Tooth Development And Eruption Part 1 Flashcards
What is odontogenesis?
Odontogenesis is the process of tooth development.
Can developmental disturbances occur during odontogenesis?
Yes, developmental disturbances can occur during each stage of odontogenesis.
How can developmental disturbances affect the tooth?
They can affect the physiological processes taking place during development.
What are the potential clinical implications of developmental disturbances in odontogenesis?
These disturbances may have ramifications that affect the clinical treatment of a patient.
What does the term ‘dentition’ refer to?
The term ‘dentition’ refers to the natural teeth in the jaws.
How many types of dentitions are there?
There are two types of dentitions: primary and permanent.
When does the primary dentition develop?
The primary dentition develops during the prenatal period.
How many teeth are included in the primary dentition?
The primary dentition consists of 20 teeth.
What happens to the primary dentition teeth before the permanent teeth erupt?
They will be exfoliated (shed).
How many teeth are included in the permanent dentition?
The permanent dentition consists of 32 teeth.
How does odontogenesis take place?
Odontogenesis takes place in stages, which occur sequentially for both dentitions.
When does odontogenesis of the primary dentition begin?
It begins between the sixth and seventh week of prenatal development, during the embryonic period.
What are the initial identifiable stages in tooth development after initiation?
The initial identifiable stages are the bud stage, cap stage, and bell stage.
What stage follows the bell stage in odontogenesis?
Odontogenesis progresses to the apposition stage after the bell stage.
What happens during the apposition stage?
The apposition stage involves the formation of partially mineralized dental tissue types, including enamel, dentin, and cementum.
What is the final stage of odontogenesis?
The final stage is the maturation stage, where the dental tissues fully mineralize.
What physiologic processes take place during odontogenesis?
The physiologic processes include induction, proliferation, differentiation, morphogenesis, and maturation.
Are the processes of odontogenesis separate or overlapping?
Except for induction, many of these processes overlap and are continuous during odontogenesis.
Although the physiologic processes during odontogenesis may occur simultaneously,
one process will tend to be predominant, marking each stage of odontogenesis.
What is the first stage of tooth development?
The first stage of tooth development is the initiation stage.
What physiologic process is involved in the initiation stage?
The initiation stage involves the physiologic process of induction.
What is induction in the context of tooth development?
Induction is an active interaction between embryologic tissue types.
What happens at the beginning of the 6th week of prenatal development?
At the beginning of the 6th week, the stomodeum (primitive mouth) is lined by ectoderm.
What does the outer part of the ectoderm give rise to?
The outer part of the ectoderm gives rise to the oral epithelium.
What does the oral epithelium consist of?
The oral epithelium consists of two horseshoe-shaped bands of tissue at the surface of the stomodeum.
What will the horseshoe-shaped bands of tissue form?
These bands will form the dental arches.
What happens if there is a lack of initiation within the dental lamina?
A lack of initiation within the dental lamina results in the absence of teeth.
What is anodontia?
Anodontia, also called hypodontia, is the absence of teeth due to a failure in the initiation process.
How can anodontia manifest?
It can manifest as a single missing tooth, multiple missing teeth, or the absence of an entire dentition.
What is partial anodontia?
Partial anodontia refers to one or more missing teeth but not the entire dentition.
What is complete anodontia?
Complete anodontia refers to the absence of an entire dentition.
Which type of anodontia is more common?
Partial anodontia is more common than complete anodontia.
Which teeth are most commonly affected by anodontia?
The most commonly affected teeth are the permanent third molars, maxillary lateral incisors, and mandibular second premolars (in order of occurrence).
What are some etiologic factors for anodontia?
Etiologic factors include hereditary conditions, endocrine dysfunction, systemic disease, and excessive radiation exposure.
With which syndrome is anodontia associated?
Anodontia can be associated with ectodermal dysplasia.
Why is ectodermal dysplasia linked to anodontia?
Ectodermal dysplasia affects components of the tooth germ that are indirectly or directly derived from ectodermal origin.
What can result from abnormal initiation of the dental lamina?
Abnormal initiation can result in the development of one or more extra teeth.
What are extra teeth called?
Extra teeth are called supernumerary teeth or hyperdontia.
What causes supernumerary teeth?
Supernumerary teeth are initiated from persisting clusters of the dental lamina and have a hereditary etiology.
Which regions of the dentition commonly have supernumerary teeth?
Common regions include:
• Between the maxillary central incisors (mesiodens)
• Distal to the maxillary third molars (distomolar or ‘fourth molar’)
• In the premolar region of both dental arches (perimolar)
What is the size of supernumerary teeth compared to normal teeth?
Supernumerary teeth are often smaller than usual.
Can supernumerary teeth erupt?
Yes, they may be either erupted or nonerupted.
What complications can arise from supernumerary teeth?
Complications include dentition displacement, crowding, delayed eruption of adjacent teeth, and occlusal disruption.
How are supernumerary teeth treated?
Treatment often involves surgical removal and/or orthodontic therapy.
What can smaller-than-normal dental placodes lead to?
They can lead to missing and microdontic teeth.
What do larger placodes induce?
Larger placodes induce supernumerary and macrodontic teeth.
What is the second stage of tooth development?
The second stage of tooth development is the bud stage.
When does the bud stage occur?
It occurs at the beginning of the 8th week of prenatal development for the primary dentition.
What happens to the dental lamina during the bud stage?
The dental lamina undergoes extensive proliferation into buds.
What are buds in the context of the bud stage?
Buds are three-dimensional oval masses that penetrate into the surrounding ectomesenchyme.
How many buds form in each dental arch at the end of the proliferation process?
Each dental arch (maxillary and mandibular) will have 10 buds.
What does the ectomesenchyme do during the bud stage?
The ectomesenchyme undergoes proliferation and begins to condense around the buds.
What remains between the dental lamina bud and the surrounding ectomesenchyme?
A basement membrane remains between them.
What do the buds and surrounding ectomesenchyme develop into?
They develop into a tooth germ and its associated supporting tissue types.
What can abnormal proliferation during the bud stage cause?
It can cause a single tooth, multiple teeth (partial), or an entire dentition (complete) to be larger or smaller than normal.
What is macrodontia?
Macrodontia refers to abnormally large teeth.
What is microdontia?
Microdontia refers to abnormally small teeth.
How common is complete microdontia?
Complete microdontia is rare in either dentition.
With which conditions can complete microdontia be associated?
It can be associated with hypopituitarism or Down syndrome.
What systemic condition can produce complete macrodontia?
Childhood hyperpituitarism (gigantism) can produce complete macrodontia.
What is the most common type of microdontia?
True partial microdontia, which is often hereditary.
Which teeth are commonly affected by partial microdontia?
The permanent maxillary lateral incisor (peg lateral) and the permanent third molar (peg molar) are commonly affected.
What is the third stage of tooth development?
The third stage of tooth development is the cap stage.
When does the cap stage occur?
It occurs between the 9th and 10th week of prenatal development, during the fetal period.
What happens to the enamel organ during the cap stage?
The enamel organ grows and forms a cap over the tooth bud, shaping the tooth’s outer layer.
What processes are involved in the cap stage?
The cap stage involves proliferation and differentiation to form the tooth germ, the primordium of a primary tooth.
What causes the cap shape of the enamel organ to form?
Unequal growth in different parts of the tooth bud leads to the formation of a three-dimensional cap shape overlying the ectomesenchyme.
What forms during the cap stage?
The tooth germ, which contains each primordial tissue necessary to develop the future tooth, forms during this stage.
What is the predominant physiologic process in the cap stage?
Morphogenesis is the predominant physiologic process during the cap stage.
What results from the combined physiologic processes during the cap stage?
A depression forms in the deepest part of each tooth bud of the dental lamina, creating the cap shape of the enamel organ.
What is the future role of the enamel organ?
The enamel organ will produce enamel on the outer surface of the crown of the tooth.
From what is the enamel organ originally derived?
The enamel organ is originally derived from ectoderm, making enamel an ectodermal product.
What forms on the innermost margin of the cap shape during the cap stage?
A cluster of non-dividing epithelial cells called the enamel knot forms.
What is the function of the enamel knot?
The enamel knot acts as a signaling center that directs the shape and position of tooth cusps.
The enamel knot determines the overall morphology of the tooth and is a key component in tooth morphogenesis.
It regulates cell growth and differentiation within the developing tooth germ.
What happens to the ectomesenchyme deep to the buds during the cap stage?
It condenses into a mass within the concavity of the cap of the enamel organ.
After development of the cap shaped enamel organ during the cap stage, What is the condensed mass of ectomesenchyme now considered?
It is now considered the dental papilla.
What will the dental papilla produce in the future?
The dental papilla will produce the future dentin and pulp for the inner part of the tooth.
What separates the enamel organ and the dental papilla during the cap stage?
A basement membrane separates the enamel organ and the dental papilla.
What is the significance of this basement membrane?
It is the site of the future dentinoenamel junction (DEJ).
From where is the dental papilla derived?
The dental papilla is derived from ectomesenchyme, which is in turn derived from neural crest cells (NCCs).
What is the origin of dentin and pulp?
Dentin and pulp are of mesenchymal origin.
What happens to the remaining ectomesenchyme surrounding the enamel organ?
It condenses into the dental sac (or dental follicle).
What will the dental sac produce in the future?
The dental sac will produce the periodontium, including cementum, the periodontal ligament, and the alveolar process.
What separates the enamel organ and the dental sac?
A basement membrane separates the enamel organ and the dental sac.
What is the origin of the supporting dental tissue from the dental sac?
The supporting dental tissue is of mesenchymal origin, derived from ectomesenchyme.
What structures together form the tooth germ at the end of the cap stage?
The enamel organ, dental papilla, and dental sac together form the tooth germ, which is the primordium of the tooth.
When does initiation for permanent teeth occur?
Initiation occurs at the 10th week of prenatal development during the cap stage for each primary tooth.
Which teeth are the first permanent teeth to initiate development?
The anterior teeth of the permanent dentition are the first to initiate development.
Which teeth follow the anterior teeth in the initiation process?
The premolars of the permanent dentition follow the anterior teeth in the initiation process.
Where and how does the primordium for permanent teeth form?
The primordium appears as an extension of the dental lamina into the ectomesenchyme lingual to the developing primary tooth germs.
What is the site of origin for the primordium of permanent teeth?
The site of origin is called the successional dental lamina.
Which permanent teeth are considered succedaneous?
Permanent teeth with primary predecessors, such as anterior teeth and premolars, are considered succedaneous.
Where do the crowns of permanent succedaneous teeth erupt in relation to their primary predecessors?
They erupt lingual to the roots of their primary predecessors if the primary tooth has not been fully shed.
Which permanent teeth are nonsuccedaneous?
Permanent molars are nonsuccedaneous because they do not have primary predecessors.
From where do the permanent molars develop?
They develop from a posterior extension of the dental lamina distal to the dental lamina of the primary second molar.
Which structures are involved in the development of permanent molars?
The dental lamina and its associated ectomesenchyme are involved in the development of permanent molars.
What is gemination?
Gemination occurs when a single tooth germ attempts to divide into two tooth germs.
What is the result of gemination?
It results in a large single-rooted tooth with a common enlarged pulp cavity.
How does gemination appear in the crown?
The crown exhibits “twinning,” appearing broader and falsely macrodontic.
How can gemination be differentiated from fusion?
Radiographic examination shows only one pulp cavity in gemination, with the correct number of teeth present in the dentition.
What is fusion in tooth development?
Fusion is the union of two or more adjacent tooth germs.
What may cause fusion?
Fusion may result from pressure in the area during tooth development.
How does fusion affect the appearance of the tooth?
It creates a broad, falsely macrodontic tooth, similar to gemination.
Which parts of the tooth can be involved in fusion?
Fusion can involve only the crown or both the crown and root.
How does fusion affect the total number of teeth in the arch?
The dentition with fusion will have one less tooth than normal.
How is fusion verified?
Radiographic examination shows two distinct pulp cavities with the enamel, dentin, and pulp united.
Where is fusion more commonly observed?
Fusion is more commonly seen in the anterior region of the primary dentition.
What are tubercles in tooth development?
Tubercles are small, round enamel extensions forming extra cusps.
Where are tubercles most commonly found?
They are most commonly found on the occlusal surface of permanent molars, especially third molars.
Where else can tubercles be present?
They can be present as a lingual extension on the cingulum of permanent maxillary anteriors, especially lateral incisors and canines.
What is a specific type of tubercle called?
A specific type of tubercle is called a talon cusp.
Can tubercles occur on any tooth?
Yes, tubercles can be found on any tooth in both dentitions.
What is the fourth stage of tooth development?
The fourth stage of tooth development is the bell stage.
When does the bell stage occur?
It occurs between the 11th and 12th week of prenatal development for the primary dentition.
What happens to the dental lamina during the bell stage?
The dental lamina breaks down, and the tooth germ epithelium forms a bell-shaped structure that will become the tooth’s crown.
What occurs during the bell stage at the cellular level?
Differentiation occurs at all levels to its furthest extent.
What results from the differentiation in the enamel organ during the bell stage?
Four different types of cells are found within the enamel organ:
• Outer enamel epithelium (OEE)
• Stellate reticulum
• Stratum intermedium
• Inner enamel epithelium (IEE)
How does the cap shape change during the bell stage?
The cap shape of the enamel organ deepens, forming a three-dimensional bell shape.
What happens to the tooth crown during the bell stage?
The tooth crown assumes its final shape through morphodifferentiation.
Which cells undergo further histodifferentiation during the bell stage?
Ameloblasts (enamel-forming cells) and odontoblasts (dentin-forming cells) undergo further histodifferentiation.
What are the outer cuboidal cells of the enamel organ called?
They are called the outer enamel epithelium (OEE).
What are the innermost tall columnar cells of the enamel organ called?
They are called the inner enamel epithelium (IEE).
What is the future role of the IEE?
The IEE will differentiate into enamel-secreting cells called ameloblasts.
What separates the IEE and the adjacent dental papilla?
A basement membrane separates them.
How do the IEE cells influence the dental papilla?
IEE cells exert an organizing influence on the underlying mesenchymal cells of the dental papilla, which later differentiate into odontoblasts (dentin-producing cells).
What role does the OEE play in enamel formation?
The OEE organizes a network of capillaries to bring nutrition to the ameloblasts during enamel production.
What happens to the OEE surface at the end of the bell stage?
The formerly smooth surface of the OEE becomes folded to prepare for enamel formation.
How does the adjacent mesenchyme of the dental sac respond to the folded OEE?
The adjacent mesenchyme forms papillae containing capillary loops, which supply nutrition to the avascular enamel organ.
What two layers are found between the outer and inner enamel epithelium during the bell stage?
The stellate reticulum and the stratum intermedium.
What is the stellate reticulum?
It consists of star-shaped cells in many layers, forming a network within the enamel organ.
Where is the stellate reticulum located in the enamel organ?
It is found in the center of the enamel organ in a developing tooth.
What do the cells of the stellate reticulum synthesize?
They synthesize glycosaminoglycans.
What is the stratum intermedium?
It is a compressed layer of flat to cuboidal cells.
Where is the stratum intermedium located?
It is located between the inner enamel epithelium and the newly forming cells of the stellate reticulum.
When does the stratum intermedium first appear?
It appears during the early bell stage of tooth development, around the 14th week of prenatal development.
What is the role of the stratum intermedium?
Along with the inner enamel epithelium, it is responsible for supporting the production of enamel.
What happens to the dental lamina during the bell stage?
The dental lamina disintegrates.
How does the tooth develop after the disintegration of the dental lamina?
The tooth continues to develop separated from the oral epithelium.
What may form from remnants of the disintegrated dental lamina?
Remnants may become entrapped in the tissues, forming epithelial pearls.
How is the crown pattern of the tooth established during the bell stage?
The crown pattern is established by the folding of the inner enamel epithelium (IEE).
What begins to form at the crest of the folded IEE?
Dentin and enamel begin to form at the crest of the folded IEE.
What happens to the dental papilla during the bell stage?
The dental papilla undergoes extensive histodifferentiation and differentiates into two types of tissue.
What are the two types of tissues in the dental papilla?
The outer cells of the dental papilla and the central cells of the dental papilla.
What do the outer cells of the dental papilla differentiate into?
They differentiate into odontoblasts, which are dentin-secreting cells.
What do the central cells of the dental papilla become?
They become the primordium of the pulp.
What happens to the dental sac during the bell stage?
The dental sac increases its amount of collagen fibers.
Into what does the dental sac undergo histodifferentiation?
The dental sac undergoes histodifferentiation into its mature dental tissue types.
What mature dental tissue types does the dental sac form?
The dental sac forms cementum, the periodontal ligament, and the alveolar process.
How is the dental lamina related to root development?
The disintegration of the dental lamina allows root development to proceed, separating the tooth from the oral epithelium.
What are the final stages of tooth development?
The final stages are the apposition stage and the maturation stage.
What happens during the apposition stage?
During the apposition stage, enamel, dentin, and cementum are secreted in successive layers upon the existing layers.
How are the hard dental tissue types secreted initially during the bell stage?
They are secreted as a partially mineralized matrix.
What is the matrix in the context of tooth development?
The matrix is an extracellular substance that serves as a framework for full mineralization later.
What marks the maturation stage?
The maturation stage is reached when the matrices of the dental tissues fully mineralize.
How does the level of mineralization vary among dental tissues?
Enamel is the hardest, dentin is the next hardest, and cementum is the least hard, similar in hardness to bone tissue.
Which part of the tooth does tooth development begin?
Tooth development begins in the crown and then proceeds to the root.
What happens after the formation of the inner enamel epithelium (IEE) in the enamel organ?
The innermost cells of the IEE elongate and differentiate into preameloblasts.
What occurs during the differentiation of preameloblasts?
The nucleus in each preameloblast cell moves away from the center to the position farthest from the basement membrane, a process called repolarization.
What happens to preameloblasts after inducing odontoblasts?
Preameloblasts themselves differentiate into ameloblasts, which secrete enamel.
What happens after the IEE differentiates into preameloblasts?
The outer cells of the dental papilla are induced by preameloblasts to differentiate into odontoblasts.
What process do odontoblasts undergo during differentiation?
Odontoblasts undergo repolarization, where their nuclei move to a position farthest from the basement membrane.
How do the repolarized odontoblasts align?
They line up adjacent to the basement membrane.
What is the next step for odontoblasts after alignment?
Odontoblasts begin dentinogenesis, which is the appositional growth of dentin matrix (predentin), laying it down on their side of the disintegrating basement membrane.
Where is the basement membrane located during this stage?
The basement membrane is located between the IEE of the enamel organ and the odontoblasts in the dental papilla.
What happens after odontoblasts form predentin?
The basement membrane between the preameloblasts and the odontoblasts disintegrates.
What does the disintegration of the basement membrane allow?
It allows preameloblasts to contact the newly formed predentin.
What does contact of the preameloblasts with the predentin induce in preameloblasts?
It induces preameloblasts to differentiate into ameloblasts.
What do ameloblasts begin producing?
Ameloblasts begin amelogenesis, the appositional growth of enamel matrix.
What side of the basement membrane is the enamel matrix laid down?
It is laid down on their side of the disintegrating basement membrane.
From where is the enamel matrix secreted?
The enamel matrix is secreted from Tomes’ process, a histologic feature of ameloblasts.
What is Tomes’ process?
Tomes’ process is a projection of the ameloblast surrounded by developing enamel during its formation.
What happens when the enamel matrix contacts the predentin?
Mineralization of the disintegrating basement membrane occurs.
What does mineralization of the basement membrane form in the context of tooth development?
It forms the dentinoenamel junction (DEJ), which is the inner junction between the dentin and enamel tissues.
What do odontoblasts leave behind as they move away from the DEJ?
Odontoblasts leave attached cellular extensions called odontoblastic processes.
Where are odontoblastic processes located?
They are located in the length of the predentin.
What surrounds the odontoblastic processes?
Each process is contained within a mineralized cylinder called a dentinal tubule.
What are dentinal tubules?
Dentinal tubules are microscopic channels that run from the pulp of a tooth through the dentin and end just beneath the enamel.
What is the function of dentinal tubules?
They transport nutrients from the pulp to the dentin and transmit sensations such as touch and temperature.
What can interfere with the metabolic processes of ameloblasts?
Certain factors can interfere, leading to enamel dysplasia.
What is enamel dysplasia?
Enamel dysplasia is the faulty development of enamel.
What types of causes can lead to enamel dysplasia?
Enamel dysplasia can have either local or systemic causes.
What can cause local enamel dysplasia?
Local enamel dysplasia may result from trauma or infection affecting a small group of ameloblasts.
What can cause systemic enamel dysplasia?
Systemic enamel dysplasia may result from traumatic birth, systemic infections, nutritional deficiencies, or dental fluorosis.
