Clinical Occlusion Flashcards
OIA Masseter
O: inferior border and medial surface of zygomatic arch
I: Lateral surface of ramus and angle of md
A: Elevate and protrude md
OIA Lat pterygoid
O: 2 heads- upper: sphenoid
lower head: lateral surface of lateral pterygoid plate
I: pterygoid fovea on neck of md, capsule and articular disc of TMJ
A: Depresses and protrudes MD
OIA Med pterygoid
O: 2 heads- superficial head: tuberosity
Deep head- medial surface of lateral pterygoid plate
I: Medial surface of angle of md
A: Elevates and protrudes
OIA Temporalis
O: floor of temporal fossa
I: coronoid process
A: Elevate and retract md
What is curve of spee
Curved line in occlusal table from anterior teeth to posterior teeth
What is curve of wilson
transverse occlusal curve that goes from left to right when viewed from posterior
What must be considered when building VDO?
Curve of Spee
What is balanced occlusion
the bilateral, simultaenous, anterior AND posterior occlusal contact of teeth in centric and eccentric position
When is the only time you actually want to have balanced occlusion?
Complete dentures
- so that retention isnt unbalanced and falls off
What is mutually protected occlusion? (theory)
Anterior teeth protect the posteriors in eccentric movements (canine guidance)
Posterior teeth protect the anteriors in maximal intercuspation
How do anterior teeth support posterior teeth? (4)
Canine disclude posteriors in lateral movements
Incisors disclude in protrusive movements
When contact point is away from hinge axis, less force is applied on teeth
When posteriors are separated, less muscle activity during mastication
How do posterior teeth support anterior teeth? (3)
Can endure vertical forces better by:
- More roots
- More surface area
- Orientation of force is along long axis
But.. not good for lateral forces. Thats why anteriors are important
Describe the movement of condyle within the TMJ
First 20-25mm- only rotational mvmt
> 20mm- condyle and disk move forward and down of articular eminence- **translation **
3 planes of movement in posselts envelope
sagittal
frontal
horizontal
CR aka?
Retruded axis position
Terminal position
Most anterior and superior position of the condyle in the glenoid fossa
Most reproducible position
What is RCP?
Retruded Contact Position
- First point of contact in CR/RAP
When to restore teeth in ICP?
Fully dentate patients with no VDO changes (majority of patients)
Should you restore in ICP or CR in partially dentate patients?
If ICP = CR, ICP. (Doesnt matter?)
If ICP doesnt equal CR, but well-defined, ICP.
If ICP doesnt equal CR but is not welldefined, CR
Missing posterior teeth? CR.
What is “condylar angle”
During lateral excursion, the head of the condyle on non-working side moves forward, medially, and downward
- angle between downward movement and horizontal plane is the condylar angle
What is “Bennet movement” aka “immediate side shift”
During lateral excursion, the working-side condyle makes an initial immediate lateral movement
contact vs interference
when contacts interrupt normal function / occlusion - interference
Role of anterior guidance on protrusion
Too shallow might be from class 2, or perio path migration
How to develop ideal anterior guidance?
Provisional crowns and bridges by adding or grinding palatal acrylic
When may anterior guidance be impossible?
Class 3 or edge to edge
What does ideal occlusion look like at an articulatory level (4)
CO = CR (rare)
Freedom in CO
Anterior guidance
Canine guidance
What does ideal occlusion look like at a patient level
Within neuromuscular tolerance of the patient at that age
What does ideal occlusion look like on the tooth level (5)
Multiple simultaneous contact- cusp tip to fossa
No cuspal incline contacts (likely to frac)
Occ forces directed along long axis of tooth
Smooth anterior guidance is possible
Mutually protected
What is a facebow used for
Transfers the relationship between maxillary arch and TMJ which enables mounting of mx cast on adjustable articulator
Ways of putting pt into RCP / CR (4)
Schuyler technique - tongue to back of palate
operator guided method
- chin point guidance
- Dawson method
Lucia Jig (best)
Describe the chin-point guidance method of establishing RCP
Operator guided method
Pt seated upright
Soft 2-layer wax is pushed against mx for indentations
Registration material (pvs) placed on md surface
Operators thumb and index guide jaw posteriorly and superiorly until md occlusion indent the wax
Risk- condyles can be over-retruded
Describe the bimanual manipulation (Dawson method) of establishing RCP
Operator guided method
- Pt supine
- Pinky placed behind angle of md
- ring fingers in front of angle
- middle fingers placed inferior to body of md
- indexs submentally
- thumbs lateral to symphysis
Open/close a few times so pt can relax, then registration can be taken
What is a Lucia Jig? How does it work?
Method of de-programming and relaxing MMoM to RCP record can be taken. Anterior guidance.
- Useful for bruxirs, where masseter is very strong and cant relax enough for operator guided methods
- Acrylic device that covers central incisors designed to disclude the posteriors
- When posteriors arent in contact, muscles can relax
- Repeated contact on splint breaks down programmed paths of closure and allows operator to guide md into RCP
- BEST WAY / most accurate TO TAKE RCP- poyan
What is this and what is it used for?
Leaf Gauge used for anterior guidance
- Allows for taking more accurate RCP positions
- Leafs help achieve disclusion of anteriors so MMoM arent working so hard, can take RCP
- Same principle as lucia jig but not as accurate
How to mount study cast/models into SAA
- Upper model placed in first using facebow record
- Mix plaster and add it to the space btw cast and mounting plate
- Close the SAA so pin contacts table
- Wait 20-30 min before cleaning
- Add occlusal record (bite reg) to maxilla
- Mount the lower cast/model against the opposing bite reg + maxilla
What is MODJAW?
Pros (3) and cons (2)
Digital tech of visualising and recording occlusion, articulation
Pros:
- more efficient (faster)
- Communication with pts easier
- Storage of models
Cons:
- Cost
- lack of evidence and availability of compatible systems in local labs
What happens when you open the posterior by 1mm
1mm in posterior = 2-3 mm in anterior
For each 3mm opening in anterior = 2mm horizontal change / increased overjet
Why should you build new OVD less than the point of RCP with condyle in CR?
It will provide the necessary interocclusal space without altering the contracted length of elevator muscles
HOWEVER
Sometimes you don’t need to open the bite up that much, remember that 1mm posterior = 3mm anterior
- Use this approach in cases with mild-mod tooth surface loss (not that much VDO lost)
What is a “transitional phase”
When changing the occlusion, VDO, must “test drive” the new bite with provisionals for around 6 months. If no problems, move to crowns and onlays
What must be done for severe / excessive wear and flattened posterior teeth? (collapsed dentition) when building up VDO
Build the new OVD more than the point of RCP with condyle in CR, provides interocclusal space via increasing the length of elevator muscles
if very collapsed, and pt is fine after 6 months of provisionals, repeat process of occlusion recording the exisiting provisions with imp, as well as imp of preps, then jack up the occlusion some more
What material should be used for long term provisionals (6 months)
Acrylics like PMMA, PEMA
NOT
luxatemp
What is the most common restorative approach when building up in CR
Building the new OVD at the point of RCP with condyle in CR position
- Provides interocclusal space without altering contracted length of elevator muscles
- For occlusion with decent amount of tooth surface loss
