Registration: Stage II intermaxillwry Relation Flashcards
What happens if there is an error in recording the intermaxillary jaw relation
Dentures will be uncomfortable or unwearable and may even have the potential to produce lasting damage to many elements of the stomatognathic system
What are the three elements to be recorded at the intermaxillary relation record stage
Vertical relationship Horizontal plane (antero posterior relationship) Coronal plane (lateral relations of the jaw)
What is the first of the intermaxillary relationship records
Vertical relationship
Establishes the amount of jaw separation
What is the RVD
Resting vertical dimension
What does resting vertical dimension mean
FWS = RVD - OVD
What is the FWS
Individuals that have their natural dentition demonstrate a space between the occlusal surfaces of the teeth and the opposing Jaws when they are at rest and with the head upright
What is another name for the FWS
Interocclusal distance
What is the FWS determined by
A balance between the elevator and depress or muscles attached to the mandible and the elastic nature of the sorrounding soft tissue in a natural dentition
How is the FWS measured
Indirextly by noting the difference between the resting vertical dimension of the face using a Willis gauge and subtracting from this the vertical dimension of occlusion with the teeth in occlusion
How is the RVD measured
Willis gauge
Is the RVD a stable measurement
The RVD may differ in a pt after they become edentulous compared to when teeth were present. RVD is not a stable position throughout life for a given individual
Is RVD the starting point
Yes. This measurement can also be used to determine the appearance of the denture wearing pt
Why is head position important when measuring RVD
Tilting the head backwards pulls the mandible away from the maxilla and a forward inclination pushes the mandible and attached structures closer to the maxilla
How is the RVD measured? What reference points are required?
Two measuring points are required in the midline of the face - one related to the nose, and one to the chin
What is important about the two points required on the chin and nose when measuring the RVD
The points must be on sites of minimal influence from the muscles of facial expression to avoid skin movement and should be chosen only after careful observation of the patient seated normally in the dental chair with the head erect
How is the RVD measurement made? At what stage?
The measurement is made with the pt in a relaxed and comfortable position while wearing the previously developed upper base and rim.
What might help in recording the RVD? What can you ask the pt to do?
It may be helpful if the pt moisten the lips with his or her tongue and brings them into light contact prior to recording the measurement.
Asking the pt to swallow and relax the Jaws is also a useful method.
Verification of the measured value can be attempted by asking the pt to say the letter m and to hold the facial expression whilst the measurement is made.
Carefully observe
What might be observed if the upper and lower base and rim are placed in the mouth and there is excessive OVD
Orbicularis iris muscle group straining to effect a seal
What can an insufficient OVD look like
Ageing effect on the pt
How can you establish the height of the lower rim?
- The relative height of the upper and lower rim should be considered
- An element of reasonable balance between the two rims is desirable
- Excessive height of the lower rim can have the effect of walling in the tongue causing a resultant unstable lower denture
- On the other hand, deficient depth of the lower rim can result in poor aesthetics and further may result in tongue biting.
- The occlusal plane should be below the dorsum of the tongue at rest
What effect will excessive reduction in. The height of the lower rim have?
‘walling in’ the tongue
Causing a resultant unstable lower denture
What effect will a deficient depth of the lower rim result in?
Poor aesthetics
Tongue biting
Should the occlusal plane be below the dorsum of the tongue at rest
Yes
Should the RVD be established first, before the upper and lower rims are placed in the mouth?
Yes
Do you mould the upper rim first?
Yes
How is the OVD established?
- Mould upper rim
- Reduce lower rim height until it contacts evenly the upper rim at VDO 2-4 mm less than the established RVD
- Ensure FWS of 2-4mm
What may be the consequences of excessive OVD
- Increased risk of trauma to the tissues underlying the Dentures as the absence of a freeway space effectively causes continuous clenching of the teeth
- Painful mucosa over the denture bearing areas and muscle soreness, particularly associated with the masseter muscle
- Teeth are liable to contact (causing clicking during speech)
- Difficulty in bringing the lips together for p b m sounds
- Poor aesthetics
- Tmjd
Is clicking of the teeth a manifestation of insufficient or excessive OVD
Excessive OVD may cause clicking as the teeth are liable to contact during speech and the pt will have difficulty with other softer sounds p b m
What trauma may result to the pt due to excessive OVD
Absence of freeway space effectively causes continuous clenching
Painful mucosa over the denture bearing areas and muscle soreness
What may be the results of insufficient OVD
Lack of support of the angles of the mouth
Causes dribbling and possible angular Cheilitis may be present
Reduced masticatory efficency
Poor aesthetics lack of adequate support of the lips and cheeks may be seen
Chin protrusion on closure of the Jaws
What should be remembered about the FWS
FWS is an average value
Pt dependent
Some pts may require a larger or smaller value
Eg where atrophic mucosa exists in middle aged adult an increased FWS might prevent or redu e trauma to the residual mandibular tissues
How can you verify the OVD
There are several methods to verify OVD
However occlusal rims are so different from the form of teeth to be used that it is very difficult to apply tests for suitability of the chosen value at this stage
Checks on OVD will need to be made at a later stage - the trial stage
How is the antero posterior position of the mandible measured
Using the retruded contact position
To measure AP position of the mandible relative to maxilla
What is the retruded contact position used for
To measure the antero posterior position of the mandible relative to the maxilla
Why use the RCP to measure the AP position of the mandible relative to the maxilla
RCP is a reproducible position in the edentulous pt
A normal contact between opposing Dentures when set up in other than the retruded relationship results in denture instability.
What is the apparatus used for reproducing relevant jaw relationships
Articulator
What is the articulators used for
Reproducing jaw relationships
What point does the articular operate at
RCP
What may happen if the RCP is incorrectly recorded or the pts Dentures are not made to RCP
Abnormal tmj activity
As the pt tries to accommodate incorrect occlusal relations
What can the clinician advise the pt to do to check that the occlusal rims are in the selected OVD
Rims should be inserted into the mouth and pt persuaded to close gently with the mandible the retruded jaw relationship
The word bite should be avoided as it suggests to the pt that forceful closure is required. Results in mandibular position that is protrusive
How can the mandible be manipulated into RCP
Some pts have the capacity to relax the muscles attached to the mandible so that the operator can readily move the mandible up and down as it rotates about the condyles.
The mandible is in the retruded position and can be guided there during the registration procedure
Other pts are able to retruded the mandible when the tongue is curled back in the roof of the mouth to feel the posterior border of the upper base or a shallow ridge of wax placed on the palatal area of the base posterior to the first molar region
What is the most positive and successful method of identifying the RCP
Gothic arch or arrowhead tracing method readily identifies the most retruded position of the mandible relative to the maxilla from which lateral excursions can be made
What is RJR (retruded jaw relations) and what methods are used to record it
This is the measurement taken when upper and lower rims are fixed in position with the mandible in its most retruded position and with the Jaws separated by the established OVD
Wax squash bite (and its predecessor, the T block system)
Wax rims with ‘manchester’ blocks
Intra oral tracing (gothic arch tracing)
Extra oral tracing
What is the wax squash bite technique for recording retruded jaw relations
A horseshoe shaped roll of softened wax is placed between the upper and lower rims and the pts Jaws are closed
The lower rim is first reduced in height to provide space for the wax
Why is the wax squash bite a poor bite reg technique
Results using this method are uncertain because of the lack of control of the vertical dimension, the common difficulty of obtaining mandibular retrusion and the fact that the record takes no account of mandibular movements other than the final act of closure
If the wax is not uniformly softened throughout its length
An unstable relationship with the underlying tissues is recorded
Why is the wax rim technique using Manchester blocks a better wya of recording jaw reg compared to wax squash bite
Wax rims including Manchester blocks for jaw reg:
Good control of OVD good base stability if PMMA used
Good occlusion development with facebow mounting
What do the Manchester rims look like
Manchester rims have carding wax added to the labial segment of the lower rim - help create a functional modelling of the denture space anteriorly
“The lower base has two pillars of wax attached to it in the region of the 2nd premolar/1st molar teeth”
If after any of the three techniques have been used and the casts are approximated and examined and the heels are found to contact. What should be done
The gypsum contact should be removed prior to Articulation otherwise a posterior bite will be incorporated into the setup and will be evident at the trial Insertion
What can be done to manage atrophic mucosa in a pt requiring full Dentures
Intentionally increasing in FWS might reduce trauma to the denture bearing tissues of the mandibular denture
An efficient masticatory apparatus with an optimal FWS might result in trauma to the mandibular ridge
What are wax rims how are they used?
The conventional method that has a higher degree of success, involves the use of wax interposed between the rims to secure the registration
When the upper rim (aesthetic control base) has been formed and prescribed to suit the pt the lower rim is placed in the mouth and trimmed until it contacts the upper rim evenly in RCP at the selected OVD. This is done by selectively removing points of first contact. These large wax rims may pose problems in inexperienced hands even in experienced hands it is not always easy to detect premature contacts along the lengths of the rim bilaterally
How does the Manchester block method work
Utilising pillars attached to the lower base provides control over the OVD ensures a stable relationship between. The bases and underlying tissues and also provides a record that can be simply returned to the mouth to verify its accuracy
How can a functional impression of the labial component of the lower arch be recorded using the Manchester block method?
Carding wax or putty may be attached to the labial aspect of the rim and a closed mouth impression used to determine the anterior denture spaced form
What are the drawbacks of using the Manchester blocks
Uncertainty of achieving the most reteuded mandibular position
Lack of info on eccentric mandibular movements provided
Is using an intra oral tracing a good reg technique?
Yes there is
Good control of OVD good base stability good control of RCP and other mandibular activity
Excellent occlusion and Articulation development with facebow mounting
The gothic arch tracing or _____ ____ ________ is based on rotation about the ________ when lateral mandibular excursions are made.
The gothic arch tracing or intra oral tracing is based on rotation about the condyles when lateral mandibular excursions are made
What principle does the gothic arch tracing method rely on
Rotation of the condyles when lateral mandibular excursions are made
When the mandible moves to the left from a central position it rotates about which condyle
Left condyle
When the mandible moves to the right from a central position it rotates about the _____condyle
Right
Right lateral movement causes rotation about the right condyle. True or false
True
When do the condyles assume their most retruded position
Between each lateral excursion
What apparatus is needed for gothic arch tracing
Two pieces
One for each arch
Both mounted on rigid stable bases
Usually made of light cured PMMA
Upper apparatus comprises of:
metallic plate
Spans the maxiary arch
Lower applianxe:
A bar containing an adjustable central bearing screw 1mm thread mounted on wax or compound pivots added to a light cured PMMA base
What does the lower arch of the gothic arch tracing apparatus consist of
A bar containing an adjustable central bearing screw 1mm thread mounted on wax or compound pivots added to a light cured PMMA base
What does the upper arch apparatus of the intra oral gothic arch tracing consist of
Upper apparatus comprises of:
metallic plate
Spans the maxillary arch
The adjustable central bearing screw is made to contact the upper plate at right angles and at the selected OVD
During lateral excursions what areas of the two appliances contact
The central bearing pin contacts the upper plate only
What is the pt instructed to do once the upper and lower apparatus for measuring goth arch tracing is in place
Swallow - to indicate a central RCP position
Asked to make three left lateral excursions and the to return to RCP
Then three right lateral excursions and return to RCP
The process is then repeated after coating 5he upper plate in felt top pen and asking the pt to repeat the protrusive and lateral movements
What is the purpose of the screw in the gothic arch tracing appliance
It scribes on the upper plate two arcs of rotation which intersect in a position corresponding to RCP
It is from this point that an intersection with the protrusive movement is also traced
How can the RCP be validated from the tracing
Perforated perspex cover slip is positioned with the perforation over the arrowhead and waxed in place. The pt is then asked to swallow and confirmation of RCP is achieved by central bearing screw engaging the perforation
Gothic arch tracing, wax rims and squash bite all record what?
What else is needed
Antero posterior intermaxillary relations
The coronal relationship should be recorded using pvs putty placed between the bases
How is the coronal relationship recorded after the gothic arch appliances have measured the vertical and AP relationship
Pvs putty placed between the bases and the ce tr bearing screw
What is extra oral tracing
Same as intra oral tracing except that the tracing apparatus is attached to plates that protrude between the lips
Not considered to be as accurate as that of the intra oral method for edentlus pts because the protrusion of the recording apparatus is so far forward of the pivotal area that tilting and or deflection of the bases is likely
What articulators are used to construct complete dentures
Simple hinge plane line
Moveable fixed condyle path
Semi adjustable
How does the simple hinge articulators work
Allows the construction of a central occlusion only
What is the advantage of the fixed condylar path articulator compared with the simple hinge
Allows some lateral and protrusive movement
What are the limitations of using a simple hinge articulator
Few simple hinge articulators have provision for accepting a facebow record so that this further limits their usefulness
Which types of articulator accept facebow records
Semi adjustable and fixed condylar
Allow protrusive and lateral interocclusal records
How do facebows improve the lab process
They improve the accuracy of cclusal development of articulators
How is the maxillary vast mounted on the articulator? What is needed
The maxillary cast is mounted via a facebow transfer and the mandibular arch related to the maxillary arch via the gothic arch tracing therefore the development of satisfactory eccentric lateral and protrusive occlusion and articulation is possible
How is the mandibular arch related to the maxillary arch on the articulator
Using the gothic arch tracing
What is the sequence of events in the gothic arch technique
- Gothic arch tracing recorded
- Verify the RCP on the arrowhead tracing of the mandibular movement using perspex locator placed over the arrowhead point
- Once reproducibility of RCP is confirmed take PVS putty mould between the upper and lower bases to provide a coronal relationship
