Questions and Answers
At what stage of tooth development do epithelial cells begin to proliferate into the ectomesenchyme of the jaw?
What is the term used to describe the morphology of the developing tooth?
What is the number of local thickenings on the dental lamina in each alveolar process?
What forms around the mouth in the presumptive upper and lower jaws at 37 days of development?
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What is the term used to describe the process of teeth formation in relation to the alveolar process?
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From which cells do the ectomesenchymal cells accumulate around the outgrowths in tooth development?
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What happens to the peripherally placed undifferentiated ectomesenchymal cells of the dental papilla during enamel formation?
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What is the name of the membrane that separates the enamel organ and dental papilla just before dentin formation?
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What is the role of the dental lamina in tooth formation?
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What is the result of the breaking up of dental lamina during the bell stage?
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What is the typical direction of matrix formation and mineralization in dentin?
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How many deciduous teeth are formed from each placode in the primary epithelial band?
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What is the result of the reversal of polarity in the inner enamel epithelial cells?
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What is the function of collagen fibrils in the dental follicle during the bell stage?
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What is the process by which ameloblasts and odontoblasts differentiate?
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What is the importance of the inner enamel epithelial cells in dentin formation?
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What is the characteristic of the advanced bell stage?
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What influences the differentiation of odontoblasts?
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What can be formed by the cell rests of Serres in the dental lamina?
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What layer of cells is responsible for the formation of radicular dentin?
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What marks the beginning of root development?
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What outlines the dentinoenamel junction during advanced bell stage?
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What is the region where dentin formation typically begins?
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What is the composition of Hertwig's epithelial root sheath?
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Study Notes
Tooth Development
- Tooth formation begins from ectoderm and ectomesenchyme at 37 days of development, with a continuous band of thickened epithelium forming around the mouth in the presumptive upper and lower jaws.
- Each band of epithelium, called the primary epithelial band, gives rise to two subdivisions: dental lamina and vestibular lamina.
- Initiation of tooth development starts with formation of localized thickenings or placodes within the primary epithelial bands.
- Ten epithelial thickenings in dental lamina form enamel organs, which later develop into deciduous teeth.
Stages of Tooth Development
- Bud stage: characterized by formation of a tooth bud, proliferation of epithelial cells into the ectomesenchyme, and differentiation of odontoblasts to form organic matrix of dentin.
- Cap stage: not mentioned explicitly in the text, but implied as a transitional stage between bud and bell stages.
- Bell stage:
- Odontoblasts differentiate and form organic matrix of dentin along the dentinoenamel junction.
- Inner enamel epithelial cells elongate and exhibit reversal of polarity, turning into functional ameloblasts.
- Ameloblasts produce an organic matrix of enamel against the newly formed dentin.
Reciprocal Induction
- Terminal differentiation of ameloblasts and odontoblasts, leading to formation of enamel and dentin.
- Differentiation of odontoblasts influenced by inner enamel epithelial cells.
- Reciprocal induction: differentiation of ameloblasts and odontoblasts is interdependent.
Root Formation
- Begins when dentinoenamel line reaches the future cementoenamel junction.
- Hertwig's epithelial root sheath formation occurs from the cervical portion of the enamel organ, determining the shape, length, size, and number of roots.
- Dental papilla in bell stage: undifferentiated ectomesenchymal cells increase in size, occupy the acellular zone, and differentiate into odontoblasts.
Crown Pattern Determination
- Bell stage: dental lamina breaks up, and crown pattern of the tooth is determined (morphodifferentiation).
- Dental follicle: collagen fibrils occupy extracellular spaces, orienting themselves circularly around the enamel organ and dental papillae, later differentiating into periodontal fibers.
Advanced Bell Stage
- Characterized by the beginning of mineralization and root formation.
- Peripheral ectomesenchymal cells of the dental papilla differentiate into odontoblasts under the influence of inner enamel epithelial cells.
- Mineralization occurs, and the dentinoenamel junction is outlined.
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Description
This lecture covers the development of teeth, including the role of dental lamina and stages of tooth formation, as well as changes in the process of calcification and tooth form. Students will inform about tooth development and its various stages.
