FREE NDEB Prosthodontics and Restorative Dentistry Questions and Answers

Question 1

A patient presents with a completely edentulous maxilla opposing natural mandibular anterior teeth and a bilateral distal-extension removable partial denture. The patient exhibits significant resorption of the premaxilla, papillary hyperplasia of the palate, and supra-eruption of the mandibular incisors. Which of the following is the most accurate diagnosis for this clinical presentation?

Accepted Answer

Combination Syndrome

Answer

Combination Syndrome, first described by Ellsworth Kelly, presents with a characteristic pattern of signs resulting from the specific occlusal forces generated by an edentulous maxilla opposing natural mandibular anterior teeth. These signs include loss of bone from the anterior maxillary ridge, overgrowth of the maxillary tuberosities, papillary hyperplasia of the hard palate, extrusion of the mandibular anterior teeth, and bone loss under the mandibular partial denture bases.

Question 2

When preparing an endodontically treated molar for a full coverage crown, what is the most critical factor for ensuring long-term resistance to fracture and dislodgement of the restoration?

Accepted Answer

Achieving a 2.0 mm ferrule effect

Answer

The ferrule effect is the 360-degree collar of sound tooth structure that a crown encircles coronal to the margin. A ferrule of 1.5 to 2.0 mm in height is widely considered a critical determinant for the long-term success of restoring an endodontically treated tooth, as it provides resistance to fracture by bracing the tooth against functional lever forces. While post type, material choice, and margin design are important, the presence of an adequate ferrule has the most significant impact on fracture resistance.

Question 3

A clinician is preparing a maxillary first molar for a full gold crown. To ensure adequate retention and resistance form, what is the ideal total occlusal convergence (taper) of the axial walls?

Accepted Answer

6-10 degrees

Answer

While perfectly parallel walls would offer maximum theoretical retention, they are clinically impossible to create without causing undercuts. A total occlusal convergence (the sum of the taper on opposing walls) of 6 to 10 degrees is widely accepted as the clinical ideal. This taper allows for the restoration to seat completely while providing sufficient parallelism to resist dislodgement from functional forces.

Question 4

A patient requires a removable partial denture for a mandibular arch that is missing all teeth posterior to the second premolars on both sides. According to Kennedy's classification, how would this edentulous situation be classified?

Accepted Answer

Class I

Answer

Kennedy's classification is a system used to categorize partially edentulous arches. A Kennedy Class I describes a situation with bilateral edentulous areas located posterior to the remaining natural teeth. This is the most common classification for free-end or distal-extension cases.

Question 5

Which of the following occlusal schemes is most frequently recommended for complete dentures to enhance stability during parafunctional movements and accommodate patients with resorbed ridges?

Accepted Answer

Lingualized occlusion

Answer

Lingualized occlusion is an occlusal scheme where the maxillary lingual cusps articulate with the central fossae of the mandibular teeth. This setup centralizes occlusal forces, minimizes tipping forces, and provides bilateral balance, which is highly advantageous for denture stability, especially in patients with significant ridge resorption. Canine guidance and group function are concepts primarily applied to natural dentition and fixed prosthodontics and can create destabilizing forces in complete dentures.

NDEB - National Dental Examining Board Practice Test

NDEB - National Dental Examining Board Practice Test

FREE NDEB Prosthodontics and Restorative Dentistry Questions and Answers