Most Widely Asked Viva Questions - Dental Materials (BDS 2nd Year)

1. Dental Amalgam

• What is dental amalgam? Give its classification.
• What is the composition of a high-copper amalgam alloy? How does it differ from low-copper alloy?
• Explain the setting/amalgamation reaction of dental amalgam (both conventional and high-copper).
• What is trituration? Describe the stages of trituration and the effect of over/under trituration.
• What is creep? How does it affect amalgam restorations?
• Define condensation - why is it important and what methods are used?
• What are the manipulative variables that affect the properties of amalgam?
• What is mercury hygiene? Describe safe handling of mercury in a dental clinic.
• What is the ADA specification for amalgam alloy?
• What is the gamma-2 phase? Why is it clinically significant?
• Compare admixed vs lathe-cut vs spherical amalgam alloys.

2. Composite Resins

• Define composite resin. Classify composite resins based on filler particle size.
• What are the components of a composite resin? Describe the matrix and filler phases.
• What is the role of the coupling agent (silane) in composites?
• What is polymerization shrinkage? What are its clinical implications?
• Differentiate between macrofilled, microfilled, hybrid, and nanofilled composites.
• What is a posterior composite? Discuss its advantages and limitations.
• What is incremental placement technique and why is it used?
• Describe light-curing units - types and wavelength requirements.
• What is the C-factor (cavity configuration factor)?
• What are the ideal requirements of a restorative material?

3. Glass Ionomer Cement (GIC)

• Give the composition of glass ionomer cement. Explain the setting reaction.
• What is the mechanism of adhesion of GIC to tooth structure?
• Classify GIC. What are the different types and their uses?
• What is the anti-cariogenic property of GIC and how is it achieved?
• What is resin-modified GIC (RMGIC)? How does it differ from conventional GIC?
• What are compomers? How do they differ from GIC and composite?
• What is the role of polyacrylic acid in GIC?
• What is metal-modified (cermet) GIC?
• Describe the maturation of GIC - initial and final set.
• What are the recent advances in glass ionomer cements?

4. Zinc Phosphate Cement

• Give the composition of zinc phosphate cement (powder and liquid).
• Explain the setting reaction of zinc phosphate cement.
• Why is zinc phosphate cement mixed on a cool, thick glass slab?
• What is the pH of freshly mixed zinc phosphate cement and its clinical significance?
• Describe the incremental addition technique for mixing zinc phosphate cement.
• What are the uses of zinc phosphate cement? What type is used as a luting agent?

5. Zinc Oxide-Eugenol (ZOE) Cement

• What is the composition and setting reaction of ZOE?
• What are the uses of ZOE cement in dentistry?
• What is EBA cement? How does it improve upon ZOE?
• What are non-eugenol ZOE alternatives and why are they used?
• What is the effect of eugenol on pulp tissue?

6. Calcium Hydroxide

• What is the role of calcium hydroxide as a pulp-capping agent?
• Describe the mechanism by which Ca(OH)2 stimulates reparative dentin formation.
• What are the forms in which calcium hydroxide is available clinically?

7. Dental Cements - General

• Classify dental cements based on use (luting, lining, base, restorative).
• What is a cavity varnish? How does it differ from a cavity liner?
• What is a cavity base? What are the ideal requirements of a base?
• What is zinc polycarboxylate cement? Describe its composition and mechanism of adhesion.
• What is pit and fissure sealant? Classify and describe.

8. Impression Materials

• Classify impression materials with examples.
• What is an elastic vs non-elastic impression material? Give examples of each.
• Describe the composition and setting reaction of alginate (irreversible hydrocolloid).
• What is syneresis and imbibition in hydrocolloids? What are their clinical implications?
• Describe the composition, setting reaction and properties of addition silicone (PVS) vs condensation silicone.
• What is the difference between addition and condensation type silicones?
• What is a reversible hydrocolloid (agar)? How is it used?
• Describe zinc oxide-eugenol impression paste - composition and use.
• What is dimensional stability? Which impression material has the best dimensional stability?
• What is electronegativity inhibition in PVS impressions?
• What is a custom tray and why is it used?

9. Dental Waxes

• Classify dental waxes with examples.
• What is the composition of inlay wax? What are its requirements per ADA spec?
• What is flow in wax? How does it affect clinical use?
• Describe boxing wax, baseplate wax, and utility wax - their uses.
• What is the thermal expansion of wax and its relevance in casting?

10. Gypsum Products

• Classify gypsum products used in dentistry.
• Explain the setting reaction of dental plaster and stone (calcium sulfate hemihydrate to dihydrate).
• What is the difference between alpha and beta hemihydrate? How are they manufactured?
• What is setting expansion and how is it controlled?
• What is W:P ratio? What is the effect of increasing W:P ratio on setting time and strength?
• What is die stone (Type IV gypsum)? What properties make it ideal for dies?
• What are accelerators and retarders in gypsum setting?

11. Casting Alloys and Metals

• Classify dental casting alloys. Compare Type I, II, III, and IV gold alloys.
• What is the composition of chrome-cobalt (Cr-Co) alloy? What are its advantages in dentistry?
• What is heat treatment (hardening and softening) of gold alloys?
• Describe casting defects and their causes.
• What is a wrought alloy? Give examples and their uses.
• What is annealing? When and why is it performed?

12. Dental Ceramics

• Classify dental ceramics.
• What is the composition of dental porcelain? What is the role of leucite?
• What is metal-ceramic (PFM) restoration? Describe the bonding mechanism.
• What is the coefficient of thermal expansion and why must it match metal and ceramic?
• What are all-ceramic systems (IPS e.max, Zirconia)?

13. Denture Base Resins (Acrylic)

• Classify denture base resins.
• Describe the composition and polymerization of PMMA (heat-cured acrylic).
• What is the dough stage and why is packing done at this stage?
• What are the differences between heat-cured, cold-cured, and light-cured acrylic?
• What is porosity in acrylic and what causes it?
• What is MMA monomer? What are the hazards of residual monomer?

14. Properties of Dental Materials (Frequently Tested)

• Define: stress, strain, proportional limit, elastic limit, yield strength, ultimate tensile strength.
• What is Young's modulus (modulus of elasticity)?
• Define hardness. Name tests used to measure hardness (Vickers, Knoop, Brinell, Rockwell).
• What is fatigue failure?
• What is toughness vs brittleness?
• What is thermal conductivity and its relevance in pulp protection?
• What is coefficient of thermal expansion?
• What is solubility and disintegration of dental materials?
• Define biocompatibility - what factors affect it?
• What is corrosion? Types of corrosion seen in dental metals (galvanic, crevice, stress corrosion).

15. Abrasives and Polishing

• Define abrasion, attrition, and erosion.
• Classify abrasives used in dentistry.
• Describe the procedure for polishing acrylic resin and chrome-cobalt dentures.

High-Probability One-Liner Questions