DDS Prosthodontics and Restorative Dentistry 2 — Questions and Answers
Question 1: Porcelain-fused-to-metal (PFM) crowns most commonly fracture at which location?
- At the metal-ceramic interface (cohesive failure)
- At the facial margin-porcelain junction
- Within the occlusal porcelain over functional contacts (Correct answer)
- At the connector between adjacent units in a bridge
Correct answer: Within the occlusal porcelain over functional contacts
Porcelain fractures most frequently in the occlusal porcelain in areas bearing functional load, as ceramic is brittle and has low tensile strength under repeated occlusal stress.
Question 2: A ferrule effect in crown preparation refers to:
- The use of a chamfer finish line to guide die-spacer application
- Encirclement of sound tooth structure above the cement margin by the crown walls (Correct answer)
- The creation of a 1 mm shoulder preparation at the gingival finish line
- Using dual-cure cement to bond the crown to dentin
Correct answer: Encirclement of sound tooth structure above the cement margin by the crown walls
The ferrule is a band of sound coronal tooth structure between the preparation finish line and the core, encircled by the crown, which provides anti-fracture resistance to root stress.
Question 3: In dental implant terminology, osseointegration is defined as:
- The growth of bone into the macro-roughened surface of the implant fixture
- Direct structural and functional contact between living bone and the implant surface at the light microscopic level (Correct answer)
- Fibrous encapsulation of the implant by dense connective tissue
- Integration of the abutment with the soft tissue cuff
Correct answer: Direct structural and functional contact between living bone and the implant surface at the light microscopic level
Osseointegration (Brånemark's definition) is a direct bone-to-implant contact at the light microscopic level without any intervening fibrous tissue layer.
Question 4: The occlusal scheme most commonly recommended for complete dentures is:
- Canine-guided occlusion
- Lingualized occlusion or bilateral balanced occlusion (Correct answer)
- Group function occlusion
- Edge-to-edge bite
Correct answer: Lingualized occlusion or bilateral balanced occlusion
Bilateral balanced occlusion (contacts on both sides in all excursive movements) or lingualized occlusion is recommended for complete dentures to stabilize the denture base and prevent tipping.
Question 5: The smear layer created during cavity preparation:
- Improves adhesion of all bonding systems equally
- Must always be completely removed before bonding
- Can be modified or removed depending on the bonding system (total-etch vs. self-etch) (Correct answer)
- Has no effect on the bond strength of glass ionomer cements
Correct answer: Can be modified or removed depending on the bonding system (total-etch vs. self-etch)
Total-etch systems remove the smear layer with phosphoric acid before priming, while self-etch systems incorporate and modify (but don't remove) the smear layer during bonding.
Question 6: When replacing a missing mandibular first molar with a three-unit fixed bridge, the abutment teeth most commonly used are:
- Second premolar and second molar (Correct answer)
- First premolar and third molar
- Second premolar and first premolar
- Canine and second molar
Correct answer: Second premolar and second molar
The second premolar and second molar serve as the natural abutments flanking the missing first molar space, providing the shortest span and most predictable bridge design.
DDS Prosthodontics and Restorative Dentistry 2
Porcelain-fused-to-metal (PFM) crowns most commonly fracture at which location?