CDT CAD/CAM Digital Dentistry 2 — Questions and Answers
Question 1: Which file format is the industry standard for sharing digital impression data between scanners and milling software?
- STL (Standard Tessellation Language) (Correct answer)
- DXF (Drawing Exchange Format)
- SVG (Scalable Vector Graphics)
- PDF (Portable Document Format)
Correct answer: STL (Standard Tessellation Language)
STL is the most widely accepted open format for sharing 3D scan data across CAD/CAM systems.
Question 2: When milling zirconia, which milling stage requires the material to be in its pre-sintered (soft) state?
- Green-state milling before sintering (Correct answer)
- Post-sintering milling only
- Hot isostatic pressing stage
- Glazing and staining stage
Correct answer: Green-state milling before sintering
Pre-sintered (green-state) zirconia is milled before the final sintering cycle that shrinks and densifies the material.
Question 3: What does the term 'emergence profile' refer to in CAD design of a crown?
- The contour of the restoration as it exits the gingival margin (Correct answer)
- The occlusal surface contact points
- The internal fit accuracy at the margin
- The shade gradient from cervical to incisal
Correct answer: The contour of the restoration as it exits the gingival margin
Emergence profile describes how the restoration transitions from the subgingival finish line through the gingival tissue.
Question 4: Which milling parameter most directly affects the surface roughness of a milled ceramic restoration?
- Stepover distance between toolpaths (Correct answer)
- Spindle cooling water temperature
- CAD file polygon count only
- Color of the milling blank
Correct answer: Stepover distance between toolpaths
A smaller stepover distance between adjacent toolpaths produces a smoother surface by reducing the scallop height.
Question 5: In a chairside CAD/CAM workflow, which component captures the optical impression directly in the patient's mouth?
- Intraoral scanner (Correct answer)
- Cone beam CT unit
- Desktop laboratory scanner
- Photopolymer printer
Correct answer: Intraoral scanner
An intraoral scanner uses structured light or laser to capture a digital impression without impression material.
Question 6: What is the primary reason zirconia restorations must be sintered at high temperatures after milling?
- To convert the crystalline phase and achieve final strength and density (Correct answer)
- To add translucency through glass fusing
- To remove internal porosity via steam autoclaving
- To bond the porcelain veneer layer chemically
Correct answer: To convert the crystalline phase and achieve final strength and density
Sintering transforms porous pre-sintered zirconia into dense, high-strength tetragonal-phase ceramic.
Question 7: Which occlusal design concept in CAD software distributes occlusal forces through the long axis of posterior teeth?
- Centric stops with axially directed contacts (Correct answer)
- Protrusive guidance on the second molar
- Lateral group function on premolars only
- Deep vertical overlap with steep incisal guidance
Correct answer: Centric stops with axially directed contacts
Axially directed centric stops minimize lateral forces and protect both the restoration and the periodontal structures.
CDT CAD/CAM Digital Dentistry 2
Which file format is the industry standard for sharing digital impression data between scanners and milling software?