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DENTAL MATERIALS  Lesson #1 Dental materials: Background and history Ancient Origins Dental material Science that deals with the study of materials used in dentistry, which includes chemical properties, p...

DENTAL MATERIALS  Lesson #1 Dental materials: Background and history Ancient Origins Dental material Science that deals with the study of materials used in dentistry, which includes chemical properties, physical properties, manipulation, and their applications in dental practice Classifications of dental materials 18th century: Developing profession Preventive Dental materials Pit and Fissure Sealant, Glass Ionomers Ambroise Paré (1509-1590), a surgeon to four kings, used lead or cork for tooth fillings. Restorative Materials repair or replace tooth structure may be used as short-term (temporary) or long-term, direct or indirect material Queen Elizabeth I (1533-1603) Auxiliary Materials used cloth fragments to fill the cavities in her teeth. Ideal Restorative Material Biocompatible Bond permanently to tooth structure Modern dentistry Similar properties to enamel, dentin and Begun when Fauchard published a treatise other tissues describing many types of dental restorations, Natural appearance including construction of denture made of ivory Initiates tissue repair or regeneration Pierre Fauchard (1678-1761), known as the Father of modern dentistry used tin foil or lead cylinders to fill tooth cavities  PROPERTIES OF DENTAL MATERIALS Advances in Science and Education - 19th century Brief History 1728 - Pierre Fauchard described a method for the construction of artificial dentures by carving them from ivory. In 1935 polymerized acrylic resin was introduced as 1895 - Dr. G.V. Black developed many a denture base material to support artificial teeth. scientific principles involved in the selection 1907, Taggert developed a more refined method for and manipulation of dental materials, Many of producing cast inlays those fundamentals are valid for materials used today. 1919 - National Bureau of Standards (National Institute of Standards and Technology) - dental amalgam 1928 - dental research was taken over by the American Dental Association (ADA) ADA Council on Scientific Affairs (CSA) ADA Standards Committee for Dental Products (SCDP) International Standards Fédération Dentaire Internationale (FDI) International Organization for Standardization (ISO) Types of Dental Materials ADA SPECIFICATION NUMBER Restorative ANSI/ADA No. Indirect Restorative Material No. 1 Alloy for Dental Amalgam Direct Restorative Material Temporary Restorative Material Preventive Auxiliary Materials No. 25 Dental Gypsum No. 3 Dental Impression Compound Common ADA Specification number for Dental Material Esthetic ADA Nos. 6 - Dental Mercury ADA Nos. 7 - Dental Wrought Gold Wire Alloy ADA Nos. 8 - Dental Zinc Phosphate Cement ADA Nos. 9 - Dental Silicate Cement ADA Nos. 11 - Dental Agar impression material ADA Nos. 18 - Alginate impression material Color and Optical Effect ADA Nos. 19 - Dental Elastomeric Impression Material Esthetics - the art and science applied to ADA Nos.25 - Dental Gypsum Products create or enhance the beauty of an ADA Nos. 26 - Dental Xray Equipment individual within functional and physiological ADA Nos. 27 - Resin-based filling materials limits. Restoring the color and appearance ADA Nos. 32 - Onthodontic wires of natural dentition ADA Nos. 39 - Pits and Fissure Sealants Hue: The dominant color of an object Rheology (red, blue, yellow, green etc) The study of the deformation and flow characteristics of matter Value: known as the gray scale, lightness or darkness of a color Chroma: the degree of saturation of a particular hue Viscosity - resistance of a fluid to flow measured in units of megapascals (MPa) per second or centipoise (cP) Fluidity - Measure of Ease and Flow High viscous materials flows slowly Low Viscous Materials flows fast Thermal Properties THERMAL CONDUCTIVITY is the physical Thixotropy property that governs heat transfer through a A thixotropic material has a low flow under material by the conductive flow. no load but flows readily when placed under Conductors - high thermal conductivity a load. - higher ability to transmit Structural Relaxation thermal energy Creep The progressive deformation of material at constant stress Is defined as the time dependent plastic Insulators - low thermal conductivity strain of a material under a static load or - materials that has low thermal constant stress. conductivity - lower ability to transmit thermal energy Thermal Properties THERMAL DIFFUSIVITY is a measure of the speed with which a temperature change will spread through an object when one surface is heated. COEFFICIENT OF THERMAL EXPANSION is defined as the change in length per unit of the original length of a material (material expand) when its temperature is raised 1 Celsius Clinical Application (CTE) COEFFICIENT OF THERMAL EXPANSION is defined as the change in length per unit of the original length of a material (material expand) when its temperature raised 1 °C. Electrochemical Properties Corrosion a result of electrochemical reactions and occurs when most or all of the atoms on the metal surface are oxidized, damaging the entire surface. - Dissolution of metals in the mouth Galvanism - the generation of electrical currents that the patient can feel - results from the presence of DISSIMILAR metals in the mouth Tarnish the surface reaction and discoloration of metals in the mouth from components in saliva or foods  LESSON #2 MECHANICAL PROPERTIES OF DENTAL MATERIALS 2. Compressive stress Deformation: Shrinkage Mechanical properties - physical science dealing with forces that act on bodies and the resultant motion, 3. Shear stress deformation, or stresses that those Deformation: shear bodies experience. Force: shear 4. Twisting moment STRESS Deformation: Torsion Stress is the force (applied) per Force: Twisting moment unit area Force strength or energy as an attribute of physical or 5. Bending moment movement Newton - SI unit of Deformation: Bending force (N) Force: Bending moment STRAIN STRESS: BITING FORCE The change in length per unit length of a material produced by stress Example of force STRENGTH Ability of the prosthesis to resist an TYPES OF STRESS induced stress without fracture or 1. Tensile stress permanent deformation (plastic strain) Deformation: Elongation A. Yield strength Force: Axial The stress and material can we stand without permanent formation or a point at which it will no longer return to its original dimensions.  B. Ultimate strength HOOKE’S LAW The stress at which fracture occurs Law of elasticity Robert Mooke ; 1660 STRESS-STRAIN CURVE States that force needed to extend or compress Gives the relationship between stress and strain a spring is proportional to that distance The curve helps us to understand how a given material deforms with increasing loads or force CONDITION: object returns to its original shape and size upon removal of the load Proportional limit The maximum stress that a dental materials sustains without any deviation Highest stress at which the stress-strain curve is a straight line/linear ELASTIC AND PLASTIC DEFORMATION Elastic Deformations This diagram shows us stress train intention for A temporary shape dental gold alloy. As you can see, the stress is change that is self-reversing after the measured as megapascal, which is actually a unit for force is removed, so that the object force and we have strain here. Now as the material returns to its original shape Temporary/ is subjected to greater force from zero to around Reversible 275 megapascal, note the change in linear or Plastic Deformations straight pattern. This is called the proportional Stress is sufficient to permanently limit. After that, the material has started the show deform the metal Permanent/ permanently formations on strength on this phase Irreversible the line is not straight anymore, but curve until it reaches ultimate strength around 600 megapascal where it fractured. Fracture occurs from tensile stress = tensile strength Fracture occurs from Compressive stress = compressive strength Fracture occurs from Shear stress = shear strength  Hardness The resistance of the material to indentation. Ductility Knoop harness the ability of a material to sustain a large a test mechanical hardness obtained by permanent deformation under a tensile load up to measurement of the length of an the point of fracture. indentation from a diamond indenter and calculating the number in kilograms required to give an indentation of 1 mm2. Malleability the ability of a material to sustain considerable permanent deformation without rupture under compression, as in hammering or rolling into a Vickers’s test sheet (e.g. Gold, iron, aluminum) referred to as a microhardness test method, is mostly used for small parts, thin sections, or case depth work Dimensional Change change is the percentage of shrinkage or expansion of a material. Wettability the measure of the affinity of a liquid for a solid as indicated by spreading a drop. Low Contact Angle = hydrophilic: good wettability High contact angle = hydrophobic; poor wettability Percent Elongation Amount of formation that a material can withstand before rupture is reported under tensile stress or compressive stress. Resilience and Toughness Resilience Ability of a material to absorb energy when elastically deformed and release it when unloaded. Toughness Material to absorb energy before a fracture occurs.