1. which of the following is the proper amount of copper in amalgam according to the ADA specifications?
· 65 percent C. 6 percent
·25 percent D. 2 percent
C. According to ADA Specifications number 1 the proper amount of copper in a silver alloy is 6 percent.
2. which of the following is not found in amalgam alloy?
· Tin c. silver
·Zinc D. magnesium
D. Tin, zinc and silver are the primary constituents of an amalgam alloy. Magnesium is not involved.
3. the primary reason for triturating amalgam is:
· To bring the mercury in contact with the alloy particles
·To clean the surfaces of the particles by slight abrasion
·Both of the above D. neither of the above
A. By definition, trituration is a mixing process that combines the mercury with alloy particles
4. Touching the amalgam with the fingertips after trituration
· Exerts no effect on the amalgam
·May cause contamination and affect the physical properties
·Is indicated to mold the amalgam
·None of the above
B. Oils or moisture contaminants on the fingers and hands can potentially affect the physical properties of the amalgam. Hand manipulation should be avoided whenever placing this type of restoration.
5. In a cavity preparation
· The outline form is dictated, in part, by the carious involvement
·The restoration form may be compromised
·Retention is not important in an amalgam restoration
·None of the above
A. Because of extensive caries it is difficult to make the ideal cavity outlines. The gingival, proximal and occlusal form must be altered from the ideal to properly restore the tooth.
6. The retention form in an amalgam restoration
· Is always parallel to the horizontal axis
·Should be parallel to the roof of the pulp chamber
·Neither of the above
B. Ideally, the occlusal of a Class I cavity preparation should be parallel to the roof of the pulp chamber. If this is not observed the pulpal tissue can be exposed. A rule of thumb is to make the floor of the cavity preparation, or pulpal floor, parallel to the tips of the cusps.
7. The retention form in an amalgam restoration
· Is placed in the enamel if possible
·Is placed in the dentin
·May be omitted if the support of a cusp is endangered
D. none of the above
B. Retention is placed in the dentin, so as not to undermine the enamel, which can cause free of support and result in fracture.
8. Acrylic resin restorations
· Should be avoided when possible
·May be loosened by excessive stress
·Have a coefficient of expansion approximately seven times that of tooth structure
·All of the above E. none of the above
D. The coefficient of linear expansion or contraction for resin materials is approximately seven times that of tooth structure. Consequently, acrylic restorations should be avoided because this type of warpage can result in marginal percolation and recurrent caries. In addition these restoration should be avoided because they wear excessively and may be loosened under stress.
9. In mixing a silicate cement:
· The slab should be heated to about 100 degree F.
·The slab should be cooled to temperature just above the dew point
·The mix may be carried out on dry white paper
·None of the above
B. In mixing a silicate cement the slab should be cooled to a temperature just above the dew point. If it is cooled excessively, moisture will form on the slab and consequently alter the silicate mixture and setting time.
10. which of the following base materials are contraindicated under an acrylic resin material?
· Calcium hydroxide C. Zinc oxyphosphate cement
·Eugenol base D. no contraindications
B. Eugenol base materials are essential oils which will attack acrylic resin materials, preventing final setting; therefore they are contraindicated for use as a cementing media.
11. which of the following is done to minimize a gingival margin discrepancy between a tooth preparation and a cemented MOD casting?
A. a hard wax is used to form the pattern since it gives the most accurate reproduction
B. the pattern is formed directly on the preparation
C. composite resin is used as the sealing agent.
D. the die is relieved in the laboratory
E. a gingival bevel is placed on cavosurface margins.
E. A gingival marginal bevel is provided on the preparation to reduce the magnitude of the discrepancy between the casting and the preparation. A margin is enhanced by the bevel and reduces the cement liner that will be exposed to oral fluids.
12. Which of the listed instruments could be used for placing a proximal bevel on an inlay, onlay or shoulder preparation?
A. flame shaped diamond C. 700 fissure bur
B. Wedelstaedt chisel D. cleoid discoid
E. Gethro knife F. two of the above
A. small flame-shaped gingival diamonds are useful for forming the bevel. They are placed on the margin and revolved slowly to form the accurate bevel.
13. the contact time of gingival retraction cord and chemical used is:
A. 1 min D. 10 min
B. 2 min E. none of the above
C. 3 min
E. The contact time of gingival retraction cord varies with the type of chemical used. Some solutions act as astringents and are caustics if left in contact with the tissue for lengthy periods.
14. Reversible hydrocolloid impression should be poured:
A. immediately
B. 30 minutes after taking the impression
C. 60 minutes after taking the impression.
D. when convenient after placing in a humidor
E. none of the above.
A. A reversible hydrocolloid impression must be poured immediately upon removal of the tray from the mouth. The dimensional change that results if an impression is allowed to stand for 15 minutes is sufficient to produce an inaccurate model. This includes the time during which the impression is placed in 2 percent, potassium sulfate to harden the stone.
15. Castings are placed in a solution of hydrochloric or sulfuric acid and equal parts of water which is a process known as pickling. This process:
A. removes bubbles
B. removes oxides and improves the color of the casting
C. removes an incremental amount of gold which aids in seating the restoration.
D. all of the above
E. none of the above
D. Castings are placed in a solution of hydrochloric or sulfuric acid and equal parts of water. This process called “pickling” primarily removes the surface oxides from the casting. The color of the gold will change after the oxides are removed.
16. A carious process, often involving a large number of teeth, which is rapid and often results in pulpal exposures is termed:
A. primary C. Chronic
B. acute D. secondary
B. An acute carious process is a rapid process involving a large number of teeth. This is also termed a rampant caries process and usually results in exposure of the pulp.
17. A carious process, in which the decalcified dentin is dark brown in color and leathery in consistency, is termed.
A. primary C. chronic
B. acute D. secondary
C. Chronic carious lesions are usually long standing involvement in which the decalcified dentin is dark brown and leathery in consistency. The dentin is dark because it picks the stains up from the diet and bacteria.
18. Secondary caries
A. are lesions that are always dark brown in color and have a leathery consistency
B. is best described because of location rather than the extent of damage
C. is observed around the edges of restoration
D. is rampant
C. Secondary or recurrent caries is observed around the edges of restorations. The common cause of secondary involvement is the rough or overhanging margins and fractures on surfaces in posterior teeth.
19. Dentin contains about:
A. 70% mineral, 20% organic, 10% water
B. 20% mineral, 70% organic, 10% water
C. 10% mineral, 80% organic, 10% water
D. 50% mineral, 50% organic
A. Dentin contains 70 percent mineral matter and 10 percent water. The mineral matter is hydroxyapatite, such as that found in enamel, but the crystals in dentin are estimated to be only one-tenth the size of those in enamel. The organic matrix is composed of collagen.
20. different types of restorative materials
A. are placed in the same cavity outline extensions
B. Are used with different cavity outline extensions.
C. can be mixed in the same cavity preparation
D. should never be used on the same tooth.
B. Different types of restorative materials are used with different extensions. Direct gold and amalgam restorations are treated conservatively because of the limited marginal strength and esthetic problems. The cast inlay is more extended to promote finishing and better marginal cleansing. Tooth colored materials are placed in limited extended outlines to preserve tooth structure and because of the short clinical life associated with silicate and resins.
