Odontogenesis: Stages & Tissue Origins

Stages of tooth development

Stage	What happens	Disturbance examples
Initiation (dental lamina, about week 6)	Oral ectoderm thickens into the dental lamina over neural crest–derived ectomesenchyme	Anodontia, hypodontia, supernumerary teeth
Bud	Lamina proliferates into round buds, one per tooth	Macrodontia or microdontia (some texts place these at morphodifferentiation)
Cap	Enamel organ caps the condensing dental papilla; dental follicle surrounds both (the tooth germ); enamel knot signals cusp formation	Gemination, fusion, dens invaginatus, tubercles
Bell	Histodifferentiation and morphodifferentiation: inner and outer enamel epithelium, stellate reticulum, stratum intermedium; crown shape is set	Peg lateral incisor and other shape anomalies
Apposition and maturation	Dentin, then enamel matrix laid down and mineralized	Enamel hypoplasia, Turner tooth, concrescence; AI and DI are usually listed here (some texts list them under histodifferentiation)

Embryonic tissue	Becomes
Enamel organ (ectoderm)	Enamel (ameloblasts), reduced enamel epithelium, Hertwig's root sheath
Dental papilla (ectomesenchyme)	Dentin (odontoblasts) and pulp
Dental follicle (sac)	Cementum, periodontal ligament, alveolar bone proper

Reciprocal induction: inner enamel epithelium induces the outer papilla cells to become odontoblasts; the first dentin then induces ameloblasts to secrete enamel. Dentin forms before enamel.
Hertwig's epithelial root sheath (inner + outer enamel epithelium, no stellate reticulum) maps the root and induces root dentin; its remnants are the epithelial rests of Malassez (source of radicular cysts).
Dental lamina remnants are the rests of Serres (gingival cysts; odontogenic keratocysts are thought to arise here).
Reduced enamel epithelium covers the crown until eruption, then helps form the junctional epithelium; fluid between it and the crown gives a dentigerous cyst.
Permanent successors come from the successional lamina lingual to each primary tooth; permanent molars come from the distal extension of the dental lamina.

Saying enamel forms before dentin: the first dentin layer must be present before ameloblasts secrete enamel.
Deriving cementum from the dental papilla: cementum, PDL and alveolar bone proper come from the follicle.
Confusing rests of Malassez (HERS, in the PDL) with rests of Serres (dental lamina, in the gingiva).
Putting the stellate reticulum in Hertwig's root sheath: HERS has only the inner and outer enamel epithelium.

Pick an answer to see right away whether it is correct and why.

Gemination and fusion are disturbances of which stage?
Which tissue forms from the dental follicle?
The epithelial rests of Malassez are remnants of:
Which event must happen before ameloblasts secrete enamel matrix?
A cyst forms around the crown of an unerupted tooth from fluid collecting under the reduced enamel epithelium. It is a:

0 of 5 answered

Answer key: 1 D · 2 D · 3 A · 4 B · 5 A

Dental School Map · Original study material, written and checked by our team; always confirm clinical decisions against current guidelines.