jaw relationships and registration Flashcards
What is the resting face height?
Relaxed and condyles in neutral position
~ distance between 2 fixed points when mandible is in habitual postural position
What is the occlusal face height?
Distance between 2 fixed points when upper and lower denture are contacting in maximum intercuspation
How do the OFH and RFH compare?
The RFH is approx 2-4mm greater than the OFH
This is the freeway space
Increasing the OFH reduces the freeway space
What is the intercuspal position?
Position of mandible compared to maxilla when teeth are maximally intercuspated
What is centric relation?
Position of maxilla compared to mandible when the condyle disc is in the most superior position in the glenoid fossa
Jaw hinges here for approx 20-25mm
What is the Fox’s Plane Guide?
Gets the wax block parallel to the inter-pupillary line and the alatragal plane
How do you know if the lip is supported?
The nasiolabial angle should be near 90 degrees
How do you determine the occlusal face height?
Measure the OFH w old dentures
Measure RFH w old dentures
Why is the occlusal face height of the old dentures so important?
Can make a reasonable assumption on whether the patient looks right, mildly/grossly overclosed or no FWS
OFH of older dentures- easier as patient has something to bite on
Patients struggle to adapt to large changes
Not always natural for lips to touch (esp class 2 and 3)
What equipment is needed?
Wax registration rims Wax knife heater Dividers Fox’s plane guide Occlusal rim inclinator Hot plate Safe air burner
How can you relax your patient to find RFH?
Touch lips v gently whilst looking at distant object
1,2,3 test- keep whispering, lips come together at 3
Gentle imperceptible blow
Say ‘mmm’, ‘mmm’
Look away and wait until patient forgets and relaxes
Beware mobile mentalis in chin and slowly closing mandible
Measure patient w one denture in
Not perfect- high margin of error
How should you mark your measurements in the face?
Paper triangles- rub off easily
Pen marks much more effective
How should you work on the upper block?
2 planes-
~intrapupillary plane (horizontal line between pupils, IP is parallel)
~ala tragal plane (use a Fox bite plane which is parallel to this)
How do you add wax to improve lip support?
Make sure both surfaces of wax are hot to stick to eachother
How do you insert the lower block?
Make sure upper block is perfect
Manipulate patient into centric relation
Trim lower block to give even contact between upper and lower
What is the rim inclinator used for?
Place lip at posterior of back of cast for correct angulation of lower plane from tip of incisors to distal of retromolar pads
Why do we use finger rests on reg blocks?
Finger rests in the form of notches on lowers
Allows operator to maintain secure hold of mandible and prevent block from moving during process
What should be done once the blocks meet eachother in the mouth correctly?
Mark centre and canine lines using the midline frenum as a key reference
Why do you add notches to the rims?
Should oppose eachother and be bilateral
Should be on lowers initially anyways for finger rests
Allows accurate mutual location using some form of intermediate rigid fixation
Allow silicone to seal blocks together in unique position
Allows technician to reattach blocks in correct position
How do you use silicone bite registration paste?
Applied to finger rest notches via gun
Fast setting
Manipulate into RCP by half closing mouth then retracting tongue to palate and completing bite
How should you stick the blocks together?
If blocks touch at correct OVD, gently warm lower block
Full notches w silicon intra orally
What do heel clash?
Should always check for this
Put blocks back on master cast
If blocks clash, the cast must be trimmed
How can you confirm the shade and mould?
Use old set as guide- ask patient if they like them or not and why
If no old set- see if they have an old picture of their teeth
If neither- use patients size and face shape
How can the mould be selected?
Small/medium/large-
~depends on face size/shape
K- tapered (unisex)
O- oval (softer, feminine)
S- square (masculine)
Make sure you ask patient
How can you customise the teeth?
Can add elements of wear/staining/diastema
