jaw relationships and registration

Question 1

What is the resting face height?

Answer 1

Relaxed and condyles in neutral position

~ distance between 2 fixed points when mandible is in habitual postural position

Question 2

What is the occlusal face height?

Answer 2

Distance between 2 fixed points when upper and lower denture are contacting in maximum intercuspation

Question 3

How do the OFH and RFH compare?

Answer 3

The RFH is approx 2-4mm greater than the OFH
This is the freeway space
Increasing the OFH reduces the freeway space

Question 4

What is the intercuspal position?

Answer 4

Position of mandible compared to maxilla when teeth are maximally intercuspated

Question 5

What is centric relation?

Answer 5

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

Question 6

What is the Fox’s Plane Guide?

Answer 6

Gets the wax block parallel to the inter-pupillary line and the alatragal plane

Question 7

How do you know if the lip is supported?

Answer 7

The nasiolabial angle should be near 90 degrees

Question 8

How do you determine the occlusal face height?

Answer 8

Measure the OFH w old dentures

Measure RFH w old dentures

Question 9

Why is the occlusal face height of the old dentures so important?

Answer 9

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)

Question 10

What equipment is needed?

Answer 10

Wax registration rims
Wax knife heater
Dividers
Fox’s plane guide
Occlusal rim inclinator 
Hot plate
Safe air burner

Question 11

How can you relax your patient to find RFH?

Answer 11

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

Question 12

How should you mark your measurements in the face?

Answer 12

Paper triangles- rub off easily

Pen marks much more effective

Question 13

How should you work on the upper block?

Answer 13

2 planes-
~intrapupillary plane (horizontal line between pupils, IP is parallel)

~ala tragal plane (use a Fox bite plane which is parallel to this)

Question 14

How do you add wax to improve lip support?

Answer 14

Make sure both surfaces of wax are hot to stick to eachother

Question 15

How do you insert the lower block?

Answer 15

Make sure upper block is perfect
Manipulate patient into centric relation
Trim lower block to give even contact between upper and lower

Question 16

What is the rim inclinator used for?

Answer 16

Place lip at posterior of back of cast for correct angulation of lower plane from tip of incisors to distal of retromolar pads

Question 17

Why do we use finger rests on reg blocks?

Answer 17

Finger rests in the form of notches on lowers

Allows operator to maintain secure hold of mandible and prevent block from moving during process

Question 18

What should be done once the blocks meet eachother in the mouth correctly?

Answer 18

Mark centre and canine lines using the midline frenum as a key reference

Question 19

Why do you add notches to the rims?

Answer 19

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

Question 20

How do you use silicone bite registration paste?

Answer 20

Applied to finger rest notches via gun
Fast setting
Manipulate into RCP by half closing mouth then retracting tongue to palate and completing bite

Question 21

How should you stick the blocks together?

Answer 21

If blocks touch at correct OVD, gently warm lower block

Full notches w silicon intra orally

Question 22

What do heel clash?

Answer 22

Should always check for this
Put blocks back on master cast
If blocks clash, the cast must be trimmed

Question 23

How can you confirm the shade and mould?

Answer 23

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

Question 24

How can the mould be selected?

Answer 24

Small/medium/large-
~depends on face size/shape

K- tapered (unisex)
O- oval (softer, feminine)
S- square (masculine)
Make sure you ask patient

Question 25

How can you customise the teeth?

Answer 25

Can add elements of wear/staining/diastema