INBDE Restorative Dentistry and Dental Materials 2 — Questions and Answers
Question 1: What is the primary purpose of acid etching enamel before bonding?
- Remove the fluoride-rich surface layer
- Create microporosities for micromechanical retention (Correct answer)
- Increase the surface energy of dentin
- Activate the primer component
Correct answer: Create microporosities for micromechanical retention
Phosphoric acid (30–40%) selectively dissolves enamel hydroxyapatite, creating microporosities that allow resin tags to form and provide micromechanical retention.
Question 2: The working time of zinc phosphate cement can be extended by:
- Adding more liquid to the mix
- Spatulating on a cold, thick glass slab (Correct answer)
- Increasing the powder-to-liquid ratio
- Mixing rapidly in a circular motion
Correct answer: Spatulating on a cold, thick glass slab
Cooling the glass slab to 18°C slows the exothermic setting reaction, extending working time; large slab area also dissipates heat.
Question 3: Which impression material provides the highest dimensional accuracy and detail reproduction?
- Alginate (irreversible hydrocolloid)
- Polysulfide rubber
- Zinc oxide eugenol paste
- Polyvinyl siloxane (PVS/addition silicone) (Correct answer)
Correct answer: Polyvinyl siloxane (PVS/addition silicone)
Polyvinyl siloxane (addition silicone) provides the highest dimensional accuracy, excellent detail reproduction, and good dimensional stability over time.
Question 4: A cusp that is fully included within the outer cusp ridges of the opposing arch during maximum intercuspation is classified as a:
- Stamp cusp
- Supporting cusp (centric holding cusp) (Correct answer)
- Non-supporting cusp (non-centric cusp)
- Shearing cusp
Correct answer: Supporting cusp (centric holding cusp)
Supporting (centric holding) cusps — maxillary palatal and mandibular buccal — contact the opposing tooth in centric occlusion, maintaining vertical dimension.
Question 5: Secondary caries (recurrent caries) occurs most frequently at which location of an existing restoration?
- Occlusal surface
- Proximal gingival margin (Correct answer)
- Axial wall
- Pulpal wall
Correct answer: Proximal gingival margin
The proximal gingival margin is the most common site for recurrent caries due to difficulty in cleaning, plaque accumulation, and microleakage at the cervical margin.
Question 6: Which crown-to-root ratio is generally considered the minimum acceptable for a tooth to serve as an abutment?
- 1:1 (Correct answer)
- 1:2
- 2:3
- 1:1.5
Correct answer: 1:1
A crown-to-root ratio of 1:1 is generally considered the minimum acceptable for a tooth to be used as a fixed prosthetic abutment, with 2:3 being ideal.
INBDE Restorative Dentistry and Dental Materials 2
What is the primary purpose of acid etching enamel before bonding?