Marginal leakage and microhardness evaluation of low-shrinkage resin-based restorative materials

Self Instruction Exercise No. 322
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Exercise No. 322
Subject Code: 017
Dental Materials

The 15 questions for this exercise are based on the article, Marginal leakage and microhardness evaluation of low-shrinkage resin-based restorative materials, on pages 46-50. This exercise was developed by Steven E. Holbrook, DMD, MAGD, in association with the General Dentistry Self-Instruction committee.

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

  • recognize the components of low-shrinkage resin-based restorative materials;
  • recognize the factors that contribute to their microhardness;
  • identify the advantages of reducing polymerization shrinkage in them; and
  • understand how they compare to conventional materials.

Answers for this exercise must be received by December 31, 2013.

  1. Which restorative material used in this study incorporates a modified monomer matrix in an attempt to reduce polymerization shrinkage?

    A. Compomers
    B. Ormocers
    C. Hybrids
    D. Siloranes

  2. Which of the following is an inherent disadvantage of a composite restoration?

    A. Inadequate esthetics
    B. Inadequate wear resistance
    C. Inadequate biocompatibility
    D. Inadequate marginal seal

  3. The surface hardness was measured utilizing

    A. Knoop hardness values.
    B. plastic deformation variables.
    C. Vickers hardness numbers.
    D. Kruskal-Wallis testing.

  4. A restorative material’s ability to undergo plastic flow during the early phases of polymerization causes a/an _______________ in polymerization contraction stress and _______________ microleakage.

    A. reduction; less
    B. increase; more
    C. increase; less
    D. reduction; more

  5. Polymerization shrinkage stress is dependent upon all of the following except one. Which is the exception?

    A. Elastic modulus
    B. Curing speed
    C. Volumetric shrinkage
    D. Bonding agent

  6. When compared to conventional resin composites, ormocers exhibit all of the following properties except one. Which is the exception?

    A. Lower shrinkage
    B. Less cytotoxicity
    C. Less rigid resin matrix
    D. Lower water solubility

  7. Surface hardness is relevant to all of the following with regard to a restorative material except its ability to

    A. be polished.
    B. withstand scratching.
    C. withstand occlusal stress.
    D. resist polymerization shrinkage.

  8. Spectrum TPH and what other restorative material exhibited the greatest amount of microleakage at the gingival margins?

    A. Microhybrid
    B. Nanohybrid
    C. Ormocer
    D. Silorane

  9. Which restorative material contains methacrylate-modified silicon dioxide containing nanofiller and a matrix of highly dispersed methacrylate-modified polysiloxane particles?

    A. Hybrid
    B. Nanohybrid
    C. Microhybrid
    D. Ormocer

  10. Which of the following materials exhibited the highest hardness ratio?

    A. Microhybrid
    B. Ormocer
    C. Silorane
    D. Hybrid

  11. Silorane-based composite material provided a marginal seal comparable to that of microhybrid or nanohybrid resin composites. Silorane-based composite material exhibited a microhardness significantly higher than that of microhybrid or nanohybrid resin composites.

    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.

  12. Which material exhibited the lowest hardness ratio?

    A. Microhybrid
    B. Ormocer
    C. Silorane
    D. Hybrid

  13. The contraction stress associated with polymerization shrinkage can lead to cracks in healthy tooth structure. No statistically significant difference in the hardness ratio was found among the restorative materials.

    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.

  14. The resin-based restorative materials evaluated were used in combination with _______________ adhesive system.

    A. a self-etching primer and
    B. total etch and a two-step
    C. a one-bottle
    D. manufacturer’s recommended

  15. There is a positive correlation between surface hardness of a resin composite restoration and the

    A. inorganic filler content.
    B. modulus of elasticity.
    C. contraction stress.
    D. plastic flow.


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
 
Did this exercise achieve its objectives? Yes No
Did this article present new information? Yes No
How much time did it take you to complete this exercise? mins


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