Impression Materials
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
www.indiandentalacademy.com
Plaster Non-elastic
Compound Waxes
Impression Materials
ZnO - Eugenol Agar (reversible)
Aqueous Hydrocolloids
Alginate (irreversible)
Elastic
Polysulfide Non-aqueous Elastomers
Condensation
Silicones Polyether
Addition
www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Aqueous Hydrocolloids Elastic
Agar (reversible) Alginate (irreversible) Polysulfide
Non-aqueous Elastomers
Condensation
Silicones Polyether
Addition
www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Impression Materials • Non-elastic • Elastic – Aqueous hydrocolloids • Agar • Alginate
– Non-aqueous elastomers • Polysulfide • Silicones – Condensation – Addition
• Polyether
www.indiandentalacademy.com
Indications • Diagnostic casts – preliminary – opposing
• Indirect reconstruction – fixed – removable
• Bite registration www.indiandentalacademy.com Giordano Gen Dent 2000
Elastomeric Impression Materials • Viscoelastic – physical properties vary • rate of loading
• Rapidly remove – decreases permanent deformation • chains recoil from a recoverable distance
– increases tear strength www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Aqueous Hydrocolloids • Colloidal suspensions – chains align to form fibrils – traps water in interstices
• Two forms – sol • viscous liquid
– gel • elastic solid
• Placed intra-orally as sol – converts to gel • thermal or chemical process www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Aqueous Hydrocolloids • Semi-permeable membranes – poor dimensional stability
• Evaporation • Syneresis – fibril cross linking continues • contracts with time • exudes water
• Imbibition – water absorption • swells
www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Reversible Hydrocolloid (Agar) • Indications – crown and bridge • high accuracy
• Example – Slate Hydrocolloid (Van R)
www.indiandentalacademy.com
Composition • Agar
• Potassium sulfate
– complex polysaccharide
– improves gypsum surface
• seaweed
• Water (85%)
– gelling agent
• Borax – strength cool to 43 C
agar hydrocolloid (hot) (sol)
agar hydrocolloid (cold)
heat to 100 C
(gel)
www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Manipulation • Gel in tubes – syringe and tray material
www.indiandentalacademy.com
Manipulation • 3 chamber conditioning unit – (1) liquefy at 100°C for 10 minutes • converts gel to sol
– (2) store at 65°C – place in tray – (3) temper at 46°C for 3 minutes – seat tray – cool with water at 13°C for 3 minutes • converts sol to gel www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Advantages • Dimensionally accurate • Hydrophilic – displace moisture, blood, fluids
• Inexpensive – after initial equipment
• No custom tray or adhesives • Pleasant • No mixing required www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Disadvantages • Initial expense – special equipment
• Material prepared in advanced • Tears easily • Dimensionally unstable – immediate pour – single cast
• Difficult to disinfect www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Irreversible Hydrocolloid (Alginate) • Most widely used impression material • Indications – study models – removable fixed partial dentures • framework
• Examples – Jeltrate (Dentsply/Caulk) – Coe Alginate (GC America) www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Composition • Sodium phosphate
• Sodium alginate
– retarder
– salt of alginic acid
• Filler • Potassium fluoride
• mucous extraction of seaweed (algae)
• Calcium sulfate
– improves gypsum surface
– reactor
2 Na3PO4 + 3 CaSO4 Na alginate + CaSO4 (powder)
Ca3(PO4)2 + 3 Na2SO4 H2 O
Ca alginate + Na2SO4
www.indiandentalacademy.com
(gel)
O’Brien Dental Materials & their Selection 1997
Manipulation • Weigh powder • Powder added to water – rubber bowl – vacuum mixer
• Mixed for 45 sec to 1 min • Place tray • Remove 2 to 3 minutes – after gelation (loss of tackiness) www.indiandentalacademy.com Caswell JADA 1986
Advantages • Inexpensive • Easy to use • Hydrophilic – displace moisture, blood, fluids
• Stock trays
www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Disadvantages • Tears easily • Dimensionally unstable – immediate pour – single cast
• Lower detail reproduction – unacceptable for fixed pros
• High permanent deformation • Difficult to disinfect www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Non-Aqueous Elastomers • Synthetic rubbers – mimic natural rubber • scarce during World War II
• Large polymers – some chain lengthening – primarily cross-linking
• Viscosity classes – low, medium, high, putty – monophasic www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Aqueous Hydrocolloids Elastic
Agar (reversible) Alginate (irreversible) Polysulfide
Non-aqueous Elastomers
Condensation
Silicones Polyether
Addition
www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Polysulfide • First dental elastomers • Indications – complete denture – removable fixed partial denture • tissue
– crown and bridge
• Examples – Permlastic (Kerr) – Omni-Flex (GC America)
www.indiandentalacademy.com
Composition • Base – polysulfide polymers – fillers – plasticizers
• Catalyst – lead dioxide (or copper) – fillers
• By-product – water
www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Polysulfide Reaction --SH
HS---------------------SH = Pb
S H
O
S + 3PbO + H O 2 S
=
=
Pb
-S-S---------------S-S-
O
=
O
HS--
O = Pb = O
O
H S mercaptan + lead dioxide
polysulfide rubber + lead oxide + water
www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Manipulation • Adhesive to tray • Uniform layer – custom tray
• Equal lengths of pastes • Mix thoroughly – within one minute
• Setting time 8 – 12 minutes • Pour within 1 hour www.indiandentalacademy.com
Advantages • Lower cost – compared to silicones and polyethers
• • • •
Long working time High tear strength High flexibility Good detail reproduction www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Disadvantages • Poor dimensional stability – water by-product – pour within one hour – single pour
• Custom trays • Messy – paste-paste mix – bad odor – may stain clothing
• Long setting time www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Condensation Silicone • Indications – complete dentures – crown and bridge
• Examples – Speedex (Coltene/Whaledent) – Primasil (TISS Dental)
www.indiandentalacademy.com
Composition • Base – poly(dimethylsiloxane) – tetraethylorthosilicate – filler
• Catalyst – metal organic ester
• By-product – ethyl alcohol www.indiandentalacademy.com
Phillip’s 1996 Phillip’s Science of Dental Materials 1996
CH3
Condensation Silicone Reaction
CH3
HO – Si – O – Si - O - H CH3
CH3
C2H5O
OC2H5
n Si
CH3
CH3
HO – Si – O – Si - O - H CH3
CH3
C2H5O
OC2H5
n metal organic ester
CH3
CH3
HO – Si – O – Si - O CH3
CH3
OC2H5 n
+ 2C2H5OH
Si CH3
CH3
HO – Si – O – Si - O CH3
ethanol
CH3
OC2H5 www.indiandentalacademy.com n Phillip’s Science of Dental Materials 1996
Manipulation • Mix thoroughly – paste - paste – paste - liquid
• Putty-wash technique – reduces effect of polymerization shrinkage – stock tray • putty placed • thin plastic sheet spacer • preliminary impression – intraoral custom tray
• inject wash material www.indiandentalacademy.com
Advantages • Better elastic properties • Clean, pleasant • Stock tray – putty-wash
• Good working and setting time
www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Disadvantages • Poor dimensional stability – high shrinkage • polymerization • evaporation of ethanol
– pour immediately • within 30 minutes
• Hydrophobic – poor wettability www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Addition Silicones • AKA: Vinyl polysiloxane • Indications – crown and bridge – denture – bite registration
• Examples – – – – –
Extrude (Kerr) Express (3M/ESPE) Aquasil (Dentsply Caulk) Genie (Sultan Chemists) Virtual (Ivoclar Vivadent) www.indiandentalacademy.com Click here for DIS evaluations
of VPS impression materials
Composition • Improvement over condensation silicones – no by-product
• First paste – vinyl poly(dimethylsiloxane) prepolymer
• Second paste – siloxane prepolymer
• Catalyst – chloroplatinic acid www.indiandentalacademy.com
Phillip’s 1996 Phillip’s Science of Dental Materials 1996
CH3 ---O – Si – CH = CH2
Addition Silicone Reaction CH3
O H - Si – CH3
CH3
O
CH3 CH = CH2 – Si – O ---
CH3 - Si - H
CH3
O
O
Chloroplatinic Acid Catalyst
---O – Si – CH2 - CH2 - Si – CH3 CH3
O
CH3
CH3 - Si - CH2 - CH2 – Si – O --O
CH3
www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Manipulation • Adhesive to tray • Double mix – custom tray • heavy-body
– light-body to prep
• Putty-wash – stock tray
www.indiandentalacademy.com Craig Adv Dent Res 1988
Advantages • Highly accurate • High dimensional stability – pour up to one week
• • • •
Stock or custom trays Multiple casts Easy to mix Pleasant odor www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Disadvantages • Expensive • Sulfur inhibits set – latex gloves – ferric and Al sulfate retraction solution
• Pumice teeth before impressing • Short working time • Lower tear strength • Possible hydrogen gas release – bubbles on die – palladium added to absorb
www.indiandentalacademy.com Manikos Aust Dent J 1998
Addition Silicones • Surfactants added – reduce contact angle – improved • castability – gypsum
• wettability?? – still need dry field clinically
www.indiandentalacademy.com
Pratten J Dent Res 1987 Mandikos Aust Dent J 1998
Polyether • Indications – crown and bridge – bite registration
• Examples – – – – –
Impregum F (3M/ESPE) Permadyne (3M/ESPE) Pentamix (3M/ESPE) P2 (Heraeus Kulzer) Polygel (Dentsply Caulk)
www.indiandentalacademy.com
Composition • Base – difunctional epimine-terminated prepolymer – fillers – plasticizers
• Catalyst – aromatic sulfonic acid ester – fillers
• Cationic polymerization – ring opening and chain extension www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Polyether Reaction R
R
base
CH3 – CH – CH2 – CO2 – CH – (CH2)n – O – CH – (CH2)n – CO2 –CH2 – CH –CH3 m N
N H2C
CH2
H2C
+ R+
CH2
catalyst SO3-
R– N+ H2C
N
+ CH2
H2C
R – N – CH2 – CH2 – N + CH2
ring opening www.indiandentalacademy.com
H2C
CH2
Phillip’s Science of Dental Materials 1996
Manipulation • Adhesive to tray – stock or custom tray • very stiff
• Paste-paste mix • Auto-mixing – hand-held • low viscosity
– mechanical dispenser • high viscosity www.indiandentalacademy.com
Advantages • • • • •
Highly accurate Good dimensional stability Stock or dual-arch trays Good surface detail Pour within one week – kept dry
• Multiple casts • Good wettability www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Disadvantages • Expensive • Short working time • Rigid – difficult to remove from undercuts
• Bitter taste • Low tear strength • Absorbs water – changes dimension www.indiandentalacademy.com Phillip’s Science of Dental Materials 1996
Handling Properties Agar
Alginate Polysulfide
Condensation Silicone
Addition Silicone
Polyether
Preparation
Boil, temper, store
Powder, water
2 pastes
2 pastes or paste/liquid
2 pastes
2 pastes
Ease of Use
Technique sensitive
Good
Fair
Fair
Excellent
Good
Patient Reaction
Thermal Shock
Pleasant, clean
Unpleasant, stains
Pleasant, clean
Pleasant
Unpleasant clean
Ease of removal
Very easy
Very easy
Easy
Moderate
Moderate
Moderate to difficult
Disinfection
Poor
Poor
Fair
Fair
Excellent
Fair
www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Handling Properties Condensation Addition Silicone Silicone
Agar
Alginate
Polysulfide
Polyether
Working Time (min)
7 – 15
2.5
5–7
3
2 –4.5
2.5
Setting Time (min)
5
3.5
8 – 12
6–8
3–7
4.5
Stability
1 hour 100% RH
Immediate pour
1 hour
Immediate pour
1 week
1 week kept dry
Wettability and castability
Excellent
Excellent
Fair
Fair
Fair to good
Good
Cost
Low
Very low
Low
Moderate
High to very high
Very high
www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Properties Agar
Alginate Polysulfide
Condensation Silicone
Addition Silicone
Polyether
Elastic Recovery (%)
98.8
97.3
94.5 – 96.9
98.2 – 99.6
99 – 99.9
98.3 – 99.0
Flexibility (%)
11
12
8.5 – 20.0
3.5 – 7.8
1.3 – 5.6
1.9 – 3.3
Flow (%)
--
--
0.4 – 1.9
< 0.10
< 0.05
< 0.05
Shrinkage, 24 hours (%)
Extreme
Extreme
0.4 – 0.5
0.2 – 1.0
0.01 – 0.2
0.2 – 0.3
Tear Strength (g/cm)
700
380 – 700
2240 – 7410
2280 – 4370
1640 – 5260
1700 4800
www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Comparison of Properties • Working time – longest to shortest • agar > polysulfide > silicones > alginate = polyether
• Setting time – shortest to longest • alginate < polyether < agar < silicones < polysulfide
www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Comparison of Properties • Stiffness – most to least • polyether > addition silicone > condensation silicone > polysulfide = hydrocolloids
• Tear strength – greatest to least • polysulfide > addition silicone > polyether > condensation silicone >> hydrocolloids www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Comparison of Properties • Cost – lowest to highest • alginate < agar = polysulfide <condensation silicone < addition silicone < polyether
• Dimensional stability – best to worst • addition silicone > polyether > polysulfide > condensation silicone > hydrocolloid Phillip’s 1996 www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Comparison of Properties • Wettability – best to worst • hydrocolloids > polyether > hydrophilic addition silicone > polysulfide > hydrophobic addition silicone = condensation silicone
• Castability – best to worst • hydrocolloids > hydrophilic addition silicone > polyether > polysulfide > hydrophobic addition silicone = condensation silicone www.indiandentalacademy.com O’Brien Dental Materials & their Selection 1997
Summary • Study models – Alginate most widely used • • • •
inexpensive displaces moisture lower detail reproduction dimensionally unstable
www.indiandentalacademy.com
Summary • Prosthodontics – Addition silicones most popular • • • •
accurate dimensionally stable user friendly expensive
www.indiandentalacademy.com
• A good Impression must aid to fulfill M.M. Devan’s dictum: “It is the perpetual preservation of what already exists and not the meticulous replacement of what is missing.”
www.indiandentalacademy.com
â&#x20AC;˘ DEFINITION â&#x20AC;˘ A COMPLETE DENTURE IMPRESSION is the negative registration of the entire denture bearing, stabilizing and border seal areas, of either the maxillas or mandible in a plastic material that becomes relatively hard or set while in contact with these tissues. www.indiandentalacademy.com
A PRELIMINARY IMPRESSION is made for the purpose of diagnostic treatment planning and the construction of a custom tray while a FINAL IMPRESSION is used for making the master cast over which the denture bases are fabricated.
www.indiandentalacademy.com
â&#x20AC;˘ According to GPT, 7th Edition, 1999 Impression is defined as a negative likeness or copy in reverse of the surface of an object; an imprint of the teeth and adjacent structures for use in dentistry
www.indiandentalacademy.com
• The five objectives of an impression as stated by Carl.D. Boucher in 1944 are • 1) PRESERVATION OF THE ALVEOLAR RIDGES. This is achieved by using impression techniques which cover maximum supporting areas as possible and using pressure within physiologic limit of the tissue. • (2) RETENTION - The factors of retention are (1) adhesion (2) cohesion (3) interfacial surface tension (4) mechanical locking into undercuts (5) peripheral seal and atmospheric pressure and (6) oral and facial musculature. Henry A. Collet in 1965 stated that primary retention depends upon close adaptation to the tissues and is proportionate to the area covered. www.indiandentalacademy.com
â&#x20AC;˘ . (3) STABII.ITY - It is the relationship of the denture base to the underlying bone. â&#x20AC;˘ Samuel Friedman in 1957, stated that stability is developed in the impression technique through more intimate contact of the labial and buccal flanges with the labial and buccal slopes and of the lingual flanges with the lingual slopes of the ridges. Boucher stated that stability requires maximum use of all bony foundations where the tissues are firmly and closely attached to bone. www.indiandentalacademy.com
â&#x20AC;˘ . (4) SUPPORT - Support is provided by the maxillary and the mandibular bones and their covering of mucosal tissue. It is enhanced by selective placement of pressures that are in harmony with the resiliency of the tissues that make up the basal seat. â&#x20AC;˘ (5) ESTHETICS - Role of esthetics in impression making refers to the development of the labial and buccal borders, so that they are not only retentive but also support the lips and cheeks properly. www.indiandentalacademy.com
• Fisher R.D. in 1951 laid down six fundamental rules for making full denture impressions – • (1) Roentgenographics, visual and digital examination of the oral cavity • (2) Surgical removal of such abnormal formations as would prevent successful completion of impressions. • (3) the require extension outlines. • (4) the location and position for area of variable tissue displaceability ( • 5) the required retention outline and www.indiandentalacademy.com • (6) the required adaptation.
• IMPRESSION TECHNIQUES may be classified depending on, [A] Amount of pressure used (Based on the theories of impression). • Pressure technique based on pressure theory • Minimal pressure technique - based on mucostatic theory. • Selective pressure technique -based on selective pressure theory.
www.indiandentalacademy.com
• [B] 1. Open or • 2. Closed mouth • [C] 1. Hand-manipulation or • 2. Functional movements
www.indiandentalacademy.com
• [D] Type of tray • 1. Stock tray : 1. Caulks Edentulous Rimlock Trays. • 2. McGowen Winkler Trays (mandibular) • 3. STO-K Trays. (Square, round or Tapering shapes of ridges). • • • •
2. Custom or special tray 1. Shellac 2. Acrylic 3. Wax. www.indiandentalacademy.com
Thank you www.indiandentalacademy.com Leader in continuing dental education
www.indiandentalacademy.com