Dental Materials Chapter 3

Ceramic Resin Denture Base

• Ceramic resin denture base combines the benefits of ceramics and resin materials.

Advantages of Ceramic Resin Denture Base

• Provides an esthetic appearance that is satisfactory.
• The glazed surface produces a restoration that is color stable and compatible with soft tissues.
• Porcelain is inert.

Disadvantages of Ceramic Resin Denture Base

• Requires removal of additional tooth structure.
• Has a high hardness number, which may result in excessive wear of opposing teeth.
• Has low tensile strength and is brittle.
• Can produce a clicking sound when in contact with opposing teeth.

Indications and Uses of Ceramic Resin Denture Base

• Used in denture teeth.
• Used in jacket crowns.
• Used in porcelain-metal crown and bridge work.
• Used in simple inlays.

Contraindications of Ceramic Resin Denture Base

• Not suitable for individuals with para-function (bruxism).
• Not suitable for short clinical crowns.
• Not suitable for immature teeth.
• Not suitable for unfavorable occlusion.

Classification of Ceramic

• Classified into four types based on fusion temperature:
  • High-fusing (1300°C)
  • Medium-fusing (1100-1300°C)
  • Low-fusing (850-1100°C)
  • Ultra-low-fusing (<850°C)

Manipulation of Ceramic

• Compaction is done by mixing ceramic powder with distilled water.
• Three methods of compaction:
  • Mild vibration to pack the wet powder densely.
  • Using a small spatula to apply and smooth the wet porcelain.
  • Adding dry porcelain powder to absorb excess water.

Firing Procedure

• Purpose is to sinter the powder particles.
• Changes during firing include loss of water and porcelain fusion.
• Sintering is the process responsible for the fusion of powder particles.

Glazing

• Reached in the last firing.
• Self-glaze porcelain or low-fusing glass is added.
• Self-glaze porcelain is preferred due to its higher firing temperature and resistance to oral fluids.
• Glazing produces a smooth, shiny surface.

Cooling

• Slow cooling is necessary to avoid surface crazing.

Criteria for an Ideal Denture Base Material

• Adequate strength to resist fracture.
• Adequate resilience to absorb energy without deformation.
• High impact strength to resist fracture.
• Good abrasion resistance.
• High thermal conductivity for biophysical comfort.
• Radio-opacity.
• Easy to process and repair.
• Aesthetically satisfactory.

Denture Bases

• Can be classified into:
  • Metallic (e.g., gold alloy type IV)
  • Non-metallic (e.g., acrylic resin)
  • Combination of metallic and non-metallic

Complete Denture Construction

• Steps involved:
  • Diagnosis and X-ray
  • Primary impression and cast
  • Secondary impression and cast
  • Occlusion blocks
  • Jaw relation and mounting on articulator
  • Setting of teeth
  • Try-in
  • Procedure for transforming the temporary denture base into a permanent one.

Acrylic Resin

• Can be heat-cured or self-cured.
• Laboratory stages of polymerization:
  • Sandy
  • Stringy
  • Dough
  • Rubbery
  • Stiff¹