AGD Prosthodontics: Fixed and Removable 2 — Questions and Answers
Question 1: Which cement is most appropriate for final cementation of a metal-ceramic crown on a vital tooth with a short clinical crown?
- Zinc oxide eugenol
- Resin-modified glass ionomer (Correct answer)
- Zinc phosphate
- Polycarboxylate
Correct answer: Resin-modified glass ionomer
Resin-modified glass ionomer provides superior retention through adhesion and is biocompatible, making it ideal for vital teeth with limited retention form.
Question 2: A patient presents with a Kennedy Class II partial denture that has significant rocking movement. The most likely cause is:
- Inadequate number of clasps
- Lack of indirect retainers (Correct answer)
- Poor occlusal rest seat preparation
- Excessive undercut engagement
Correct answer: Lack of indirect retainers
Indirect retainers placed anterior to the fulcrum line prevent rotational movement of distal-extension partial dentures under occlusal load.
Question 3: The biologic width in a healthy periodontium averages approximately:
- 0.5 mm
- 1.0 mm
- 2.04 mm (Correct answer)
- 3.5 mm
Correct answer: 2.04 mm
Biologic width comprises the junctional epithelium (~0.97 mm) and connective tissue attachment (~1.07 mm), averaging approximately 2.04 mm total.
Question 4: When fabricating a complete denture, the vertical dimension of occlusion is best evaluated by:
- Measuring phonetics of sibilant sounds only
- Using a combination of methods including physiologic rest position and phonetics (Correct answer)
- Relying solely on the closest speaking space
- Comparing with pre-extraction records only
Correct answer: Using a combination of methods including physiologic rest position and phonetics
No single method is entirely reliable; combining rest position minus freeway space, phonetic tests, swallowing, and facial aesthetics provides the most accurate VDO.
Question 5: Which of the following clasp assemblies provides the most favorable stress distribution for a distal-extension removable partial denture?
- Circumferential clasp on the mesial of the abutment
- RPI (rest, proximal plate, I-bar) clasp system (Correct answer)
- Ring clasp engaging the distolingual undercut
- Back-action clasp on the buccal surface
Correct answer: RPI (rest, proximal plate, I-bar) clasp system
The RPI system allows the I-bar retainer to disengage and move gingivally under load, reducing torquing forces transmitted to the abutment tooth.
Question 6: A porcelain-fused-to-metal crown shows a gray discoloration at the gingival margin six months after cementation. The most likely cause is:
- Inadequate porcelain thickness over the metal collar
- Secondary caries at the margin
- Sulcular fluid staining the luting cement
- Gingival recession exposing the metal substructure (Correct answer)
Correct answer: Gingival recession exposing the metal substructure
Gingival recession exposing the metal collar of the PFM crown is the most common cause of grayish discoloration at the gingival margin after cementation.
Question 7: The primary purpose of a surveyor in removable partial denture design is to:
- Measure the amount of bone support for abutment teeth
- Determine the path of insertion and identify usable undercuts (Correct answer)
- Evaluate the occlusal vertical dimension
- Assess the need for tooth preparation
Correct answer: Determine the path of insertion and identify usable undercuts
The dental surveyor determines the path of insertion/removal, identifies retentive and non-retentive areas, and locates interferences to the chosen path.
AGD Prosthodontics: Fixed and Removable 2
Which cement is most appropriate for final cementation of a metal-ceramic crown on a vital tooth with a short clinical crown?