Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
39 Cards in this Set
- Front
- Back
|
What are the 3 types of rigid impression materials?
|
1. Impression dental compound
2. Impression plaster 3. Zinc oxide-eugenol |
|
|
What are the principle applications of impression dental compounds?
|
Preliminary impressions of edentulous patients (type I)
Border molding of impressions (type II) |
|
|
What is the composition of impression dental compound?
|
50% fillers and organic pigments
40% Natural resins 7% Waxes 3% Steric acid (Lubricant & plasticizer) |
|
|
What is the primary use of impression plaster?
|
To mount casts on an articulator
|
|
|
What are the uses for zinc oxide-eugenol?
|
To take final impression of edentulous patients
Rarely used anymore |
|
|
What are the two types of elastic impression materials?
|
Hydrocolloid
Non-aqueous elastomers |
|
|
What are the two types of hydrocolloid impression materials?
|
Reversible hydrocolloid (agar)
Irreversible hydrocolloid (alginate) |
|
|
What are the advantages of alginate (irreversible) hydrocolloid?
|
1. Easy to mix and manipulate
2. Minimum equipment is required 3. Flexibility of the set impression 4. Accuracy if it is properly handled 5. Low cost |
|
|
What are the disadvantages of alginate hydrocolloid?
|
1. Don't transfer as much surface detail to gypsum as rubber and agar do
2. Restrict the choice of model & die materials to gypsum type 3. Need quick pour-up of impression |
|
|
What is the normal setting time for alginate?
|
3-4.5 minutes
|
|
|
What is the fast setting time for alginate?
|
1-2 minutes
|
|
|
Increasing the temperature of the water used with alginate will _________ the working and setting times.
|
shorten
|
|
|
What is the alginate reaction?
|
Sodium alginate + CaSO4 * H20
yields Calcium alginate + Na+ + SO4-2 + H2O Paste to a gel |
|
|
How much permanent deformation occurs with an alginate impression?
|
2-4%
Occurs during the removal of the impression |
|
|
What % of flexibility do we typically see with alginates?
|
5-18%
|
|
|
Alginates:
More water does what to its flexibility? |
Increases flexibility
|
|
|
What is the best way to remove an alginate impression to avoid tearing?
|
Remove rapidly
|
|
|
Alginate:
What is the best way to store an impression? How long? |
Store in humid air approaching 100% humidity--least dimensional change.
Too dry-shrinks Too wet-expands No more than 1 hour of storage |
|
|
What is the best way to disinfect alginate?
|
10 minute wait after spraying the impression with 0.5% sodium hypochlorite.
|
|
|
What are some facts about agar hydrocolloid?
|
The first successful elastic material used in dentistry.
High flexibility during removal allows for appearance of undercut areas. Alginate and rubber materials have mostly replaced it. |
|
|
High-viscosity fluids ______ flow. Low-viscosity fluids ________ flow.
|
High-viscosity-resist flow
Low-viscosity-easily flow |
|
|
What are the 3 types of non-aqueous elastomers?
|
Polysulfides
Silicones Polyethers |
|
|
What are some advantages of polysulfides?
|
1. The best tear strength
2. Relatively inexpensive 3. Long working & set time 4. Good reproduction 5. Good flow before setting 6. Good bond with tray adhesive 7. Stable in disinfectant solutions |
|
|
What are some disadvantages of polysufides?
|
1. Cannot be repoured
2. Unpleasant odor and taste 3. Poor recovery from deformation 4. Poor dimensional stability 5. Should be poured within one hour 6. Should be used with custom trays 7. Staining of clothes due to the lead oxide |
|
|
How can you disinfect polysulfide impressions?
|
Immerse in sodium hypochlorite
|
|
|
What are the two types of silicone materials?
|
Condensation silicone
Addition silicone |
|
|
What are the advantages of condensation silicone?
|
1. Good recovery from deformation
2. Good tear strength 3. Good accuracy 4. Adjustable working times 5. No bad taste or odor 6. Stable in disinfectant solution 7. Relatively inexpensive |
|
|
What are the disadvantages of condensation silicone?
|
1. Poor dimensional stability
2. Hydrophobic: poor moisture compatibility 3. Immediate pour required 4. Poor bond to tray adhesive |
|
|
What is the most important brand of addition silicone?
|
Aquasil
|
|
|
What are the advantages of addition silicone?
|
1. Most accurate material available
2. Good tear strength 3. Excellent recovery from deformation 4. Long term dimensional stability 5. Hydrophilic 6. No bad taste or odor 7. Stable in disinfectant solution 8. Available in automixing devices |
|
|
What are the disadvantages of addition silicone?
|
1. Some are hydrophobic
2. Relatively expensive 3. Materials are sensitive to contaminants |
|
|
Addition silicones:
What do you need to keep in mind...what is the major draw back? |
Easily contaminated...be sure to remove latex gloves before manipulating putty.
|
|
|
How should you disinfect addition silicones?
|
10-15 minutes immersion in 10% hypochlorite or 2% glutharaldehyde solutions
|
|
|
What are the important brand names of polyether impression materials?
|
Permadyne
Impregum penta |
|
|
What are the advantages of polyethers?
|
1. Rigid
2. Long term dimensional stability 3. Good accuracy 4. Hydrophilic 5. Good reproduction of surface details 6. Good tear strength 7. Good bond with tray adhesive 8. Easy to use |
|
|
What are the disadvantages of polyethers?
|
1. Can be too stiff
2. Bad taste and odor 3. Poor recovery from deformation 4. Unstable in disinfectant solutions 5. Difficult to mix 6. May cause allergic reaction-sulphonic acid ester |
|
|
List from most flexible to least flexible:
Condensation Silicone Polyether Polysulfides Addition Silicone |
Polysulfides > Cond. Silicone > Addition Silicone > Polyether
|
|
|
Elastic Recovery:
List from most to least: Condensation Silicone Polyether Polysulfides Addition Silicone |
Add. Silicone > Cond. Silicone > Polyether > Polysulfides
|
|
|
Most important characteristic of each of the following:
Polysulfides Condensation Silicones Polyether Addition Silicone |
Polysulfides-The best tear strength
Condensation Silicones-Poor dimensional stability Polyether-Very rigid Addition Silicone-Most accurate |
