Tooth Development and Root Formation

Stages of Tooth Development

• Tooth Germ Stages: The tooth germ undergoes various stages during development.
• Advanced Bell Stage: This is the stage where mineralization starts.
  • Enamel and Dentin Deposition: Begins at incisal or cuspal tips and proceeds cervically.

Root Formation

• Initiation: Begins at the cervical loop after enamel reaches it, then moves apically.
• Composition: Root is made of dentin and cementum, no enamel.

Hertwig's Epithelial Root Sheath (HERS)

• Formation: Begins in the Advanced Bell Stage.
  • Originates from cervical loop and grows into ectomesenchyme.
  • Consists of two-cell layer:
    • Inner Enamel Epithelium
    • Outer Enamel Epithelium
  • No Stellate Reticulum or Stratum Intermedium.
• Function: Signals Dental Papilla to differentiate into Odontoblasts for dentin deposition.
• Degeneration: Ends function after dentin deposition begins, leaving Cell Rests of Malassez.

Cell Rests of Malassez

• Nature: Remnants of HERS, found in periodontal ligament.
• Potential: May lead to pathologies (e.g., tumors, cysts).

Cementum Formation

• Process: Dental Sac contacts dentin, differentiating into Cementoblasts.
• Cementoblasts' Role: Deposit cementum on the root.

Root Morphology

• Common Process: Histological stages are consistent across all teeth.
• Hertwig's Epithelial Root Sheath Morphology:
  • Varies between single and multi-rooted teeth.
  • Forms epithelial diaphragm reducing cervical opening size to form apical foramen.
  • Single Rooted Teeth: One cervical opening.
  • Multi-Rooted Teeth: HERS grows extensions to multiple cervical openings, forming multiple roots.