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Dental Materials
Amalgam
| Question | Answer |
|---|---|
| Why has there been a reduction in the use of dental amalgam over the past 20 years? | Concerns about mercury and its lack of esthetics |
| What is the reaction called when silver-based alloy particles are mixed with mercury? | amalgamation |
| Modern dental amalgams are higher in what component now than they were years ago? | copper |
| What shape of alloy requires more mercury to wet the particles? | lathe cut particles |
| What shape of alloy particles sets up more slowly? | lathe cut particles |
| Which of the modern alloys uses the least amount of mercury? | spherical |
| How long after placement does it take many high-copper spherical amalgams to gain 50% of its compressive strength? | 1 hour |
| Which is the strongest phase in the setting reaction of amalgam? | the first phase (gamma phase) |
| In what phase does the mercury react with silver? | second phase (gamma-1) |
| Which setting phase does not occur in high-copper alloys? | third phase (gamma-2) |
| Which metal in the amalgam alloy controls the rate of the set of the amalgam? | tin |
| Which metals in the amalgam alloy dissolve into the liquid mercury until the solution is saturated with them? | silver and tin |
| What causes amalgam to discolor and the margins to deteriorate? | corrosion |
| Between high-copper amalgams and low-copper amalgams, which is more durable? | high copper |
| Between high-copper amalgams and low-copper amalgams, which has more deterioration at the margins? | low copper |
| Between high-copper amalgams and low-copper amalgams, which has less corrosion? | high copper |
| Between high-copper amalgams and low-copper amalgams, which has lesser strength? | low copper |
| What is creep? | the gradual change in shape of the restoration from compression |
| Which phase of setting reaction is creep associated with? | gamma-2 |
| Between high-copper amalgams and low-copper amalgams, which is most often associated with creep? | low copper |
| What happens if a newly placed amalgam contracts excessively? | It will cause gaps leading to open margins |
| What happens if a newly placed amalgam expands excessively? | it can put pressure on the cusps and cause pain with biting pressure, or it may result in fracture of the cusps |
| Amalgams are relatively weak in ________ and _________ strength. | tension and shear |
| Amalgams are stronger in ___________ than composites or glass ionomers. | compression |
| Comparing spherical high-copper dental alloys with admixed dental alloys, which has more resistance to condensation? | admixed |
| Comparing spherical high-copper dental alloys with admixed dental alloys, which has higher compressive strength? | spherical |
| Comparing spherical high-copper dental alloys with admixed dental alloys, which requires more mercury? | admixed |
| Comparing spherical high-copper dental alloys with admixed dental alloys, which feels softer? | spherical |
| What mechanical device mixes the dental amalgam alloy and mercury? | triturator |
| What type of appearance does undertriturated amalgam have? | dry, crumbly |
| What type of appearance does overtriturated amalgam have? | too wet |
| Why does the undertriturated amalgam set too quickly, resulting in a weaker restoration? | because the components have not completely mixed, leaving a higher level of unreacted mercury and alloy particles |
| Why does the overtriturated amalgam set too quickly, resulting in a weaker restoration? | because of the heat produced by the prolonged mixing |
| Why is the cavity preparation slightly overfilled during the placement and condensation of amalgam? | allows enough material to carve and remove excess mercury |
| How long should patients be told to avoid chewing on a newly placed amalgam restoration? | 8 hours |
| How should amalgam restorations be polished? | wet with a light touch |
| What is true regarding levels of mercury in dental offices? | most are far below OSHA’s recommended minimum |
| Is the elemental mercury used in amalgam more or less toxic than organic mercury? | less |
| What ingredient is substituted for mercury in the “mercury-free” amalgam? | gallium |
| Where is the “mercury-free” amalgam used? | countries other than the United Stated |
| Amalgam restorations are a combination of which alloys? | copper, tin, silver, indium, zinc, and palladium |
| Which percentage of mercury contamination from waste water entering the public water system is contributed by dental offices? | 50% |
| Of the three setting phases of amalgam, which is the weakest? | gamma-2 |
| Why is it not as necessary to polish today’s generation of amalgam restorations as it was to polish earlier amalgams? | They are high in copper, which is shiny. |
| What is the result if an amalgam restoration corrodes? | it weakens over time, stains surrounding teeth, breaks down margins |
| Compared to composites or glass ionomers, amalgams are higher in what? | compressive strength |
| Compared to composites or glass ionomers, amalgams are weaker in what? | tension and shear |
| What will occur if an occlusal amalgam is overcarved? | restoration is more likely to fracture |
| What will occur if an occlusal amalgam is undercarved? | creates an irregular margin that tends to collect plaque and contribute to recurrent caries. |
| Why are carpets and tiled floors with seams not recommended when working with amalgam? | they tend to trap amalgam particles and mercury droplets |
| Why is the wet resin technique used under an amalgam restoration? | Bond the amalgam to the tooth |
| What will occur if one attempts to carve amalgam once the amalgam is set? | Damage the margins |
| What is it called when the design of the cavity preparation is what holds the amalgam restoration in place? | mechanical retention |
| What do the manufacturers of dental amalgam control? | alloy composition, particle size, rate of setting reaction |
| When placing amalgam, how is excess mercury removed? | excess mercury is brought to the surface and is removed using the HVE |
| When condensing amalgam, what side of the condenser should be used first? | the smallest end |
| What does properly triturated amalgam look and feel like? | a cohesive mass that is slightly warm to the touch with a smooth plastic-like feel |
| Why should the used amalgam capsule be reassembled immediately? | to minimize mercury vapors escaping into the air |
| When amalgam is condensed, what is brought to the surface and is removed using the HVE? | Excess mercury |
| What do the manufacturers control in regards to dental amalgam? | particle size, alloy composition, rate of setting reaction |
| What is the purpose of trituration? | mix alloy and mercury together by wetting the alloy with the mercury |
| What is the term used when the design of the cavity preparation is what holds the amalgam restoration in place? | mechanical retention |
| What ingredient of dental amalgam alloy contributes greatly to its strength? | silver |
| What does finishing and polishing an amalgam restoration accomplish? | reduces the ability of plaque to adhere, will not have voids |
| As the restoration increases in size, what happens to internal stresses? | it decreases |
| Why is the used amalgam capsule reassembled immediately? | to minimize mercury vapors escaping into the air. |
| In a traditional or low copper amalgam restorations, what does tin react with? | mercury |
| Which of the modern alloys uses the least amount of mercury? | spherical |
| What will occur if an occlusal amalgam is undercarved or overcarved? | There is the potential for an open margin or a fracture of the restoration. |
Created by:
BrendaAlberts