. Flashcards
What is odontogenesis?
Tooth development is the complex process by which teeth form from embryonic cells, grow, and erupt into the oral cavity
It is a continuous process that takes place in many stages.
What are the stages of tooth development?
- Bud Stage
- Cap Stage
- Bell Stage
These stages describe the morphology of the developing tooth germ but do not encompass the functional changes.
What is the primary epithelial band?
A band of epithelium that has invaded the underlying ectomesenchyme along the future dental arches
It forms when certain areas of basal cells of the oral ectoderm proliferate more rapidly.
What is the dental lamina?
It serves as the primordium for the ectodermal portion of the deciduous teeth
Later, during the development of the jaws, the permanent molars arise from a distal extension of the dental lamina.
At what age does the development of the first permanent molar begin?
At the fourth month in utero
The second molar is initiated at about the first year after birth, and the third molar at the fourth or fifth years.
What happens to the dental lamina as teeth develop?
Teeth lose their connection with the dental lamina and may leave remnants called epithelial pearls or islands
These remnants can persist in the jaw and gingiva.
What is the enamel organ?
It consists of peripherally located low columnar cells and centrally located polygonal cells
It is critical to normal tooth development.
What characterizes the cap stage of tooth development?
Unequal growth in different parts of the tooth bud leads to a shallow invagination
This stage is where the formative elements of the tooth and its supporting tissues become identifiable.
What is the stellate reticulum?
Polygonal cells that become star-shaped and form a cellular network
These cells support and protect the delicate enamel-forming cells.
Define the dental papilla.
The formative organ of the dentin and the primordium of the pulp
It forms under the organizing influence of the proliferating epithelium of the enamel organ.
What occurs during the bell stage?
Continued growth of the tooth germ leads to the bell shape of the enamel organ, and the crown completes its morphodifferentiation
Cell differentiation also proceeds gradually cervically.
What is the enamel knot?
A densely packed cluster of cells in the center of the enamel organ
It acts as a signaling center and plays an important role in determining the shape of the tooth.
What are the four types of epithelial cells in the enamel organ during the early bell stage?
- Outer enamel epithelium
- Inner enamel epithelium
- Stellate reticulum
- Stratum intermedium
This structure is critical for enamel production.
True or False: The dental lamina remains intact throughout tooth development.
False
The dental lamina fragments during the bell stage, separating the developing tooth from the oral epithelium.
What is the function of the inner enamel epithelium?
It consists of tall columnar cells that will eventually form enamel
These cells undergo differentiation during the bell stage.
Fill in the blank: The _______ is the area of intense mitotic activity between the inner and outer enamel epithelium.
[junctional epithelium]
This area is critical for the growth and differentiation of the enamel organ.
What is the stratum intermedium?
A few layers of squamous cells between the inner enamel epithelium
It indicates high metabolic activity and is associated with alkaline phosphatase activity.
What is the role of the outer enamel epithelium during enamel production?
Serves as a supporting layer for the enamel organ
The cells shorten to a low cuboidal form.
What is the inner enamel epithelium primarily composed of?
A single layer of tall columnar cells called preameloblasts
These cells exert an organizing influence on the dental papilla.
What characterizes the stellate reticulum?
Cells are star-shaped with long processes and expand due to intercellular fluid
This layer collapses before enamel formation begins.
What is the function of odontoblasts?
To produce dentin
They differentiate from the peripheral cells of the dental papilla.
What separates the dental papilla from the enamel organ?
A basal lamina
Fine fibrils extend into an acellular zone.
What is the membrana preformativa?
The basement membrane that separates the enamel organ and the dental papilla prior to dentin formation
It plays a critical role in the development of the tooth.
What is the dental follicle?
Ectomesenchyme that surrounds the enamel organ
It is distinguished by a higher density of collagen fibrils.
What occurs during the late bell stage of tooth development?
Folding of the basement membrane and formation of capillary loops in the adjacent mesenchyme
This compensates for the loss of nutritional supply from the dental papilla.
What is the process of apposition in tooth development?
The deposition of the matrix of the hard dental structures
It occurs after crown formation.
What is histodifferentiation?
The phase where formative cells undergo morphologic and functional changes
This phase reaches its highest development in the enamel organ.
Fill in the blank: A lack of initiation results in the absence of a single tooth or multiple teeth, known as _______.
partial anodontia
This is commonly seen in specific permanent teeth.
What is the role of Hertwig’s epithelial root sheath?
To induce odontoblast differentiation and root development
It consists only of the outer and inner enamel epithelium.
What happens if the continuity of Hertwig’s root sheath is broken?
Defects in the dentinal wall of the pulp may occur
This can lead to accessory root canals.
What is the ectomesenchyme?
A type of connective tissue containing neural crest cells
It is crucial for the development of cranial structures and dental tissues.
What does the dental papilla give rise to?
Dental pulp
This occurs after the first calcified matrix (dentin) appears.
What is the dental sac?
Condensed ectomesenchyme that surrounds the enamel organ and dental papilla
It gives rise to cementum, periodontal ligament, and alveolar bone.
What defines morphodifferentiation?
The establishment of the basic form and relative size of the future tooth
This process involves differential growth.
What results from the differentiation of odontoblasts in the dental papilla?
The formation of predentin
This process is induced by the inner enamel epithelium.
What happens during the development of multi-rooted teeth?
Differential growth of the epithelial diaphragm causes division of the root trunk
This results in the formation of multiple root openings.
What are epithelial cell rests of Malassez?
Remnants of Hertwig’s epithelial root sheath found in the periodontal ligament
They can differentiate into ameloblasts and produce enamel.
What is the dental sac?
Condensed ectomesenchyme with circular collagen fibers that encloses the enamel organ and dental papilla
It gives rise to cementum, periodontal ligament, and alveolar bone.
What does the outer enamel epithelium refer to?
Cells that make up the outer convex surface of the enamel organ
This layer is essential for the formation of enamel.
What is the inner enamel epithelium?
Cells that make up the inner concave surface of the enamel organ
They transform into ameloblasts in the late bell stage and secrete the enamel matrix.
What is the stellate reticulum?
Central cells of the enamel organ forming a network of star-shaped cells due to intercellular fluid accumulation
Seen between OEE and IEE in cap stage, and between OEE and stratum intermedium in bell stages.
What is the stratum intermedium?
Two to three layers of flattened cells seen between stellate reticulum and IEE in the bell stages
They are rich in alkaline phosphatase enzyme.
What is the cervical loop?
Region where the OEE folds and becomes the IEE
This structure is crucial for the development of the tooth roots.
What does HERS stand for?
Hertwig epithelial root sheath
It is a downward extension of the cervical loop, made up of OEE and IEE, and determines the shape of roots.
What is the epithelial diaphragm?
Horizontal extension of the HERS near the apical end
It corresponds to the future apical foramen region of the teeth and determines the number of roots.
