Occlusion Flashcards
Where are the functional cusps located in the maxillary and mandibular posterior teeth?
Maxillary: palatal
Mandibular: buccal
(beware in cross bite situations it is the opposite)
Where does the DB cusp of the mandible sit?
Central fossa of maxillary molars
Where does the MP cusp of the maxilla sit?
Central fossa of mandibular molars
Where does the palatal cusp of maxillary bicuspid contact?
MR of mandibular bicuspid and 1st molar
What is the definition of centric stops?
Where the mandibular teeth contact the maxillary teeth in complete intercuspation, holding the teeth in a stable position
Where do the supporting cusps contact?
- The opposing inclines leading to the fossae; ideally with a buccal and lingual contact for each cusp
- Also the SC has at least one mesial or distal contact with opposing marginal, triangular, transverse or oblique ridge
What is the definition of tripdism?
A supporting cusp in occlusion is held in firm position with at least three contacts
Explain the process of incisor guidance?
During protrusion the mandibular incisal edges glide down the palatal inclines of the maxillary incisors, with many teeth involved
In what direction does the working side condylar head move during lateral excursion?
Laterally, this movement is immediate and non-progressive
How is the condylar angle formed? and What is its average value?
- From the downward movement of the non working condyle to the horizontal plane
- 30
How is the Bennett’s angle formed?
- Angle is formed by the medial movement of the non-working condyle to the vertical plane
Explain the process of the Bennett’s movement? And how far it will move?
The working side condyle moves laterally in the direction of lateral excursion and slightly downwards
- This bodily laterals shift of the mandible is bennett’s movement
- Average at 1.5mm
What is the definition of centric relation?
Position of the mandible to the maxilla, with the intra-articular disc in place, when the head of the condyle is against the most superior part of the distal facing incline of the glenoid fossa
What are the 6 main factors that help decide which articulator to use?
- Intended use
- Patient’s occlusion
- Availability of equipment
- Operator skill
- Technician skill
- Expense
Why use an articulator?
- It simulates the maxillary and mandibular relationship of the patient
- To mount both casts, giving the registered relationship of the teeth
- Study dynamic occlusion
- Diagnostic aid
- Aid development of restorations
What important rule must we follow when using articulators?
Ensure that what is presented on the articulator is identical to what the patient experiences in their mouth
What is a face bow?
A caliper like device used to record the spatial relationship of the maxillary arch to the TMJ and another reference plane
What does a face bow allow us to understand?
- The transfer of the TMJ relationship to the articulator
- The maxillary cast will have the same relationship to the opening axis of the articulator, as the maxillary arch had to the TMJ
Which anterior reference point does an Hanau FB use?
Orbitale
Which anterior reference point does an Whip mix FB use?
Nasion
What does a facebow record?
- The distance from the centrically related horizontal axis of rotation of the joints to the upper teeth
- The relationship between the axis-orbital plane (Frankfort plane)
- The distance between condyles
Name the 2 forms of facebow registration?
Arbitrary and Kinematic
What armamentarium is needed for the arbitrary facebow?
- Ear plug
- Anterior reference pointer
- Intercondylar distance scale
- Finger lock screw
- Centre lock wheel
- Sight
- Bite fork
- Reference point locator
Name the 2 types of arbitrary facebow?
Earpiece and Facia
What type of anterior reference point does earpiece facebow use?
Orbitale
- located suing the denar reference point locator
Nasion
Where is the caliper of the facia face bow positioned?
- 13mm anterior to the auditory meatus on the cantho-tragal line
- this locates the true hinge axis within a 5mm margin of error
What is the definition of the true hinge axis?
- The condylar hinge axis is an imaginary line passing through the centre of the condyles when the mandible rotates in the sagittal plane
- This rotation is within 5-12 degree, when axis of rotation coincides with centric relation called THA
How to place the average face bow on a patient?
- Attach the softened beauty wax on fork
- Place fork against incisal and occlusal surfaces of maxillary teeth
- Ensure the midlines are coincident
- Important that the tips of the cusps and the incisal edges do not touch the fork
What movement occurs in the superior synovial cavity?
Retraction
Protraction
Lateral excursion
(Superior = sliding)
What movements occur in the inferior synovial cavity?
Rotational movement (opening and closing of the mouth) InferioR = rotational
What memory trick to remember for superior and inferior synovial cavity?
Superior = sliding
InferioR = rotational
Name the functional cusps of the maxilla and mandible?
Maxillary palatal
Mandibular buccal
What is the function of the tripoding contact of the molar teeth and where do they contact?
Buccal cusp of maxillary teeth is outside the mandibular opposite tooth, and the palatal cusp of maxillary teeth are the functional cusp as they sit in the central fossa of the mandibular opposite tooth, gives centric holding and tripoding contact and the transfer of occlusal forces
How do the functional cusps change for a crossbite?
In a crossbite situation the Maxillary buccal and the mandibular lingual cusps will be the functional cusps – ensure to check occlusion before starting any restoration
How do individual supporting cusps contact each other?
In ICP, the contact is not at the tip or the deepest part of the fossa. The actual point of contact is called a centric stop
How do molars present a tripoding contact with the opposing molar?
Buccal aspect of mandibular tooth contacts the palatal facing cusp of maxillary molar and the palatal facing incline of the buccal cusp (DB) contact the facing slope of the palatal cusp, and another contact at the marginal ridge
What is the function of tripoding contact?
Stability
What is the definition of incisal guidance?
In protrusion the mandibular incisal edges glide down along the palatal inclines of the maxillary incisors, a poor guidance can lead to non-axial forces causing trauma to the tooth
What is the definition of mutually protected occlusion and give examples on how this can be shown?
- Anterior teeth protect the posterior from cutting forces
- Posterior teeth protect the anterior teeth from grinding forces
- During lateral excursion, only the anterior teeth contact, creating the space called the Christensen’s phenomenon
- During static occlusion, the posterior teeth protect the anterior teeth from the bulk load of pressure
What occurs if the disc of the TMJ becomes displaced?
It changes tooth contacts and mandibular movements
What is the size of the condylar angle?
30 degrees, measured in the horizontal plane
What is the definition of the working side?
The side the mandible is moving towards
What is the definition of the non-working side?
The side which the mandible isn’t moving towards
What are the movements of the non-working side condyle?
Forwards
Downwards
Medially
What are the movements of the working side condyle?
It undergoes an immediate non-progressive lateral movement known as the Bennett movement (pulling the condyle towards the WS)
How is the Bennett angle measured?
On the non-working side in the vertical plane of movement
What do these acronyms mean - BMW and BAN?
- Bennett movement on the working side (BMW)
- Bennett angle on the non-working side (BAN)
What is the definition of the Bennett movement?
The movement of the working side condylar head outwards during lateral excursion (immediate and non-progressive)
Why does immediate side shift happen?
It is the effect of the downward, forward, and inward movement of the non-working side condyle during lateral excursion
How is the condylar angle formed?
By the downward movement of the non-working condyle to the horizontal plane
How is the Bennett angle formed?
Formed by the medial movement of the non-working condyle to the vertical plane
What movement and what side is considered to be the orbiting side?
Forward, downward, inward and translation
NWS
What movement and what side is considered to be the rotating side?
Rotates around self
WS
What is the definition of the centric relation?
Position of the mandible to the maxilla, with the intra-articular disc in place, when the head of the condyle is against the most superior part of the distal facing incline of the glenoid fossa
Condyle is in the uppermost and foremost position within the glenoid fossa
Why can the centric relation be an asset for an edentulous patient?
Most relaxed position of the mandible
Does not depend on teeth occlusion
What are the important points of the Posselt’s envelope of motion?
RCP - Retruded contact point ICP - Intercuspal position r - rest position (vertical reference point) Tr - Transition from rotation to translation MO - Maximum opening h - habitual opening/closing movement MP - maximal protrusive contact E2E - edge to edge
What is the RCP of Posselt’s envelope of motion?
Retruded contact point
What is the ICP of Posselt’s envelope of motion?
Intercuspal position
What is the MP of Posselt’s envelope of motion?
Maximal protrusive contact (mandible retruded, reaches E2E then slides into ICP)
What is the Tr of Posselt’s envelope of motion?
Transition from rotation to translation
What is the MO of Posselt’s envelope of motion?
Maximum opening
What is the E2E of Posselt’s envelope of motion?
Edge to edge
What is the h of Posselt’s envelope of motion?
Habitual opening/closing movement
What is the r of Posselt’s envelope of motion?
Rest position (no contact with teeth)
What is the average size of Tr?
20-25mm
What are the classification of Angle’s incisal relationship?
CI - normal; in front of cingulum
CII DI - abnormal behind the cingulum
CII DII - abnormal next to cingulum
What is the definition of the ideal occlusion?
An occlusion which is in sync with the other elements of the stomatognathic system such as neuromuscular elements, TMJ elements and teeth and supporting structures
What is the size of the Bennett movement?
1.5 mm towards the lateral position corresponding to an end-to-end position of the cuspids on the working side
Is the Bennett angle and Bennett movement mutually exclusive?
No, the angle can exist without the movement
What is the contact and non-contact for the intra-border characteristic?
Contact: ICP
Non-contact: rest
What is the contact and non-contact for the border characteristic?
Contact: RCP
Non-contact: any position on the terminal hingle opening path
What are the classification of Ackerly of traumatic incisal overlap?
CI - lower incisor impinge into palatal mucosa
CII - Lower incisors incisal edge occlude into palatal gingival crevices of maxillary teeth
CIII - CII DII type of insicor relationship
CIV - lower incisor causing progressive abrasion of palatal surfaces of maxillary teeth
What is the incisor relationship and signs of trauma for CI Ackerly classification?
CI - lower incisor impinge into palatal mucosa
Trauma - inflammation of palatal mucosa with lower incisal edge imprints
What is the incisor relationship and signs of trauma for CII Ackerly classification?
CII - Lower incisors incisal edge occlude into palatal gingival crevices of maxillary teeth
Trauma - labial splaying of maxillary incisors (palatal pockets)
What is the incisor relationship and signs of trauma for CIII Ackerly classification?
CIII - CII DII type of insicor relationship
Trauma - Stripping of the gingiva in relation to palatal surfaces of upper anterior teeth and labial surfaces of lower anterior teeth
What is the incisor relationship and signs of trauma for CIV Ackerly classification?
CIV - lower incisor causing progressive abrasion of palatal surfaces of maxillary teeth
Trauma - Abrasion of palatal surfaces of upper anterior teeth. (dentine hypersensitivity)
What is the definition of an articulator?
Is a mechanical instrument that represents the temporomandibular joints and jaws, to which maxillary and mandibular casts may be attached to simulate some or all mandibular movements
How many types of articulators are there?
4
What is the definition of the a class I articulator?
A simple holding instrument capable of accepting a single static registration; vertical motion is possible
Not really an articulator
Why must a CI articulator not be used for restorations?
Inaccurate representation of any TMJ relationship between the maxilla and mandible
What is the definition of a class II articulator?
An instrument that permits horizontal as well as vertical motion but does not orient the motion to temporomandibular joints
What value is the condylar path fixed for a CII articulator?
Between 25-40 degrees
What is the definition of a class III articulator?
An instrument that simulates condylar pathways by using average values or adjustable mechanical equivalents for all or part of the motion
What are the 2 types of CIII articulators?
Arcon and Non-arcon
What can an Arcon articulator measure?
RCP and ICP
How do Arcon articulators work when expressing occlusion?
Fossae are on upper member
Condyle on lower member
Simulates the TMJ and jaw
What are the condylar angle, progressive side shift and immediate side shift values for an Arcon articulator?
Condylar angle: 0-60
Progressive side shift: 0-15
Immediate side shift: 0-2mm
What is the definition of progressive side shift?
Is the path that the orbiting condyle follows on the medial wall of the fossa as it orbits around the rotating condyle
How do Non-arcon articulators work when expressing occlusion?
Fossae on lower member
Condyles on upper member
What can’t the non-arcon articulator measure?
RCP and ICP
What can be adjusted on a semi-adjustable articulator?
TMJ to incisor distance
Bennett angle and movement
Condylar guidance angle
Incisal guidance table
What to be wary about when using a semi-adjustable articulator?
Protrusive movements are guided by flat condylar paths, and so only a rough copy for protrusive and lateral movements
When using an articulator what are some typical errors result from?
A limited ability to adjust progressive side shift
Limited ability for reproduction of bodily sideshift Limited adjustability for protrusive settings No adjustability, or only limited, of the the distance between the condyles
What is the definition of a CIV articulator?
An instrument that will accept three dimensional dynamic registrations; these instruments allow for orientation of the casts to the temporomandibular joints and simulation of mandibular movements
What can be adjusted on a CIV articulator?
Posterior wall
Superior wall inclination Medial wall – Progressive Side Shift
Condylar angle Intercondylar (& glenoid fossa) distance
Medial wall - Immediate Side Shift
What should you change if RCP is not equal to ICP?
Need a semi-adjustable articulator
Slide from RCP to ICP
Why should we use an articulator?
To see how teeth relate to each other
To recreate the TMJ relationship
To plan, design and construct restorations
Improve aesthetics
Why should we use an arcon semi adjustable articulator for fixed prosthodontics?
During closure the path followed by the articulator arm must be the same as the rotatory path of the mandible
During closure the path followed by the articulator arm must be the same as the rotatory path of the mandible
How important is the value of distance from condyle to teeth?
Very important, as it will change the interaction between the teeth
What are the requirements for an articulator?
Simulate major non-working and working side posterior protrusive interferences
Hold casts accurately
if casts mounted in RCP, articulator must allow cast to be related in ICP
When can hand articulation be used?
With an adequate number of teeth
What is the definition of hand articulation?
Being able to place the maxillary and mandibular casts in ICP
What to do if hand articulation is not possible?
Interocclusal registration
How to produce interocclusal registration?
Wax occlusal rim on self cure acrylic base
bite registration block
What are the requirements for use of a facebow?
Good quality casts
Facebow record
Appropriate jaw reg
