AGD Prosthodontics: Fixed and Removable Questions and Answers — Questions and Answers
Question 1: A 65-year-old patient requires a new maxillary complete denture. Upon delivery, the patient immediately complains of a persistent gagging sensation. Clinical examination reveals the denture is stable and retentive. Which of the following is the most probable cause of the patient's complaint?
- The posterior border of the denture is overextended onto the soft palate. (Correct answer)
- The vertical dimension of occlusion is excessive.
- The buccal flanges are underextended, compromising the peripheral seal.
- The post-palatal seal is insufficiently compressed.
Correct answer: The posterior border of the denture is overextended onto the soft palate.
The gag reflex is triggered by stimulation of the soft palate. If the posterior border of a maxillary denture extends beyond the vibrating line (the junction of the hard and soft palate) and onto the movable soft palate, it will elicit a gagging sensation. While other factors can cause issues, overextension in this specific area is the most direct cause of gagging.
Question 2: A patient requires a three-unit fixed partial denture to replace tooth #30. According to Ante's Law, which of the following principles must be met for abutment selection?
- The crown-to-root ratio of the abutment teeth must be at least 1:1.
- The combined root surface area of the abutment teeth should be equal to or greater than that of the tooth being replaced. (Correct answer)
- The abutment teeth must be vital and free of any endodontic treatment.
- The combined buccolingual width of the abutments must exceed the width of the pontic.
Correct answer: The combined root surface area of the abutment teeth should be equal to or greater than that of the tooth being replaced.
Ante's Law is a fundamental guideline in fixed prosthodontics which states that for a fixed partial denture to have a favorable long-term prognosis, the combined pericemental area (root surface area) of the abutment teeth should be equal to or greater than the pericemental area of the tooth or teeth being replaced. This ensures the abutments can withstand the additional occlusal load.
Question 3: When designing a fixed partial denture for a posterior, non-esthetic area, which pontic design is considered the most hygienic due to its lack of contact with the residual ridge?
- Modified ridge lap
- Ovate
- Sanitary (or hygienic) (Correct answer)
- Saddle (or ridge lap)
Correct answer: Sanitary (or hygienic)
The sanitary or hygienic pontic is designed with a significant space between the pontic and the underlying tissue. This complete clearance allows for easy cleaning and optimal tissue health, making it the most hygienic option, though it is generally not used in esthetic zones.
Question 4: A patient presents with a Kennedy Class I removable partial denture (RPD) opposing a complete denture. What is the primary function of an indirect retainer in this RPD design?
- To provide the primary occlusal support for the prosthesis.
- To directly engage an undercut for retention.
- To stabilize the abutment teeth against mesial drifting.
- To counteract lifting forces on the distal extension bases. (Correct answer)
Correct answer: To counteract lifting forces on the distal extension bases.
In a distal extension RPD, a fulcrum line exists between the most posterior rests. When sticky foods create lifting forces on the denture base, the denture can rotate around this fulcrum line. The indirect retainer, placed anterior to the fulcrum line, acts as a lever to resist this rotational movement and prevent the denture base from lifting away from the tissues.
Question 5: A patient with limited interocclusal clearance (less than 1.0 mm) on a mandibular second molar requires a full coverage crown. The patient has a history of bruxism. Which of the following materials is most suitable for this situation?
- Feldspathic porcelain
- Lithium disilicate
- Full-contour zirconia (Correct answer)
- Leucite-reinforced ceramic
Correct answer: Full-contour zirconia
Full-contour zirconia has very high flexural strength, allowing it to be used in thin sections. It requires the least amount of occlusal reduction, with a minimum of 0.5 mm, and an ideal of 1.0-1.5 mm. This makes it the ideal choice for posterior crowns in areas with limited occlusal space and high occlusal forces, such as in a patient with bruxism. Other ceramic materials require significantly more reduction (typically 1.5-2.0 mm) to achieve adequate strength.
Question 6: For a mandibular Kennedy Class I removable partial denture using the canines as the terminal abutments, which clasp assembly is specifically designed to be 'stress-releasing' by minimizing torquing forces on the abutment teeth during function?
- A cast circumferential (Akers) clasp with a distal rest.
- A double embrasure clasp engaging both the canine and lateral incisor.
- An RPI system (mesial Rest, Proximal plate, I-bar clasp). (Correct answer)
- A ring clasp originating on the mesiolingual surface.
Correct answer: An RPI system (mesial Rest, Proximal plate, I-bar clasp).
The RPI system is a stress-releasing clasp assembly designed for distal extension cases. The mesial rest moves the fulcrum away from the edentulous space, the distal proximal plate guides the path of insertion and disengages during function, and the I-bar clasp engages a minimal undercut. This combination allows the denture base to move slightly toward the tissue under load without transmitting harmful torque to the abutment tooth.
AGD Prosthodontics: Fixed and Removable Questions and Answers
A 65-year-old patient requires a new maxillary complete denture.
Upon delivery, the patient immediately complains of a persistent gagging sensation.
Clinical examination reveals the denture is stable and retentive.
Which of the following is the most probable cause of the patient's complaint?