5. Trial dentures

Question 1

Complete Dentures- Trial denture assessment- aims

Answer 1

• assess on articulator
• assess in mouth (in the patient) (upper first then lower)
• correction of errors
• post-dam

Question 2

Describe the assessment of trial dentures on
an articulator

Answer 2

check…

1. waxed up to full extension and well adapted
2. polished surfaces correctly shaped
3. tooth position satisfactory
4. centric occlusion
5. balanced articulation

Question 3

checking that 3. tooth position satisfactory?

Answer 3

Middle of base
not too lingual not too labial
Level of occlusal plane – below the resting tongue level
Good interdigitation

Question 4

Describe the assessment of trial dentures with
the patient (upper first then lower)

Answer 4

check…

1.Upper anterior tooth
position
2.Jaw relationship

Question 5

checking that 1. Upper anterior tooth position

Answer 5

Does the trial conform to the treatment plan?
Patient wishes / expectations?

Compare to previous denture
Classic guidelines
Mould and shade
Centre line
Lip support
Anterior occlusal plane / posterior occlusal plane
Show patient – leave alone, bring in relative/friend

Question 6

what if there are errors in upper anterior tooth position

Answer 6

Correct at chair side – move 1-2 teeth as guide
Mark new centre line
Choose new mould / shade
‘Labial plumping’ –used to compensate for incorrect anterior tooth placement
Complete prescripton instructions to laboratory!

Question 7

Aim of 2. Jaw position?

Answer 7

Even contact into ICP at RCP –
1. Antero-posterior (protrusive)
2. Vertical components

Question 8

Jaw position errors are caused by:

Answer 8

1 registration rims not in correct RCP at recording
time (operator error)
2 error in mounting rims on articulator esp. posterior
contacts between rims and casts preventing rims
seating correctly on the casts
3 warpage / distortion of base plates of rims

Question 9

(2. protrusive error A-P) What are the common errors in jaw registration:

Answer 9

1. protrusive registration - did not get jaw into its
   most posterior position i.e. at trial can get mandible further ‘back’ than ICP
2. retrusive registration - pushed lower rim
   backwards off ridge i.e. at trial cannot get mandible ‘back’ into ICP
3. lateral registration - (always associated with a
   protrusive error) usually to the side of the
   operator
4. premature contact - (uneven contact in RCP)

resulting in registration rims not being in correct RCP at recording time

Question 10

(2. protrusive error A-P )The consequence of the common errors in jaw registration

Answer 10

Registration rims not being in correct RCP at recording time

Question 11

What are the options after assessment of RCP (A-P)

Answer 11

• Appears satisfactory and accepted
• Minor error (esp. premature contact) accept
  and modify occlusion at insertion
• Re-register- to rearticulate casts on articulator -
  and reset teeth for re-try

Question 12

Describe the correction of errors in trial
dentures

Answer 12

1. Vertical component error:
   If errors in OVD in combination with A-P error:
   they are corrected at the re-registration by
   trimming the wax on the lower to the appropriate
   OVD and A-P i.e. the correct RCP

Correction of errors when the A-P relation
is correct: are done in the laboratory by
altering the separation of the trial
dentures by the appropriate amount and
re-setting teeth

(2. protrusive error A-P)
Re-registration of jaw relationship (to rearticulate casts on articulator and reset teeth for re-try) ( explain … see associated card)

Question 13

Re-registration of jaw relationship

(to rearticulate casts on articulator and reset teeth for re-try)

(2. protrusive error A-P)

Answer 13

• Changes made to lower as upper usually acceptable or easily made so
• Remove those teeth in occlusal contact in the correct RCP (usually posteriors but can involve anteriors)
• Replace teeth with wax to even contact in correct RCP
• Vaseline upper teeth and put paste on the lower wax

Question 14

Re-articulating casts on articulator

(2. protrusive error A-P)

Answer 14

using new record
(the lower cast is remounted as it is the upper cast that
maintains Bonwill’s triangle relationship on the A-V
articulator)

Question 15

2. Vertical components - ie. OVD
   when A-P is also wrong?
   and when A-P is correct?

Answer 15

If errors in OVD in combination with A-P error:
they are corrected at the re-registration by
trimming the wax on the lower to the appropriate
OVD and A-P i.e. the correct RCP

Correction of errors when the A-P relation
is correct: are done in the laboratory by
altering the separation of the trial
dentures by the appropriate amount and
re-setting teeth
(when in the most posterior A-P position
the mandible opens on the hinge axis +
changes in OVD are therefore possible
without causing any change in A-P
relationship)

Question 16

How to re-set the teeth by altering the separation of trial dentures? (in the lab when OVD is wrong but A-P is correct?)
e.g
1. Problem: OVD (over-open) too large

2. Problem:OVD (over-closed) too small

Answer 16

Incisal rod is set at ZERO when 1st articulated
Incisal rod on incisal table and incisal pin at upper incisal mid-line edge, guide rod level at zero

1. Raise articulator pin by appropriate amount, mms, and reset teeth until pin contacts table again (casts now
   closer together)
2. Drop articulator pin by appropriate amount, mms, and reset teeth (casts now further apart)

Question 17

Define post dam

Answer 17

The posterior palatal seal-
The raised portion of the denture base at the posterior
extent of the upper denture located on its fitting surface

Question 18

Describe the design of the post-dam

Answer 18

• Depth varies with tissue displacement
• Palpate with round ended burnisher
• Broad rounded dam better tolerated than sharp V-shape
• Anterior limit depends on soft palate flexion – steep = narrow, shallow = broad
• Broader laterally as tissue more compressible - Cupid’s Bow’

Question 19

How to create functional post dam (posterior palatal seal) for a denture

Answer 19

Score/ mark and carve the posterior limit (from hamular notch to hamular notch) on the cast with round-ended instrument
Making it broader and deeper laterally
(therefore maximising the peripheral seal and retention in the upper denture)

Question 20

Error in post dam area? How do you correct?

Answer 20

Produced using chemically activated acrylic (BMA + PEMA) at chairside

Apply to posterior limit of upper denture in good width and depth

trim and polish
and
to optimise retention of the denture.
THIS DOES NOT HAVE THE MECHANICAL PROPERTIES OF PMMA AND WILL NEED TO BE REPLACED AFTER A NUMBER OF MONTHS…

(needs to be rep bc this material irritates the mouth- at insertion use chem act acrylic in the short term and then eventually replace)

Question 21

Replacement post dam in lab…

Answer 21

At chairside : posterior wash impression in ZnO2 Egenol (+/- greenstick)-
The lab will then replace with heat cured PMMA

Question 23

Replacement post-dam in laboratory

Answer 23

Posterior wash impression in ZnO2 eugenol (+/-
greenstick)

Question 24

Replacement post dam in lab…

Answer 24

At chairside : posterior wash impression in ZnO2 Egenol (+/- greenstick)-
The lab will then replace with heat cured PMMA

Question 25

Summarise the stages of trial for complete dentures

Answer 25

Assess on articulator
Assess in mouth – upper first then lower
Correction of errors
Post-dam – mark and carve!