An accurate detailed negative reproduction or mold of the patient's teeth and surrounding tissue.
Impressions
A positive reproduction of the structure.
Model
Characteristics of Impressions
Well defined developmental grooves and gingival margins.
Should include frenum, muscle attachments and periphery.
Two categories of trays
Stock trays
Custom trays
Stock trays in three sizes
Quadrant
Section
Full arch
Stock tray size that covers half of the arch
Quadrant
Stock trays size that is used for the anterior of the mouth
Section trays
Stock tray size that covers the entire arch
Full arch trays
Stock trays in different types of materials
Perforated metal
Perforated plastic
Metal rim lock
Metal rimless edentulous tray
Triple tray
Disposable styrofoam
Are made to fit the mouth of a specific patient. These are made from a preliminary impression and model of the patients mouth.
Custom trays
Working casts used for
Used for fabricating Dentures, partial dentures, retainers, custom trays
What type of stone is poured up for working casts?
Class I stone
An exact replica or reproduction of the tooth which has been prepared for a crown, bridge, inlay and onlay.
Dies
What type of stone is poured up for dies?
Class II stone
Desirable properties of impression materials
Pleasant odor, taste and color.
Not toxic and irritating to the tissue.
Requires minimal equipment.
Satisfactory texture and accurate detail reproduction.
Compatible with gypsum products.
Measurement of time the manufacturer specifies that a material should be mixed.
Mixing time
The measure of time that follows the mixing time, that a material can be manipulated before it begins to set.
Working time
Measure of time from beginning of mix until material is completely set.
Setting time
Changes the state of the material when it is mixed with another medium (material).
Chemical reaction
Changes the state of a material when it is subjected to temperature changes.
Physical/Thermal Reaction
Types of impression materials
Hydrocolloid (irreversible&reversible)
Elastomeric (polysulfide, polysiloxane, polyvinyl siloxane & polyether)
Inelastic (impression plaster, tray/cake compound & ZOE impression paste)
Means water
Hydro
Means gelatinous
Colloid
Two physical phases of Hydrocolloid
Sol: solution, soft stage
Gel: solid, harder stage
Another term for alginate
Irreversible Hydrocolloid
Used for preliminary impression.
Used for dentulous or edentulous patients.
Brand name are jeltrate and algitec.
Not very accurate.
Irreversible Hydrocolloid or alginate
Setting time for alginate
Normal set 4 1/2 minutes
Fast set 1-2 minutes
Removal of water, which causes the impression to shrink.
Syneresis
Absorption of additional water, which causes the impression to expand.
Imbibition
Factors that affect the setting time of alginate
Temperature of water
Water and powder ratio
Rate of spatulation
Manufacturers process
Temperature and humidity
Warm water will ______ the setting time.
Decrease
Cold water will ______ the setting time.
Increase
More water will ______ the setting time.
Increase
Less water will ______ the setting time.
Decrease
Mixing faster will ______ the setting time.
Increase
Mixing slower will ______ the setting time.
Decrease
Adding accelerators will _____ the setting time.
Decrease
Adding retarders will _____ the setting time.
Increase
High temperature or humidity will _____ the setting time.
Decrease
cold temperature or humidity will _____ the setting time.
Increase
What is the best way to control the setting time?
Changing the water temperature
What type of reaction does alginate go through?
Chemical
Another term for reversible Hydrocolloid
Agar
Used for final impression.
Taken only by dentist.
Used for dentulous and edentulous patients.
Reversible Hydrocolloid
Setting time for reversible Hydrocolloid
5 minutes
Physical characteristics of reversible Hydrocolloid
More difficult to work with more equipment.
Very accurate and detailed.
Reusable
Reheated
The gel state of the material changes to a ____ state when it is ______.
Sol state
When heated
The sol state of the material changes to a ____ state when it is ______.
Gel state
When cooled
Chemical characteristics of reversible Hydrocolloid
Agar: 8-15 extracted from sea kelp
Water: 80-85% by weight main ingredient
Filler materials
Reversible Hydrocolloid conditioning unit
Boiling tank
Storage tank
Tempering/Conditioning tank
Water cooled rim(lock trays)
Tray hoses
Hydrocolloid syringe or leur (lock syringe)
Purpose of tempering
So it is not boiling hot when to place it in the patients mouth
Advantages of reversible Hydrocolloid
Accurate
Detailed
Reusable
Reheatable
Can store material in the storage tank
Disadvantages of reversible Hydrocolloid
-A lot of equipment
-Inaccurate and distorted impression when the tray is removed from the mouth too soon, improper removal or inadequate amount of material in tray.
-Grainy material caused by insufficient boiling or keeping the storage temperature too lo
Indicates having elastic or rubber like qualities.
Elastomeric
Type of impression materials used for final impressions when great detail is needed. It is easy to remove, does not tear or distort. It is supplied as a base and catalyst.
Elastomeric
Forms of elastomeric
Light bodied
Regular and Heavy bodied
Form of elastomeric that is placed around the prepared tooth and flow easily, a.k.a syringe type and wash type.
Light bodied
Form of elastomeric that is thicker and placed in the tray. The stiffness of the material helps force the light bodied material into the prepared tooth a.k.a tray type.
Regular or heavy bodied
Types of elastomeric
Polysulfide
Polyether
Polysiloxane/silicone (2steps)
Polyvinyl siloxane (1step)
Type of elastomeric that is also known as rubberbase (mercaptan), non-aqueous impression material and used for 10-20 mins. For final impression. Brand name is Coe flex.
Polysulfide
Physical Characteristics of Polysulfide
Minimal equipment
Dimensionally stable
Detailed and accurate
Low shrinkage
Easy to work with not stiff
Flexible
Chemical Characteristics of Polysulfide
Stink
Contains sulfur
Cannot be used with patients with sulfur allergies.
Stains
What should do next after taking impression using polysulfide?
Rinse under water
Spray with disinfectant or submerge (no more than 10 mins.)
Pour within 1 hour due to shrinkage factor
What type of reaction does polysulfide go through?
Chemical
Type of elastomeric that is also known as condensation silicone. It used for 3-5 mins. For final impression. for dentulous patient.
Polysiloxane (2 steps)
Physical Characteristics of Polysiloxane
Some shrinkage
Odor free
Not as messy as rubberbase
Disinfection is the same as polysulfide.
Polysiloxane is supplied in ______.
Paste and paste system
(Putty for trays.)
(Wash material for syringe.)
Type of elastomeric used for 3 mins. For final impression for dentulous patient. It is for crowns, bridges, inlays and onlays.
Polyvinyl Siloxane (1step)
Physical Characteristics of polyvinyl siloxane
Very detailed impression
Low shrinkage
Can be poured up to 7 days after taking impression.
Polyvinyl siloxane is supplied in ______.
Paste and paste
Putty
Cartridges (most popular- gun and automix)
Are Polysiloxane and polyvinyl siloxane stronger than alginate?
Yes
Type of elastomeric that is non aqueous impression material that is used for 6-10 mins.for final impression for dentulous patients. It has a brand name Impregnum.
Polyether
Physical Characteristics of Polyether
Medium viscosity
Low shrinkage
Accelerator made of sulfanic acid ester
Must mix base and accelerator evenly.
Direct contact with accelerator will irritate the tissue.
Polyether is supplied in _______.
Paste and paste form
Cartridges
Gun
Automix
Disinfection for using elastomeric Polyether material.
Rinsed with water.
Sprayed with disinfectant
Placed in bag for 10 mins.
Rinsed again after pouring.
Does Polyether come in a heavy and light body material?
Yes
Type of impression material that is used for dentures and cannot be used for dentulous patient.
Inelastic
Types of inelastic material
Impression plaster
Tray or cake compound
Zinc oxide eugenol
Type of inelastic material that is a gypsum product. It is used for preliminary impression and edentulous patients. Brand name is snowy white.
Impression plaster
Physical Characteristics of impression plaster
Brittle when set
Type of inelastic material that is also known as cake compound or impression compound. It is used for preliminary impression for edentulous patients.
Tray compound
Physical Characteristics of Tray compound
For denture construction
Dark reddish - brown color
Very hard at room temperature
Low thermal conductivity
Thermal plastic
Needs to be softened with a water bath
Most critical property
What is term used to softens when heated and hardens when cooled?
Thermalplastic
Tray compound impression technique
Soften material with water bath
Place in edentulous tray
Put tray back in water bath
Dentist places in patients mouth
Removed from mouth when hardened.
Type of inelastic that is also known as metallic oxide paste that is used for 10 mins for final impression for edentulous patients.
Zinc oxide eugenol paste
What is the primary used of zinc oxide eugenol?
To take more detailed impression of the edentulous patient for denture construction.
True or False
Adding small drops of water will decrease the setting time of ZOE paste.
True
True or False
ZOE paste is often put into the tray which contains the impression plaster and is reseated for the final impression.
False
ZOE paste is often put into the tray which contains the TRAY COMPOUND and is reseated for the final impression.
Advantages of ZOE paste
Fine detail
Stable
Strong
Disadvantages of ZOE
Cannot be used if undercuts are present
Long setting time
Material sticks easily