Prosthodontics and Operative Dentistry Flashcards
6 cards from real NBDE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Prosthodontics and Operative Dentistry flashcards as text
A patient with a Kennedy Class I removable partial denture complains that the denture lifts away from the tissue when they eat sticky foods. Which component is specifically designed to counteract this rotational movement away from the tissues on the opposite side of the fulcrum line?
Answer: Indirect retainer
An indirect retainer is a component of an RPD that assists the direct retainer in preventing the displacement of a distal extension base. It functions through lever action on the opposite side of the fulcrum line to counteract forces that would lift the denture base away from the tissues.
When preparing a posterior tooth for a full cast gold crown, what is the generally accepted ideal total occlusal convergence (taper) between opposing axial walls to provide adequate retention and resistance form?
Answer: 6-10 degrees
A total occlusal convergence of 6-10 degrees is considered ideal for crown preparations. This taper allows for the restoration to seat properly while providing sufficient parallelism of the axial walls to retain the crown through friction and resist dislodging forces. While a range of 10-22 degrees is sometimes cited as clinically achievable, the ideal goal is closer to 6 degrees.
A patient complains of poor retention of their new maxillary complete denture, noting it frequently drops when they talk or yawn. Which of the following is the most critical factor for maintaining the peripheral seal and retention of a maxillary complete denture?
Answer: Proper placement of the posterior palatal seal
The posterior palatal seal (PPS) is the most critical element for the retention of a maxillary complete denture. It creates an intimate contact with the displaceable soft tissue at the junction of the hard and soft palates, completing the peripheral seal and utilizing atmospheric pressure to hold the denture in place.
Which of the following describes a G.V. Black Class II carious lesion?
Answer: Caries on the proximal surface of a posterior tooth
According to G.V. Black's classification system, a Class II lesion is defined as caries affecting the proximal (mesial or distal) surfaces of posterior teeth (premolars and molars).
The primary purpose of applying 37% phosphoric acid to enamel during an adhesive restorative procedure is to:
Answer: Remove the smear layer and create microporosities for mechanical retention
Acid etching with phosphoric acid demineralizes the enamel surface, selectively dissolving hydroxyapatite crystals to create microscopic irregularities or 'tags'. This process increases the surface area and creates microporosities, allowing the adhesive resin to flow in and establish a strong micromechanical bond upon polymerization. It also removes the smear layer.
Conventional glass ionomer cements (GICs) are composed of a powder and a liquid that undergo an acid-base reaction. The liquid component is primarily an aqueous solution of which acid?
Answer: Polyacrylic acid
The liquid component of a conventional glass ionomer cement is an aqueous solution of a polyalkenoic acid, most commonly polyacrylic acid. This acid reacts with the fluoroaluminosilicate glass powder to initiate the setting reaction.