Ceramics in Dentistry PDF

**CERAMICS** **1. Fundamental Properties and Characteristics of Ceramic Materials Used in Dentistry** - **Definition**: Ceramics are inorganic, non-metallic materials typically composed of compounds like oxides, carbides, and silicates. - **Key Properties**: - **Aesthetic**: Ex...

**CERAMICS** **1. Fundamental Properties and Characteristics of Ceramic Materials Used in Dentistry** - **Definition**: Ceramics are inorganic, non-metallic materials typically composed of compounds like oxides, carbides, and silicates. - **Key Properties**: - **Aesthetic**: Excellent translucency and ability to mimic natural tooth color. - **Biocompatibility**: Non-toxic and chemically inert in the oral environment. - **Hardness**: Highly resistant to wear, making them durable. - **Brittleness**: Prone to fracture under tensile or shear stress. - **Low Thermal Conductivity**: Prevents discomfort due to temperature changes. - **Stain Resistance**: Resists discoloration over time. **2. Differentiation Between Traditional and Advanced Ceramics** **Feature** **Traditional Ceramics** **Advanced Ceramics** ------------------ --------------------------------------- --------------------------------------------------------- **Composition** Predominantly feldspar-based Engineered materials like zirconia and alumina **Aesthetic** Excellent translucency, mimics enamel Some (e.g., zirconia) are less translucent but stronger **Strength** Moderate strength, brittle High strength and fracture toughness **Applications** Veneers, crowns Core materials, full-contour crowns, implants **Examples** Feldspathic porcelain Zirconia, alumina, lithium disilicate **3. Classification of Dental Ceramics** - **By Composition**: 1. **Feldspathic Ceramics**: High aesthetics, used for veneers. 2. **Glass Ceramics** (e.g., Lithium Disilicate): Combines strength and translucency. 3. **Polycrystalline Ceramics** (e.g., Zirconia): Opaque but extremely strong. - **By Processing Technique**: 4. **Sintered Ceramics**: Made by heating powdered material. 5. **Pressed Ceramics**: Molded under heat and pressure for high density. 6. **CAD/CAM Ceramics**: Milled from pre-sintered or fully sintered blocks. - **By Clinical Application**: 7. **Veneers and Inlays/Onlays**: Feldspathic and glass ceramics. 8. **Crowns and Bridges**: Glass ceramics and zirconia. 9. **Implants and Substructures**: Zirconia for strength. **4. Mechanical Properties of Dental Ceramics** - **Hardness**: High hardness means resistance to wear but can wear opposing teeth if polished poorly. - **Strength**: - Flexural Strength: Ability to resist bending (e.g., zirconia \> lithium disilicate \> feldspathic porcelain). - **Fracture Toughness**: - Measures resistance to crack propagation. Zirconia has the highest toughness among dental ceramics. - **Elastic Modulus**: Reflects stiffness; high in ceramics, but this contributes to brittleness. - **Limitations**: Brittle behavior under tensile stress; prone to chipping or fracturing. **5. Processing Techniques for Dental Ceramics** - **Sintering**: - Powdered ceramics are heated below their melting point to bond particles. - Common in zirconia and alumina fabrication. - **Firing**: - Involves heating ceramics with glaze to improve aesthetics and strength. - Used for feldspathic porcelains. - **Pressed Ceramics**: - Ceramic material is heated and injected into a mold under pressure. - Common for lithium disilicate restorations. - **CAD/CAM Milling**: - Computer-aided design and manufacturing. - Ceramics are milled from blocks (e.g., zirconia, lithium disilicate). - Offers precision, speed, and consistency. - **Glazing and Polishing**: - Enhances aesthetics and reduces surface roughness, improving wear resistance and preventing opposing tooth wear. **Summary Table** **Aspect** **Key Points** ----------------------------- ------------------------------------------------------------------------------- **Properties** Aesthetic, biocompatible, brittle, stain-resistant **Traditional vs Advanced** Aesthetic focus vs strength and toughness **Classification** By composition (feldspathic, glass, polycrystalline), processing, application **Mechanical Properties** Hardness, strength, fracture toughness, elastic modulus **Processing Techniques** Sintering, firing, pressing, CAD/CAM milling, glazing