CDT CAD/CAM Digital Dentistry 3 — Questions and Answers
Question 1: What is the typical linear shrinkage percentage of zirconia blanks during the sintering process?
- Approximately 20–25% (Correct answer)
- Less than 1%
- Approximately 50%
- Approximately 5–8%
Correct answer: Approximately 20–25%
Zirconia pre-sintered blanks shrink approximately 20–25% linearly during sintering, and CAD software compensates by enlarging the milled design.
Question 2: Which scanning technology uses a structured light pattern projected onto a model to capture surface geometry?
- White-light or blue-light structured light scanning (Correct answer)
- X-ray fluorescence scanning
- Magnetic resonance scanning
- Ultrasonic pulse-echo scanning
Correct answer: White-light or blue-light structured light scanning
Structured light scanners project a known pattern of light and use triangulation to calculate surface coordinates with high accuracy.
Question 3: When designing a full-contour monolithic zirconia molar crown in CAD software, which anatomical landmark is most critical to replicate accurately for occlusal function?
- Cusp tip positions and fossa locations (Correct answer)
- Crown-to-root ratio only
- Color gradient at the cervical third
- Pontic ridge width
Correct answer: Cusp tip positions and fossa locations
Accurate cusp tip positions and fossa locations determine proper occlusal contact and chewing efficiency.
Question 4: In a CAD/CAM implant workflow, what is the function of a scan body placed on the implant before intraoral scanning?
- To encode implant position and angulation in the digital impression (Correct answer)
- To protect the implant from contamination during scanning
- To record the vertical dimension of occlusion
- To indicate the shade of the final restoration
Correct answer: To encode implant position and angulation in the digital impression
Scan bodies have known geometries that allow CAD software to identify exact implant platform position and angulation.
Question 5: Which milling strategy uses a large-diameter bur first followed by progressively smaller burs to refine detail?
- Roughing then finishing toolpath strategy (Correct answer)
- Single-pass uniform milling
- Electrochemical machining
- Laser ablation protocol
Correct answer: Roughing then finishing toolpath strategy
Roughing removes bulk material quickly while finishing passes use smaller burs to achieve accurate margins and fine anatomical detail.
Question 6: What does 'connector width' refer to when designing a CAD/CAM fixed partial denture (bridge)?
- The cross-sectional dimension of material joining the pontic to the retainer (Correct answer)
- The width of the pontic at the tissue contact area
- The occlusal table width of the abutment crown
- The distance between implant fixtures
Correct answer: The cross-sectional dimension of material joining the pontic to the retainer
Adequate connector width is essential for structural strength; minimum dimensions vary by material (e.g., zirconia requires larger connectors than metal).
Question 7: Which factor most significantly affects the fit accuracy of a CAD/CAM crown at the finish line?
- Quality of the digital margin detection and preparation design (Correct answer)
- The brand of the milling machine only
- The sintering furnace brand
- The shade of the blank selected
Correct answer: Quality of the digital margin detection and preparation design
Accurate digital margin tracing in CAD software is the most critical step for achieving a precise marginal seal.
CDT CAD/CAM Digital Dentistry 3
What is the typical linear shrinkage percentage of zirconia blanks during the sintering process?