**Complete Dentures**
Preclinical
**Secondary**
**Impression**
**Complete Denture Overview**
**Treatment Schedule**
| Visit | Operator | Procedure |
| :------- | :--------- | :------------------------------------------------- |
| Visit 1 | Clinician | Patient evaluation & primary impressions |
| | Laboratory | Diagnostic casts & special trays |
| Visit 2 | Clinician | **Secondary impressions** |
| | Laboratory | Bead & box, master casts, base & rims |
| Visit 3 | Clinician | Contour rims, OVD, MMR, shade & mould selection |
| | Laboratory | Articulation & tooth setting |
| Visit 4 | Clinician | Wax try-in |
| | Laboratory | Finalisation & processing |
| Visit 5 | Clinician | Assessment & issue |
| | | Instructions for care |
| Visit 6 | Clinician | Post operative review, post insertion instructions |
**Secondary Impressions**
** Intraoral Anatomy**
Maxilla
**Secondary Impressions**
**Intraoral Anatomy**
Posterior Palatal Seal
**Posterior limit:**
The distal demarcation of the movable and non-movable
tissues of the soft palate (vibrating line) – usually ~ 2mm
anterior to Fovea Palatini
**Anterior limit:**
The junction of the hard and soft palates on which
pressure, within physiologic limits, can be placed
**Lateral extension:**
Hamular notch
**Secondary Impressions**
**Intraoral Anatomy**
**Maxilla**
MAXILLARY DENTURE AREA
TRANSVERSE SECTION
Nasal cavity
Maxillary sinus
Palatine artery
Muco-periosteum
Tuberosities
Buccinator
Maxilla
Tongue
Sublingual G.
Mandible
Hamular notch
**Secondary Impressions**
**Intraoral Anatomy**
Maxillary Tuberosity
Occlusal Plane
Transverse section through the tuberosities
**Secondary Impressions**
**Intraoral Anatomy**
Maxillary Tuberosity
An intimately fitting denture
cannot be forced over the
enlarged ridge
THE UNIVERSITY OF
**WESTERN**
**AUSTRALIA**
Oral Health Centre
of Western Australia
**Secondary Impressions**
**Intraoral Anatomy**
**Maxillary Tuberosity**
Solution 1.
Cut back the denture
from one undercut area
Seat this
side first
Then rotate into position
THE UNIVERSITY OF
WESTERN AUSTRALIA
Oral Health Centre
of Western Australia
Solution 2.
Block out one of the undercuts on the processing cast and fabricate a fully extended denture.
Seat this side first
Then rotate into position
**Secondary Impressions**
**Intraoral Anatomy**
Maxillary Tuberosity
Solution 3.
Surgically remove one
undercut prior to
secondary impression-
making and fabricate a
fully extended denture.
**THE UNIVERSITY OF**
**WESTERN**
**AUSTRALIA**
**Oral Health Centre**
**of Western Australia**
**Secondary Impressions**
**Intraoral Anatomy**
Mandible
**Basal Bone**
THE UNIVERSITY OF
**WESTERN**
AUSTRALIA
Oral Health Centre
of Western Australia
**Secondary Impressions**
**Intraoral Anatomy**
**Mandible**
**Secondary Impressions**
**Impression Objectives**
Retention
Is dependent upon atmospheric pressure, adhesion, cohesion (which depends on
peripheral seal), mechanical locks and muscle control.
Stability
Close tissue adaptation reduces horizontal movement of the denture.
Support
Maximum coverage ensures minimal pressure applied at any individual point.
Aesthetics
Peripheral thickness should be varied according to the facial contours and lip support
required.
Ridge preservation
With the loss of stimulation of the natural dentition the alveolar ridge will atrophy or
resorb, the process can be hastened or retarded by local factors.
The tendency of
different molecules to
stick together
The tendency of
like entities to
stick together
**Secondary Impressions**
**Impression Materials**
Thermoplastic
Agar hydrocolloid
Impression waxes
**Chemical Reaction**
Alginate
Zinc-oxide eugenol paste
Plaster of Paris
Polyvinyl siloxane
Polyether
**Digital**
Intra-oral scan
Extraoral scan of secondary impression/cast
(Stock Water-cooled Tray)
(Custom Tray)
***The University of Western Australia***
Oral Health Centre of Western Australia
**Secondary Impressions**
**Impression Types**
**Mucostatic**
The state of the oral mucosa as recorded when not displaced by external forces.
Advantages:
Dentures conform closely to the shape of the mucosal surface
Physical retention is optimal (when denture not under load)
Disadvantages:
The occlusal loads will be uneven
Difficult to obtain true static impression
**Functional**
Tissue state recorded using a custom tray under “functional” load.
All tissues loaded equally regardless of their load-bearing ability
**Selective Pressure**
Tissue state recorded under load in custom tray with maximum coverage but relief in specific areas
Advantages:
More even displacement under occlusal load
Disadvantages:
Less retention to be obtained when the teeth are apart
No controlled studies have been identified to support an advantage due to any of the following factors:
border moulding, post dam, mucostatic, functional or selective pressure impressions. Carlsson GE, 2013.
**Mucostatic Impression**
**Reversible Hydrocolloid**
**THE UNIVERSITY OF**
**WESTERN**
**AUSTRALIA**
**Oral Health Centre**
**of Western Australia**
**Mucostatic Impression**
**Intraoral Scan**
<br>
**Scan Strategy**
<br>
<br>
<br>
TRIOS 3 Wired
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
THE UNIVERSITY OF
**WESTERN**
**AUSTRALIA**
<br>
Oral Health Centre
of Western Australia
**Selective Pressure Impression**
**Denture Bearing Areas**
**THE UNIVERSITY OF**
**WESTERN**
**AUSTRALIA**
**Oral Health Centre**
**of Western Australia**
**Area to be relieved**
**in impression tray**
**Impression**
**Tray**
**2mm**
**12 mm**
**8 mm**
**Selective Pressure Impression**
**Denture Bearing Areas**
MAXILLARY STRESS BEARING AREAS
**Normal Maxilla**
MAXILLARY STRESS BEARING AREAS
**Compromised Maxilla**
**Selective Pressure Impression**
**Maxillary Relief Area**
❖ Simple geometry and the
histology of the area dictates
that the width of the maxillary
relief area is related to the
cross-sectional shape of the
palate and thickness of the
underlying tissue
❖ Denture stability is enhanced by
appropriate relief
= Wax Relief
**NARROW**
(V-Shape)
**NORMAL**
**FLAT**
**Mucosa**
**Alveolar bone**
**Impression tray**
**Secondary Impressions**
**Denture Bearing Areas**
**Masticatory Force**
**Impression**
**tray**
**Wax relief**
**Selective Pressure Impression**
**Tray Fabrication**
Design Objectives
* Custom-made for final impressions to address individual anatomical variations
* Well adapted to tissues
* 2 – 3 mm thick
* Border extensions 1 mm short of the vestibule when the intraoral tissues are at rest and 1mm short of the frenula when they are active
* Handle design should not impinge on the vestibule nor distort the lips
* Fabricated of strong, stable, biocompatible material
* Relief provided where indicated
* Maximum coverage to minimise the pressure applied to the underlying tissues
**Selective Pressure Impression**
<img align="right" src="https://i.imgur.com/gK9C1lR.png" alt="University of Western Australia and Oral Health Centre of Western Australia logos" width="200"/>
**Tray Fabrication**
**Design Outline**
* Outline to full extension
* Identify the cut-back requirements
* Identify areas on the cast that require wax relief
* Produce a laboratory prescription that outlines a request for a special tray
**Selective Pressure Impression**
**Tray Fabrication**
**Wax Relief**
Undercut on labial of alveolar ridge has been blocked
out with wax.
Outline for wax relief of incisive papilla and central
palate shaded in pink.
Minimal wax block-out of lingual undercut on left
alveolar ridge and lingual aspect of the ridge in the
midline.
Outline for wax relief of crest of alveolar ridge shaded
in pink. Note the minimal width.
**Selective Pressure Impression**
**Tray Fabrication**
Light curing material
Palatray light-curing tray material
Polylux light-curing box
Completed Tray
# Selective Pressure Impression
# **Completed Tray**
3D Printed
Check
o Stability
o Rigidity
o Even thickness
o Accurate adaptation to cast
o Maximum surface area coverage
o No over-extensions in sulcus or at frena
o Smooth to touch
o Adequate space to allow accurate muscle moulding
# <font color="#2e74b5">Selective Pressure Impression</font>
## <font color="#2e74b5">Zinc Oxide Eugenol Paste</font>
### **KERR** **ACCELERATOR**
### **LURALITE**
### **KERR** **BASE**
### **LURALITE**
### **55 -60°C**
### **65 -70°C**
### <font color="#2e74b5">THE UNIVERSITY OF</font>
### <font color="#2e74b5">WESTERN</font>
### <font color="#2e74b5">AUSTRALIA</font>
### <font color="#2e74b5">Oral Health Centre</font>
### <font color="#2e74b5">of Western Australia</font>
**Selective Pressure Impression**
**Palatal Vent Holes**
**palatal vent hole allows for:**
- escape of air and excess material
- minimizes aspiration risk
- reduces pressure
**Selective Pressure Impression**
**Polyether Material**
Armamentarium
THE UNIVERSITY OF
WESTERN
AUSTRALIA
Oral Health Centre
of Western Australia
**Selective Pressure Impression**
**Polyether Material**
Loading tray & seating in mouth
* Add Impregum Soft into the tray
* Remember – only small amount required
* Spread evenly to avoid air bubbles
* Ensure that material is extended onto the margins
* Seat tray from the posterior forward to reduce the risk of aspiration
* Remove excess with a dental mirror head
* If imminent aspiration risk – use suction
**Selective Pressure Impression**
Oral Health Centre
**Border Moulding**
Selective Pressure Impression
**Polyether Impression**
Separate tray from model
Check for “burn through” and other
defects
Trim excess with scalpel or scissors
Reinsert to check the retention and
stability (only for clinical cases)
**Selective Pressure Impression**
**Polyether Impression**
**special tray | final impressions | master models**
**THE UNIVERSITY OF**
**WESTERN**
**AUSTRALIA**
**Oral Health Centre**
**of Western Australia**
**Flashback**
**Dental Student Clinic**
Operative dentistry student clinic circa 1960’s at Perth Dental Hospital in Wellington St.
**Thank**
**You**
Any questions? Contact me
Dr Ian Lander
**ian.lander@uwa.edu.au**
**THE UNIVERSITY OF**
**WESTERN**
**AUSTRALIA**
**Oral Health Centre**
**of Western Australia**
