AGD Prosthodontics: Fixed and Removable 3 — Questions and Answers
Question 1: When preparing a tooth for a full-coverage metal-ceramic crown, the recommended axial reduction on the facial surface is:
- 0.3–0.5 mm
- 0.5–0.8 mm
- 1.2–1.5 mm (Correct answer)
- 2.0–2.5 mm
Correct answer: 1.2–1.5 mm
Facial reduction of 1.2–1.5 mm is required for porcelain-fused-to-metal crowns to provide adequate space for the metal substructure and overlying ceramic layer.
Question 2: A patient's maxillary complete denture has a high-pitched whistling sound during the 'S' sound. This indicates:
- The vertical dimension of occlusion is too high
- The anterior teeth are positioned too far labially
- The closest speaking space is insufficient (Correct answer)
- Excessive freeway space
Correct answer: The closest speaking space is insufficient
A whistling sibilant 'S' sound indicates the anterior teeth are too close together, leaving insufficient speaking space for air to flow correctly.
Question 3: Which impression technique is most appropriate for a patient with a severely resorbed mandibular ridge for complete denture fabrication?
- Stock tray with irreversible hydrocolloid
- Custom tray with selective pressure technique (Correct answer)
- Rubber base in a stock tray
- Border-molded tray with plaster of Paris
Correct answer: Custom tray with selective pressure technique
A custom tray with selective pressure (mucocompressive in stress-bearing areas, mucostatic elsewhere) maximizes stability and support over resorbed ridges.
Question 4: Posterior cantilever fixed partial dentures are contraindicated primarily because:
- They require more preparation than conventional FPDs
- They create excessive torquing forces on the abutment tooth (Correct answer)
- Porcelain cannot be used in cantilever designs
- The esthetic outcome is poor
Correct answer: They create excessive torquing forces on the abutment tooth
Cantilever FPDs create lever-arm forces that apply torque and tipping moments to abutment teeth, risking periodontal damage and restoration failure.
Question 5: A patient with a Kennedy Class I removable partial denture reports that the denture drops during swallowing. The most appropriate adjustment is to:
- Add more retentive clasps
- Reline the denture bases with tissue conditioner
- Adjust the border extensions in the distal flange area (Correct answer)
- Reduce the vertical dimension of occlusion
Correct answer: Adjust the border extensions in the distal flange area
Overextended posterior flanges interfere with the action of the pterygomandibular raphe and buccinator muscle, causing the denture to unseat during swallowing.
Question 6: The most critical factor in the long-term success of a fixed partial denture with a pier abutment (middle abutment) is:
- Using a rigid connector throughout
- Incorporating a non-rigid connector at one end (Correct answer)
- Increasing the taper of all abutment preparations
- Selecting all-ceramic materials for the pontic
Correct answer: Incorporating a non-rigid connector at one end
A non-rigid connector at the distal aspect of the middle abutment allows independent movement and prevents differential tooth movement from dislodging the retainer.
Question 7: Which occlusal scheme is most appropriate for a patient with a complete maxillary denture opposing natural mandibular teeth?
- Balanced occlusion
- Lingualized occlusion
- Monoplane (flat plane) occlusion (Correct answer)
- Canine-guided occlusion
Correct answer: Monoplane (flat plane) occlusion
Monoplane occlusion with no cuspal inclines minimizes horizontal forces transmitted to the maxillary denture when opposing natural teeth with fixed proprioception.
AGD Prosthodontics: Fixed and Removable 3
When preparing a tooth for a full-coverage metal-ceramic crown, the recommended axial reduction on the facial surface is: