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101 Cards in this Set
- Front
- Back
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What is a dental amalgam? |
The powdered metal is predominately silver with a little tin (made of silver and mercury) |
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Name two kinds of amalgam alloy |
1) Lathe cut-from grinding an ignot 2) Spherical alloys-from spraying molten metal into an inert atmosphere |
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When was amalgam initially developed? |
Developed in France in the 1800's Not in the USA until 1933 |
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What is the composition of low copper amalgam? |
65% silver 25% tin less than 6% copper 1% zinc |
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What is the function of silver in amalgam? |
Silver: causes setting expansion and increases strength and corrosion resistance
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What is the function of tin in amalgam? |
Tin: causes setting contraction and decreases strength and corrosion resistance |
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What is the function of copper in amalgam? |
Copper: functions much the same as silver |
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What is the function of zinc in amalgam? |
Zinc: reduces oxidation of other metals |
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What is the weakest and most corrosion prone phase of low copper? |
Sn-Hg (tin-mercury), the gamma two phase |
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What % copper is in high copper amalgams? |
10-30% copper |
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What two factors affect the handling and performance of amalgam? |
1) Manufacturer 2) Dentist |
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Amalgam has high _________ strength |
Compressive |
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Amalgam has low ___________ strength |
Shear **Don't want this in a class IV filling |
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What is creep? |
A slow change in shape caused by compression |
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Dental amalgam is not recommended for what class restoration? |
Class IV |
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Why can zinc cause an amalgam to expand? |
Zinc reacts with water to produce hydrogen gas which causes the amalgam to expand. |
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What percent of patients have mercury toxicity? |
0.1% of patients |
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Gold foil restorations are limited to what class restoration? |
Small restorations like class V because of low strength |
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What are luting agents? |
Luting agents glue things together (crown to tooth) |
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Name two things that provide pulp protection |
1) Liners-may stimulate secondary dentin formation (calcium hydroxide) 2) Bases-provide thermal insulation |
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What protects the pulp from an irritating base or cement? |
Varnish |
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Name 3 liquids used in dental cements |
1) Eugenol 2) Phosphoric Acid 3) Polyacrylic Acid |
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What are the components of Eugenol? |
Oil and cloves |
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What liquid used in dental cements may be irritating to the pulp? |
Phosphoric Acid |
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Name 5 kinds of dental cements |
1) ZOE cement 2) Zinc phosphate cement 3) Polycarboxylate cement 4) Glass-ionomer cement 5) Composite cement |
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The 2 disadvantages of ZOE cement are..? |
1) Inadequate strength 2) High solubility |
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A disadvantage of zinc phosphate cement is..? |
It irritates the pulp (creates a low pH) |
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Why is a cooled glass slab used when mixing zinc phosphate cement? |
Because the setting reaction is exothermic
EXOTHERMIC REACTION |
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What are 2 advantages of glass-ionomer cements? |
1) Releases fluoride 2) Bonds to tooth structure, stainless steel and alloys |
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What is the cement of choice for luting metal or ceramometal crowns? |
Resin modified glass ionomer |
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A MAJOR disadvantage of polycarboxylate cement is..? |
It is NOT strong |
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The 3 advantages of polycarboxylate cements are..? |
1) Bonds to tooth structure 2) Very biocompatible 3) Releases fluoride |
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What liner promotes the formation of secondary dentin? |
Calcium hydroxide liners (Dycal) |
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What is the composition of Temp Bond, a temporary cement? |
Zinc oxide and vegetable oil |
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Name 3 types of impression trays |
1) Stock trays 2) Custom trays 3) Special use trays--Triple trays |
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Name 3 types of impression materials |
1) Inelastic 2) Aqueous elastomeric 3) Nonaqueous elastomeric |
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What are the 3 types of inelastic impression materials? |
Plaster Wax ZOE |
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How many types of inelastic impression materials are there? |
3 |
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How many types of aqueous elastomeric impression materials are there? |
2 |
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How many types of nonaqueous elastomeric impression materials are there? |
4 |
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What are the 2 types of aqueous elastomeric impression materials? |
Alginate and Agar |
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The 4 types of nonaqueous elastomeric impression materials are..? |
Polysulfides Condensation silicones Polyethers Addition silicones |
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Which type of impression material returns to its original form after deformation? |
Elastomeric |
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What will not reverse to a sol once it is set as a gel |
Alginate |
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Warm water ____________ the setting rate of alginate |
Increases |
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Used for study models and casts |
Alginate |
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Requires special impression trays that circulate cooling water |
Agar (reversible hydrocolloid) |
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What is a by product of condensation silicones? |
Alcohol |
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What are the most popular type of elastomeric impression materials? |
Addition silicones |
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Name 3 disadvantages of polysulfides |
1) Odor 2) Stains clothing 3) Long working time |
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Hydrocolloids will absorb water and distort. What is this called? |
Inbibition |
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What is the calcination process? |
CaSO4 2H2O + heat ---> (CaSO4)2 + H2O |
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What are the 3 types of gypsum products? |
1) Plaster 2) Stone 3) Improved Stone |
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Which gypsum product is the weakest and least expensive? |
Plaster |
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Which type of gypsum product is yellow and referred to as alpha-hemihydrate? |
Stone
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What color is plaster? |
White
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What color is stone? |
Yellow |
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What color is high strength, or improved stone? |
Pink |
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Which type of gypsum product is used to make dies? |
Improved Stone |
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What is the setting reaction when hemihydrate is mixed with water? |
Exothermic |
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What is the water/powder ratio for plaster? |
45-50 ml/100g |
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What is the water/powder ratio for stone? |
28-30 ml/100g |
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What is the water/powder ratio for improved stone? |
19-24 ml/100g |
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The final setting time for gypsum products is..? |
30-45 minutes |
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A retarder used to increase the setting time is? |
Borax (sets slower) |
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Product used to accelerate the setting time..? |
Calcium sulfide |
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A ________ water powder ratio decreases the setting time (sets faster) |
Lower (makes a thicker mix) |
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Which has the most expansion: plaster or stone? |
Plaster |
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Dry strength is measured when? |
When there is no excess water in the sample |
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Dry strength may be ________ times stronger than wet strength |
2 to 3 times stronger |
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What is placed in the mixing bowl first: water or powder? |
Water |
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Indirect restoration are constructed where? |
Outside the mouth Usually in the lab |
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Onlays restore what? |
One or more cusps |
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Crowns restore what? |
Teeth that have lost a significant amount of tooth structure Teeth that have had a RCT |
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Dental bridges replace what? |
Missing teeth |
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Veneers are placed where? |
On the facial surfaces of anterior teeth |
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Ceramic materials lack what? |
Toughness & fracture resistance
**this is not true nowadays |
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Another name for a temporary restoration..? |
Provisional restoration |
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The name of the wax used for crowns |
Inlay casting wax
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The name of the wax used in the fabrication of dentures |
Baseplate wax |
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Attached to the wax pattern to create an opening for the mold |
Sprue |
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What color are inlay casting waxes? |
Dark blue |
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What color is sticky wax? |
Yellow |
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What color is baseplate wax? |
Pink |
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What color is boxing wax? |
Red |
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The mold must expand to compensate for what? |
The shrinkage of the metal |
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What is a refractory? |
It improves the investments resistance to heat (Usually silica) |
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What is burnishing? |
Pushing metal against the tooth to close any gap |
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What are the noble metals? |
1) Gold 2) Platinum 3) Palladium |
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How many noble metals are there? |
3 |
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What are the precious metals? |
Noble metals + Silver |
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Carat is parts per ______? |
24 |
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Fineness is parts per _________? |
1000 |
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Twelve carats is ______ fineness? |
500 |
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High noble is _____% gold or noble elements |
68%
**Will be on test |
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Base metals are less than ____% noble elements |
25% |
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What is sintering porcelain? |
Taking a powder and heating it up.
Firing the porcelain causes the powders to be sintered, which changes the porcelain from powder to solid. |
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What is the material of choice for dental implants? |
Titanium |
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What metal is commonly used now in partial dentures? |
Either nickel-chromium or cobalt-chromium |
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What is a PFM crown? |
PFM stands for: Porcelain fused to metal |
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What does CAD/CAM mean? |
computer-aided design/computer-aided manufacturing |
