Physical Properties of Dental Materials PDF

# Textbook of Dental Materials ## Physical Properties of Dental Materials - Optical properties - Relative density - Thermal properties - Imbibition - Solubility - Viscosity - Wetting - Adhesion ## Optical Properties Optics is a part of physics studying the behavior and properties of ligh...

# Textbook of Dental Materials ## Physical Properties of Dental Materials - Optical properties - Relative density - Thermal properties - Imbibition - Solubility - Viscosity - Wetting - Adhesion ## Optical Properties Optics is a part of physics studying the behavior and properties of light. - Light is an electromagnetic wavelength of 380 to 760 nm, visible to the human eye. It causes a visual sensation. - The white light is heterochromatic; it contains all rays with wavelengths of the visible area. - The colored light is monochromatic, with a specific wavelength of the visible electromagnetic spectrum, perceived by the human eye as a single color. The monochrome light is obtained in two ways: - **From the white light:** by omitting only waves with a certain frequency through an optical device - filter or monochromator. - **From laser sources:** the word "laser" is an abbreviation from Light Amplification by Stimulated Emission of Radiation. A laser is a powerful source of monochromatic coherent light radiation that can pass great distances without any distraction, and can be focused with a high precision. ## Color The optical properties of the materials are a result from the interaction of light and human eye, and its awareness in the cortex. The color is a property of materials to absorb and reflect the visible light. 1. **Hue:** The hue is a color tone, e.g., red, green, blue. It is determined by the dominant wavelength of the reflected light. 2. **Chroma:** Chroma is the density, the intensity of the color. It determines the intensity of the selective reflection of the dominant reflected rays. 3. **Value:** Value is the brightness of the color. It is determined by the degree of the non-selective reflection of the light rays from the material, or by the amount of white, gray, or black in the color. ## Transparency and Opacity - The dental enamel has a high transparency, and as a result, the incisal edges of the anterior teeth look grayish. - The reverse quality of transparency is the opacity. Tooth dentin has a great opacity, and gives the basic color of the tooth with its hue, chroma, and value. - The combination of transparent and opaque materials creates a unique appearance. Teeth look semi transparent, or translucent. ## Fluorescence Some organic substances, called luminophores, tend to shine under certain impacts, such as heating, stress, friction, or ultraviolet light irradiation. This phenomenon is known as luminescence. - **Fluorescence**: a short illumination during the impact. - **Phosphorescence**: illumination continues after the termination of the exposure. # Thermal Properties ## Melting The melting is the process of passing a substance from a solid into a liquid state. It is most often from a crystalline state with arranged building elements into a liquid state where the orderliness disappears. | Material | Melting Temperature (°C) | |---|---| | Noble alloys | 750° - 1100° | | Chromium alloys | 1250° - 1450° | | Titanium alloys | 1600° - 1690° | | Platinum | 1769° | | Gold | 1063° | | Low-fusing porcelain | 960° | | Quartz | 1700° | | Bees wax | 60° - 64° | ## Thermal Conductivity Thermal conductivity is a transfer of thermal energy among the building elements of the bodies, without their translocation in the space. - **Coefficient of Thermal Conductivity (CTC)**: the quantity of heat in calories (cal) passing for a second (sec) through the body in the length of 1 cm, with a cross-section of 1 cm², when the temperature difference of both ends of the body is 1° C. | Material | Thermal Conductivity (cal cm/cm² sec °C) | |---|---| | Dental dentin | 0.0015 | | Dental enamel | 0.0022 | | Acrylic resin | 0.0005 | | Water | 0.0013 | | Porcelain | 0.0025 | | Composite material | 0.0026 | | Zinc phosphate cement | 0.0028 | | Gypsum | 0.0031 | | Silver | 1.000 | | Copper | 0.918 | | Gold | 0.710 | | Zinc | 0.270 | | Nickel | 0.220 | | Chromium | 0.160 | ## Thermal Volume Changes During the processes of heating and cooling, the materials increase or decrease their volume. The enlargement is proportional to the temperature. - **Coefficient of Thermal Expansion:** the change in the length of the material in mm.10s, when heating the material by 1° C. | Material | Coefficient of Thermal Expansion (mm.10-6) | |---|---| | Dental dentin | 10 | | Dental enamel | 15 | | Titanium | 11.9 | | Glass ionomer cement | 13 | | Low-fusing porcelain | 12-14 | | Nickel-chromium alloy | 14 | | Gold | 14.4 | | Gold alloy | 15 | | Silver amalgam | 25-30 | | Composite material | 30-70 | | Acrylic resin | 90 | | Modeling wax | 350 | ## Imbibition The imbibition or the absorption is the property of materials to absorb liquids. | Material | Water Absorption (mg/cm²) | |---|---| | Heat-curing acrylic resin | 0.69 | | Cold-curing acrylic resin | 2.08 | | Composite material | 2.6 | ## Solubility The solubility is the reduction of the volume of materials in contact with liquids. ## Viscosity The viscosity is the resistance of the liquid materials to the flow. | Material | Temperature (°C) | Viscosity (cps) | |---|---|---| | Water | 21 | 1 | | Acetone | 21 | 3 | | Gasoline | 21 | 5 | | Blood | 37 | 10 | | Zinc phosphate cement | 18 | 94700 | | | 25 | 43200 | | Zinc polyacrylate cement | 25 | 101000 | | | 18 | 109800 | | Alginate | 37 | 252000 | | Silicone impression cream | 37 | 95000 | | Silicone impression paste | 37 | 420000 | | Silicone impression putty | 37 | 1400000 | ## Wetting The wetting is a phenomenon on the boundary layer between the liquid and the solid bodies. It defines the ability for spreading a drop of liquid on a solid basis. The wetting is explained by the degree of cohesion forces in the liquid and the adhesion forces between the liquid and the solid. - **Contact angle (θ):** between the surface of the liquid and the solid. ## Adhesion The adhesion is the process of permanent connection, or bonding, between different materials and tissues. ### Mechanical - **Macromechanicl:** visible with the naked eye - **Micromechanicl:** visible with a microscope ### Chemical - **Ionic Bond** - **Van der Waals forces** ## Relative Density The density of a material is its mass per unit volume, and presented as g/cm³. | Material | Relative Density (g/cm³) | |---|---| | Wax | 0.96 | | Water | 1.00 | | Acrylic resin | 1.24 | | Porcelain | 2.4 | | Dentin | 2.14 | | Enamel | 2.97 | | Noble alloys | 14.0 - 18.0 | | Base alloys | 7.0 - 8.0 | | Gold | 19.3 | | Platinum | 21.45 | | Palladium | 12.02 | | Silver | 10.49 | | Copper | 8.96 | | Chromium | 7.19 | | Nickel | 8.9 | | Titanium | 4.51 |