resto

1. The function of a matrix is to:

a.)  Act as a retaining wall

b.) Assist in contouring and shaping the restoration

c.)  Prevent rubber dam from being incorporated into the restoration

d.) Prevent saliva or blood from seeping into the restoration

e.)  All of the above are correct

e.) Matrix selection and placement is an important step in the proper placement of two-surface amalgam restorations. A little time devoted to perfecting the preparation and the adaptation of the matrix can greatly improve the resulting restoration.

2. Wedges may be used to:

a.)  Protect the gingival during hand or rotary instrumentation

b.) Act as a quick separating agent

c.)  Stabilize band material placed between teeth to prevent abrading the proximal surface adjacent to the one being treated

d.) All of the above are correct

         

d.) Wedges have many potential but are primarily placed to separate teeth sufficiently to accommodate the width of the matrix band material, to insure restoration of proper contact, and to prevent overflow (overhang) of amalgam at the gingival margin

3. Failure to finish and polish an amalgam restoration:

a.)  Leaves a rough surface subject to corrosion

b.) Leaves a surface conducive to plaque accumulation

c.)  Encourages galvanic action

d.) Leaves a surface difficult to keep clean

e.)  All of the above are correct

e.) Good operative technique requires that amalgam restorations be finished and polished. This should not be done until at least 24 hours have elapsed since placement of the restoration.

4. Overheating an amalgam restoration when finishing and polishing will:

a.)   Bring mercury to the surface

b.) Cause eventual corrosion

c.)  Result in early fracturing at the margins

d.) Result in surface pitting

e.)  All of the above are correct

e.) Overheating (above 140^oF) will bring mercury to the surface which results in surface pitting, marginal fracture of amalgam, and eventual corrosion in addition, it is irritating to the pulpal tissues and if excessively over-heated may result in irreversible pulpal damage.

5.  The cohesive gold used only as a bulk filler is:

a.)  Mat gold

b.) Electrology

c.)  Spherical (powdered)

d.) Gold foil

a.) Electrology may be used for both core and finishing; spherical (powdered gold) may also serve in the dual capacity. Mat gold should not be used for finishing. It does not take a smooth , finish and becomes harsh when worked. Foil, of all the cohesive golds, is most suitable for finishing. It takes a high polish and maintains it but has little bulk and therefore is most often limited to small restorations or as a final veneer in the finishing of other cohesive golds.

6.  Bases compatible with cohesive gold restorations are:

a.)  Zinc oxide and eugenol preparations hardened with zinc acetate crystals

b.) Proprietary calcium hydroxide preparations

c.)  IRM (intermediate restorative materials)

d.) Zinc phosphate cement

d.) Zinc phosphate cement should be placed when basing is required following previous application of base or liner to preclude irritation of the pulp. It has a minimum compressive strength of 9960 psi(ADA specification no. 8); most of those manufactured exhibit strengths above 15,000 psi. although IRM has a relatively high compressive strength it may chip and contaminate the restoration and the others would be too soft to withstand compaction.

7.  Annealing by passing cohesive gold through a pure alcohol flame is the preferred method for:

a.)  Spherical (powdered) gold

b.) Mat gol

c.)  Electrology

d.) Gold foil

a.)  Each piece is speared with a nichrome (or stainless steel) wire and passed through the flame by drawing the wire then the gold through the flame. As the pellet enters the flame an indicator burns bright yellow. As this subsides and the pellet begins to flow a dull red. It is removed from the flame and carried to the cavity. Electrology may also be annealed in a similar manner but can be prepared by heating on an electric annealer.

8.  The gold alloys used for casting contain at least ______ percent of precious metals

a.)  55 %

b.) 65 %

c.)  75 %

d.) 85%

                             c.) According to ADA specification no. 5

9.  If a gold alloy has a fineness of 750, it has how many carats?

a.)  14

b.) 16

c.)  18

d.) 20

                   c.) A 24 carat gold is pure gold and the equivalent of 1000 fine

10.                        In a Class II, MO inlay preparation the gingival bevel should be placed at :

a.)  40 – 60 degrees

b.) 60 – 75 degrees

c.)  30 – 45 degrees

d.) 15 – 30 degrees

b.) There is some variation between the authorities but there is a consistency of opinion that the gingival bevel should be in the range of 30 to 45 degrees. Anything greater is too difficult to finish and burnish. Figure 14 – 12 shows the gingival and occlusal bevel.

11.                        When  subjected to displacement forces, a cast gold restoration is retained in position in the tooth primarily by:

a.)  Retention and resistance form of the preparation

b.) The cement or luting media

c.)  Sharp line angles or point angles

d.) All of the above are correct

a.)  Most cement for luting castings are not adhesive to the tooth or casting Polycarboxylate cements are adhesive to enamel and dentin but not to gold.

12.                       Direct wax patterns should be constructed with:

a.)  Type A inlay casting wax

b.) Type B inlay casting wax

c.)  Type C inlay casting wax

b.) Type B is a wax that may be used for direct wax patterns. Type C should be limited to the indirect technique as specified by the ADA Council on Materials and Devices

13.                       The proper zone of a gas-air blowpipe flame used for melting casting gold alloys is:

a.)  The oxidizing zone

b.) The reducing zone

c.)  The zone closest to the nozzle

d.) Combination of the oxidizing and reducing zone

b.) Oxidation of gold during melting should be avoided. Electric casting machines that provide for accurate temperature control without the use of a flame are also available

14.                        Gold is cast into a hot mold to:

a.)  Hasten solidification of the gold

b.) Maintain thermal expansion of the investment

c.)  Eliminate oxides on the gold casting

d.) Maintain molecular tension

b.) When using the thermal expansion technique to compensate for shrink age of the gold during casting this is particularly important.

15.                       The advantages exhibited by fused porcelain in lays are:

a.)  Good marginal intergrity

b.) Insoluble in the oral fluids

c.)  High degree of edge strength

d.) Color harmony with surrounding tooth structure

b.)  Fused porcelain inlays exhibit poor marginal integrity because the margins cannot be “drawn”. They do have a high degree of color harmony but the cementing media is subject to dissolution and staining after a period of time.

16.                        Which of the following elastic impression materials may be put aside for up to one hour before pouring a model?

a.)   Agar hydrocolloids

b.) Alginate

c.)  Mercaptan rubber (polysulfides)

d.) Silicone rubber

a.)     and c.) Because of the stability of the impression material. Agar may be set aside for up to one hour only if kept at 100% relative humidity and the mercaptan rubber up o one hour on the bench. The other materials must be poured immediately.

17.                        Which of the following materials exhibit adhesive qualities?

a.)  Zinc phosphate cement

b.) Polycarboxylate cement

c.)  ASPA (aluminosilicate polyacrylate cement)

d.) BIS-GMA resins (composites)

b.) and c) tehse are adhesive to tooth structure

18.                        Setting time of zinc phosphate cement may be increased by:

a.)  Using a slab cooled to just above the dew point

b.) Using a lower ratio of liquid to powder

c.)  Using a longer mixing time

d.) Adding the increments of powder slowly

e.)  a), b), c)

f.)   a), c), d)

g.) b), c), d)

h.) all of the above are correct

f.) The more liquid employed in ratio to the powder, the slower is the setting rate.

19.                        Which of the following are disadvantages of a silicate restoration?

a.)  High acidity initially

b.) High alkalinity on setting

c.)  It does not take a smooth finish

d.) It will desiccate if not kept moist

e.)  a), c), d)

f.)   a), b), d)

g.) all of the above are correct

e.)  Following the final setting of a silicate restoration the pH rises but a remains in the range of 5 to 5.5

20.                       Mixing of silicate powder and liquid should :

a.)  Be done on a glass slab at room temperature

b.) Be done with an agate spatula

c.)  Be done over a large area of the mixing slab

d.) Be done slowly

b.) A metal spatula may be scratched by the undissolved particles. The mix should be completed within one minute on a cool slab ( not below the dew point) over a small area as quickly as possible and while wetting each powder particles