CDT Prosthodontic & Orthodontic Appliance Fabrication 2 — Questions and Answers
Question 1: Which alloy system is most commonly used for fabricating removable partial denture frameworks due to its strength and biocompatibility?
- Type IV gold alloy
- Cobalt-chromium alloy (Correct answer)
- Nickel-titanium alloy
- Tin-silver alloy
Correct answer: Cobalt-chromium alloy
Cobalt-chromium alloys are the industry standard for RPD frameworks because they offer high strength, rigidity, and excellent biocompatibility at lower cost than gold alloys.
Question 2: When investing a wax pattern for a full-cast crown, which type of investment is most appropriate for high-gold alloys?
- Phosphate-bonded investment
- Gypsum-bonded investment (Correct answer)
- Ethyl silicate investment
- Calcium sulfate investment
Correct answer: Gypsum-bonded investment
Gypsum-bonded investments are used with high-gold alloys because their expansion characteristics match gold's thermal behavior at lower casting temperatures.
Question 3: In orthodontic appliance fabrication, what is the primary purpose of incorporating an expansion screw into an acrylic palatal expander?
- To retain the appliance on posterior teeth
- To apply gradual transverse force to separate the mid-palatal suture (Correct answer)
- To provide anterior torque control
- To reduce the vertical dimension of the appliance
Correct answer: To apply gradual transverse force to separate the mid-palatal suture
The expansion screw incrementally widens the appliance, transmitting lateral forces to the alveolar ridges and mid-palatal suture to create skeletal expansion.
Question 4: A technician is fabricating a metal-ceramic crown. At what stage should the metal coping be evaluated for proper ceramic support and spacing?
- After glazing the ceramic
- After the bisque bake
- After degassing and prior to opaquing (Correct answer)
- After cementation by the dentist
Correct answer: After degassing and prior to opaquing
The metal coping is evaluated for contour, fit, and ceramic support space after degassing but before opaquing to allow any metal adjustments without contaminating the porcelain layers.
Question 5: Which type of clasp arm provides the greatest flexibility and is most appropriate for engaging deep undercuts on abutment teeth in an RPD?
- Cast circumferential clasp arm
- Wrought-wire clasp arm (Correct answer)
- Combination clasp ring terminal
- Embrasure hook clasp
Correct answer: Wrought-wire clasp arm
Wrought-wire clasp arms are more flexible than cast arms, allowing them to engage deeper undercuts without generating excessive stress on abutment teeth.
Question 6: When fabricating a mandibular complete denture, why is a broad, flat posterior ridge crest generally considered more favorable than a knife-edged ridge?
- It requires less relining over time
- It provides greater denture base surface area for load distribution and retention (Correct answer)
- It allows for thinner flanges
- It requires less occlusal reduction of posterior teeth
Correct answer: It provides greater denture base surface area for load distribution and retention
A broad flat ridge provides a larger bearing area to distribute occlusal loads and allows greater mucosal contact, improving both stability and retention.
Question 7: In constructing a Hawley retainer, the labial bow is most commonly fabricated from which wire gauge?
- .014-inch stainless steel
- .018-inch stainless steel (Correct answer)
- .030-inch stainless steel
- .040-inch stainless steel
Correct answer: .018-inch stainless steel
The .018-inch stainless steel wire is the standard for Hawley labial bows, providing sufficient rigidity to maintain arch form while allowing minor adjustments.
CDT Prosthodontic & Orthodontic Appliance Fabrication 2
Which alloy system is most commonly used for fabricating removable partial denture frameworks due to its strength and biocompatibility?