Early Tooth Development
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What is the name for tooth formation?
Odentogenesis
When does tooth development begin?
6 weeks
What are the three overlapping PHASES of tooth development?
Initiation, morphogenesis and histogenesis
Initiation - what happens during the 6th week?
Oral epithelium of stomodeum thickens and invaginates to form the primary epithelial band. This corresponds to the position of the future dental arches.
Initiation - what happens during the 7th week?
The primary epithelial band divides to form the vestibular lamina and the dental lamina
What are the two components of the tooth germ, present in the 8th week?
The epithelial swelling and the ectomesenchyme cells.
What are the three STAGES of tooth development?
Bud, cap and bell stage
When does the bud stage occur? What happens during this stage?
During the 8th week, the dental lamina proliferates (lengthens) and forms a swelling at 10 different points around each dental arch (for deciduous teeth)
When does the cap stage occur? What happens during this stage?
Occurs at 11 weeks. Here the enamel epithelium cells further proliferate, and the deeper surface invaginates to form a cap-like structure due to unequal growth.
Name the five layers of cells at the 12th week during cap stage. (12th week - differenciation of cells has begun)
Stellate reticulum, internal enamel epithelium, external enamel epithelium, dental papilla and dental follicle/sac
What is the future dental tissue of the: • enamel organ? • dental papilla? • dental follicle/sac?
• enamel • dentin and pulp tissue • periodontal ligament, cementum and parts of alveolar bone
What is the time frame for the bell stage of tooth development?
Early - 14 weeks Late - 18 weeks
What happens in the early bell stage (14 weeks)?
• Enamel organ loses contact with oral epithelium as the dental lamina breaks down • Cap surface deepens, forming a 3D bell shape • Folding of IEE maps out occlusal pattern of tooth crown • Dental papilla cells differenciate into outer cells (future odontoblasts) and inner cells (primordium of the dental pulp tissue)
What happens during the late bell stage (18 weeks)?
The hard dental tissues are deposited - inner enamel epithelium cells differenciate into ameloblasts which produce enamel, and the outer cells of the dental papilla differenciate into odontoblasts, which produce dentin. Dentin formation precedes enamel formation
In what order does differentiation of the IEE and outer dental papilla cells, then production of enamel and dentin occur?
IEE line up upon basement membrane > preameloblasts > outer dental papilla cells line up > odontoblasts > dentin matrix formation > mineralised > ameloblasts form > enamel produced