DEH 103: Histology & Embryology
Chapters 5 & 6: Development, Eruption, and Shedding of Teeth
Chapters 5 & 6: Development, Eruption, and Shedding of Teeth
This is the vertical movement of the tooth.
Active eruption
This occurs with aging, recession no actual tooth movement.
Passive eruption
What are the 3 phases involved in eruption?
- Pre-eruptive phase
- Pre-functional phase
- Functional phase
FYI: This is a continous process that ends only when the tooth is lost
This phase includes the time of tooth initation until the time of crown completion.
Pre-eruptive phase
This phase starts with root formation and ends when teeth reach occlusal contact.
Pre-functional eruptive phase
What are the 4 major events durring the pre-functional phase?
- Root formation: proliferation of the root sheath and rooth dentin; formation of pulp tissue
- Movement: incisal or occlusal movement due to the need for space of the enlarging roots; reduce enamel epithelium fusing with the oral epithelium.
- Penetration: into the oral cavity
- Intraoral occlusal or incisal movement: until clinical contact with opposing crown occurs, apical shipt of gingival attachment.
This is an overlying tissue change that is formed by the dental follicle.An inverted triangular area of degenerating connective tissue is formed.
Eruption pathway
These are follicular fibers that will guide the tooth movements in the eruption pathway.
Gubernacular cord
What is the function of an osteoclast during the pre-functional phase?
They function to resorb hard tissue by secreting hydrlytic enzymes. They will be modified b/c they will increase their surface area to maximize their resorption function.
What are the 2 phases of hard tissue resorption?
- Extracellular: mineral is separated from colalgen
- Intracellular: osteoclasts ingest these fragments
This is a region at the apex of the root which accomodates the growing root. Fibroblasts are abudant in this reion to form collagen fibers and calcifed trabeculae at the apex.
Fundic region
This is the phase after teeth are functioning and as long as theya re present.
Functional phase
How long does it take for root formation to be completed?
- 1-1.5 years for primary teeth after occlusion is made
- 2-3 years for permenent teeth after occlusion is made
What are 4 types of tooth movement?
- Occlusal / incisal
- Horizontal
- Rotation & lateral movement
- Mesial drift
What is mesial drift?
Lateral movemement of the tooth on both sides of the mouth, woards the mildline. Contacts wear due to mastication. Pressure on the mesila side of the scoket causes resprotion of lamina dura and tension of the PDL on the disal side which causes growth and shit in the position of tooth socket.
True/False:
1st permanent molars develop approximately where they will erupt. However, mandibular 2nd and 3rds develop in the ramus with the occlusal table pointed distal?
False: 2nd and 3rd are in the ramus with the occlusal table pointed mesial
Where do maxillary 2nd and 3rd molars develop and what direction is their occlusal tables pointed?
- Maxillary tuberosity
- Occlusal surfaces bucally & distal
This is the term for 2 dentitions (primary / permenent).
Diphyodont
This is the loss of primary dentition by the physiologic resorption of their roots.
Shedding
What are some key deifferences in primary and permenent dentiion?
- Primary enamel is prismless
- Primary enamel is 1/2 as thick
- Primary enamel is less pigmented
- Primary dentin softer
- Primary pulps larger
- Primary have less nerves
True/False
Tooth development takes place in many stages (it is continuous). The primary and permenent teeth have the same stages of development.
True
Teeth develop from ____ to ____ and ____ before ____?
- Anterior
- Posterior
- Mandibular
- Maxillary
True/False:
Teeth have the shortest developmental period of any set of organs in the body.
False: longest developmental period
What are the 6 stages of tooth growth?
- Initation stage
- Bud stage
- Cap stage
- Bell stage
- Apposition stage
- Maturation stage
When is the initiation stage occuring?
3th -7th week in utero
When is the bud stage occuring?
8th week in utero
When does the cap stage occur?
9th -10th weeks in utero
When does the bell stage occur?
11-12th weeks in utero
When do the apposition and maturation stages occur?
It varies per tooth
Odontogenesisi starts with the initiation stage at 6-7 weeks prenatal. The stomodeum is lined by ___ which gives rise to ____.
- Ectoderm
- Oral epithelium
What forms the enamel organ which in turn forms enamel.
Oral epithelum
What forms the dental papilla which in turn forms the dental papilla?
Mesenchymal cells
By the end of the 7th week what has happend?
Growth of the oral epithelium has occured giving rise to the dental lamina.
What is the dental lamina?
It is a layer of epithelial cells that gives rise to the 20 primary tooth buds.
This forms a cleft that becomes the vesibule of the oral cavity. It has rapid cell enlargment and then degeneration.
Vestibular lamina cells
This stage is characterized by rounded, localized growth of epithelium surrounded by mesenchymal cells.
Bud stage
Lable 1-3
- Tooth bud
- Oral epithelium
- Mesenchyme
This forms into the primary teeth and will continue to grow into the ____ to form the permanent teeth.
- Primary lamina
- Successional lamina
This is what forms into the permanent molars.
General lamina
Durring the cap stage (9-10 weeks) what 3 things continues to occur?
- Proliferation
- Differentiation
- Morphogenesis
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Flashcards
True/False
Tooth development takes place in many stages (it is continuous). The primary and permenent teeth have the same stages of development.
True
Teeth develop from ____ to ____ and ____ before ____?
- Anterior
- Posterior
- Mandibular
- Maxillary
True/False:
Teeth have the shortest developmental period of any set of organs in the body.
False: longest developmental period
What are the 6 stages of tooth growth?
- Initation stage
- Bud stage
- Cap stage
- Bell stage
- Apposition stage
- Maturation stage
When is the initiation stage occuring?
3th -7th week in utero
When is the bud stage occuring?
8th week in utero
When does the cap stage occur?
9th -10th weeks in utero
When does the bell stage occur?
11-12th weeks in utero
When do the apposition and maturation stages occur?
It varies per tooth
Odontogenesisi starts with the initiation stage at 6-7 weeks prenatal. The stomodeum is lined by ___ which gives rise to ____.
- Ectoderm
- Oral epithelium
What forms the enamel organ which in turn forms enamel.
Oral epithelum
What forms the dental papilla which in turn forms the dental papilla?
Mesenchymal cells
By the end of the 7th week what has happend?
Growth of the oral epithelium has occured giving rise to the dental lamina.
What is the dental lamina?
It is a layer of epithelial cells that gives rise to the 20 primary tooth buds.
This forms a cleft that becomes the vesibule of the oral cavity. It has rapid cell enlargment and then degeneration.
Vestibular lamina cells
This stage is characterized by rounded, localized growth of epithelium surrounded by mesenchymal cells.
Bud stage
Lable 1-3
- Tooth bud
- Oral epithelium
- Mesenchyme
This forms into the primary teeth and will continue to grow into the ____ to form the permanent teeth.
- Primary lamina
- Successional lamina
This is what forms into the permanent molars.
General lamina
Durring the cap stage (9-10 weeks) what 3 things continues to occur?
- Proliferation
- Differentiation
- Morphogenesis
There is (equal / unequal) growth in different parts of the tooth bud that results in a cap shape that is attached to the ____.
- Unequal
- Dental lamina
What 2 things are formed during the cap stage?
- Enamel organ: will form enamel
- Denal papilla: will form the dentin and pulp
FYI: there is a basement membrane between the enamel organ and dental papilla that will later form into the dentoenamel junction
The concave surface forms in the deepest part of each tooth bud and forms the cap also known as?
Enamel organ
Below the enamel organ is the ___ which forms the future dentin and pulp tissues.
Dnetal papilla
This is connective tissue that surrounds part of the enamel organ and papilla. It will later develop into what?
- Dental sac / follicle
- Forms:
- PDL
- Cementum
- Alveolar bone
This includes the rneamel organ, dental papilla, and dental sac.
Tooth germ
The tooth germ develops what while the successional dental lamina develops the permanent dentition at what time?
- Primary dention
- At the same time
As the tooth germ grown the cap-shaped enamel organ changes to look like a "bell." What are the 4 distiguisable enamel organ layers at this time?
- Outer enamel epithelium
- Stellate reticulum
- Stratum intermedium
- Innter enamel epithelum
This is the outer layer of the enamel organ. It is composed of cuboidal cells. It functions to organize a network of capillaries that will bring nutrition to the ameloblasts.
Outer enamel epithleium
Just inside the outer enamel epithelium layer. It is composed of a loose network of star-shaped epithelial cells.
Steliate reticulum
*Selestial*
This layer is between the steilate reticulum and the internal enamel epithelium. The layers are closely packed, flat epithelial cells, that assist the ameloblast in the formation of enamel.
Stratum intermedium
This lines the inside of the enamel organ. It is a single layer of cuboidal cells, which become the ameloblasts that fomr the enamel of each crown.
Inner enamel epithelium
What are the two types of tissue layers that the dental papilla is made up of during the bell stage?
- Dentin secreting cells (odontoblasts): outter cells of the dental papilla
- The inner cells become the dental pulp
This occurs at the end of the bell stage when the enamel organ's inner and outer epitheliual cell layers meet and are continousous with each other.
Cervical loop
What occurs around the same time as the cervical loop is complete?
Mesenchymal cells migrate to from the periphery of the enamel organ to start development of the future periodontium
These cells are formed by the inner enamel epithelium.
Ameloblasts
These cells are formed by peripheral cells of the dental papilla.
Odontoblasts
This is cell growth stage?
Apposition stage
When does formation of the hard tissues begin?
When the ameloblasts and odontoblasts have differentiated on either side of the basement membrane durring the same time as teh mandible and maxilla bones are forming
Once the preameloblasts are formed on one side of the basement membrane the other side consists of odontoblasts which form what?
Predentitn
