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Dental Waxes & Polymers (Acrylics)

Dental Materials • NEET MDS Study Guide • AI-Generated Notes

⭐ High-Yield Facts for Exam

  • PMMA = denture base (heat-cure strongest).
  • Gaseous porosity = overheating (most common).
  • Contraction porosity = inadequate pressure/material.
  • Lost-wax: pattern → invest → burnout → cast.
  • Benzoyl peroxide = initiator.

Dental Waxes & Acrylic Polymers

Acrylics (PMMA)

Polymethyl methacrylate is the standard denture base material (heat-cured for strength; self/cold-cured for repairs). Polymerisation is an addition reaction (initiator: benzoyl peroxide).

Porosity in Acrylic

  • Gaseous porosity — from monomer boiling when curing temperature is too high (most common; uniform spheres in thick areas).
  • Contraction (shrinkage) porosity — insufficient pressure/material.
  • Granular porosity — monomer evaporation from the surface.

Lost-Wax Technique

Wax pattern → investing → wax burnout → casting. Inlay/casting waxes must have low residue on burnout and minimal flow at mouth temperature.

Exam Tips ⭐

PMMA = denture base; gaseous porosity = overheating (most common); lost-wax = pattern → invest → burnout → cast.

📝 Practice MCQs — Dental Waxes & Polymers (Acrylics)

Q1. The standard denture base material is:
A. Polyether
B. PMMA (acrylic)
C. GIC
D. Zinc phosphate
Show Answer
✅ Answer: B
Polymethyl methacrylate (PMMA) is the denture base of choice.
Q2. Gaseous porosity in acrylic is caused by:
A. Low temperature
B. Monomer boiling from overheating
C. Excess pressure
D. Too much polymer
Show Answer
✅ Answer: B
Overheating boils the monomer producing gaseous porosity.
Q3. The lost-wax technique sequence is:
A. Cast → invest → burnout
B. Wax pattern → invest → burnout → cast
C. Burnout → cast → invest
D. Invest → cast → wax
Show Answer
✅ Answer: B
Pattern, then investing, wax burnout, then casting.
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Related Topics

Mechanical Properties of MaterialsDental Casting Alloys & InvestmentDenture Problems & Relining