imprints, their classification, method of receipt. classification of materials of imprint. clinical,...
TRANSCRIPT
Imprints, their classification, method of receipt. Classification of materials of
imprint. Clinical, physical and chemical descriptions of materials for imprint
• Impression is a negative (reverse) reflection of any organ of the dentomaxillar system: teeth, alveolar sprout or part, palate, nose,
• ear and others like that.
• Impression is a negative (reverse) reflection of hard and soft tissues, placed in the area of dental prosthesis and it’s borders which
• Is being taken by means of the special impression materials
Types of impressions:•Previous•Final
Final impressions:•Anatomical•Functional
Types ofTypes of impressionsimpressions
• Single layer
• Double layer
• Combined
Types ofTypes of impressionsimpressions• Anatomical
(orientation)– take with standard or individual tray in the state of calmness of tissues of prosthetic bed and tissues, which are placed on a border with them.
• Functional - take with individual tray by means of the special functional tests, in the case of making of removable constructions of dentures :
compression - in the case of pressing of buffer areas of prosthetic bed, by masticatory pressure or by the hand of doctor;
decompression - in the case of minimum pressure on the tissues of prosthetic bed
• Double layer – an exact reflection of gingival edge is taken by means of impression materials of the same group (previous layer + correction layer)
• Combined– is taken by means of impression materials of different groups (previous layer + correction layer)
• Occlusal–for taking impression in position of central occlusion
Impression traysImpression trays
• Standard: made factory- On maxillae different sizes- On mandible different sizes• Individual: made in dental
laboratory• By material:- plastic- metallic- waxen• Presence of retentin
points- perforated- unperforated
Impression trays for taking impression at the same time
Placing of impression tray in oral cavity
Impression of maxillae
Double layer impression
Impression Materials• Non-elastic• Elastic
– Aqueous hydrocolloids• Agar• Alginate
– Non-aqueous elastomers• Polysulfide• Silicones
– Condensation– Addition
• Polyether
Indications
• Diagnostic casts– preliminary– opposing
• Indirect reconstruction– fixed– removable
• Bite registration
Elastomeric Impression Materials
• Viscoelastic– physical properties vary
• rate of loading
• Rapidly remove– decreases permanent
deformation• chains recoil from a recoverable distance
– increases tear strength
Impr
essi
on
Mat
eria
ls
Non-elastic
Elastic
Aqueous Hydrocolloids
Non-aqueous Elastomers
Polysulfide
Silicones
Polyether
Condensation
Addition
Agar (reversible)
Alginate (irreversible)
Plaster
Compound
ZnO - Eugenol
Waxes
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
Aqueous Hydrocolloids
• Semi-permeable membranes– poor dimensional stability
• Evaporation• Syneresis
– fibril cross linking continues• contracts with time• exudes water
• Imbibition– water absorption
• swells
Elastic
Aqueous Hydrocolloids
Non-aqueous Elastomers
Polysulfide
Silicones
Polyether
Condensation
Addition
Agar (reversible)
Alginate (irreversible)
Reversible Hydrocolloid (Agar)
• Indications– crown and bridge
• high accuracy
• Example– Slate Hydrocolloid (Van R)
Composition• Agar
– complex polysaccharide• seaweed
– gelling agent
• Borax– strength
• Potassium sulfate– improves gypsum
surface
• Water (85%)
agar hydrocolloid (hot) agar hydrocolloid (cold)
(sol) (gel)
cool to 43ºC
heat to 100ºC
Manipulation
• Gel in tubes– syringe and tray material
Manipulation• 3-chamber conditioning unit
– (1) liquefy at 100C for 10 minutes
• converts gel to sol
– (2) store at 65C– place in tray– (3) temper at 46C for 3 minutes– seat tray– cool with water at 13C for 3 minutes
• converts sol to gel
Advantages
• Dimensionally accurate• Hydrophilic
– displaces moisture, blood, fluids
• Inexpensive– after initial equipment
• No custom tray or adhesives• Pleasant flavor• No mixing required
Disadvantages
• Initial expense– special equipment
• Material must be prepared in advanced• Tears easily• Dimensionally unstable
– Must be poured immediately– Can only be used for a single cast
• Difficult to disinfect
Elastic
Aqueous Hydrocolloids
Non-aqueous Elastomers
Polysulfide
Silicones
Polyether
Condensation
Addition
Agar (reversible)
Alginate (irreversible)
Irreversible Hydrocolloid (Alginate)
• Most widely used impression material
• Indications– study models– removable fixed partial dentures
• framework
• Examples– Jeltrate (Dentsply/Caulk)– Coe Alginate (GC America)
Composition• Sodium alginate
– salt of alginic acid• mucous extraction of
seaweed (algae)
• Calcium sulfate– reactor
• Sodium phosphate– retarder
• Filler• Potassium fluoride
– improves gypsum surface
2 Na3PO4 + 3 CaSO4 Ca3(PO4)2 + 3 Na2SO4
Na alginate + CaSO4 Ca alginate + Na2SO4
(powder) (gel)
H2O
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)
Advantages
• Inexpensive
• Easy to use
• Hydrophilic– displace moisture, blood, fluids
• Stock trays
Disadvantages
• Tears easily• Dimensionally unstable
– immediate pour – single cast
• Lower detail reproduction– unacceptable for fixed pros
• High permanent deformation• Difficult to disinfect
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
Elastic
Aqueous Hydrocolloids
Non-aqueous Elastomers
Polysulfide
Silicones
Polyether
Condensation
Addition
Agar (reversible)
Alginate (irreversible)
Polysulfide
• First dental elastomers• Indications
– complete denture– removable fixed partial denture
• tissue
– crown and bridge
• Examples– Permlastic (Kerr)– Omni-Flex (GC America)
Composition• Base
– polysulfide polymers– fillers– plasticizers
• Catalyst– lead dioxide (or copper)– fillers
• By-product– water
--SH HS---------------------SH HS--
S H
O
=
Pb
=
O
O
=
Pb
=
OO = Pb = O
HS
-S-S---------------S-S-
S
S
+ 3PbO + H2O
mercaptan + lead dioxide polysulfide rubber + lead oxide + water
Polysulfide Reaction
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
Advantages
• Lower cost– compared to silicones and polyethers
• Long working time
• High tear strength
• High flexibility
• Good detail reproduction
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
Elastic
Aqueous Hydrocolloids
Non-aqueous Elastomers
Polysulfide
Silicones
Polyether
Condensation
Addition
Agar (reversible)
Alginate (irreversible)
Condensation Silicone
• Indications– complete dentures– crown and bridge
• Examples– Speedex (Coltene/Whaledent)– Primasil (TISS Dental)
Composition
• Base– poly(dimethylsiloxane)– tetraethylorthosilicate– filler
• Catalyst– metal organic ester
• By-product– ethyl alcohol
Phillip’s 1996
HO – Si – O – Si - O - H
CH3
CH3 CH3
CH3 n
HO – Si – O – Si - O - H
CH3
CH3 CH3
CH3 n
C2H5O OC2H5
Si
C2H5O OC2H5
HO – Si – O – Si - O -
CH3
CH3 CH3
CH3 n
HO – Si – O – Si - O -
CH3
CH3 CH3
CH3 n
OC2H5
Si
OC2H5
+ 2C2H5OH
Condensation Silicone Reaction
metal organic ester
ethanol
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
Advantages
• Better elastic properties
• Clean, pleasant
• Stock tray– putty-wash
• Good working and setting time
Disadvantages
• Poor dimensional stability– high shrinkage
• polymerization
• evaporation of ethanol
– pour immediately• within 30 minutes
• Hydrophobic– poor wettability
Elastic
Aqueous Hydrocolloids
Non-aqueous Elastomers
Polysulfide
Silicones
Polyether
Condensation
Addition
Agar (reversible)
Alginate (irreversible)
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)
Composition
• Improvement over condensation silicones– no by-product
• First paste– vinyl poly(dimethylsiloxane)
prepolymer
• Second paste– siloxane prepolymer
• Catalyst– chloroplatinic acid
Phillip’s 1996
O
H - Si – CH3
O
CH3 - Si - H
O
---O – Si – CH = CH2
CH3
CH3 CH = CH2 – Si – O ---
CH3
CH3
O
- Si – CH3
O
CH3 - Si -
O
---O – Si – CH2 - CH2
CH3
CH3
CH2 - CH2 – Si – O ---
CH3
CH3
Chloroplatinic Acid Catalyst
Addition Silicone Reaction
Manipulation
• Adhesive to tray
• Double mix– custom tray
• heavy-body
– light-body to prep
• Putty-wash– stock tray
Advantages
• Highly accurate
• High dimensional stability– pour up to one week
• Stock or custom trays
• Multiple casts
• Easy to mix
• Pleasant odor
Disadvantages• Expensive• Sulfur inhibits set
– latex gloves– ferric and Al sulfate
retraction solution
• Pumice teeth beforeimpressing
• Short working time• Lower tear strength• Possible hydrogen gas release
– bubbles on die– palladium added to absorb
Addition Silicones
• Surfactants added– reduce contact angle– improved
• castability– gypsum
• wettability– still need dry field clinically
Elastic
Aqueous Hydrocolloids
Non-aqueous Elastomers
Polysulfide
Silicones
Polyether
Condensation
Addition
Agar (reversible)
Alginate (irreversible)
Polyether
• Indications– crown and bridge– bite registration
• Examples– Impregum F (3M/ESPE)– Permadyne (3M/ESPE)– Pentamix (3M/ESPE)– P2 (Heraeus Kulzer)– Polygel (Dentsply Caulk)
• Base– difunctional epimine-terminated prepolymer– fillers– plasticizers
• Catalyst– aromatic sulfonic acid ester– fillers
• Cationic polymerization– ring opening and chain extension
Composition
SO3-
+ R+
CH3 – CH – CH2 – CO2 – CH – (CH2)n – O – CH – (CH2)n – CO2 –CH2 – CH –CH3
N
H2C CH2
R R
m
N
H2C CH2
N
H2C CH2
R – N – CH2 – CH2 – +N
H2C CH2
N
H2C CH2
R – + +
Polyether Reaction
catalyst
base
ring opening
Manipulation
• Adhesive to tray– stock or custom tray
• very stiff
• Paste-paste mix• Auto-mixing
– hand-held• low viscosity
– mechanical dispenser• high viscosity
Advantages
• Highly accurate• Good dimensional stability• Stock or dual-arch trays• Good surface detail• Pour within one week
– kept dry
• Multiple casts• Good wettability
Disadvantages• Expensive
• Short working time
• Rigid– difficult to remove from undercuts
• Bitter taste
• Low tear strength
• Absorbs water– changes dimension
Impression Material Usage*Civilian General Dentists
• Crown & Bridge– vinylpolysiloxane 81%– alginate 38%– polyether 28%
• Inlays and Onlays– vinylpolysiloxane 71%– polyether 22%– alginate 20%
Impression Material Usage*Civilian General Dentists
• Complete dentures– alginate 58%– vinylpolysiloxane 55%– polyether 27%
• Partial dentures– alginate 78%– vinylpolysiloxane 43%– polyether 15%
Handling Properties
Agar Alginate PolysulfideCondensation
SiliconeAddition Silicone
Polyether
PreparationBoil,
temper, store
Powder, water
2 pastes2 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
PleasantUnpleasant
clean
Ease of removal
Very easy
Very easy
Easy Moderate ModerateModerate to difficult
Disinfection Poor Poor Fair Fair Excellent Fair
Handling Properties
Agar Alginate PolysulfideCondensation
SiliconeAddition Silicone
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 hourImmediate
pour1 week
1 week kept dry
Wettability and
castabilityExcellent Excellent Fair Fair
Fair to good
Good
Cost Low Very low Low ModerateHigh to
very highVery high
Properties
Agar Alginate PolysulfideCondensation
SiliconeAddition 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)
700380 – 700
2240 – 7410 2280 – 43701640 – 5260
1700 - 4800
Comparison of Properties
• Working time– longest to shortest
• agar > polysulfide > silicones > alginate = polyether
• Setting time– shortest to longest
• alginate < polyether < agar < silicones < polysulfide
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
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
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
Regularly-Used Impression Materials*Civilian Practitioners
• Alginate 88%
• Polyvinyl Siloxane 85%
• Polyether 27%
• Other 6%
Summary
• Study models– Alginate most widely used
• inexpensive
• displaces moisture
• lower detail reproduction
• dimensionally unstable
Summary
• Prosthodontics– Addition silicones most popular
• accurate
• dimensionally stable
• user friendly
• expensive