Chapter 10, 13, 18 Flashcards
The alloy powder portion of an amalgam capsule can contain which of the following?
a. Aluminum, tin, copper, and zinc
b. Silver, tin, copper, and zinc
c. Silver, platinum, tin, and zinc
d. Mercury, silver, copper, and tin
b. Silver, tin, copper, and zinc
Rationale:
The alloy powder portion of amalgam usually consists of silver, tin, and copper, with zinc, palladium, or indium being added in small quantities for specific qualities. Aluminum and platinum are not used in dental amalgam. Mercury is a liquid metal and therefore not contained in the alloy powder.
The type of amalgam that contains both round and lathe-cut particles is:
a. a hybrid.
b. an admix.
c. a lathe cut.
d. spherical.
b. an admix.
Rationale:
Admix amalgam contains a combination of both spherical and lathe-cut particles. Spherical amalgam contains spherical amalgam particles only, whereas lathe-cut amalgam contains only lathe-cut shavings. Hybrid is a type of composite.
All of the following are properties of high-copper amalgams except:
a. a low rate of corrosion.
b. creation of tin-copper compounds.
c. γ-2.
d. γ-1.
c. γ-2.
Rationale:
High-copper amalgams do not have a γ-2 phase, because copper reacts with the tin. This makes them superior in strength and gives them clinical longevity, a reduced rate of corrosion, and marginal integrity. Low corrosion, tin-copper compounds, and γ-1 phase are all properties of high-copper amalgams that make them superior to low-copper amalgams.
Mercury from ingested amalgam particles is not absorbed well and is usually excreted.
a. True
b. False
a. True
Your next patient is scheduled for a distal occlusal (DO) amalgam due to deep distal decay on #30. Which matrix band would be the best choice?
a. Universal matrix band
b. Sectional matrix
c. MOD band
d. None of the above
c. MOD band
Rationale:
An MOD band has extensions to cover deep mesial and distal restoration preps. A universal band would likely be too short to cover the whole tooth and the deep preparation. Sectional matrix bands are used for composite resin restorations.
If you have a mercury spill you should use a vacuum to quickly contain it.
a. True
b. False
b. False
Amalgam can be disposed in bags marked biohazard.
a. True
b. False
b. False
The trap attached to the high-volume evacuation (HVE) suction is a way to reduce mercury exposure to those in the dental office.
a. True
b. False
b. False
What is the safe/acceptable amount of mercury exposure for the dental professional?
a. 05 mg/m3 per week
b. 2 g per day
c. 50 mg per day
d. 5.0 mg/m3 per week
a. 05 mg/m3 per week
Rationale:
The Occupational Safety and Health Administration has set the acceptable level of mercury exposure for those workers at .05 mg/m3 per week, in a 40-hour work week. 2 g per day is the average amount of mercury released from amalgam and is in relation to the patient’s exposure. 50 mg per day is not the recommended exposure amount. 5.0 mg/m3 per week is many times above the recommended amount.
Amalgam fractures can be repaired. Flowable composite resin can be used to fill in a gap at the margin of an amalgam to repair and extend its life.
a. Both statements are true.
b. Both statements are false.
c. The first statement is true; the second statement is false.
d. The first statement is false; the second statement is true.
a. Both statements are true
Which of the following amalgam types tends not to displace the matrix band in class II restorations, requiring a larger wedge to separate the teeth more for good proximal contact?
a. Admix
b. Spherical
c. Lathe-cut
d. All of the above
b. Spherical
Rationale:
Spherical amalgams do not have much resistance to condensation and therefore tend not to displace the matrix band in class II restorations, requiring a larger wedge to separate the teeth more for good proximal contact. Admix amalgams do not have this issue.
When opening the sterilizer, a person should stand at least an arm’s length away to avoid inhaling any mercury vapors that may be released from instruments that were used in amalgam procedures.
a. True
b. False
a. True
The final setting time for amalgam is:
a. 1 hour.
b. 6 hours.
c. 8 hours.
d. 24 hours.
d. 24 hours.
Rationale:
While some amalgams can reach 50% of their final strength within an hour after placement, most amalgams take 24 hours to reach maximum strength and final set. Incorrect trituration and mixing times can alter setting times.
Amalgam should be polished immediately following placement to ensure a smooth surface that will not retain biofilm. Final polishing of composite should be done with an aluminum oxide polishing paste.
a. Both statements are true.
b. Both statements are false
c. The first statement is true; the second statement is false.
d. The first statement is false; the second statement is true.
d. The first statement is false; the second statement is true.
Rationale:
Amalgam must set for 24 hours before it reaches its final set and should not be polished before then. The final polishing step for composites should be done with a submicron aluminum oxide polishing paste.
Finishing and polishing can cause aerosol hazards.
a. True
b. False
a. True
Which of the following abrasives is used to prepare restorations for final cementation?
a. Aluminum oxide
b. Silicon carbide
c. Diamond
d. Tin oxide
a. Aluminum oxide
Rationale:
Aluminum oxide has a Moh’s rating of 9 and is a synthetic abrasive used to sandblast restorations in preparation for final cementation. Silicon carbide is used on disks as a beginning step of polishing restorations. Diamonds are used to prep teeth for crown and bridge procedures, as well as to finish and polish composite restorations in finer degrees. Tin oxide is very fine and is used as a polishing agent for enamel and restorations.
Abrasives are all naturally occurring substances for biocompatibility.
a. True
b. False
b. False
A toothbrush and mild cleansing agent are sufficient to remove most plaque and stains from dentures.
a. True
b. False
a. True
Prophy paste is a universal abrasive for cleansing that can be used on all restorations and tooth surfaces.
a. True
b. False
b. False
All of the following affect the rate of abrasion except:
a. irregularity.
b. pressure.
c. expiration date.
d. speed.
c. expiration date.
Rationale:
The shelf/expiration date does not affect the rate of abrasion. The size, irregularity, and hardness of particles, as well as the number of particles, the speed, and the pressure at which they are applied, all affect the rate of abrasion.
- An occlusal composite restoration has been placed and there is composite material beyond the cavosurface margin over to the mesial marginal ridge. The process of removing this excess composite material is called _____________.
a. overhang
b. margination
c. flash
d. none of the above
b. margination
Rationale:
The process of removing restoration prematurities is called margination. Overhang is excessive material at the cervical cavosurface margin, usually found interproximally. If an overhang is not too severe, it can be corrected with margination. Flash is feather-like, excess material on occlusal and proximal surfaces.
You are polishing a substrate material with a Moh’s scale of 6. Ideally, in what range on the scale should the material you use to polish it be?
a. It doesn’t matter; use whatever you prefer.
b. 1-3
c. 3-6
d. 7-9
d. 7-9
Rationale:
These abrasives are lower in hardness than the substrate being abraded and therefore must be 1-2 Moh’s units harder. If the surface or substrate being abraded is harder than the abrasive, there will be little to no effect; therefore the clinician must choose an abrasive harder than the substrate. An abrasive of equal hardness will merely result in cleaning the surface.
Which of the following abrasives is not used intraorally?
a. Pumice
b. Tin oxide
c. Rouge
d. Sodium bicarbonate
c. Rouge
Rationale:
Rouge (iron oxide) is used on a rag wheel to polish precious and semiprecious metal alloys and is not used intraorally. Pumice is used to polish tooth structure and amalgam intraorally. Tin oxide is used to polish enamel and other restorations. Sodium bicarbonate is used intraorally for air polishing and is also found in toothpastes.
Which of the following is not a consideration when finishing and polishing?
a. Speed
b. Grit
c. Substrate
d. Patient preference
d. Patient preference
Rationale:
Patient preference is not a consideration when finishing and polishing. It is at the discretion of the operator to analyze the substrate material and select the appropriate abrasives. Speed, grit, and the substrate that is being finished and polished are all considerations that must be analyzed when choosing an abrasive and finishing/polishing.