Jaw relations and registration

Question 1

RFH and OFH

Answer 1

Rest face height > occlusal face height
Vertical jaw relations
Rest face height = relaxed, not fixed
Occlusal face height is fixed position

Question 2

Freeway space

Answer 2

Difference between RFH and OFH
Ideally 2-4mm
Some pxs need larger freeway space to aid adaptation
Increasing OFH reduces FWS (inversely proportional)

Question 3

Horizontal jaw relations

Answer 3

ICP and retruded position

Question 4

Retruded position

Answer 4

First point of ccontact at desired occlusal face height in rotational movement of lower jaw (centric relation)
RP + (RFH-3mm) = pain-free dentures

Question 5

ICP

Answer 5

Intercuspal position

Point of maximum intercuspation

Question 6

Clinical procedure

Answer 6

1. Special equipment
2. Lip support and tooth position
3. Record jaw relations
   - occlusal face height
   - retruded jaw position
4. Confirm tooth characteristics: shape, size, shade

Question 7

Blocks

Answer 7

Wax registration rims

Question 8

Special equipment

Answer 8

Dividers
Foxes plane guide
Wax knife heaters
Rim inclinator
Hot pate 
Hot air burner

Question 9

Three key measurements

Answer 9

The OFH with old dentures in
The RFH with px’s most comfortable denture in
Determine what you want OFH to be when new dentures are made

Question 10

Why is OFH of old set so important?

Answer 10

View px from front & profile when in occlusion
Make reasonable assumption on px: if right, midly overclosed, grossly overclosed or has no FWS
OFH of old dentures much easier to measure than RFH as px has something to bite against that is relatively reproducible
Pxs struggle to adapt to large changes in OFH
Beware mobile metalis
Not always natural for lips to be touching in severe class 2 and class 3 cases

Question 11

Beware mobile mentalis

Answer 11

Mentalis can change occlusal face height - they need to be relaxed

Question 12

How can I relax my px to find RFH

Answer 12

Ask px to touch lips together very gently whilst staring at distant object
1, 2, 3 test
Gentle imperceptible blowing
Say 'mmm'
Look away and wait until px is relaxed
Measure with px only wearing one denture

Question 13

Fox’s Bite Plane

Answer 13

Measures Ala-tragal line
Upper teeth should slope up parallel to plane
Mark incisal plane parallel to interpupillary line at approx. level of upper lip
Mark posterior occlusal plane parallel to alar of nose/ tragus of ear

Question 14

Adjust rim using

Answer 14

Inclinator and hot air burner
Confirm occlusal plane is approx parallel to alar/ tragus line using Fox’s plane guide
Wax can be added to improve lip support
Insert lower block & trim until meeting evenly in retruded position at predetermined OFH

Question 15

Why do we use finger rests on registration blocks?

Answer 15

Finger rests allow clinician to maintain secure hold of mandible and prevent registration blocks from moving during registration process
Put silicone in gaps

Question 16

Centre line marking

Answer 16

Face in line with px
Look where midline frenum is
If dealing with Class II ensure scribed centre line goes through occclusal plane

Question 17

Notching of both rims function

Answer 17

To allow accurate mutual location using some form of intermediate rigid fixation

Question 18

Why do we use occlusal notches on both upper and lower registration blocks?

Answer 18

They allow silicone to seal blocks together in unique position & allow technicians to reattach blocks in correct position if they come apart

Question 19

How do we notch rims

Answer 19

Upper and lower opposing occlusal notches should be placed bilaterally
Place small amount of registration paste on either side in region of notches
Lower jaw manipulated into retruded arc of closure - tongue retraction, & occlusion, extruding registration paste into location notches

Question 20

If blocks touch perfectly at correct OVD

Answer 20

Use gently warmed wax

Question 21

Remove part of rim

Answer 21

Which appears likely to interfere with occlusion

Question 22

Confirm tooth characteristics

Answer 22

Match shade of tooth with px’s complexion but make sure px agrees with choice
Select appropriate shape and size, using px’s face shape and body size as reference points

Question 23

What gives realism to teeth

Answer 23

Use of simulated attrition and stains

Question 24

Mould selection

Answer 24

Are teeth small medium or large
If face round, tapered or square
Ask px