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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- 1 / 89
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Lernkarten
What happens to the basement membrane once the predentitn has formed?
Desentegrates
The contact between predentin and preameloblasts caused by the desentigration of the basement membrane initiates what?
Preameloblasts differentiate into ameloblasts and enamel formation begins
Where does enamel formation begin?
At cusp tips and incisal edges
The odontoblasts leave attached cellular extentions in the length of the predentin which are called ____. These processes are contained in a mineralized cylinder known as _____?
- Odontoblastic process
- Dentinal tubules
The enamel matrix is secreted by what?
Tomes' Process: an angled part of each ameloblast that faces the disintigrated basement membrane created as the ameloblasts move away from the dentin interface.
What occurs to the previously desentigrated basement membrane?
It is mineralized forming the denoenamel junction
This appears at the junction of the cell body and Tomes' process to maintain cell contact.
Terminal bar apparatus
When is the maturation stage reached?
When the dental tisue types fully mineralize
Where are mineralis deposited shortlya fter the matrix is formed?
Mineralized at the DEJ 1st
Enamel being the most highly calcified tissue in the body is ____% mineral content?
95%
What is the mineral contenet of dentin?
70%
This is a cellular organic covering secreted by the ameloblasts. It is a cuticleon the surface of the enamel that contains enzymes from the epithelium that will aid in tissue disintegration giving way to the eruption pathway. It is removed once the tooth erupts into th oral cavity. It also helps in the formation of the junctional epithelium near the CEJ.
Reduced enamel epithelium
When does root foramtion begin?
It begins as the tooth starts to erupt into the oral caivty
What forms the root?
Cervical loop
What are teh 2 layers of the cervical loop?
- Inner enamel epithelium
- Outer enamel epithelium
This is the double layered structure which if fomred from apex of the cervical loop region.
Hertwig's root sheath
The outer root sheeth functions in the deposition of?
Intermediat cementum: the 1st layer of highly calcificed cementum at the junction of the cemenum and dentin.
This is the 45* angle at the end of the rooth sheath.
Epitheilal diaphragm
When does cementogenesis occur?
After the degredation of the rooth sheeth
The degredation allows for the contact of the dental sac cells with the dnetin surface which induces?
Cementoblast cell formation
Cementoblasts undergo cementogenesis which is the lying down of?
Non-calcified cemntoid on the intermdiate cementum
True/False:
All teeth begin as a single rooted tooth.
True: multi rooted teeth have a root trunk which is their single root once it reaches the end of the trunk the epitheilum will differenitate into the 2 or 3 roots.
What cells that surrond the dental sac/folice consens to form the PDL and alveoal bone?
Mesenchymal cells
The cells of the disitegrated root sheath develop into what?
Islands of epithelial cells (Rests of Malassez)
What are the rests of Malassez?
They have no known function, but are thoght to be responsible for the development of radicular cysts.
When does the PDL reach full maturation?
When the tooth is in full occlusion
This is the bone that lies between the roots.
Interradicular bone
This is the bone that lines the tooth socket.
Alveolar bone proper
This bone covers the mandible and is composed of cacellous and compact bone.
Supporting bone
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
