Applied Health Science Technology Chapter 2

Chapter Two: Matter

• This chapter is for Applied Health Science Technology students in Fall 2024.
• The professor is Dr. Yasser Mostafa Abdallah.

Biomaterial Classification

• Biomaterials can be classified by their nature:
  • Metals: Amalgam, metallic denture base
  • Polymers: Acrylic resin (also called polymeric materials or adhesive materials)
  • Ceramics: Dental porcelain

Properties of Materials

• Materials are categorized based on microscopic and macroscopic properties.

Microscopic Properties

• Atomic structure: Includes atomic arrangement, e.g., sodium and chlorine.
• Crystal structure: Shows crystal lattice examples: cubic body centered (bcc), cubic face centered (fcc), hexagonal. Examples include Fe, V, Nb, Cr; Al, Ni, Ag, Cu, Au; Ti, Zn, Mg, Cd.

Macroscopic Properties

• Physical Properties: Based on physics laws. Describe mass, energy, force, heat, electricity, color, density, and thermal conductivity.
• Mechanical Properties: A subgroup of physical properties. Describe material's ability to resist forces.
• Chemical Properties: Describe setting reactions and corrosion.
• Biological Properties: Describe material's effect on living tissues.

Chemical Bonding

• A chemical bond is an attraction between atoms from sharing or complete transfer of electrons.

• Primary Bonds:

  • Ionic Bond: Electrons are completely transferred from one atom to another. This forms charged ions (cations and anions) that are attracted electrostatically. Example: Sodium (Na) reacts with Chlorine (Cl).
  • Covalent Bond: Atoms share one or more pairs of electrons, achieving a full valence shell.
    • Different types: Polar or nonpolar
      • Polar Covalent bond: Electrons are unequally shared between atoms due to differences in electronegativity.
      • Nonpolar Covalent bond: Electrons are shared equally. Example: H₂
  • Metallic Bond: Metal atoms lose their outer electrons to form metal cations. These free electrons are delocalized and move throughout the metal lattice. This delocalization of electrons accounts for conductivity and bonding in metals.

• Secondary Bonds:

  • Hydrogen Bond: Attractive force between a hydrogen atom bonded to a highly electronegative atom (like oxygen, nitrogen, or fluorine) and another electronegative atom in a separate molecule.
  • van der Waals Force: Weak, temporary attractive forces between atoms or molecules due to fluctuating charges.

Examples for the Different Bonds in Dentistry

• Covalent bonds join monomers in dental resin.
• Ionic bonds are found in gypsum investment, phosphate cement, and ceramic.
• Metallic bonds are not directly mentioned as used in dental materials but can be part of an alloy.

Periodic Table

• The periodic table is arranged by increasing atomic number.
• Groups or families (vertical columns) and Periods or series (horizontal rows) are shown.

Specific Element Groups

• Group IA (Alkali Metals): Soft metals, reactive, have one valence electron, soluble in water. Important elements include Li, Na, K, Rb, Cs, and Fr.
• Group IIA (Alkaline Earth Metals): Harder than alkali metals. They have two valence electrons. They are less reactive than alkali metals, but still react to oxygen and water. Important elements include Be, Mg, Ca, Sr, Ba, and Ra.
• Group VIA (The Oxygen Family): Contains oxygen and sulfur as common elements. Important elements for this group include O and S. They exist in multiple states and forms.