DOMA

• Enamel


  Hardest calcified tissue in the human body

  
• Enamel


  • Forms a resistant covering of the teeth, rendering them suitable for mastication
  • 96% inorganic material
  • 4% organic substance and water

  
• Enamel rods/prism


  • Many rods resemble fish scales
  • Common pattern: keyhole or paddle-shaped prism

  
• Enamel rods/prism


  • Rods are oriented at right angles to the dentin surface
  • Direction of rods on permanent teeth in the cervical region deviate in an apical direction

  
• Gnarled enamel


  Optical appearance of rod arrangement in the region of cusps of incisal edges appear to intertwine more irregularly

  
• Hunter-Schreger bands


  • Alternating dark and light strips of varying width
  • Change in the direction of rods is responsible for this appearance
  • Diazones - dark bands
  • Parazones - light bands
• Incremental lines of Retzius


  • Brownish bands
  • Demonstrate the incremental pattern of the enamel, that is, the successive apposition of layers of enamel during formation of the crown

  
• Perikymata


  • Transverse, wave-like grooves, believed to be the external manifestations of the striae of Retzius
  • Ridge/crest - elevations
  • Groove/furrow - depressions

  
• Neonatal line/ring


  • Enamel of deciduous teeth develops partly before and partly after birth
  • Accentuated incremental line of Retzius marking the boundary between the two portions of enamel in deciduous teeth
  • Result of abrupt change in the environment and nutrition of the newborn infant

  
• Enamel lamellae


  • Thin, leaf-like structures that extend from the enamel surface toward the DEJ
  • May develop in planes of tension where a short segment of the rod may not fully calcify
  • May be a site of weakness in a tooth and may form a road of entry for bacteria that initiate caries

  
• Enamel tufts


  • Arise at the DEJ and reach into the enamel
  • Resemble tufts of grass
  • Hypomineralized structure

  
• Dentinoenamel junction (DEJ)

  • Appears as a scalloped line
  • Convexities of the scallops are directed toward the dentin
  • The surface of dentin at the DEJ is pitted. Shallow depressions of the dentin fit rounded projections of enamel

  
• Enamel spindles


  Occasionally odontoblast process pass across the DEJ