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Questions and Answers
What is the primary function of the enamel knot during the cap stage?
What is the primary function of the enamel knot during the cap stage?
Which structure separates the dental papilla from the enamel organ during the cap stage?
Which structure separates the dental papilla from the enamel organ during the cap stage?
What type of cells primarily compose the outer dental epithelium (O.D.E.)?
What type of cells primarily compose the outer dental epithelium (O.D.E.)?
Which statement accurately describes the enamel cord?
Which statement accurately describes the enamel cord?
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What does the dental sac primarily consist of?
What does the dental sac primarily consist of?
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What structure forms the cleft that becomes the vestibule between the cheek, lip, and jaws?
What structure forms the cleft that becomes the vestibule between the cheek, lip, and jaws?
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Which part of the tooth germ is responsible for the formation of enamel?
Which part of the tooth germ is responsible for the formation of enamel?
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At what stage does the dental lamina develop 10 ectodermal swellings for deciduous teeth?
At what stage does the dental lamina develop 10 ectodermal swellings for deciduous teeth?
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What is the primary function of the dental sac (dental follicle)?
What is the primary function of the dental sac (dental follicle)?
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Which of the following is NOT part of the tooth germ?
Which of the following is NOT part of the tooth germ?
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What shape does the bud take during the bud stage of tooth development?
What shape does the bud take during the bud stage of tooth development?
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In the cap stage, what is the relationship between the outer enamel epithelium and the dental sac?
In the cap stage, what is the relationship between the outer enamel epithelium and the dental sac?
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Which significant event occurs during the formation of the vestibular lamina?
Which significant event occurs during the formation of the vestibular lamina?
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What is the role of the stratum intermedium in dental development?
What is the role of the stratum intermedium in dental development?
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What primarily happens at the late bell stage of dental development?
What primarily happens at the late bell stage of dental development?
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What is the function of the dental papilla in tooth development?
What is the function of the dental papilla in tooth development?
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What characterizes the stellate reticulum in the dental enamel organ?
What characterizes the stellate reticulum in the dental enamel organ?
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How does the cervical loop contribute to tooth development?
How does the cervical loop contribute to tooth development?
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Which structure is known to undergo changes to gain a nutritional source from the dental sac?
Which structure is known to undergo changes to gain a nutritional source from the dental sac?
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What is the primary component of the dental sac that shows a circular arrangement of fibers?
What is the primary component of the dental sac that shows a circular arrangement of fibers?
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Which organelle is involved in the secretion of dentin matrix by odontoblasts?
Which organelle is involved in the secretion of dentin matrix by odontoblasts?
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What is one of the primary functions of the Enamel Organ?
What is one of the primary functions of the Enamel Organ?
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Which cell type is responsible for controlling fluid diffusion into and out of ameloblasts?
Which cell type is responsible for controlling fluid diffusion into and out of ameloblasts?
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What does the Dental Papilla primarily give rise to?
What does the Dental Papilla primarily give rise to?
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How does the epithelial root sheath of Hertwig contribute to tooth development?
How does the epithelial root sheath of Hertwig contribute to tooth development?
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What is the primary cause of accessory root canals?
What is the primary cause of accessory root canals?
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Which function is NOT associated with the stellate reticulum?
Which function is NOT associated with the stellate reticulum?
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From which structure does the periodontal ligament develop?
From which structure does the periodontal ligament develop?
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What role does the outer dental epithelium play in tooth development?
What role does the outer dental epithelium play in tooth development?
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What are the remnants of the lateral dental lamina called?
What are the remnants of the lateral dental lamina called?
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Which cells differentiate into ameloblasts under the influence of dentine formation?
Which cells differentiate into ameloblasts under the influence of dentine formation?
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What happens to the stellate reticulum during enamel formation?
What happens to the stellate reticulum during enamel formation?
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What is the role of the stratum intermedium in enamel development?
What is the role of the stratum intermedium in enamel development?
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In which stage does the differentiation of odontoblasts and ameloblasts occur?
In which stage does the differentiation of odontoblasts and ameloblasts occur?
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Which of the following correctly represents the initiation stage in dental development?
Which of the following correctly represents the initiation stage in dental development?
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What occurs during the apposition stage of tooth development?
What occurs during the apposition stage of tooth development?
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What is formed from the dental papilla during tooth development?
What is formed from the dental papilla during tooth development?
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Study Notes
Vestibular Lamina Development
- Develops at 6 weeks in utero as an ectodermal proliferation facial to the dental lamina.
- Cells rapidly proliferate, then central cells degenerate to form a cleft, creating the vestibule between the cheek, lip, and jaws.
Dental Lamina & Vestibular Lamina
- The vestibular lamina will grow down and split on the tooth’s facial side, creating alveolar and labial/buccal mucosae.
Bud Stage
- From the facial side of the dental lamina, 10 ectodermal swellings for deciduous teeth in each jaw appear, shaped like buds. These are called the dental (enamel) organ.
- Dental Organ: Responsible for enamel formation.
- Dental Papilla: Located on the lingual side, formed of ectomesenchymal cells beneath the epithelial bud, responsible for dentine and pulp formation.
- Dental Sac (Dental Follicle): Encircles the enamel organ and dental papilla, responsible for forming alveolar bone proper, cementum, and periodontal ligaments.
- The dental organ, dental papilla, and dental sac together make up the tooth germ.
Bud Stage (Formation of a bud from the dental lamina)
- Facial side
Cap Stage (Differentiation of the Bud)
- Differential growth of the dental organ changes the bud's shape into a cap.
- Outer convex: Faces the dental sac.
- Inner concave: Faces the dental papilla.
- The enamel organ has a short and broad connection to the dental lamina.
Cap Stage Components
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Enamel Organ
- Outer dental epithelium (ODE): Single layer of cuboidal cells with deeply stained round nuclei.
- Inner dental epithelium (IDE): Single layer of columnar cells with deeply stained round nuclei.
- Stellate reticulum: Star-shaped cells connected by desmosomes, with mucopolysaccharides fluid in the intercellular space.
- Enamel knot: Condensation of IDE cells.
- Enamel cord: Polyhedral cells extending from the enamel knot to the ODE.
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Dental Papilla:
- Condensation of ectomesenchymal cells.
- Separated from the enamel organ by a cell-free zone containing cytoplasmic processes of ectomesenchymal cells and argyrophilic fibers.
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Dental Sac:
- Condensation of ectomesenchymal cells and fibers around the enamel organ and dental papilla.
- Has a more vascular inner surface facing the dental papilla and enamel organ.
Induction
- The IDE influences the differentiation of odontoblasts in the dental papilla.
Late Bell Stage
- Starts with the formation of the first layer of dentine.
- Changes in the enamel organ occur to obtain nutrition from the dental sac as it relies on the dental papilla for nourishment.
Enamel Matrix Formation
-
Dental lamina: The lateral dental lamina degenerates, leaving remnants called epithelial rests of Serres or Serres' pearls.
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Enamel Organ:
-
ODE:
- Surface folds to increase surface area for fluid exchange.
- Cells flatten.
- Develop microvilli, cytoplasmic vesicles, and increased mitochondria.
-
IDE:
- Differentiates into ameloblasts under the influence of the first layer of dentine (reciprocal induction).
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ODE:
-
Stellate Reticulum:
- Shrinks after fluid loss, starting from the cusp tip cervically.
-
Stratum intermedium:
- Rich in alkaline phosphatase, acid mucopolysaccharides, and glycogen.
Dental Papilla and Dental Sac
- Dental Papilla: Becomes the dental pulp.
- Dental Sac: Becomes more vascular and located near the ODE.
Histophysiological Stages of Tooth Development
- Initiation: Represented by the dental lamina and bud stage.
- Proliferation: Represented by the dental lamina, bud, cap, and early bell stages before hard dental tissue formation.
- Histodifferentiation: Represented by early and late bell stages, with differentiation of stratum intermedium, odontoblasts, and ameloblasts.
- Morphodifferentiation: Represented by early and late bell stages.
- Apposition: Occurs at the late bell stage. Dentine is formed on the pulpal surface and cementum from the other side of the united projections.
Functions of the Enamel Organ
- Forms the future crown shape.
- Forms enamel.
- Induces the differentiation of odontoblasts to form dentine.
Functions of the Enamel Organ's Cells
- Outer Dental Epithelium (ODE): Active transport of materials from the dental sac to the dental organ, especially after hard dental tissue formation. Forms the cervical loop with IDE.
- Stellate Reticulum: Acts as a buffer against physical forces that may distort the developing amelodentinal junction, it keeps room for the developing enamel, and acts as a storehouse for nutritive materials.
- Stratum Intermedium: Controls fluid diffusion into and out of the ameloblasts and provides alkaline phosphatase needed for mineralization.
- Inner Dental Epithelium (IDE): Arranged in a pattern to determine the future morphology of the crown, transports nutritive materials from the dental papilla to the enamel organ before hard dental tissue formation, it exerts an organizing influence on the undifferentiated cells of the dental papilla to differentiate into odontoblasts, it lays down enamel matrix, and helps in its mineralization.
Functions of the Dental Papilla and Dental Sac
- Dental Papilla: Gives rise to dentin and pulp, and provides nutrition.
- Dental Sac: Gives rise to cementum, periodontal ligament, and alveolar bone proper, and provides nutrition.
Function of the Epithelial Root Sheath of Hertwig
- Molds the shape of the root.
- Initiates root dentine formation.
Clinical Considerations: Accessory Root Canal
-
Accessory Root Canal: An opening connecting the pulp cavity with periodontal tissue, rather than the apical foramen.
-
Mechanism of Formation:
- Early degeneration of the epithelial root sheath of Hertwig before odontoblast differentiation.
- Occurs in areas where the developing root meets a large blood vessel, where dentine forms around it.
- Lack of complete union of the tongue-like projections at the floor of the pulp chamber.
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Description
Test your knowledge on the intricacies of dental development, focusing on the vestibular lamina and dental lamina formation. Explore key stages such as the bud stage and the roles of different dental structures. This quiz is ideal for students studying oral biology or dental anatomy.
