CDT CDT Ceramics & Porcelain Techniques 2 — Questions and Answers
Question 1: What is the purpose of degassing (oxidizing) a metal coping before porcelain application?
- To increase metal hardness
- To remove surface oxides that prevent porcelain bonding
- To create a controlled oxide layer that promotes porcelain adhesion (Correct answer)
- To reduce the melting point of the alloy
Correct answer: To create a controlled oxide layer that promotes porcelain adhesion
Degassing creates a controlled, thin oxide layer on the metal surface that chemically bonds with the opaque porcelain.
Question 2: Which type of ceramic is most commonly used for full-contour posterior restorations due to its strength and wear resistance?
- Feldspathic porcelain
- Leucite-reinforced glass ceramic
- Zirconia (Correct answer)
- Lithium disilicate
Correct answer: Zirconia
Zirconia offers the highest flexural strength among dental ceramics, making it ideal for full-contour posterior crowns and bridges.
Question 3: What does 'value' refer to in the Vita shade system?
- The hue or color family of the tooth
- The chroma or saturation of the color
- The lightness or darkness of the shade (Correct answer)
- The translucency level of the porcelain
Correct answer: The lightness or darkness of the shade
Value describes the relative lightness or darkness of a shade, ranging from very light (high value) to very dark (low value).
Question 4: What is the recommended firing temperature range for most feldspathic dental porcelains?
- 400–600°C
- 700–850°C (Correct answer)
- 900–1000°C
- 1100–1300°C
Correct answer: 700–850°C
Feldspathic dental porcelains typically fire between 700°C and 850°C, depending on the specific formulation and manufacturer guidelines.
Question 5: What is 'metamerism' in shade matching?
- The tendency of porcelain to crack under thermal cycling
- Two colors that appear to match under one light source but differ under another (Correct answer)
- The chemical reaction between metal and porcelain during firing
- A technique for blending incisal and body porcelains
Correct answer: Two colors that appear to match under one light source but differ under another
Metamerism occurs when two materials look like the same color under one light condition (e.g., dental light) but differ under another (e.g., natural daylight).
Question 6: Which finishing technique is used to create surface texture on ceramic restorations that mimics natural enamel?
- Grinding with a coarse diamond bur
- Selective glazing with stains
- Characterization with porcelain texturing stones and polishing (Correct answer)
- Sandblasting with 50-micron alumina
Correct answer: Characterization with porcelain texturing stones and polishing
Texturing stones and rubber polishing points are used to create perikymata, stippling, and other natural enamel surface features before glazing.
CDT CDT Ceramics & Porcelain Techniques 2
What is the purpose of degassing (oxidizing) a metal coping before porcelain application?