Marginal gap, cement thickness, and microleakage of 2 zirconia crown systems luted with glass ionomer and MDP-based cements

Self-Instruction Exercise No. 348
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Exercise No. 348
Subject Code: 017
Dental Materials

The 15 questions for this exercise are based on the article, "Marginal gap, cement thickness, and microleakage of 2 zirconia crown systems luted with glass ionomer and MDP-based cements", on pages 67-70. This exercise was developed by Anthony S. Carroccia, DDS, MAGD, ABGD, in association with the General Dentistry Self-Instruction committee.

Reading the article and successfully completing this exercise will enable you to:

  • identify the effects of either luting agent on zirconia restorations;
  • recognize that efficiency is not reduced by using either cement; and
  • understand the advantages of microleakage studies.

Answers for this exercise must be received by February 28, 2015.
  1. What is the most significant advantage of using CAD/CAM technology for zirconia crowns?

    A. eliminates phase transformation
    B. fully sintered ceramic
    C. partially sintered blocks
    D. homogeneous structures

  2. All of the following methods have been used successfully to reveal leakage except one. Which is the exception?

    A. cement thickness
    B. bacterial tests
    C. dyes
    D. radioactive isotopes

  3. The intent of the study was to evaluate all of the following except one. Which is the exception?

    A. internal gap
    B. marginal gap
    C. cement thickness
    D. microleakage

  4. Which type of finish line was achieved?

    A. shoulder bevel
    B. half chamfer
    C. circumferential chamfer
    D. knife edge

  5. The specimens were in the fuchsine dye for

    A. 5000 thermocycles.
    B. 15 to 30 seconds.
    C. 10 minutes.
    D. 24 hours.

  6. All of the sectional measurements were used except one. Which is the exception?

    A. buccal
    B. occlusal
    C. mesial
    D. distal

  7. Which tested parameter showed significant differences between the zirconia systems?

    A. microleakage
    B. cement thickness
    C. marginal gap
    D. internal gap

  8. Axial wall preparations were said to have

    A. 4 mm height.
    B. 6 degrees of occlusal convergence.
    C. 6 degrees of occlusal divergence.
    D. 6 mm height.

  9. Which marginal gap showed an increased rate of solubility?

    A. 150 µm
    B. 120 µm
    C. 75 µm
    D. 25 µm

  10. Leakage that extended along the full axial wall to the occlusal surface was demonstrated by

    A. bacteria and their byproducts.
    B. radioactive isotope isomers.
    C. fuchsine dye diffusion.
    D. variances in cement thicknesses.

  11. The marginal gap values were significantly higher for which system?

    A. Cercon
    B. DC-Zirkon
    C. Vivaglass CEM
    D. Panavia F 2.0

  12. Which zirconia phase transformation is associated with a volume expansion of 3%-4%?

    A. monoclinic phase
    B. tetragonal phase
    C. tetragonal phase to monoclinic phase
    D. monoclinic phase to tetragonal phase

  13. The perpendicular measurement from the internal surface of the restoration to the margin is known as

    A. marginal fit.
    B. marginal gap.
    C. internal fit.
    D. internal gap.

  14. The mean cement thickness values were significantly different. Zirconia framework crowns were filled with light body polyether prior to insertion.

    A. Both statements are true.
    B. The first statement is true; the second is false.
    C. The first statement is false; the second is true.
    D. Both statements are false.

  15. Which leakage score showed leakage toward just one third of the axial wall?

    A. Score 1
    B. Score 2
    C. Score 3
    D. Score 4

Evaluation
Please respond to the statements below, using the following scale:
1 Poor; 2 Below average; 3 Average; 4 Above average; 5 Excellent
Practicality of the content 1 2 3 4 5
Benefit to your clinical practice 1 2 3 4 5
Quality of illustrations 1 2 3 4 5
Clarity of objectives 1 2 3 4 5
Clarity of exercise questions 1 2 3 4 5
Relevance of exercise questions 1 2 3 4 5
 
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