CCE Ceramic Application & Contouring 4 — Questions and Answers
Question 1: When building proximal contacts in ceramic, the ceramist must ensure contact is located:
- At the height of contour in the middle third of the proximal surface (Correct answer)
- In the gingival third, close to the papilla
- At the incisal or occlusal third only
- Exactly at the midpoint of the crown height regardless of tooth position
Correct answer: At the height of contour in the middle third of the proximal surface
Proximal contacts are ideally in the middle third (or junction of middle and incisal thirds for anteriors) to protect the interdental papilla and allow natural embrasure form.
Question 2: Which ceramic mixing technique minimizes air bubble incorporation during porcelain preparation?
- Vigorous stirring with a metal spatula to break up clumps
- Folding and pressing the mixture against the pad using a flat spatula with gentle strokes (Correct answer)
- Adding extra liquid and shaking the mixing pad
- Using a vibrator at maximum speed throughout the entire mix
Correct answer: Folding and pressing the mixture against the pad using a flat spatula with gentle strokes
Folding and pressing ceramic against a mixing pad incorporates moisture evenly while minimizing air entrapment compared to stirring or shaking.
Question 3: A fired ceramic crown shows a gray shadow visible through the facial surface. The most probable cause is:
- Insufficient glaze layer over body ceramic
- Metal show-through due to inadequate opaque coverage or insufficient ceramic thickness (Correct answer)
- Over-firing of the dentin ceramic layer
- Using incorrect firing atmosphere in the oven
Correct answer: Metal show-through due to inadequate opaque coverage or insufficient ceramic thickness
Gray shadow is the classic sign of metal show-through, caused by too little opaque or body ceramic that allows the dark metal substructure to be visible through the translucent porcelain.
Question 4: When contouring a full-contour zirconia crown using diamond burs chairside, which cooling method prevents microcrack formation in the zirconia surface?
- Dry grinding with intermittent pressure to avoid heat buildup
- High-volume air cooling only
- Continuous water cooling during all adjustment procedures (Correct answer)
- Alcohol spray applied after each grinding stroke
Correct answer: Continuous water cooling during all adjustment procedures
Continuous water cooling prevents frictional heat from inducing phase transformation stress in zirconia, which can initiate surface microcracks that compromise restoration integrity.
Question 5: The 'condensation' step in ceramic buildup involves which action?
- Compressing ceramic particles together using vibration or blotting to increase density and reduce porosity (Correct answer)
- Applying a thin wash coat of liquid over built-up ceramic
- Pressing the ceramic framework into a silicone putty index
- Firing the ceramic at low temperature before full buildup
Correct answer: Compressing ceramic particles together using vibration or blotting to increase density and reduce porosity
Condensation removes excess liquid and compresses particles together, increasing ceramic density and reducing porosity in the fired restoration.
Question 6: Which surface texture technique, applied before final glaze, best simulates the natural perikymata texture of enamel on an anterior ceramic crown?
- Polishing with diamond paste to a high gloss
- Adding horizontal fine-line grooves with a pointed instrument parallel to the incisal edge (Correct answer)
- Sandblasting the entire surface at high pressure
- Applying a thick glaze and pulling it with a brush
Correct answer: Adding horizontal fine-line grooves with a pointed instrument parallel to the incisal edge
Fine horizontal grooves etched with a pointed instrument before glazing replicate the natural perikymata ridges present on natural enamel surfaces for a lifelike appearance.
Question 7: When fabricating a three-unit ceramic bridge, where should the ceramist direct particular attention during the pontic contour phase?
- Occlusal contacts of the retainer crowns only
- The tissue surface of the pontic and its ridge relationship (Correct answer)
- The connector width between retainers and pontic
- The glaze thickness on the facial surface of retainers
Correct answer: The tissue surface of the pontic and its ridge relationship
The pontic's tissue surface contour and ridge relationship are critical for tissue health, esthetics, and cleansability; an ovate or modified ridge lap design is commonly used.
CCE Ceramic Application & Contouring 4
When building proximal contacts in ceramic, the ceramist must ensure contact is located: