5. Trial dentures Flashcards
Complete Dentures- Trial denture assessment- aims
- assess on articulator
- assess in mouth (in the patient) (upper first then lower)
- correction of errors
- post-dam
Describe the assessment of trial dentures on
an articulator
check…
- waxed up to full extension and well adapted
- polished surfaces correctly shaped
- tooth position satisfactory
- centric occlusion
- balanced articulation
checking that 3. tooth position satisfactory?
Middle of base
not too lingual not too labial
Level of occlusal plane – below the resting tongue level
Good interdigitation
Describe the assessment of trial dentures with
the patient (upper first then lower)
check…
1.Upper anterior tooth
position
2.Jaw relationship
checking that 1. Upper anterior tooth position
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
what if there are errors in upper anterior tooth position
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!
Aim of 2. Jaw position?
Even contact into ICP at RCP –
1. Antero-posterior (protrusive)
2. Vertical components
Jaw position errors are caused by:
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
(2. protrusive error A-P) What are the common errors in jaw registration:
- protrusive registration - did not get jaw into its
most posterior position i.e. at trial can get mandible further ‘back’ than ICP - retrusive registration - pushed lower rim
backwards off ridge i.e. at trial cannot get mandible ‘back’ into ICP - lateral registration - (always associated with a
protrusive error) usually to the side of the
operator - premature contact - (uneven contact in RCP)
resulting in registration rims not being in correct RCP at recording time
(2. protrusive error A-P )The consequence of the common errors in jaw registration
Registration rims not being in correct RCP at recording time
What are the options after assessment of RCP (A-P)
- 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
Describe the correction of errors in trial
dentures
- 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)
Re-registration of jaw relationship
(to rearticulate casts on articulator and reset teeth for re-try)
(2. protrusive error A-P)
- 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
Re-articulating casts on articulator
(2. protrusive error A-P)
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)
- Vertical components - ie. OVD
when A-P is also wrong?
and when A-P is correct?
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)
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
- Problem:OVD (over-closed) too small
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
- Raise articulator pin by appropriate amount, mms, and reset teeth until pin contacts table again (casts now
closer together) - Drop articulator pin by appropriate amount, mms, and reset teeth (casts now further apart)
Define post dam
The posterior palatal seal-
The raised portion of the denture base at the posterior
extent of the upper denture located on its fitting surface
Describe the design of the post-dam
- 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’
How to create functional post dam (posterior palatal seal) for a denture
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)
Error in post dam area? How do you correct?
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)
Replacement post dam in lab…
At chairside : posterior wash impression in ZnO2 Egenol (+/- greenstick)-
The lab will then replace with heat cured PMMA
Replacement post-dam in laboratory
Posterior wash impression in ZnO2 eugenol (+/-
greenstick)
Replacement post dam in lab…
At chairside : posterior wash impression in ZnO2 Egenol (+/- greenstick)-
The lab will then replace with heat cured PMMA
Summarise the stages of trial for complete dentures
Assess on articulator
Assess in mouth – upper first then lower
Correction of errors
Post-dam – mark and carve!
