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DENTAL MATERIALS
Indirect restorations
| Question | Answer |
|---|---|
| Indirect restoration | A restoration constructed outside the mouth in a laboratory |
| Alloy | Combination of pure metal and one or more other elements |
| Pure metal | Only a single metal |
| All metals are --------and possess high thermal and electrical conductivity, ductility, opacity and luster. | crystalline |
| What is a crystalline property? | A regular order or arrangement of atoms |
| Metals: Requirements for dental materials: | *Strong and hard enough to withstand occlusal forces, biologically compatible, high resistance to corrosion and tarnish, can be relatively easily cast into complicated shapes |
| Noble/Precious metals: | Gold, platinum, palladium, Iridium, Ruthenium, Niobium, Osmium |
| Why don't we use pure gold (24 K)? | It is not strong enough to withstand chewing stresses, and it is the most conductive material in restorative dentistry. |
| What does copper do? | Increases strength and hardness |
| What does platinum do? | Protects against tarnish and corrosion |
| What does silver do? | tones down the red in Cu. It is not stable in the oral enviroment unless alloyed with platinum or palladium. |
| What does palladium do? | Increases tarnish resistance. |
| What does zinc do? | prevents oxidation during casting procedures, acts as a scavenger. |
| What is a scavenger? | A substance added to a mixture to remove or inactivate impurities. |
| What metals whiten alloy? | Gold, platinum, and palladium |
| Type I alloy: | Used for inlays NOT subjected to stress. Used for gingival cavities. |
| Type II alloy: | Used for inlays NOT subjected to stress, but harder than type I alloy. |
| Type III alloy: | Crown and bridge abutments. Lighter in color. Harder than I and II. Contains more palladium and platinum. |
| Type IV alloy: | Large castings of long span bridges, partial dentures clasp and bars, HARDEST AND STRONGEST!! |
| Elongation: | the ability of a material to be stretched without breaking. Stretching elongation is burnishing the alloy. |
| Base metal alloys: | Alloy that does not contain noble metals. i.e. steel, brass and aluminum alloys |
| Why are base metal alloys of chromium, aluminum and titanium used for implants? | because they are the most biocompatible metal |
| Ceramometal: | combo that supplies both strength and esthetics i.e. PFM |
| A temporary restoration is also called? | A provisional restoration |
| Sprue | metal stick |
| Once we get the pattern created in the gypsum, how do we get the gold in? | Centrifugal force |
| Cast metals | metal alloys used in the casting process |
| How are cast metals classified? | according to noble elements which are corrosion resistant |
| How are precious metals classified? | based on cost |
| Precious metals are noble metals plus what? | silver...silver is NOT noble |
| Classification by gold: | Percents is parts per 100, Carats is parts per 24, Fineness is parts per 1000 |
| ------- and ------ are non precious metals that are white and have a high melting point. | Nickel and chromium, chromium is inexpensive. |
| High gold or high noble alloys contain -- gold. | 60% |
| Low gold or low noble alloys contain --noble metals with gold replaced by silver. | 25% |
| Alloys with less than 25% noble called? | base metals |
| ------------- is used to describe metals with NO noble elements. | nonprecious |
| ------ that forms on the surface of the metal when heated help the porcelain chemically bond to the metal | Oxide |
| What is the material of choice for dental implants and why? | titanium because it is biocompatible |
| Another name for porcelain crowns is? | Porcelain jacket crowns |
| C.A.D | Computer Aided Design , Optical impression uses a computer and machine to create restorations. |