Enamel

• Enamel Lamellae:

  • Thin leaf-like structures in enamel that extend from varying depths from the surface of enamel towards DEJ
  • Visible in ground sections of tooth, better in cross-section
  • Seen in carefully demineralized/ decalcified sections of human enamel due to higher organic content
  • Defects formed during enamel development, filled with organic material
• Classification of enamel lamellae:

  • Type A: Group of poorly calcified enamel rods
  • Type B: Filled with odontogenic degenerated cells
  • Type C: Cracks filled with organic matter
  • Develop in lines of stress where calcification may be incomplete, becoming a site of weakness in enamel for bacterial entry
• Formation of enamel lamellae:

  • Develop in lines of stress where calcification may be incomplete
• Clinical significance of enamel lamellae:

  • Form a route for bacterial entry due to weakness in enamel
• Differentiation between type C enamel lamellae and crack:

  • Use careful demineralization, crack disappears while lamella is retained due to higher organic content
• Dentino-enamel junction (DEJ):

  • Junction between dentin and enamel, established during formation of dentin and enamel
  • Scalloped appearance, revealed as a series of ridges under scanning electron microscope
  • Ridging more pronounced in coronal region to prevent shearing of enamel during function
• Enamel spindle:

  • Spindle-shaped structures seen in enamel at DEJ
  • Formed by developing odontoblast processes extending into ameloblasts layer before enamel formation
  • Demonstrated in ground sections, surrounded by interrod enamel
  • More spindles in incisal and cuspal regions, appear dark in transmitted light and lighter in reflected light
• Formation of enamel spindles:

  • Developing odontoblast processes extend into ameloblasts layer before enamel formation
• Gnarled enamel:

  • Structure seen at incisal edge or cusp tips, formed by intertwining of enamel rods
  • Arrangement withstands masticatory forces, formed due to irregular movement of ameloblasts during enamel deposition
• Formation of gnarled enamel:

  • Irregular movement of ameloblasts during enamel deposition due to overcrowding