Dental Assistant Practice Test

Dental Dental Materials Practice Questions

Dental Materials makes up 4 of every 50 questions on a Tigertest Dental practice test. Here are 10 of the 16 questions on it, each with the answer and the reason.

Updated 2026-11-10 by the Tigertest team. Weighted to the DANB GC, RHS (March 2025) and ICE (March 2025) outlines. Expanded functions vary by state.

1. 1. The assistant mixes alginate for a maxillary impression using very warm tap water. The likely result is that the material:

   • A.Becomes stronger and more accurate
   • B.Sets faster with less working time
   • C.Sets slower with more working time
   • D.Will not set until it cools

   Answer: B. Alginate is mixed with room temperature water because warmer water speeds the set and shortens working time. Cool water slows the set.

2. 2. An alginate impression was left uncovered on the counter for two hours before pouring. It is likely distorted from:

   • A.Polymerization shrinkage of the adhesive
   • B.Heat released during the setting reaction
   • C.Imbibition, absorbing water and swelling
   • D.Syneresis, losing water and shrinking

   Answer: D. Alginate left in air loses water by syneresis and shrinks, so it should be poured within an hour. Imbibition is the opposite problem, swelling from storage in water.

3. 3. An alginate impression has been rinsed and disinfected, but it cannot be poured for 20 minutes. The assistant should store it:

   • A.In a sealed bag with a damp towel
   • B.In the freezer compartment
   • C.Submerged in a cup of tap water
   • D.Uncovered on the counter to stay dry

   Answer: A. Wrapping in a damp paper towel in a sealed bag keeps humidity at 100% without soaking. Submerging it causes imbibition, and air exposure causes syneresis.

4. 4. During a crown impression with polyvinyl siloxane, the assistant mixes the putty while wearing latex gloves. The likely problem is:

   • A.Excess bubbles in the surface
   • B.A loss of fine detail from swelling
   • C.Incomplete or inhibited setting
   • D.A faster set than normal

   Answer: C. Sulfur compounds in latex inhibit the set of polyvinyl siloxane, so the putty is mixed with vinyl or nitrile gloves. It does not speed the set.

5. 5. An elastomeric impression material is very rigid when set and absorbs water, so it must not be stored wet. This describes:

   • A.Zinc oxide eugenol paste
   • B.Polyvinyl siloxane
   • C.Polyether
   • D.Polysulfide

   Answer: C. Polyether is stiff and hydrophilic, and it absorbs water and distorts if stored wet or humid. Polyvinyl siloxane is the most dimensionally stable elastomer.

6. 6. After a crown preparation, the dentist wants to record how the patient's teeth meet in centric occlusion. The assistant prepares:

   • A.Fast-setting PVS registration paste
   • B.Alginate in a full-arch stock tray
   • C.Light-body material in a custom tray
   • D.Zinc phosphate on a cool glass slab

   Answer: A. A fast-setting polyvinyl siloxane bite registration paste is injected between the teeth to record occlusion. Light-body material in a tray records tooth detail, not the bite.

7. 7. The lab case calls for a working die for a crown that needs the greatest strength and abrasion resistance. The assistant selects:

   • A.Type II model plaster
   • B.Type III dental stone
   • C.Type I impression plaster
   • D.Type IV die stone

   Answer: D. Type IV and V die stones are the strongest gypsum products and resist abrasion during wax-up. Type III stone suits working casts for dentures, and plaster is for study models.

8. 8. While pouring a stone model, the assistant uses a vibrator and adds small increments from one end of the impression. This is done to:

   • A.Raise the water-to-powder ratio
   • B.Prevent trapped air bubbles
   • C.Stop the impression absorbing water
   • D.Speed up the setting reaction

   Answer: B. Vibration and small increments let the stone flow into the detail and push out air, preventing voids. Vibration does not change the water-to-powder ratio or speed the set.

9. 9. The assistant is trimming orthodontic study models. For proper proportion, the base of each model should be about:

   • A.Two-thirds of the total height
   • B.One-third of the total height
   • C.One-tenth of the total height
   • D.One-half of the total height

   Answer: B. Study models are trimmed so the anatomic portion is about two-thirds and the art portion (base) about one-third of the height. A base of two-thirds would look bulky.

10. 10. When mixing zinc phosphate cement, the assistant uses a cool, dry glass slab and adds powder in small increments to:

    • A.Speed up the setting reaction
    • B.Make the cement release fluoride
    • C.Increase the final film thickness of the cement
    • D.Dissipate heat and extend working time

    Answer: D. The zinc phosphate reaction is exothermic, so a cool slab and incremental mixing over a wide area dissipate heat and lengthen working time. A warm slab would speed the set.