Properties of dental materials lecture

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Properties of dental materials lecture

  1. 1. U L F A T
  2. 2. PROPERTIES OF DENTAL MATERIALS By DR. YAWAR HAYAT KHAN BDS (Pb), M.Sc. (London) Assistant Professor/Head of Department (Dental Materials) ISLAMIC INTERNATIONAL MEDICAL COLLEGE (DENTAL SECTION) U L F A T
  3. 3. STRUCTURE OF DENTAL MATERIALS <ul><li>The fundamental structure of dental materials has to be understood to understand the properties of dental materials </li></ul><ul><li>Structure of dental materials is based on </li></ul><ul><ul><ul><li>Arrangement of matter </li></ul></ul></ul><ul><ul><ul><li>Surface properties of matter </li></ul></ul></ul>
  4. 4. 1. ARRANGEMENT OF MATTER MATTER A. MICROSCOPIC B. MACROSCOPIC PRIMARY FORCES SEC O NDARY FORCES IONIC COVELANT METALLIC VAN DER WALLS SOLID LIQUID GAS COLLOID SOLIDIFICATION CONDENSATION SUBLIMATION
  5. 5. A. MICROSCOPIC ARRANGEMENT <ul><li>At microscopic level, matter is made up of atoms </li></ul><ul><li>These atoms have specific arrangements which varies for solids, liquids & gases </li></ul><ul><li>Atoms are held together by means of binding forces </li></ul><ul><li>The bonding forces may be primary or secondary </li></ul><ul><ul><ul><li>Primary </li></ul></ul></ul><ul><ul><ul><ul><li>They hold the atoms by cohesive forces </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Chemical in nature </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Three types: ionic, covalent & metallic </li></ul></ul></ul></ul><ul><ul><ul><li>Secondary </li></ul></ul></ul><ul><ul><ul><ul><li>Van der walls forces </li></ul></ul></ul></ul><ul><ul><ul><ul><li>They are secondary physical forces </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Form weaker bonds than primary bonds </li></ul></ul></ul></ul>
  6. 6. B. MACROSCOPIC ARRANGEMENT <ul><li>At macroscopic level, matter exists in one of the following forms depending on the distribution of atoms </li></ul><ul><ul><ul><li>Solids </li></ul></ul></ul><ul><ul><ul><li>Liquids </li></ul></ul></ul><ul><ul><ul><li>Gases </li></ul></ul></ul><ul><ul><ul><li>Colloids </li></ul></ul></ul><ul><ul><ul><li>Others </li></ul></ul></ul>
  7. 7. <ul><ul><ul><li>Solids </li></ul></ul></ul><ul><ul><ul><ul><li>Definite molecular strucuture </li></ul></ul></ul></ul><ul><ul><ul><ul><li>High attraction forces & kinetic energy, e.g., metals </li></ul></ul></ul></ul><ul><ul><ul><ul><li>High resistance to deformation </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Some solids are SEMI-RIGID LIQUIDS or SUPER-COOLED LIQUIDS called as AMORPHOUS SOLIDS e.g., glasses </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Atoms can be arranged in either crystalline structure or noncrystalline structure </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Crystalline structures have definite shapes, e.g., cubic, hexagonal & monoclinic (gypsum products) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Non-crystalline structures have no definite shapes and on heating they soften to liquids, e.g., dental impression compound, fused porcelain & glasses </li></ul></ul></ul></ul>
  8. 8. <ul><ul><ul><li>Liquids </li></ul></ul></ul><ul><ul><ul><ul><li>Lesser degree of arrangement than solids </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Greater mobility of atoms </li></ul></ul></ul></ul><ul><ul><ul><li>Gases </li></ul></ul></ul><ul><ul><ul><ul><li>They lack even lesser arrangement of atoms in liquids </li></ul></ul></ul></ul><ul><ul><ul><ul><li>By the process of condensation, gases can form liquids </li></ul></ul></ul></ul><ul><ul><ul><li>Colloids </li></ul></ul></ul><ul><ul><ul><ul><li>Described by Thomas Grahm in 1896 </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Greek word Kolla (Glue), Iode (like) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Basic requirement is particle size should be 1-500 nm </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Exists in two phases: dispersed phase & dispersion medium </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Most commonly used materials in dentistry hydrocolloids, e.g., alginates & agar agar </li></ul></ul></ul></ul>
  9. 9. <ul><ul><ul><li>Other types </li></ul></ul></ul><ul><ul><ul><ul><li>Allotropic forms </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>For example oxygen (O 2 ) and Ozone (O 3 ) are the allotropic forms of same element oxygen </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><li>Polymorphic forms </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>For example silica (SiO 2 ), exits in four different forms </li></ul></ul></ul></ul></ul>
  10. 10. 2. SURFACE PROPERTIES OF MATTER <ul><ul><ul><li>Interaction & exchange between phases </li></ul></ul></ul><ul><ul><ul><li>Adsorption </li></ul></ul></ul><ul><ul><ul><li>Absorption </li></ul></ul></ul><ul><ul><ul><li>Sorption </li></ul></ul></ul><ul><ul><ul><li>Cohesion </li></ul></ul></ul><ul><ul><ul><li>Adhesion </li></ul></ul></ul><ul><ul><ul><li>Surface wettability </li></ul></ul></ul><ul><ul><ul><li>Diffusion </li></ul></ul></ul>
  11. 11. <ul><ul><ul><li>Adsorption </li></ul></ul></ul><ul><ul><ul><ul><li>When dissimilar materials are in intimate contact with each other there is a surface action </li></ul></ul></ul></ul><ul><ul><ul><ul><li>There is no penetration of material from one surface into the other </li></ul></ul></ul></ul><ul><ul><ul><li>Absorption </li></ul></ul></ul><ul><ul><ul><ul><li>Substance particle usually penetrate the surface of the solid surface </li></ul></ul></ul></ul><ul><ul><ul><ul><li>A combination of adsorption & diffusion occurs </li></ul></ul></ul></ul><ul><ul><ul><ul><li>E.g., hydrocollids absorb water (imbibition) </li></ul></ul></ul></ul>
  12. 12. <ul><ul><ul><li>Sorption </li></ul></ul></ul><ul><ul><ul><ul><li>When both adsorption and absorption coexist it is called sorption </li></ul></ul></ul></ul><ul><ul><ul><ul><li>For example in denture base resins a layer of saliva is present in close contact (adsorption) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Due to sorption property some water is also absorbed into the resin </li></ul></ul></ul></ul>
  13. 13. <ul><ul><ul><li>Cohesion </li></ul></ul></ul><ul><ul><ul><ul><li>Occurs between two like particles </li></ul></ul></ul></ul><ul><ul><ul><ul><li>For example particles of saliva present beneath the denture base </li></ul></ul></ul></ul><ul><ul><ul><li>Adhesion </li></ul></ul></ul><ul><ul><ul><ul><li>Occurs between two unlike substances </li></ul></ul></ul></ul><ul><ul><ul><ul><li>For example, saliva in denture base resin </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Adhesive – material used to produce adhesion </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Adherened – substance to which adhesive is applied </li></ul></ul></ul></ul>
  14. 14. <ul><ul><ul><li>Surface Wettability </li></ul></ul></ul><ul><ul><ul><ul><li>The ability of adhesive to wet the surface of adherend </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Measured by contact angle on the surface </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Greater contract angle -> poor wetting </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Lower contact angle -> partial wetting </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Zero contact angle -> complete wetting </li></ul></ul></ul></ul>
  15. 15. <ul><ul><li>Diffusion </li></ul></ul><ul><ul><ul><ul><li>Diffusion of a solvent occurs from a higher concentration to a lower concentration through a membrane </li></ul></ul></ul></ul><ul><ul><ul><ul><li>In dentistry, diffusion occurs when from one material of a given concentration diffuses into another of a different concentration </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Diffusion into dentine occurs by this process </li></ul></ul></ul></ul>
  16. 16. THANK YOU To be continued ….

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