6) Articular surface composed of Fibrous Tissue (Not Hyaline Cartilage)
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Can Otolgia (Ear Pain) be bruxism related?
Yes, they can be referred from masticatory sources - due to common sensory innervation
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T/F: The TMJ and Middle Ear come from the same embryonic source
True - both are derived from Meckel's Cartilage and differentiate after Meckel's disappears at week 12 of embryonic growth
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What is the role of the articular disc of the TMJ?
Firm, flexible structure that changes in shape to allow movement of the condyle in the glenoid fossa and articular eminence
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What are the 3 zones of the articular disc?
Thick-Thin-Thick
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Which zone of the articular disc is more pressure exerted?
Thin Central Zone
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What is the role of synovial fluid for the TMJ?
- Lubricating to reduce friction of movement
| - Nutrition of the articular disk since it is avascular
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Describe the 2 structures of the Synovial Membrane of the TMJ
1. Superior Synovial Cavity: Along the mandibular fossa and articular eminence of the Temporal Bone
2. Inferior Synovial Cavity: Surrounding the head of the condyle
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The lateral part of the TMJ capsule is thickened to form a ligament. What is this ligament called?
Temporomandibular Ligament
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What is the function of the Temporomandibular Ligament?
Limit the movement of the mandible to it's most retruded position
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For the mandible to shift laterally (say left), what structures are engaged and what are their movements?
1. TML : Passively resisted on the working side. Permitted by medial contour of non-working side
2. Lateral Pterygoid Muscle is activated on the non-working side
3. Working Condyle moves laterally (Bennett Movement)
4. Non-working Condyle moves anteriorly, inferiorly, mediall (Bennett Angle)
* Moving Left: Working Side LHS, Non Working Side RHS
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What is the histological structure of the human condyle including the articular disc
1. Articular Zone - Dense Fibrous CT (not Hyaline Cartilage)
2. Proliferation Zone - Mesenchymal Cells
3. Fibrocartilaginous Zone - 3D network of collagen fibres that offer compression/lateral resistance
4. Calcified Cartilage Zone: site for bone remodeling
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T/F: The TMJ has motor innervation nerve fibres
False, this is provided by the muscles of mastication (CN V)
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What nerves are involved with sensory innervation of the TMJ?
Auriculotemporal Nerve
Accessory Innervation:
Masseteric Nerve
Deep Temporal Nerve
Pterygoid Nerve
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Where does the TMJ get it's blood supply?
Via Retrodiscal Tissue
Deep Auricular (Maxillary Artery)
Superficial Temporal Artery (Terminal branch of External Carotid)
Anterior Tympanic (Maxillary Artery)
