Dental Lab Technician Prometric exam questions with answers

1. Question 1All-Ceramic Restorations and CAD/CAMmedium

   A lithium disilicate CAD/CAM block is milled while it is bluish and relatively soft. What must be done before cementation?

   1. ASintering at about 1500 C for zirconia
   2. BHydrofluoric acid etch, no firing
   3. CAir abrasion with 250 micrometre alumina
   4. DCrystallisation firing in a furnace
   Show answer and explanation▾

   Answer: D. Crystallisation firing in a furnace

   Lithium disilicate CAD blocks are milled in a partly crystallised metasilicate state and then fired to crystallise, which develops full strength and final shade. The high-temperature sintering cycle applies to zirconia.

2. Question 2All-Ceramic Restorations and CAD/CAMhard

   What mechanism gives yttria-stabilised zirconia its high fracture toughness?

   1. AGlass infiltration of surface porosity
   2. BLeucite crystals dispersed in a glass matrix
   3. CIon exchange strengthening of the surface
   4. DTetragonal-to-monoclinic phase transformation
   Show answer and explanation▾

   Answer: D. Tetragonal-to-monoclinic phase transformation

   At a crack tip, metastable tetragonal grains transform to the larger monoclinic phase; the volume increase compresses the crack and resists its growth. Leucite reinforcement applies to some feldspathic glass-ceramics, not zirconia.

3. Question 3Complete Denturesmedium

   Which occlusal scheme is generally used in conventional complete dentures to improve stability during lateral and protrusive movements?

   1. ACanine-guided occlusion
   2. BBilateral balanced occlusion
   3. CGroup function only on working side
   4. DMutually protected occlusion
   Show answer and explanation▾

   Answer: B. Bilateral balanced occlusion

   Bilateral balanced occlusion keeps contact on both sides during excursions, helping to stop the dentures tipping. Canine guidance suits natural dentitions but destabilises complete dentures.

4. Question 4Dental Anatomy, Occlusion and Articulatorsmedium

   What is the main purpose of a facebow record sent with casts to the laboratory?

   1. ATo record the patient's vertical dimension of occlusion
   2. BTo record the shade of the teeth
   3. CTo record lateral condylar guidance only
   4. DTo mount the upper cast relative to the hinge axis
   Show answer and explanation▾

   Answer: D. To mount the upper cast relative to the hinge axis

   A facebow transfers the position of the maxillary arch in relation to the terminal hinge axis, so the cast is mounted correctly on the articulator. Vertical dimension is recorded with occlusal records, not the facebow.

5. Question 5Orthodontic and Other Applianceseasy

   A dentist requests a custom sports mouthguard for a rugby player. Which material is most commonly vacuum-formed or pressure-formed for this?

   1. AEthylene vinyl acetate (EVA)
   2. BHeat-cured PMMA acrylic sheet
   3. CCast cobalt-chromium alloy
   4. DType IV dental stone
   Show answer and explanation▾

   Answer: A. Ethylene vinyl acetate (EVA)

   Custom mouthguards are thermoformed from ethylene vinyl acetate sheets, which absorb impact and are comfortable. PMMA is rigid and used for denture bases and hard splints.

6. Question 6Dental Materials Sciencemedium

   Which investment is required for casting a high-fusing alloy for a metal-ceramic crown?

   1. AGypsum-bonded investment
   2. BType II model plaster
   3. CPhosphate-bonded investment
   4. DSilicone putty
   Show answer and explanation▾

   Answer: C. Phosphate-bonded investment

   Phosphate-bonded investments withstand the high casting temperatures of metal-ceramic and base metal alloys. Gypsum-bonded investments break down above about 700 C and are used only for lower-fusing gold alloys.

7. Question 7Removable Partial Dentureshard

   A cast cobalt-chromium circumferential clasp is being designed. How deep should its retentive tip engage the undercut?

   1. A0.75 mm
   2. B1.0 mm
   3. C0.25 mm
   4. D1.5 mm
   Show answer and explanation▾

   Answer: C. 0.25 mm

   Cobalt-chromium is stiff, so its clasp tips should engage only about 0.25 mm of undercut. Deeper undercuts, around 0.5-0.75 mm, are used for more flexible gold or wrought wire clasps.

8. Question 8Removable Partial Dentureseasy

   Which instrument is used to determine the path of insertion and locate undercuts on a partial denture cast?

   1. AFacebow
   2. BArticulator
   3. CDental surveyor
   4. DBoley gauge
   Show answer and explanation▾

   Answer: C. Dental surveyor

   A dental surveyor, with its analysing rod and undercut gauges, finds the path of insertion, height of contour and undercut depth. A facebow records the maxillary arch position relative to the hinge axis.

9. Question 9Dental Materials Sciencemedium

   An addition silicone impression has unset, tacky areas where it touched the putty handled by a gloved technician. What is the most likely cause?

   1. AExcess catalyst in the mix
   2. BOver-long working time
   3. CMoisture from the tray adhesive
   4. DSulfur compounds from latex gloves
   Show answer and explanation▾

   Answer: D. Sulfur compounds from latex gloves

   Sulfur compounds from latex gloves poison the platinum catalyst of addition silicones and inhibit setting. Using vinyl or nitrile gloves, or washing hands first, avoids this.

10. Question 10Fixed Prosthodontics and Metal-Ceramicsmedium

    Where should die spacer be applied on a prepared die?

    1. AOver the finish line margin only, nowhere else
    2. BOver the preparation, stopping short of the margin
    3. COn the entire die surface, including the margin
    4. DOnly on the occlusal surface
    Show answer and explanation▾

    Answer: B. Over the preparation, stopping short of the margin

    Die spacer creates room for luting cement but must stop about 0.5-1 mm short of the finish line so the casting fits closely at the margin. Covering the margin would leave an open margin.

11. Question 11Laboratory Safety, Infection Control and Ethicsmedium

    An alginate impression arrives in the laboratory in a sealed bag. What is the correct first handling step?

    1. ARinse, then disinfect for the stated time
    2. BPour it at once, without any disinfection
    3. CSoak it in tap water overnight
    4. DAutoclave it at 134 C first
    Show answer and explanation▾

    Answer: A. Rinse, then disinfect for the stated time

    Impressions are treated as contaminated: they are rinsed to remove saliva and blood, then disinfected with a compatible agent for the stated contact time before pouring. Overnight soaking distorts alginate, and autoclaving destroys it.

12. Question 12Laboratory Safety, Infection Control and Ethicsmedium

    A laboratory grinds a base metal alloy that contains beryllium. What is the main health risk?

    1. ASkin burns from contact with the alloy
    2. BChronic lung disease from inhaled dust
    3. CHearing loss from grinding noise
    4. DEye damage from ultraviolet light
    Show answer and explanation▾

    Answer: B. Chronic lung disease from inhaled dust

    Inhaling beryllium dust or fumes can cause chronic beryllium disease, a granulomatous lung disease, so local exhaust ventilation is needed during grinding and melting. The alloy itself does not cause skin burns on contact.

13. Question 13Laboratory Safety, Infection Control and Ethicsmedium

    A dentist's prescription asks for a metal-ceramic crown, but the technician thinks zirconia would look better. What should the technician do?

    1. AMake zirconia and inform the dentist later
    2. BMake both and let the patient choose
    3. CFollow the prescription without comment
    4. DContact the dentist before changing the design
    Show answer and explanation▾

    Answer: D. Contact the dentist before changing the design

    The written prescription defines the device; any change in material or design needs the prescribing dentist's agreement first. Following it silently loses the chance to raise a valid concern.

14. Question 14Orthodontic and Other Appliancesmedium

    Which stainless steel wire diameter is typically used to make an Adams clasp on a permanent first molar?

    1. A0.3 mm
    2. B0.7 mm
    3. C1.2 mm
    4. D2.0 mm
    Show answer and explanation▾

    Answer: B. 0.7 mm

    An Adams clasp on permanent molars is usually made in 0.7 mm hard stainless steel wire; 0.6 mm is used for deciduous molars. Wire of 1.2 mm is too stiff to engage the undercut.

15. Question 15Removable Partial Denturesmedium

    A maxillary arch has bilateral free-end saddles and a separate missing lateral incisor. Under Applegate's rules, how is it classified?

    1. AClass IV, modification 1
    2. BClass I, modification 1
    3. CClass II, modification 2
    4. DClass III, modification 2
    Show answer and explanation▾

    Answer: B. Class I, modification 1

    The most posterior edentulous areas determine the class (Class I), and additional spaces are counted as modifications. Class IV can never have modification spaces, so the Class IV option is wrong.

Last reviewed September 2026. Questions are original and written to the published exam blueprint; they are not taken from any real paper.