Properties of Dental Materials PDF

Lecture 2: Properties of Dental Materials a surface of a solid that is measured from the solid surface Wettability through the liquid to the Measure of the affinity of a liquid for liquid/vapor tang...

Lecture 2: Properties of Dental Materials a surface of a solid that is measured from the solid surface Wettability through the liquid to the Measure of the affinity of a liquid for liquid/vapor tangent line a solid as indicated by spreading a originating at the terminus of the drop. liquid/solid interface; used as a Degree of wetting depends on the relative. Surface energies of the measure of wettability, whereby solids and liquids and on their no wetting occurs at a contact intermolecular attraction angle of 180, and complete wetting occurs at an angle of 0. Adhesion: An attraction between two contacting surfaces Micromechanical bonding: promoted by the interfacial force Retention associated with an of attraction between the adhesive penetrating a molecules or atoms of two roughened adherend surface. different species; adhesion may Surface energy: The excess occur as chemical adhesion, energy of attraction that the mechanical adhesion (structural surface of a material (liquid and interlocking), or a combination of solid) as compared with the bulk both. of the material because molecules or atoms at the surface Adherend and adhesive: are not surrounded by their Substance that promotes fellows as those in the bulk. It can adhesion of one substance or be treated as the work (energy) material to another. An adherend required to build an area of a is a material substrate bonded to particular surface and has the another material by means of an unit of mN/m2. adhesive. Surface tension: Bonding: The action of joining objects or particles together by The tendency of fluid surfaces to means of adhesive or force of contract to the smallest surface attraction. area by an inward force caused by the imbalance of mutual Cohesion: Bonding between attraction between molecules on molecules or atoms of the same the liquid surface. species. The very inward force also keeps Contact angle: Angle of the molecules of the surface intersection between a liquid and constantly under tension.  The cohesive force keeping Terminologies molecules bonded on the surface is known as the surface tension of Stress the liquid, with the unit of mN/m. Force per unit area that develops within a material when an Wetting and wetting agent: external force is applied Wetting is the ability of a liquid to maintain contact with a solid Strain surface; it reflects the Calculated change in length intermolecular interactions when divided by the initial reference the two are brought in intimate length contact. A wetting agent is a surface-active Shear stress substance that can be applied to Time dependent plastic strain of a a solid substrate to reduce the solid under a static or constant surface tension of the liquid to be load. placed on the solid; the purpose is to promote wetting or Newtonian adhesion. Viscosity does not change Dilatant Properties Rate of flow decreases with Characteristics or trait that you increasing strain until it reaches a can use to describe matter by nearly constant value observation. Pseudoplastic Rate of flow increases with Properties of dental materials increasing strain 1. Rheology/Viscosity: Study of Plastic deformation and flow Behave like rigid material until characteristic of matter whether some minimum amount of strain liquid or solid/ Viscosity is applied Resistance to fluid flow. Thixotropic Viscosity depends on previous 2. Physical Properties deformation of the liquid. 3. Mechanical Properties Materials becomes less viscous 4. Thermal Behaviors and more flowable upon 5. Adhesion/Adherend repeated applications of 6. Working/Setting time pressure. 7. Biological Properties/Biocompatibility  Shear rate a natural, pleasing effect in the The rate at which s fluid is dentition. sheared or worked during flow. 3 Dimension of color space: Creep Hue: Dominant color of an Time dependent plastic strain of a object solid under a static or constant Value: Relative darkness or load. lightness of a color or grey Sag scale Irreversible deformation of metal Chroma: Degree of saturation frameworks of fixed dental of a particular color. prosthesis in the firing temp range of ceramic veneers. 3D Munsell Color Space Physical Properties Any property that is measurable Can be measured or observe without changing the chemical nature of the substance. Based on laws of Mechanics Acoustics Optics Thermodynamics Electricity Magnetism Radiation Atomic Structure Nuclear Phenomenon L*A*B Color chart Color Density Volume Mass Boiling point Melting point Physical Properties COLOR Esthetics: Principles and techniques associated with L: Hue development of color and A: Red-Green Axis appearance required to produce B: Yellow Blue Axis  Fluorescence Natural tooth absorbs light of short wave length, Too short to be visible to human eye. 300 nm- 400nm ultraviolet radiation Energy tooth absorb becomes light with longer wave length Protanopia The tooth becomes a light source Color blindness Reflection: Specular reflectance (Mirror Like) Diffuse reflectance Absorption Refraction A Change of direction that light undergoes when it enters a medium with a different density from the one through which it Radiopacity has been travelling. Opacity to the radio wave and x- Transmission ray portion of the Passing through unchanged electromagnetic spectrum. Opacity Radiolucency Related to amount of light it can Dark areas shown on dental x-ray absorb or scatter. Absorbs more representing a void or an area of light. tissue that is less dense. Translucency Absorbs less light Properties of Dental Materials Part ll Transparency Absorbs no light Standards for Dental Materials Transparent materials transmit ADA specification program 100% of the light. (Council of scientific affairs): Refractive index Specification number. Measure of the bending of a ray US FDA of a light when passing from one FDI specification (Federation medium to another. Dentaire Internationale) Enamel IDO (TC 106 – Dentistry) Reflect, Absorb, Refract, International Organization of Transmits some light. standardization. TC 106 responsible to standardize  terminologies, Test methods, ability to conduct electrical Develop standards for dental current either by means of frere materials. electrons in metals or via ions in Heat Transmission solution. Thermal conductivity: The Chemical corrosion: or dry quantity of heat in calories per corrosion is the direct second. combination metallic and Kelvin (Formula ppt) nonmetallic elements to yield a Thermal conductivity: Physical chemical compound properties that governs heat Anode: Surface or sight on a transfer through a material by surface where positive ions are conductive flow. formed with production of free Thermal conductors: Materials electrons with high material conductivity Cathode: Surface or sight where including metals metal ions are deposited from Thermal insulators: Materials saturated solution and consume with low thermal conductivity free electrons produced at the including resins anode. Thermal diffusivity: Measure of Electrolyte: A substance that the speed with which a produces an electrically solution temperature change will spread when dissolved in a polar solvent through an object when one such as water. surface is heated Specific heat: Quantity of heat needed to raise the temperature of a unit mass. Coefficient of thermal expansion: A Change per un its length per unit of the original length of a material. When its temperature is raised 1-degree Celsius. Electrochemical properties Tarnish: Surface discoloration on a metal or a slight loss or altercation of the surface finish or luster. Usually forerunner of corrosion. Corrosion: Electrochemical process and is dependent on the  Compressive Stress When the body is subjected to 2 sets of forces in the same straight line but directed towards each other. Tensile Stress Crevice Corrosion: Corrosion When is is subjected to 2 sets of occurring in confined spaces to forces that are directed away which the access of working fluid from each other in the same from the environment is limited. straight line. These spaces are generally called Shear Stress crevices. Result of 2 forces directed parallel to each other. Pitting corrosion occurs across Bending moment/Flexural the surface of a component Force per unit area of a material crevice it is associated with a that is subjected to flexural crevice. loading Twisting Moment/Torsion Galvanic shock: Combination of Result of 2 rotational forces similar metals are indirect directed towards/away from each physical contact may produce other. galvanic corrosion. Young’s modulus or modulus of elasticity Relative stiffness or rigidity of a Mechanical Properties material. Ratio of the stress to the strain of Types of stress: a material within elastic behavior. Compressive Tensile Shear Twisting moment/Torsion Bending moment/Flexural  Stress value just above Elastic Limit proportional limit in which there The maximum stress a material is already a permanent strain can withstand before it becomes Resilience plastically deformed. The amount of energy absorbed Maximum Flexibility within a unit volume of a Defined as the flexural strain that structure when it is stressed to its occurs when the material is proportional limit. stressed to its proportional limit. Toughness The amount of elastic and plastic Hooke’s Law deformation energy required to Law of elasticity fracture a material. For relatively small deformation of an object or the displacement or size of the deformation is directly proportional to the deforming force or load. Under these conditions the object returns to its original shape and size upon removal of the load. Proportional Limit The stress above which stress is no longer proportional to strain. Yield strength/Proof stress The stress required to produce a Flexural Strength/Transverse given amount if plastic strain. strength/Modulus of rupture. Ultimate strength Force per unit area at the instant Measure of stress required to of fracture in a test specimen fracture a material. subjected to flexural loading. Elastic limit Brittleness maximum stress which a material Is the relative inability of a can endure without undergoing material to sustain plastic plastic/permanent deformation deformation before fracture of Proportional limit the material occurs. maximum stress at which stress is Ductility proportional to strain Is the ability of a material to be Yield strength stretched plastically at a room temperature without fracturing percent elongation. Malleability a traction between molecules or The ability of a material to sustain atoms of 2 different species. a considerable permanent Success of dental materials deformation without rupture Material properties under compression as in Design of dental device hammering or rolling into a sheet Biocompatibility of component percent compression. materials. Biological Properties: Ductile Non toxic Gold, Silver and Platinum Non irritant Malleable No carcinogenic or allergic Gold, Silver, Copper potential Bioinert: Remains unchanged Hardness Test from activity of biologic Brinell (BHN): Not for brittle organisms and does not illicit materials or plastics that exhibits biologic activity. elastic recovery, For metals No adverse event. Rockwell: Not for brittle materials Biocompatibility or plastics that exhibits elastic Ability of biomaterial to perform recovery, For metals its desired function with respect Knoop: For hard, soft and brittle to a medical therapy materials. Without eliciting any undesirable Vickers (VHN): For brittle local or systemic effects in materials recipient or beneficiary of that Shore: For rubber and plastic therapy. Barcol: For rubber s and plastic Biocompatibility depends on The chemical and physical nature Bonding of its components Teeth bonding is a procedure in The types and locations of which a tooth colored resin patient’s tissue that will be material (A durable plastic exposed to the device. material) is applied and hardened Duration of exposure with a special light which Surface characteristic of a ultimately bonds the material to material the tooth to restore or improve a Amount and nature of substances person’s smile eluted from the material. Adhesion Molecular or atomic attraction Selecting Biocompatible materials between 2 contacting surfaces Define intended use and promoted by interfacial forces of indications of dental materials  Identify the main components of dental materials