Overview
This lecture explains the early embryological development of teeth, focusing on the origin, structures, and stages that lead to tooth formation.
Embryonic Origins and Tissues
- Tooth development begins in the embryo at about 6 weeks in utero.
- The stomodeum, or primitive oral cavity, is lined by oral ectoderm (stratified squamous epithelium).
- The underlying connective tissue is called ectomesenchyme, derived from neural crest cells.
Formation of Primary Epithelial Band and Laminae
- At 6 weeks, basal cells of oral ectoderm proliferate to form the Primary Epithelial Band.
- This band is horse-shoe shaped and determines the future dental arch positions in maxilla and mandible.
- Around the 7th week, the band subdivides into Dental Lamina (inner) and Vestibular Lamina (outer).
Dental and Vestibular Lamina Function
- Dental Lamina initiates tooth development and forms all deciduous teeth; extends distally for permanent molar formation.
- Vestibular Lamina forms the vestibule, the sulcus between lips/cheek and dental arches via cellular degeneration.
Tooth Germ Formation and Tooth Types
- Specific thickenings (placodes) on Dental Lamina become Enamel Organs.
- Distal extension of Dental Lamina gives rise to permanent molars at different ages (1st at 4 months fetal, 2nd at 1 year, 3rd at 5 years).
- Lingual extensions (Successional Lamina) form succedaneous teeth: permanent incisors, canines, premolars.
Fate of Dental Lamina and Related Structures
- Dental Lamina function ends after 3rd molar initiation at ~5 years and undergoes degeneration.
- Incomplete degeneration forms Cell rests of Serres, which can later cause cysts or tumors.
- The Enamel Organ forms enamel; Dental Papilla forms dentin and pulp; Dental Sac forms cementum, PDL, and alveolar bone.
- Together, Enamel Organ, Dental Papilla, and Dental Sac form the tooth germ.
Morphological Stages of Tooth Development
- Stages of tooth development: Bud stage, Cap stage, Bell stage (subdivided into Early and Advanced bell stages).
Key Terms & Definitions
- Ectomesenchyme — connective tissue from neural crest cells beneath oral ectoderm.
- Primary Epithelial Band — thickened epithelium predicting future dental arches.
- Dental Lamina — epithelial layer from which deciduous and some permanent teeth develop.
- Vestibular Lamina — layer forming the vestibule between lips/cheek and dental arches.
- Enamel Organ — epithelial structure forming enamel.
- Dental Papilla — ectomesenchyme forming dentin and pulp.
- Dental Sac (Follicle) — tissue forming cementum, periodontal ligament, and alveolar bone.
- Tooth Germ — collective term for Enamel Organ, Dental Papilla, and Dental Sac.
- Cell rests of Serres — remnants of the dental lamina that may form cysts/tumors.
Action Items / Next Steps
- Review stages of tooth development (Bud, Cap, Bell).
- Learn key functions of Dental Lamina and related embryonic structures.