خاص بمادة Dental material تقسيمة مختصرة ملمة بأنواع المواد المستخدمة في اخذ طبعة للفم والاسنان SUBJECTIVE:- Dental Material CHAPTER:- Impression Material تمت مشاركته عبر: د. أحمد طه

1. 1
Azhar Assuit - Asnan 25
Impression :- is a negative reproduction of the tissues
Cast :- is a positive reproduction of tissues.
Ideal Requirements
1-Sufficiently fluid (to reproduce all fine details).
2-Suitable setting time (to produce suitable working time).
3-Sufficient mechanical strength (not to tear or permanent deformation during insertion or removal).
4-Sufficient dimensional stability ( to pour the stone or other material).
5-Compatibility with die and cast materials (not need separation medium).
6-Safe (not toxic or irritant)
7-Acceptable to patient (acceptable taste-color-odour)
8- Good keeping qualities.
Chapter impression material
For first dental students
Done by asnan 25

2. 2
Azhar Assuit - Asnan 25
CLASSIFICATION OF IMPRESSION MATERIALS
ACCORDING BEHAVIOR AFTER SETTING
NON ELASTIC ELASTIC
Either fracture or permanent distortion during
removal from under cut
Recovered after removal from undercut
1-Plastic impression.
2-Impression compound.
3-Zn-oxideEugenol.
Hydrocollid Elastomers
1-Agar Agar
2-Alginate
1-Polysulfide.
2-Silicone (condensation)
3-Silicone (Addition)
4-Poly ether
ACCORDING TO SETTING
Chemical reaction Physical changes
Soft Hard Hard heating-cooling soft
1-Plaster impression.
2-Zn-oxideEugenol
3-Alginate.
4-Elastomers
1-Impression compound.
2-Agar Agar.
ACCORDING TO THEIR USES
Complete denture Partial denture Crowns and bridge
1- Plaster impression.
2- Zn-oxideEugenol
3- Impression compound
4- Alginate
1-Alginate.
2-Elastomers.
Elastomers

3. 3
Azhar Assuit - Asnan 25
Comparison between NON ELASTIC impression materials
AZHAR ASSUIT 1. Plaster impression 2. Impression compound 3. Zincoxide Eugenol
Fluidity & Accuracy
- Very high fluidity.
- Great accuracy.
- Record fine details.
- Low fluidity.
- Low accuracy.
- Not record fine details.
- Sufficiently fluid.
- To record all fine details.
Dimensional change
(Setting expansion)
- Minimum setting expansion
- .06%
- Due to K2SO4
- High setting expansion -0.4%
- Due to highly coefficient Of thermal
expansion
- Little setting expansion.
- 0,1%
Dimensional stability
(shrinkage degree)
- Very stable
- Small degree of shrinkage
- Low stable due to high coefficient
Thermal.
- So should be pour immediately
- Very stable
- More high temp. lead to
distortion
Elasticity
Rigid lead to fracture during
removal form cast or mouth
Rigid material Lead to permanent distortion during removal from
undercuts after its setting
Adhesion to tray Adhere Adhere Adhere
Cast compatibility
Not compatible
Need to separating medium
Compatible
Not need a separating medium
Compatible
Not need separating medium
Advantage
- Easily assembled when
fractured
- Thermoplasticity (Reversible)
- Hard --heat/cold-- Soft
- Can use in undercut area
- Thickness of Spacer is 0
Disadvantages
- Dryness sensation to patient
- Need separating medium
- Very difficult removal from
undercut area which in mouth
- Eugenol can be irritant giving
burning sensation to patient
Uses & Notebooks
- In complete denture
construction in past
1. In complete denture construction
2. As impression trays for double tech.
3. As peripheral seal material
4. Single impression with copper band
1-On complete or partial
denture without / with undercut
2- Stabilizing base plate in bite
registration

4. 4
Azhar Assuit - Asnan 25
Comparison between RUBBER BASE impression materials
AZHAR ASSUIT Cond. Silicon Addition Silicon Poly ether Poly sulfide
Composition
80% Silicon
(OH)group
20% Silica
Tin octate
Ethel
silicate
80%Silicon
(vinyl)group
20% Silica
Chloroplat
inicacid
80% polyether
(ethylene imine)
20% Silica
Sulfonic
acidester
80% polysulfide
(SH)group
20% Silica
Lead
dioxide
Fluidity
Depend on consistency ‫القوام‬ by filler as silica:- types & route of application ‫ا‬‫العجينة‬ ‫لتطبيع‬ ‫المستخدم‬ ‫لجهاز‬
1- Light body Syringe 2- Medium  Tray 3- Heavy  Tray + Syringe
Accuracy Increase with 2nd imp. Highest accuracy More accuracy Accurate
Tray & spacer thickness Should be acrylic tray -- Impression material thickness 2-4 mm
Dimensional change 0.6% .05 % 0.1 % .45% alcoholic evaporation
Shrinkage degree 0.2-1% in 24hrs Lowest shrinkage .3% in 24hrs .3-.4 %
Elastic recovery 99% 99.5% 98.5 % 96 %
Properties
1.
1. Handle mixing
2. Pouring ease
3. Pouring time
4. Tear strength
5. Cost / taste
6. Working time
7. Hydrophilic or
8. others
1. Easy mixing
2. Poor to adequate
3. Once‫توا‬or 1 hour
4. Adequate tear St.
5. Suitable ‫حونين‬
6. Long 10 min
7. Very hydrophobic
8. Less distortion
1. Very easy mixing
2. Adequate in stone
3. 60min- 1 week
4. Adequate tear St.
5. High cost
6. Short 6-8 min
7. Hydrophilic
8. Doesn’t stain
NB: should poured after
setting at least 30-60 min due
to elastic recovery
1. Moderate mixing
2. Easily poured in stone
3. (1) week
4. Adequate tear St.
5. High cost -Bitter taste
6. Short 5-6 min
7. Distort if stored in
water (hydrophilic)
8. Allergic reaction
(sulfonic acid)
1. Moderate - difficult
2. Adequate pour
3. 1 hour
4. Highest tear St.
5. Bad odder
6. Long 12-14 min
7. Hydrophilic
8. Clothing stain
- Condensation reaction

5. 5
Azhar Assuit - Asnan 25
Comparison between HYDROCOLLOIDS impression materials
AZHAR ASSUIT Alginate AGAR AGAR
Fluidity Sufficiently fluid to record fine details Highly fluid – fine record
Accuracy Less than agar More accuracy
Tray & spacer thickness Perforated stock or special tray (shellac/acrylic) Special water tray with other equipment
Dimensional change Imbibition ‫ماء‬ ‫تشرب‬ in water (expansion)
Shrinkage degree Syneresis ‫الماء‬ ‫جفاف/تساحب‬ in air
Elastic recovery 97% 98.9%
Properties
1. Handle mixing 1- Easier 1- No mixing needed
2. Pouring ease 2- Good 2- Good
3. Pouring time 3- Immediately or at less in 15 min 3- Immediately or at less in 15 min
4. Tear strength 4- Very weak tear St. 4- Weak tear strength
5. Cost / taste 5- Cheep 5- High cost
6. Working time 6- Suitable working time 6- Long and difficult working
7. Hydrophilic or 7- Hydrophilic
8- Irreversible 7- Reversible
Not use now