Quiz #1: Intro + Alginate Flashcards
What does fixed prosthodontic treatment involve?
- replacement/restoration of teeth by substitutes
- substitutes are not readily removable from mouth
What are the important qualities of the fixed prosthedontics course?
- attendance
- timeliness
- cleanliness
- protection
- ergonomics
- practice
What is the focus of restoration?
- restore function
- restore esthetics
- comfort
What is a crown prep?
When prepare tooth structure to facilitate delivery of final restoration
What are the two types of delivery of a final restoration?
- cementation
- bonding
What composes the basic amamentarium?
- handpieces (high and slow speed)
- typodont (maxillary/mandibular)
- mannequin
- burs
- mirror (to help see/retract)
What is the RPM range of the high speed handpiece?
200,000 - 400,000 RPM
How much water for microstone?
40 mL
How to mix together microstone and water?
powder to water
- water in bowl first
- then add powder
What is the use of the vibrating platform?
To release air bubbles
Describe the alginate impression material.
Irreversible hydrocolloid impression material
What is alginate composed of?
- mucous extract from brown seaweed (algae)
- 15% potassium alginate (from seaweed)
- 16% calcium sulfate
- trisodium phosphate
- 60% Diatomaceous earth
- 4% zinc oxide
- 3% potassium titanium fluoride
Why is alginate irreversible?
Once it has set, cannot be returned to liquid state
What does hydrocolloid mean?
a mixture within water
- Hydro = water
- colloid = particles of one substance that are evenly dispersed through another substance
What is the importance of trisodium phosphate in alginate?
Slows down the reaction time for mixing
reacts with calcium sulfate
What is the water soluble salt of alginic acid?
Potassium alginate
Describe the importance of calcium sulfate in alginate.
reacts with potassium alginate
forms the gel: calcium alginate
Regular or fast set types of alginate depends on the level of ___________.
trisodium phosphate
What is the retarder in alginate?
Trisodium phosphate
What is the equation of trisodium phosphate?
Na3PO4
What provides the filler for bulk of the material?
Diatomaceous earth (and zinc oxide but much less)
What is the purpose of potassium titanium fluoride in alginate?
added for surface strength
What are the phases of alginate setting?
- Sol
- Gel phase
What is the Sol phase of alginate setting?
When the alginate is in liquid or semiliquid form
What is the Gel phase of alginate setting?
When alginate is in semisolid or gelatinous phase
What is purpose of diagnostic impression?
- replicate teeth and soft tissue
- include vestibules and palate
What are diagnostic impressions most commonly used for?
Diagnosis
Are alginate diagnostic impressions accurate or inaccurate?
Inaccurate
What are some advantages of alginate?
- pleasant odor
- biocompatible
- economic
- adequate shelf life for storage/distribution
- easy to use with minimal equipment
- satisfactory consistency and texture
- elastic properties
- adequate strength
- dimensional stability (long enough to produce cast)
- no release of gas/other byproducts
What is most critical when doing alginate manipulation?
Stock tray selection/modification
Which causes alginate to set faster? Hot or cold water?
Hot
What must be removed to prevent dilution of gypsum mix, yielding a soft, chalky surface?
Free water
What is the general working time of alginate?
- Mix alginate/water - 0:30
- Working time - 1:00
- Setting time - 1:30
Total time: 3:00 minutes
When should you pour gypsum into an alginate model? Why?
Immediately
longer you leave it the more likely the impression will distort
water within it will evaporate
When should you disinfect the alginate impression?
5-10 minutes
When should you separate the model from the impression? Why?
45 min - 1 hr
If leave in too long, soluble Ca dihydrate of gypsum will react with water in gel
cause surface quality loss
What is undercut?
Imagine you fill a bucket with rubber but the bucket walls are not straight (narrower at bottom than at rim)
will pull it out, will leave some left in bucket
THAT is called undercut
calcium sulfate + potassium alginate = ________
calcium alginate
What does an impression show?
patient bite/alignment/fracture when patient is not present in the office
What is syneresis?
LOSS OF WATER
When alginate is mixed with water, the water EASILY evaporates, distorting it
Gives off water to atmosphere
What can cause inadequate impressions?
- Inadequate tray size/fit; inadequate tray retention
- Undermixing powder/liquid
- Seating or moving tray in the mouth during gelation of material
- Under seating tray
- Long delay in pour-up of impression
- Excess moisture in impression during pour-up.
- Distortion caused by removal of impression from severe undercuts
What is imbibition?
ABSORPTION OF WATER
When alginate absorbs too much water
Absorb water from atmosphere
Irreversible hydrocolloid is largely what?
Water
What is the chemical formula of calcium sulfate dihydrate?
CaSO4*2H2O
Describe calcium sulfate dihydrate.
Naturally occuring
white powdery mineral
What is the dental version of calcium sulfate dihydrate?
Calcium sulfate hemihydrate
CaSO4 * 1/2H2O
What is the difference between the ADA gypsum type products?
identical chemical formula of calcium sulfate hemihydrate BUT have different particle size and physical properties for different tasks
differ in manner of which H2O is driven off the Ca sulfate dihydrate
What is calcination?
manner in which H2O is driven off the Ca sulfate dihydrate
What causes the setting reaction for calcium sulfate hemihydrate?
Hydration of calcium sulfate hemihydrate
(adding water)
What type of gypsum did we use in sim lab?
Type III
What does MORE water in the water to powder ratio do for alginate?
- less strength
- more porosity
- less expansion
- increased setting time
_______ the amount or speed of spatulation (mixing) shortens the setting time
Increasing
The setting reaction of gypsum is an ____________ reactions.
Exothermic
What can affect the setting time?
- temperature of water
- environment
- temperature of room/body
Why are gypsum products kept in closed container?
To prevent imbibition of water from environment
How to decrease setting time of alginate
- hot water
- less water
- increased spatulation time
- use slurry water
How to increase setting time
- cold water
- more water
- decreased spatulation time
Why do we make mounted study models?
- treatment planning
- dental legal records
- provisional restorations
What is another name for gypsum?
Microstone
What makes proper tray size?
- tray should be able to capture vestibule
- maxillary tray should extend to distal most tooth and tuberosities
- mandibular tray should extend to distal most tooth and retromolar pad
How to center the tray?
- align teeth
- align handle with nose
- seat tray with equal pressure on both sides
What are abnormal piece of stone that “stick out” of the impression surface called?
positive blebs
What are the dimensions of the bases?
15 mm for maxillary
13 mm for mandibular
What are the ADA gypsum products?
- Type I: Impression Plaster. Mounting stone
- Type II: Model Plaster.
- Type III: Dental Stone (study casts, master casts).
(microstone) (all purpose) - Type IV: Hight-Strength low expansion Dental Stone (Die
stone, ). - Type V: High-Strength, high-expansion Dental stone
