Initiation Stage (Dental Lamina Stage)
Primitive oral cavity lined by stratified squamous epithelium
Formation of Primary Epithelial Band
Divides into:
Dental lamina → forms teeth
Vestibular lamina → forms oral vestibule
Dental Lamina
Appears at 6th week of intrauterine life
Forms tooth buds of all primary teeth
Gives rise to:
Successional lamina → permanent successors
Accessional lamina → permanent molars
Remnants of dental lamina = Rests of Serres
2. 🔹 Role of Ectomesenchyme
Derived from neural crest cells
Responsible for:
Formation of dentin, pulp, cementum
3. 🔹 Morphological Stages of Tooth Development
1. 🟢 Bud Stage
First sign of tooth development
Proliferation of dental lamina into ectomesenchyme
Structures:
Enamel organ (early)
Ectomesenchymal condensation
Cells:
Peripheral cuboidal cells
Central polygonal cells
2. 🟡 Cap Stage
Enamel organ becomes cap-shaped
Components formed:
Enamel organ
Dental papilla → dentin + pulp
Dental sac (follicle) → cementum, PDL
Layers in enamel organ:
Outer enamel epithelium (OEE)
Inner enamel epithelium (IEE)
Stellate reticulum ⭐
3. 🟠 Early Bell Stage
Histodifferentiation & morphodifferentiation begin
New layer:
Stratum intermedium
Important changes:
IEE → differentiates into ameloblasts
Dental papilla → forms odontoblasts
Nuclear polarity reversal
4. 🔴 Advanced Bell Stage (Apposition Stage)
Hard tissue formation begins
Sequence:
Odontoblasts form dentin first
Then ameloblasts form enamel
👉 Key Point: Dentin formation precedes enamel formation
Other features:
Stellate reticulum collapses
Enamel and dentin deposition continues
4. 🔹 Root Formation (Hertwig’s Epithelial Root Sheath - HERS)
Forms after crown formation
Function:
Shapes root
Induces dentin formation in root
Breakdown leads to:
Cementum formation
👉 Remnants of HERS = Rests of Malassez
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