occlusion 3 Flashcards
arcon articulator
articulating condyle on lower - anatomically correct
average value articulators
- Bennet Angle set at 15o
- Condylar Guidance Angle set at 30o
semi-adjustable articulator
Allows you to set the Bennet and Condylar Guidance Angles
types of articulator used for diagnostic casts
Diagnostic casts are most effectively mounted on a semi-adjustable articulator with a retruded record
- see the full range of mandibular movements for occlusal diagnosis and evaluation
depends what you are doing – if not advanced re-org, average value should be fine
to mount maxillary cast need
facebow transfer
tools needed to do facebow transfer
On the clinic you will be presented with a box of components that are joined together to construct the facebow instrument
- reference plane locator
- bite forck
- registration paste
- transfer jig assembly
- ear bow
- marker
https://www.youtube.com/watch?time_continue=475&v=m91NcwEwE1M&feature=emb_logo
first step in facebow tranfer
Mark the anterior reference point
- Mark the anterior reference point on the patient’s right side using the Reference Plane Locator and Marker.
- This is 43mm apical to the incisal edge of the anterior teeth (12 ideally)
- It is the approximate position of the infraorbital foramen (1st bony reference)
2nd step in facebow transfer
Bite registration using the bite fork
- Bite registration paste applied to bite fork.
- Bite fork arm to the right and locating notch facing up
- Firmly seat to record cusp tips of maxillary teeth.
- You can use rigid wax or bite registration paste.
- Do not engage undercuts.
- Check that it is parallel with the patients’ coronal and horizontal planes
- Align the dental midline with the locating notch
- Indentations of maxillary teeth clearly visible to allow accurate repositioning and then mounting of the maxillary cast*
- Just want cusp tips, incisal edges – allows accurate positioning of maxillary cast
earbow
measures intercondylar distance
how to assemble the earbow and transfer jig
want numbers facing you
loosen the centre wheel to allow the earbow to open/close
attach the vertical shaft to the measuring bow with clamp marked 2 on the pt right and tighten with the finger screw on earbow
make sure fingers screws 1 and 2 are loose
how to assemble the facebow on the pt
Assemble the facebow on the patient by sliding the bitefork arm through clamp marked #2
Fit the measuring bow’s earpieces tightly into the patient’s ear.
- Tighten the centre wheel on the bow.
Raise or lower the bow so that the pointer aligns precisely with the anterior reference point. – marked at start
- If you are aligned with the reference point, tighten clamps #1 and #2. Be careful not to alter the bow while tightening the clamps.
before removing the facebow ensure
the bow is parallel to the interpupillary line and floor
Make sure that the #1 and #2 clamps are secure.
- Facebow registration complete
how to remove the facebow
- Loosen the finger screw on the measuring bow, slide open the bow, and remove the facebow from the patient.
- Detach the measuring bow from the transfer jig by loosening the finger screw.
- Disinfect
what does the facebow record
- 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
mounting lower casts needss
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
2 choices of interocclusal registration to mount lower cast
Intercuspal Position (ICP)
- Conformative Approach
Retruded Contact Position (RCP)
- Reorganised Approach
ICP registration when not obvious to technician
wax wafer
silicone paste
ICP registration when there is free end saddles (casts cannot be hand articulated)
request record block
ICP registration when there are plenty of tooth contacts (ICP obvious to technician)
hand articulate
- multiple tooth contacts when the pt bites together
do not use material can make it work
wax wafer for interocclusal registration
- When there are enough teeth and the bite in ICP is obvious you don’t need wax.
- If too much wax is used and the lower cast is mounted like this the OVD will be increased and the restoration will be high in the bite when placed – now reorganised as confirmative bite changed
- When using wax you must ensure it is thin and cusp tips are visible
registration paste for bite registration
- When ICP will not be obvious to the technician
- Silicone paste that sets quickly
- A small amount is needed
- Too thick and it will increase the OVD
- Occlusal contacts must be visible through the material
registration postion options decided when
before embarking on treatment you must decide whether to place restorations in the existing occlusal scheme (conformative approach) or to change it deliberately (the reorganized approach).
- If the entire occlusal scheme is to be reorganized to create a new and stable position, the final restorations are made in the new ICP that coincides with RCP and may involve a change in the vertical dimension
NOT simple registration option
RCP registration WITH or WITHOUT OVD increase
ICP registration WITH OVD increase
REORGANISED APPROACH
simple registration option
ICP registration WITHOUT OVD increase
conformative approach
RCP registration WITH or WITHOUT OVD increase ->
reorganised approach
NOT SIMPLE
ICP registration WITH OVD increase ->
reorganised approach
NOT SIMPLE
ICP registration WITHOUT OVD increase ->
conformative approach
SIMPLE
conformative approaches to interocllusal registration
want to be able to follow as grad
- ICP registration
- RCP (centric relation) registration with no OVD change and make restorations conforming to existing ICP
unorganised approach
NOT GOOD
- 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!
- Too high restoration as not checked prior
conformative approach
- 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
- e.g. ICP registration WITHOUT OVD increase*
when to mark contacts
Mark up your contacts before you change them
- If the occlusal scheme is good – stick to it (conform)
These are called tripodised contacts and show where the opposing cusps contact (ICP stops)
- cusp tip to fossa better
issue if uneven force on tripod contacts
heavy contacts on one or more slopes; this means that either the teeth move and/or you have increased the risk an unintended CR/CO slide. Either way, you have introduced at least some level of instability.
So, what is an easier solution that will often result in a more stable occlusion?
Rather than attempting to achieve perfect tripodization on posterior teeth, you should create flat landing spots for the opposing cusps to contact - cusp to cups
when do we not use the conformative approach?
- An increase in vertical height is needed to make space for restorations
- Tooth/teeth significantly out of position (i.e. overerupted, tilted or rotated)
- A significant change in appearance is wanted
- There is a history of occlusally related failure or fracture of existing restorations
- E.g. Multiple fractures on posterior teeth
Not place restorations in ICP - need reorganised
reorganised approach
- Plan to provide new restorations to a different occlusion
- The occlusion is defined before the work is started
- Provide restorations, which change the occlusion but are well tolerated by the patient
RCP registration WITH or WITHOUT OVD increase
why use reogranised approach
- ICP is non-existent or no use
- You need space to place restorations
RAP (retruded arch path) is a reproducible position of the mandible independent of the teeth
RCP registration -> reorganised approach
how to restore this occlusion
not desirable ICP
- Poor aesthetics
- Bite poor
- Not much posterior contact
- Overeruption
- Tooth wear
ICP is non-existent or no use
Make space to place restorations – reorganise
- Used Retruded arc of closure position – one on green scale
- Tooth hit another tooth on retruded arch of closure
- Retrude the mandible until pt makes contact – manipulated
- Condyles superior anterior in fossa
- Here 23 – becomes RCP, holding contact – where new bite will be if confortable and tolerable of pt
- Take interocclusal record here
how to get interocclusal record for RCP
get into position
- The patient is guided into a terminal hinge closure to detect where initial tooth contact occurs (RCP). Most reliable techniques are
- Bimanual Manipulation
- Chin Point guidance
- Chin point guidance with anterior jig
- Can be hard in toothwear cases as muscles strong*
- The RCP record is taken at a slightly increased OVD just prior to this initial tooth contact (the mandible is rotating about its terminal hinge axis)
RCP registration
must use
registration medium
- wax, paste, record block
anterior jig
retruded arc of closure
Initial tooth contact (RCP) can occur at any point on the retruded arc of closure.
This is sometimes called a centric relation premature contact
RCP to ICP slide
If initial contact is on the posterior teeth, then there is likely to be a slide from RCP to ICP as the patient tries to achieve maximum intercuspation of the teeth
In 10% of patients RCP and ICP are the same which means 90% of patients will have a slide to achieve maximum intercuspation
- Less scope to reorganise if the same
RCP is usually infero-posterior to ICP by 0.5–2 mm
assess how to register this occlusion
considerable toothwear
- uneven, severe esp on left
group function
no space for restorations when jaw in ICP
- get jaw in retruded position – manipulate mandible
Too far away – too large an OVD
- Slide forward gradually so still on retruded arc of closure (still have RCP on 14) to close OVD and maintain occlusal stop in contact position
Enough space for restorations but more acceptable OVD
upper cast mounted using
facebow transfer
lower cast mounted using
interocclusal registration
confomative or reorganised
wax up of restorations
Diagnostic wax up of restorations on casts in new occlusal scheme
- tried to incorporate canine guidance in new occlusal scheme
- restore anteriors
can see how will look and work - pt input before placing defintives in mouth
- Stable occlusion and comfortable for pt = happy
guidance and restoration
2 options
- Copy the existing guidance custom incisal guidance table - wax
- Simple
- Conformative
- Most often
- Change guidance group function -> canine guidance
- Not simple
- Reorganised
- Less often
mutually protected occlusion guidance is
canine
space between posterior teeth when in lateral excursion protecting them from lateral forces
guidance in this case
Group function changed to canine guidance
- Many contacts touching all the time
- To canine guidance (wax up)
- space between posterior teeth when in lateral excursion protecting them from lateral forces
occlusal analysis checklist
- TMJ function and muscles of mastication activity
- Incisor relationship
- Molar relationship
- Open and/or cross bites
- Guidance – use of change?
- Wear facets/severity of tooth wear
- Restoration Fractures
- Occlusal contacts
- Deflective contacts TMD problems
- Working/Non-working side contacts
- Mount casts on an average value or semi-adjustable articulator and review all of the above
Most prudent if looking at occlusal analysis to mount casts in more retruded relationship
