Certified Dental Technician (CDT)
Certification Exam –Questions with
Verified Answers and Rationales
1. A patient presents with a severely worn dentition due to bruxism. Which
type of dental restoration material would provide the highest resistance to
wear and fracture when fabricated by the technician?
a) High-noble metal alloy
b) Direct composite resin
c) Feldspathic porcelain
d) Acrylic resin
Rationale: High-noble metal alloys (gold-platinum-palladium) exhibit excellent
wear resistance, ductility, and fracture toughness, making them ideal for
high-occlusal-load situations like bruxism.
2. During the fabrication of a full contour zirconia crown, which processing
step is most critical to prevent transformation toughening failure (aging) of
the material?
a) Steam cleaning after sintering
b) Low-speed diamond polishing without water cooling
c) Rapid cooling from 1550°C to room temperature in 5 minutes
d) Using a non-vacuum furnace for glazing
Rationale: Rapid cooling can induce tetragonal-to-monoclinic phase
transformation and microcracking. Controlled slow cooling or proper annealing
preserves the tetragonal phase and avoids aging-related fracture.
3. A technician observes that a metal-ceramic restoration exhibits interfacial
grey discoloration at the metal-porcelain junction after firing. The most
likely cause is:
a) Insufficient degassing of the metal framework
b) Excessive opaque porcelain thickness
c) Use of a low-fusing glaze
d) Over-etching of the metal surface with alumina
,Rationale: Incomplete degassing leaves surface contaminants and oxides that react
with porcelain during firing, producing a grey line. Proper degassing removes
impurities and forms a controlled oxide layer.
4. When fabricating a removable partial denture (RPD) with a rotational path
of insertion, the most challenging clasp design to execute accurately in the
laboratory is:
a) RPI (rest, proximal plate, I-bar) clasp
b) Circumferential (Akers) clasp
c) Embrasure clasp
d) Half-and-half clasp
Rationale: The RPI clasp requires precise spatial relationships among the rest,
proximal plate, and I-bar undercut; rotational path designs magnify this
complexity, demanding exact surveyor planning and waxing.
5. A technician is asked to repair a fractured porcelain margin on a
metal-ceramic crown that has already been cemented. Which intraoral or
extraoral repair system provides the highest bond strength to the existing
porcelain?
a) Silane coupling agent + microetch (aluminum oxide) + low-fusing
composite
b) Hydrofluoric acid etching + unfilled resin
c) Diamond bur roughening + flowable composite
d) Air abrasion with 50 μm glass beads + conventional PMMA
Rationale: Microetching creates mechanical retention, silane chemically bonds to
the porcelain silica network, and low-fusing composite matches thermal expansion,
yielding the strongest repair.
6. The primary function of a die spacer applied to a working die for a cast
crown is to:
a) Provide uniform space for luting cement
b) Increase retention of the casting
c) Compensate for metal shrinkage
d) Facilitate wax pattern removal
Rationale: Die spacer creates a defined film thickness (20-40 μm) for cement,
preventing hydraulic pressure build-up and ensuring complete seating of the
casting.
, 7. Which of the following polymers is most resistant to creep deformation
under repeated occlusal loads in a flexible denture base?
a) High-impact heat-cured PMMA
b) Self-cured PMMA
c) Thermoplastic polyamide (nylon)
d) Light-cured urethane dimethacrylate
Rationale: High-impact PMMA has rubber-modified particles that dissipate stress
and reduce creep, outperforming nylon and other flexible materials in long-term
dimensional stability.
8. A technician is casting a large cobalt-chromium RPD framework. The
casting shows incomplete fill at the thinnest part of the lingual plate. The
most effective modification to the sprue design to solve this problem is:
a) Increase the number of auxiliary sprues and widen the reservoir bar
b) Increase the sprue length by 10 mm
c) Reduce the sprue diameter by 2 mm
d) Place the sprue at a 30° angle instead of 45°
Rationale: Thin sections require adequate metal flow. Auxiliary sprues and a
larger reservoir ensure that molten metal reaches all areas before solidification,
preventing misruns.
9. In soldering a precious metal alloy bridge segment, the technician notices
the solder does not flow and forms a ball. The most probable cause is:
a) Insufficient flux or oxidized metal surfaces
b) Solder melting temperature too low
c) Overheating the solder
d) Too large a gap between segments
Rationale: Flux removes oxides; without adequate flux or with oxidized surfaces,
solder will not wet the metal, balling up instead.
10.When processing a maxillary complete denture using a long-cured cycle (9
hours at 74°C then 1 hour at 100°C), which property of PMMA is most
enhanced compared to a short cycle (2 hours at 74°C)?
a) Degree of monomer conversion (reduced residual monomer)
b) Surface hardness (short-term only)
c) Shade stability (decreased)
d) Flexural modulus (unchanged)
, Rationale: Extended curing at controlled temperature increases polymerization
conversion, lowering residual monomer and improving biocompatibility and
mechanical properties.
11.A porcelain-to-metal crown exhibits a sharp line of chipped porcelain
exactly at the metal-porcelain junction after the first glaze firing. The most
likely design error is:
a) Metal collar design with insufficient porcelain support (feather-edge
metal)
b) Opaque porcelain fired too hot
c) Dentin porcelain applied too thick
d) Insufficient wash firing
Rationale: Feather-edge metal margins lack bulk to support porcelain, creating a
stress concentration; a butt-joint or beveled metal margin is required to prevent
chipping.
12.What is the purpose of a refractory model in porcelain work?
a) To withstand high firing temperatures during porcelain application
b) To improve impression accuracy
c) To store wax patterns
d) To support the articulator
Rationale: Refractory models resist heat during porcelain firing and maintain
dimensional stability.
13.Which material is most commonly used for denture base fabrication?
a) Composite resin
b) Polyether
c) Polymethyl methacrylate (PMMA)
d) Alginate
Rationale: PMMA is widely used due to its strength, aesthetics, and adaptability
for denture bases.
14.What happens if the water-to-powder ratio of gypsum is increased?
a) Strength increases
b) Strength decreases
c) Setting time shortens
d) Expansion increases
Certification Exam –Questions with
Verified Answers and Rationales
1. A patient presents with a severely worn dentition due to bruxism. Which
type of dental restoration material would provide the highest resistance to
wear and fracture when fabricated by the technician?
a) High-noble metal alloy
b) Direct composite resin
c) Feldspathic porcelain
d) Acrylic resin
Rationale: High-noble metal alloys (gold-platinum-palladium) exhibit excellent
wear resistance, ductility, and fracture toughness, making them ideal for
high-occlusal-load situations like bruxism.
2. During the fabrication of a full contour zirconia crown, which processing
step is most critical to prevent transformation toughening failure (aging) of
the material?
a) Steam cleaning after sintering
b) Low-speed diamond polishing without water cooling
c) Rapid cooling from 1550°C to room temperature in 5 minutes
d) Using a non-vacuum furnace for glazing
Rationale: Rapid cooling can induce tetragonal-to-monoclinic phase
transformation and microcracking. Controlled slow cooling or proper annealing
preserves the tetragonal phase and avoids aging-related fracture.
3. A technician observes that a metal-ceramic restoration exhibits interfacial
grey discoloration at the metal-porcelain junction after firing. The most
likely cause is:
a) Insufficient degassing of the metal framework
b) Excessive opaque porcelain thickness
c) Use of a low-fusing glaze
d) Over-etching of the metal surface with alumina
,Rationale: Incomplete degassing leaves surface contaminants and oxides that react
with porcelain during firing, producing a grey line. Proper degassing removes
impurities and forms a controlled oxide layer.
4. When fabricating a removable partial denture (RPD) with a rotational path
of insertion, the most challenging clasp design to execute accurately in the
laboratory is:
a) RPI (rest, proximal plate, I-bar) clasp
b) Circumferential (Akers) clasp
c) Embrasure clasp
d) Half-and-half clasp
Rationale: The RPI clasp requires precise spatial relationships among the rest,
proximal plate, and I-bar undercut; rotational path designs magnify this
complexity, demanding exact surveyor planning and waxing.
5. A technician is asked to repair a fractured porcelain margin on a
metal-ceramic crown that has already been cemented. Which intraoral or
extraoral repair system provides the highest bond strength to the existing
porcelain?
a) Silane coupling agent + microetch (aluminum oxide) + low-fusing
composite
b) Hydrofluoric acid etching + unfilled resin
c) Diamond bur roughening + flowable composite
d) Air abrasion with 50 μm glass beads + conventional PMMA
Rationale: Microetching creates mechanical retention, silane chemically bonds to
the porcelain silica network, and low-fusing composite matches thermal expansion,
yielding the strongest repair.
6. The primary function of a die spacer applied to a working die for a cast
crown is to:
a) Provide uniform space for luting cement
b) Increase retention of the casting
c) Compensate for metal shrinkage
d) Facilitate wax pattern removal
Rationale: Die spacer creates a defined film thickness (20-40 μm) for cement,
preventing hydraulic pressure build-up and ensuring complete seating of the
casting.
, 7. Which of the following polymers is most resistant to creep deformation
under repeated occlusal loads in a flexible denture base?
a) High-impact heat-cured PMMA
b) Self-cured PMMA
c) Thermoplastic polyamide (nylon)
d) Light-cured urethane dimethacrylate
Rationale: High-impact PMMA has rubber-modified particles that dissipate stress
and reduce creep, outperforming nylon and other flexible materials in long-term
dimensional stability.
8. A technician is casting a large cobalt-chromium RPD framework. The
casting shows incomplete fill at the thinnest part of the lingual plate. The
most effective modification to the sprue design to solve this problem is:
a) Increase the number of auxiliary sprues and widen the reservoir bar
b) Increase the sprue length by 10 mm
c) Reduce the sprue diameter by 2 mm
d) Place the sprue at a 30° angle instead of 45°
Rationale: Thin sections require adequate metal flow. Auxiliary sprues and a
larger reservoir ensure that molten metal reaches all areas before solidification,
preventing misruns.
9. In soldering a precious metal alloy bridge segment, the technician notices
the solder does not flow and forms a ball. The most probable cause is:
a) Insufficient flux or oxidized metal surfaces
b) Solder melting temperature too low
c) Overheating the solder
d) Too large a gap between segments
Rationale: Flux removes oxides; without adequate flux or with oxidized surfaces,
solder will not wet the metal, balling up instead.
10.When processing a maxillary complete denture using a long-cured cycle (9
hours at 74°C then 1 hour at 100°C), which property of PMMA is most
enhanced compared to a short cycle (2 hours at 74°C)?
a) Degree of monomer conversion (reduced residual monomer)
b) Surface hardness (short-term only)
c) Shade stability (decreased)
d) Flexural modulus (unchanged)
, Rationale: Extended curing at controlled temperature increases polymerization
conversion, lowering residual monomer and improving biocompatibility and
mechanical properties.
11.A porcelain-to-metal crown exhibits a sharp line of chipped porcelain
exactly at the metal-porcelain junction after the first glaze firing. The most
likely design error is:
a) Metal collar design with insufficient porcelain support (feather-edge
metal)
b) Opaque porcelain fired too hot
c) Dentin porcelain applied too thick
d) Insufficient wash firing
Rationale: Feather-edge metal margins lack bulk to support porcelain, creating a
stress concentration; a butt-joint or beveled metal margin is required to prevent
chipping.
12.What is the purpose of a refractory model in porcelain work?
a) To withstand high firing temperatures during porcelain application
b) To improve impression accuracy
c) To store wax patterns
d) To support the articulator
Rationale: Refractory models resist heat during porcelain firing and maintain
dimensional stability.
13.Which material is most commonly used for denture base fabrication?
a) Composite resin
b) Polyether
c) Polymethyl methacrylate (PMMA)
d) Alginate
Rationale: PMMA is widely used due to its strength, aesthetics, and adaptability
for denture bases.
14.What happens if the water-to-powder ratio of gypsum is increased?
a) Strength increases
b) Strength decreases
c) Setting time shortens
d) Expansion increases
