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Questions and Answers
What is the unit of density as described in dental biomaterials?
What is the unit of density as described in dental biomaterials?
Which property measures the ability of material to transfer heat?
Which property measures the ability of material to transfer heat?
Why is low density important for an upper denture?
Why is low density important for an upper denture?
What does the co-efficient of thermal conductivity (K) represent?
What does the co-efficient of thermal conductivity (K) represent?
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What effect does low thermal conductivity have during dental procedures?
What effect does low thermal conductivity have during dental procedures?
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What is the clinical significance of thermal conductivity in dental fillings?
What is the clinical significance of thermal conductivity in dental fillings?
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What does specific heat refer to in physical properties?
What does specific heat refer to in physical properties?
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Which of the following is not a mass-related property?
Which of the following is not a mass-related property?
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What is the primary clinical significance of closely matching the coefficient of thermal expansion between restorative materials and teeth?
What is the primary clinical significance of closely matching the coefficient of thermal expansion between restorative materials and teeth?
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What occurs as a result of breakage of the marginal seal due to percolation?
What occurs as a result of breakage of the marginal seal due to percolation?
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What is defined as the temperature at which a material transitions between solid and liquid states?
What is defined as the temperature at which a material transitions between solid and liquid states?
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What does the heat of fusion measure?
What does the heat of fusion measure?
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Which of the following best describes specific heat?
Which of the following best describes specific heat?
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How does metallic denture base material contribute to tissue health?
How does metallic denture base material contribute to tissue health?
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What is represented by the linear coefficient of thermal expansion (α)?
What is represented by the linear coefficient of thermal expansion (α)?
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Why is it important for porcelain and metal to match in ceramo-metallic restorations?
Why is it important for porcelain and metal to match in ceramo-metallic restorations?
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What property distinguishes metals from non-metals regarding specific heat?
What property distinguishes metals from non-metals regarding specific heat?
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What is thermal diffusivity primarily concerned with?
What is thermal diffusivity primarily concerned with?
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What types of light production involve the passing of electric current through gas?
What types of light production involve the passing of electric current through gas?
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What is the definition of refraction in optics?
What is the definition of refraction in optics?
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Why is a smooth and polished surface important in dental restorations?
Why is a smooth and polished surface important in dental restorations?
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What effect can high thermal conductivity and low specific heat have on dental materials?
What effect can high thermal conductivity and low specific heat have on dental materials?
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What is scattering in the context of light interaction with matter?
What is scattering in the context of light interaction with matter?
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What does the refractive index represent in optics?
What does the refractive index represent in optics?
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What is one of the characteristics of laser light?
What is one of the characteristics of laser light?
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In which type of clinical application is laser used for coagulation of blood?
In which type of clinical application is laser used for coagulation of blood?
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What is defined as the degree of saturation or strength of a particular hue?
What is defined as the degree of saturation or strength of a particular hue?
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Which medium is used in a CO2 laser?
Which medium is used in a CO2 laser?
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What is the perceived color when both hue matches the adjacent dentition but the value is too high?
What is the perceived color when both hue matches the adjacent dentition but the value is too high?
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What must happen for an object to be visible?
What must happen for an object to be visible?
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Who developed the Munsell color system used to describe color dimensions?
Who developed the Munsell color system used to describe color dimensions?
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What is the purpose of using multiple light sources during color matching?
What is the purpose of using multiple light sources during color matching?
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What property of a transparent material allows light to pass through with little distortion?
What property of a transparent material allows light to pass through with little distortion?
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What defines a material as opaque?
What defines a material as opaque?
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Which property of tooth enamel is best described by allowing some light to pass while scattering or reflecting the rest?
Which property of tooth enamel is best described by allowing some light to pass while scattering or reflecting the rest?
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What phenomenon occurs when an object emits light immediately after being excited by ultraviolet waves?
What phenomenon occurs when an object emits light immediately after being excited by ultraviolet waves?
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What type of materials are formulated with fluorescing agents to enhance the aesthetic appearance in dentistry?
What type of materials are formulated with fluorescing agents to enhance the aesthetic appearance in dentistry?
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Which color of material absorbs all light colors?
Which color of material absorbs all light colors?
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What occurs during the phosphorescence process in materials?
What occurs during the phosphorescence process in materials?
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Which of the following best describes the term 'LASER'?
Which of the following best describes the term 'LASER'?
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What is metamerism in the context of color matching?
What is metamerism in the context of color matching?
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Which of the following describes an isomeric pair?
Which of the following describes an isomeric pair?
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What feature distinguishes the VITA SYSTEM 3D-MASTER shade guide?
What feature distinguishes the VITA SYSTEM 3D-MASTER shade guide?
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Which method involves taking a photograph of shade guide teeth next to a patient's teeth?
Which method involves taking a photograph of shade guide teeth next to a patient's teeth?
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What is the purpose of a dental shade guide?
What is the purpose of a dental shade guide?
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Which of the following shade guides contains 20 tabs including bleach shades?
Which of the following shade guides contains 20 tabs including bleach shades?
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How does a chair side colorimeter determine tooth shade?
How does a chair side colorimeter determine tooth shade?
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What is the main goal of shade color matching in dentistry?
What is the main goal of shade color matching in dentistry?
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Study Notes
Dental Biomaterials I - Lecture 5: Physical Properties of Dental Materials
- Physical properties are based on laws of physics (mass, heat, light, electricity, energy, force, and other physical phenomena).
- Mechanical properties are a subgroup of physical properties, dealing with force.
- This chapter provides background and preparation for later discussions on how these properties determine characteristics of dental materials.
Mass-Related Properties: Density
- Density is the mass per unit volume of a material.
- Units are gm/cm³ and pound/in³.
- Clinical importance:
- Upper dentures need low density for retention.
- Low-density molten alloys need higher pressure during casting to fill molds.
Thermal Properties
- Thermal Conductivity: Ability of a material to transfer heat. Lower conductivity means slower heat transfer.
- Coefficient of Thermal Conductivity (k): Amount of heat transported per second across a unit cube when one face is hotter.
- Thermal Coefficient of Expansion (α): Change in length per unit length for a 1°C change in temperature.
- Melting and Freezing Temperatures: Temperatures at which a material changes from solid to liquid or vice-versa. Critical for casting procedures.
- Heat of Fusion: Amount of heat required to convert 1 gram of a substance from solid to liquid state.
- Specific Heat: Amount of heat in calories needed to raise the temperature of 1 gram of a substance by 1°C. Metals have low specific heat, while non-metals have high specific heat.
- Thermal Diffusivity: Rate at which a material converts from non-uniform to uniform temperature. -Important for: -Gold or amalgam restorations: These may cause thermal shock due to their high thermal diffusivity, high thermal conductivity, and low specific heat.
Optical Properties
- Optics: Science of studying light, sight, vision (including color).
- Importance: Restorative dentistry seeks to restore tooth color/appearance. Knowledge of light & color is essential.
- Nature of Light: Light is a beam of photons, color is determined by wavelength of light.
-
Production of Light:
- Thermal (e.g., sun, hot metal)
- Electrical (e.g., passing electric current through an inert gas)
- Chemical (fluorescence, phosphorescence)
-
Interaction of Light and Matter
- Reflection (specular and diffuse): Specular reflection occurs on smooth surfaces (e.g., mirrors) where the angle of incidence equals the angle of reflection. Diffuse reflection occurs on rough surfaces, scattering light in all directions. Smooth surfaces are important for restorations to reflect light and appear natural.
- Refraction: Change in the direction of light as it enters a different medium. Important for the matching of refractive indices of restorative materials & tooth structures.
- Scattering: Redirection of light rays by inclusions (e.g., air bubbles) in a material. In composites, scattering centers (opacifiers) cause light to emerge in all directions, leading to opaque or semi-opaque materials.
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Properties of Materials Related to Light Transmission/Absorption:
- Transparency: Allows light to pass through without significant distortion (e.g., glass).
- Translucency: Allows some light to pass through, scattering or reflecting the rest (e.g., tooth enamel).
- Opacity: Prevents light from passing through (e.g., amalgam).
- Luminescence (Fluorescence and Phosphorescence): Emitting light in response to stimulation. Fluorescent emit light immediately after stimulation, while phosphorescent light continues after stimulation ceases.
-
Importance in Dentistry:
- Teeth fluoresce under UV light.
- Restorative materials used in dentistry may be formulated with fluorescent agents to create a more natural appearance.
Laser
- Light Amplification by Stimulated Emission of Radiation (LASER)
- Production of laser light: Solid, liquid, or gas medium excited by high energy to produce special light.
- Characteristics: Monochromatic (single wavelength), Coherent (waves in-phase), Collimated (parallel beams).
Clinical Application of Laser
- Surgery: Removal of soft tissue, Tissue regeneration, ulcer healing, blood coagulation.
- Dentistry: Removal of initial carious lesions, curing composite, endodontics, filling pits & fissures.
- Laboratory:* Welding of high-melting alloys, sintering of ceramics
Color
- Color perception: Object visibility depends on reflecting light. Light is reflected, focused on retina (converted to nerve impulses), transmitted to brain.
- Cone cells (retina): Responsible for color vision.
-
Color Definitions:
- Hue (dominant wavelength): Name of color.
- Chroma (spectral purity): Saturation/intensity of a color.
- Value (Luminous reflectance): Lightness or darkness of a color.
-
Color Matching:
- Color match ideal done under multiple light sources
- Metamerism: Change in color match when observed under different light sources.
- Isomeric colors: Match under all light sources.
Shade Color Matching
- Used to determine natural tooth color for restorations.
- Shade guides: Standard color standards mimicking dental structures.
- Used to visually match restorations to natural teeth.
- Popular tools like Vitapan 3D-Master and Chromascop.
- Photocolorimetry and chair-side colorimeters facilitate accurate color matching.
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Description
Test your knowledge on the physical and mechanical properties of dental materials covered in Lecture 5 of Dental Biomaterials I. This quiz focuses on concepts such as density, thermal conductivity, and their clinical implications for dental applications.
