Suck back porosity is due to_________________?

Related Mcqs:

1. Suck back porosity in the casting can be eliminated by________________?

   A. Increasing the mould metal temperature difference
   B. Increasing the flow of molten metal
   C. Flaring the point of the sprue attachment
   D. All of the above

2. In processing methyl methacrylate, the resin may show porosity if the flask is placed too soon porosity most likely occur_____________?

   A. Throughout the denture
   B. Near the borders
   C. In the thickest part
   D. On the denture surface

3. The porosity formed due to simultaneous nucleation of solid grains and gas bubbles at the first moment that metal freezes at the mold walls is called__________?

   A. Pinhole porosity
   B. Gas inclusion porosity
   C. Micro porosity
   D. Subsurface porosity

4. Subsurface porosity is due to_____________?

   A. Thermal changes
   B. Thickness of the resin
   C. Lack of temperature
   D. Packing past the dough stage

5. Subsurface porosity is due to_____________?

   A. Thermal changes
   B. Thickness of the resin
   C. Lack of temperature
   D. Packing past the dough stage

6. Porosity of denture base is due to_______________?

   A. Packing at dough stage
   B. Curing at 160°F for 9 hrs
   C. Inadequate pressure
   D. All of the above

7. Sub surface porosity can be decreased by_______________?

   A. Decreasing the sprue length
   B. Decreasing the sprue thickness
   C. Increasing the melting temperature
   D. Increasing the mould temperature

8. Localised shrinkage porosity is seen when there________________?

   A. Thin sprue
   B. No reservoir
   C. Investment heated strongly
   D. Inadequate air discharge

9. Back pressure porosity can be avoided by________________?

   A. Using asbestos linear
   B. Placing the sprue at least one quarter inch away form the end of casting ring
   C. Preventing rapid heating the investment in burnout oven
   D. Using a short and wide sprue

10. Porosity in porcelain can be prevented by_______________?

    A. Thoroughness of condensation
    B. Rapidity of firing
    C. High firing temperature
    D. All of the above