Occlusion and Restorative Dentistry 3 Flashcards
what are the 3 kinds of articulator
- Arcon
- Average Value
- Semi-Adjustable
what is an average value articulator
○ Bennet Angle set at 15˚
○ Condylar Guidance Angle set at 30˚
○ The articulating condyle is on the lower arm = anatomically correct
§ Condyle is on the lower jaw not the upper jaw
what is a semi-adjustable articulator
○ Allows you to set the Bennet and Condylar Guidance Angles
§ Quite a complex thing to do
§ Available within the dental hospital in the restorative lab on level 6
○ Can see full range of movements for diagnosis and evaluation
○ Bit advanced, most of the time we would probably be looking to use an average value articulator
what are diagnostic casts most effective mounted on
Diagnostic casts are most effectively mounted on a semi-adjustable articulator with a retruded record
You can then see the full range of mandibular movements for occlusal diagnosis and evaluation
what can be used to mount the maxillary cast onto the articulator
You can use a facebow transfer to mount the maxillary cast onto the articulator
what is used to mount the lower casts onto the articulator
Need an intra-occlusion registration to mouth the lower casts in the position you want
what is the mouth shaped part of the face bow called
Mouth shaped part = bite fork
Has a long metal part which attaches to the transfer jig assembly
what is the funny shaped ruler on the face bow called
Funny shaped ruler = reference plane locator
how can you make the ear bow looser or narrower
There is a screw near the spirit level
Can loosen / tighten the screw to make the earbow looser or narrower
how do you 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
Measure 43mm from the lateral incisor which shows the approximate position of the infraorbital foramen = this gives us a bony reference point
how is the bite registration taken
- Bite registration paste applied to bite fork. Bite fork arm to the right and locating notch facing up
- Need to locate the bite fork within the mouth by taking a registration
• Apply bite registration paste to the bite fork
○ Using a silicone based material
○ Quite a firm wax
- Apply it to the curvature along the shape of the arch
- 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
• Insert it into the patient’s mouth to capture the cusp tips of the maxillary teeth
○ Want it to be parallel with the patient’s coronal and horizontal planes
○ Have the little notch over the dental midline
what do you align the dental midline with
the locating notch on the bite fork
how does the bite registration paste allow for accurate repositioning and mounting of the cast
• Indentations of maxillary teeth clearly visible to allow accurate repositioning and then mounting of the maxillary cast
• Silicone based material
Hasn’t been made really thick to get the whole tooth impression, just want to make sure you have the cusp tips and incisal edges so we can use this to accurately mount our casts
what does the ear bow do
The earbow is the part that goes in the ear and measures the inter-condylar distance (the terminal hinge axis)
how do you open / close the ear bow
loosen centre wheel
what does the face bow need to be parallel to
Ensure the bow is parallel to the interpupillary line / floor
how do you remove a face bow from the patient
- 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 face bow record
The relationship of the maxilla to the hinge axis of rotation of the mandible
what does the face bow then allow you to do
• We can now mount the maxillary cast in an equivalent relationship on the articulator
Using an arcon articulator
what can be used to mount the mandibular cast in relation to the maxillary cast already mounted
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
what are the 2 choices of interocclusal registration you can use to mount the lower cast
○ Intercuspal Position (ICP)
§ Conformative Approach
○ Retruded Contact Position (RCP)
§ Reorganised Approach
what is an interocclusal registration
how the teeth meet together
when might you need no material for an ICP registration
If there are lots of tooth to tooth contacts in ICP and it is really obvious to the technician then you don’t need a registration to mount the lower casts as you can almost hand articulate the casts so you don’t need any material
simply:
- plenty of tooth contacts
- ICP is obvious to technician
in fact using material in this situation may make it less accurate
if the ICP is not obvious to the technician what materials would be used for the ICP registration
- wax (thin wafer wax)
- paste (silicone paste)
when would a record block be used to take an ICP registration
if the patient has free end saddles so the casts cannot be hand articulated
when do you use no material for an ICP registration
The intercuspal is obvious
There are multiple tooth contacts when the patient bites together
when do you use wax for an ICP registration
• When there are enough teeth and the bite in ICP is obvious you don’t need wax.
When using wax you must ensure it is thin and cusp tips are visible
what happens if too much wax is used
• 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
○ can Change the occlusion from conforming to the original occlusion to re-organising the occlusion because the bite has been completely changed
when do you use registration paste for an ICP registration
- When ICP will not be obvious to the technician
* A small amount is needed
what material is the registration paste normally
• Silicone paste that sets quickly
○ Short working time
what happens if too much registration paste is used
• Too thick and it will increase the OVD
Occlusal contacts must be visible through the material
what is a confirmative approach
ICP registration without OVD increase
what is a reorganised approach
ICP registration with an OVD increase
If the entire occlusal scheme is to be reorganised to create the new stable position in what ICP are the final restorations to be made
then the final restorations are made in the new ICP
before embarking on treatment what much you decide about placing restorations
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)
what sort of approach is an RCP registration with or without OVD increased
reorganised approach
not simple
what sort of approach is an ICP registration with OVD increase
reorganised approach
not simple
what sort of approach is an ICP registration without OVD increase
confirmative approach
simple
what is an unorganised approach
• 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
• Don’t want to do this approach
○ want to be methodical
○ Plan what you are doing
define the confirmative 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
what can be done to avoid the unorganised approach
Mark up your contacts before you change them
what are the 3 types of occlusal contacts
- surface to surface contact (not that desirable, tend to be more common in complete dentures)
- tripod contact (uses cusp inclines, extremely difficult to do accurately)
- cusp tip to fossa contact (tend to do the most)
While tripod contact points are great in theory, what happens when one of the point is heavier or lighter than the others?
○ The answer is simple: physics dictates that.
○ Now you have 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
what is an easier solution than tripod contact points 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.
When do we not use the conformative approach?
Ie when do we not place restorations in the ICP
- 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
○ Ie if there is significant tooth wear or the teeth are really quite shortened
• There is a history of occlusally related failure or fracture of existing restorations
what needs to be planned or decided with a reorganised approach
- Plan to provide new restorations to a different occlusion
- The occlusion is definedbeforethe work is started
- Provide restorations, which change the occlusion but are well tolerated by the patient
why use the reorganised approach
ICP is non-existent or no use
You need space to place restorations
what is RAP
Retruded axis position
RAP is a reproducible position of the mandible independent of the teeth
Need to manipulate the mandible into a more retruded position, so that the condyles are more superior-anterior in the fossa to get a tooth contact which is stable and comfortable and well tolerated by the patient
What are the reliable techniques in guiding the patient into a terminal hinge closure to detect where initial tooth contact occurs
○ Bimanual Manipulation
○ Chin Point guidance
○ Chin point guidance with anterior jig
how is the RCP record taken
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)
what is bi-manual manipulation
just letting the mandible go relaxed and floppy to gently push the mandible back into position
dentist stands behind the patient
what is chin point guidance
Lie the patient a bit supine, allow the mandible to go a bit floppy and use chin-point guidance to gently guide the mandible into a more retruded position
what can cause problems when trying to guide the patient into the position we want
Lots of these patients will have tooth wear habits and will have been clenching and grinding for years so often these muscles can be quite strong and not want to go into the position we are guiding it towards
when do you take the registration in RCP
take your registration just before the teeth contact in RCP
what materials are used for an RCP registration
- wax
- paste
- record block (free end saddles, casts cannot be hand articulated)
can do you an RCP registration without a material
you must use a registration medium
you may use an anterior jig
what is the retruded arc of closure
line on posset’s envelope between RCP and R (retruded axis aka terminal hinge axis)
where can initial tooth contact occur
can occur at any point on the retruded arc of closure
this is sometimes called a centric relation premature contact
when is there likely to be a slide from RCP to ICP
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 teteh
where is RCP usually in relation to ICP
RCP is usually infers-posterior to ICP by 0.5-2mm
in what % of patients are the RCP and ICP the same
10%
this means 90% of patients will have a slide to achieve maximum intercuspation
what 2 things can we do about guidance when restoring anterior teeth
○ Copy the existing guidance
§ Simple
§ Conformative
§ Most often
○ Change guidance
§ Not simple
§ Reorganised ~ designing / prescribing occlusion
§ Less often
what does a mutually protected occlusion have
canine guidance
what is the checklist for occlusal analysis
• TMJ function and muscles of mastication activity ○ Extra-oral examination • Incisor relationship • Molar relationship • Open and/or cross bites • Guidance • Wear facets/severity of tooth wear • Restoration Fractures ○ Multiple restoration fractures in the posterior can be indicative of a problem with the occlusion • Occlusal contacts • Deflective contacts • Working/Non-working side contacts • Mount casts on an average value or semi-adjustable articulator and review all of the above
