Elastic Impression Materials Flashcards
What are the two general types of elastic impression materials?
- Hydrocolloids
- Rubber impressions or elastomers
Are classified as a fourth state of matter, _______________, because of their difference in structure, constitution, and reaction.
Colloids
Exist in one phase, when we mix solute and solvent.
True solutions
Colloids and suspension have two phases:
A. Dispersed phase
B. Dispersion medium
Somewhere between the extremes of the very small molecules in solution and very large particles in suspensions is the colloidal solution or sol.
The size of colloidal particles ranges from ___to___nm.
Colloids and suspension
- 1 to 200nm
What are the types of colloids, and it’s meanings.
- Aerosols - liquids or solids in air
- Lysols. - gases, liquids or solids in liquids
- Foams - gases in solid
- Solid Emulsion - liquids in solid
- Solid Suspension - solids in solid
The colloidal materials used for making impressions are either _______ or ________dissolved in water they are known therefore as?
Agar or algin; hydrocolloids
What are the two types of hydrocolloids?
A. Irreversible hydrocolloids or alginate
B. Reversible hydrocolloids or agar
True or false. Please read!
Alginate impression material (irreversible hydrocolloid)
Advantages:
1. Easy to mix and manipulate, has good viscosity and has low in adhesive qualities.
2. Requires little armamentarium.
3. It allows for undercuts.
4. The process is not time consuming.
5. It makes an accurate impression.
6. Cheap and it causes no great pain to the patient.
7. Inexpensive to the dentist.
Disadvantages:
1. Cannot be used in making metal dies.
2. Less production of surface details to gypsum dies as agar and elastomers.
True
From the composition of alginate
Function: To dissolve in water
Sodium and potassium Alginate salt
In composition of alginate:
Function: to react with dissolved alginate to form insoluble calcium alginate
Calcium sulfate
In composition of alginate:
Function: to react preferentially with the calcium sulfate and reserve as a retarder
Sodium phosphate
From the composition of alginate:
Function: to control consistency of mix and flexibility of impression.
Diatomaceous earth or silicate powder
From the composition of alginate:
Function: To counteract inhibiting effect of alginate on setting of gypsum model and die materials.
Potassium sulfate and Potassium zinc fluoride
From the composition of alginate:
Function: To coat the powder particles minimize dust during dispensing.
Organic glycol
From the composition of alginate:
Function: to provide self disinfection
Quaternary ammonium compounds and chlorhexidine
From the composition of alginate:
Function: to provide color
Pigments
From the composition of alginate:
Function: sweetener
Phenylalanine
In the alginate impression material ( Irreversible hydrocolloid), what are the product of chemical reaction?
- Calcium alginate
- Sodium sulfate
- Water
PLEASE READ
The properties of the algenic impression materials:
- Mix should be _______ and _______.
- Permanent deformation - _______.
- Flexibility - ___________ = less flexible and will not register fine details.
- Strength: compressive strength
- ANSAI- ADA Spec. is 3570 g/cm2
- Commercial alginate - 5000-9000 g/cm2
- Tear strength - 380-700 g/cm2 - Dimensional change
- Accuracy
______- formation of exudate on surface of the gel.
______- absorption of water and impression. - Reproduction of detail
______- must have a capability of transferring a line of 0.075 mm. - Disinfection
- sodium hypochlorite - 10 minutes soak 0.5%
- iodophor - 10 minutes, immersed in diluted solution, 1:213
- gluteraldehyde - 20 minutes at 2%
- phenylphenol solution - 20 minutes, 1:32 dilution
- Smooth and creamy
- 2-4%
- Thicker mix
- Syneresis and imbibition
- ANSI-ADA Specification
True or false. Please Read!
The objectives for taking impressions:
- All teeth in the upper and lower arch
- The entire alveolar process
- The retromolar pad of the lower arch
- The area of the hamular notch and the upper arch
- A detailed, undistorted, and bubble free reproduction of the tissues
True
True or false. Please read
Steps in taking an alginate impression:
- Selection of impression tray
- Proportioning of alginate in water
- Mixing the alginate
- Loading the tray
- Taking the impression
True
True or false. Please read
Handling of the impression:
1. Rinse the impression with cold water.
2. Cut away any unsupported alginate.
3. Disinfect alginate impression
4. Rinse disinfected impression with cold water.
5. Remove excess water.
6. Pour gypsum model.
7. If stored, the impression should be places so that the originate is supported by the tray.
True
The first successful elastic impression?
Agar (reversible hydrocolloid)
True or false. Please read!
In the composition of Agar:
Traymaterial:
Agar - 12-15%
Borax - 0.2% - strength improver
Potassium sulfate- 1-2% - ensure proper setting of gypsum
Benzoates - 0.1% - preservative
Water - 80-85%
Filler (diatomaceous earth, silica, clay)
Syringe material:.
Agar - 6-8%
True
From the properties of Agar: Please read!
- Can be used many times
- More accurate surface details than alginate
- __________ - a phenomenal physical property of a material having different liquefaction temperature and solidification temperature.
Hysteresis
Please read!
The MANIPULATION OF AGAR requires the following.
- Agar hydrocolloid conditioner
- _________ compartment- 100°C
- _________compartment - 60-66°C
- _________ compartment - 43-46°C - Water cooled the impression trays
- Syringes
- liquifying
- storage
- temperature or tempering
What are the techniques of taking impression using agar?
- Wet field technique - uses agar alone
- Laminate technique - uses both agar and alginate
- Combination of alginate nd agar.
- The syringe type of agar will be injected to the dental arch and the alternate is used as the tray material loaded to the stock tray.
Laminate Technique
Are supplemented to the oral examination?
Diagnostic casts
- A recurring requirement in the dental office is for study models or diagnostic casts’ of patient’s teeth and adjusting tissues.
- It is a requirement for the following procedures:
a. Diagnosis
b. Fabricating crowns and dyes for presidentics appliances.
Diagnostic casts
- It is an accurate application of the anatomic form of the maxillary or manipular dental arch showing the relationships of the remaining teeth and the surrounding tissues.
- Supplement to the oral examination but in some ways they are they can reveal more.
- Permit inspection from perspectives that are impossible to obtain when looking in the patient’s mouth.
- Permit extended observations and comparisons far beyond the patient’s endurance for holding his or her mouth open and are available for study during the patient’s absence.
- Use in educating the patient about his or her dental needs and corresponding treatment plan.
An alginate is a ____________ mold of the teeth
Diagnostic casts; negative
Three steps of obtaining diagnostic cast:
- An audit impression is made directly in the patient’s mouth producing a ________ mold.
- The impression is poured and dental stone producing a __________ cast.
- The cast is expected for defects, repaired if possible, and trimmed to the proper size and shape on a model trimmer.
Negative and positive
Physical properties of Alginate:
- Alginate is an impression material that is supplied in _______ and _______.
- When set, the material is a ________ resembling rubber.
- it’s important characteristic is its ability to _______________.
- Powder form and mixed with water
- flexible gel
- rebound from stresses
Composition of Alginate:
- Alginate is classified as ____________.
- it is hydrocolloid because?
- it is irreversible because?
- the ALGINATE PARTICLES are composed of:
- salt of alginic acid a product of _________.
- an activator, usually __________.
- an inert filler to reduce stickiness, produce a smooth texture and add strength.
- Flavoring
- irreversible hydrocolloid
- it consists of particles of a gelatinous state (colloidal state) in water
- once it has jelled, it cannot be returned to a liquid solution.
- marine kelp
- Calcium Sulfate
The packaging of alginate, what is the form that is the most popular?
Bulk form
The more desirable choice when temperature change and moisture are concern of packaging of the alginate?
Preweighted package
True or false.
All types of alternate packaging must be stored in a cool and dry place
True
Is sensitive to higher temperature and moisture contamination. Those variables cause the alternate to lose strength during mixing and be more apt to distort upon removal from the mouth.
Alginate
True or false. Please read!
Mixing alginate:
- fluff or shake the powder to distribute the powder particles evenly.
- uses specific measuring devices water and powder provided by the manufacturer for mixing.
- follow the manufacturers directions regarding the ratio of water to powder.
- use exact measurements.
- after the water and powder have been measured place the water in a clean dry bowl sift the water into the water.
- adding the powder to water ensures the powder particles are wet evenly
- if mixing reverse the chemical reaction will start early with some particles setting faster than others.
- mix the originate for the specific amount of time and using a “stiff” spatula SWIPE the alternate mass against the sides of the ball to avoid entrapment of air in the mix
- care should be taken in shaking dustless can of alginate.
True
True or false. Please read!
Mixing alginate:
- fluff or shake the powder to distribute the powder particles evenly.
- uses specific measuring devices water and powder provided by the manufacturer for mixing.
- follow the manufacturers directions regarding the ratio of water to powder.
- use exact measurements.
- after the water and powder have been measured place the water in a clean dry bowl sift the water into the water.
- adding the powder to water ensures the powder particles are wet evenly
- if mixing reverse the chemical reaction will start early with some particles setting faster than others.
- mix the originate for the specific amount of time and using a “stiff” spatula SWIPE the alternate mass against the sides of the ball to avoid entrapment of air in the mix
- care should be taken in shaking dustless can of alginate.
True
