Initiation stage
The first stage of tooth development
When does the initiation stage occur ?
During week 6-7
What process does the initiation stage require?
Induction
What is the first step of induction?
The stomodeum is lined by ectoderm
What does the ectoderm give rise to?
The oral epithelium
What Is located below the oral epithelium?
The ectomesenchyme
What type of cells influence the ectomesenchyme?
Neural crest cells
What does the basement membrane separate during the induction stage?
The oral epithelium and ectomesenchyme
What will the oral epithelium create?
The dental lamina
What is the second stage of tooth development
The bud stage
When does the bud stage occur?
During the 8th week
What process does the bud stage require?
Proliferation
What is the first step of the bud stage?
The dental lamina grows into buds
How many buds will each arch have?
10 buds
What part remains during the bud stage?
Basement membrane
What will each bud develop into ?
A tooth germ
What is the third stage of tooth development?
Cap stage
When does the cap stage occur?
During week 9-10
What process does the cap stage require?
Differentiation, proliferation and morphogenesis
What is the first step of the cap stage?
Unequal growth of the parts of the tooth bud create a cap shape
What does the depression in the deepest part of the tooth bud form?
The enamel organ
What will the enamel organ produce?
Enamel
What is the second step of the cap stage?
The ectomesenchyme condensed into a mass within the cap
What is the mass of ectomesenchyme called?
The dental papilla
What will the dental papilla produce
Dentin and pulp
What still remains during the cap stage ?
The basement membrane
What will the basement membrane become?
The dentinoenamel junction
What is the third step of the cap stage?
When any remaining ectomesenchyme turns into a dental follicle
What will the dental follicle /sac produce?
Periodontum, cementum, alveolar bone
What is the last step of the cap stage?
The enamel organ, dental papilla and dental follicle all combine to create the tooth germ
What is the tooth germ?
The primordium of the tooth
When does initiation for the primary anterior teeth occur ?
During the end of the cap stage
What is the fourth stage of tooth development?
The bell stage
When does the bell stage occur?
During the 11-12th week
What process does the bell stage require?
Proliferation , differentiation and morphogenesis
What is the first step of the bell stage?
Enamel organ becomes bell shaped
What do the outer cells of the enamel organ become?
The outer enamel epithelium
What is the job of the outer enamel epithelium?
To be a protective barrier
What do the inner cells of the enamel organ become ?
The inner enamel epithelium
What is the job of the inner enamel epithelium?
To differentiate into ameloblasts
What still remains during the cap stage?
The basement membrane
What two things form between the OEE and IEE?
The stellate reticulum and stratum intermedium layers
What is the stellate reticulum layer?
The outer layer that is star shaped
What is the stratum intermedium layer?
The inner layer , flat shaped
What is the job of both stellate and stratum layers?
To help produce enamel
What is the second step in the cap stage?
The dental papilla becomes outer and central cells
What will the outer cells of dental papilla become?
Odontoblasts
What will the inner cells of the dental papilla become?
Primordium of the pulp
What is the last step in the cap stage ?
The dental follicle increases in collagen fibers
What is the fifth step in tooth development?
Apposition
What occurs during apposition?
Enamel, dentin and cementum are all secreted in layers
What process does apposition require ?
Induction and proliferation
How are the layers initially secreted?
As a matrix
What is the sixth step of tooth development?
Maturation
What happens during maturation?
full mineralization of tissues occurs.
Which cells form enamel?
Ameloblasts
Which cells form dentin?
Odontoblasts
Which cells form cementum?
Cementoblasts
Which cells form the alveolar bone?
Osteoblasts
What is odontogenesis?
The many stages of tooth development. A continuous process with no clear starting or end point between stages
Disturbances of initiation stage?
Anodontia
Supernumerary teeth
Anodontia
Absence of teeth
Supernumerary teeth
Development of extra teeth
Disturbances in the bud stage
Microdontia
Macrodontia
Successional dental lamina
Site of origin for permanent dentition
Disturbances during cap stage
Dens in dente
Gemination
Fusion
Tubercules
Dens in dente
A tooth within a tooth
gemination
A single tooth germ tries to divide into 2 tooth germs causing a large single rooted tooth
Fusion
The union of two tooth germs
Tubercules
Extra cusps on teeth
Where does tooth development begin and end?
Begins in the crown and ends in the root of the tooth
Disturbances of final stages
Enamel dysplasia
Enamel hypoplasia
Enamel hypocalcification
Fluorosis
Dentin dysplasia
Dentin imperfecta
Enamel dysplasia
Faulty development of enamel
Enamel hypoplasia
Reduction in the quantity of enamel matrix
Enamel hypocalcification
Results in a turner spot (yellow staining)
Dental fluorosis
Hypoplasia and hypocalcification occurring together to stain teeth
Dentin dysplasia
Faulty development of dentin
Dentinogenesis imperfecta
Blue gray color of teeth
How does odontoblasts form?
IEE turns into preameloblasts
IEE cells undergo repolarization
Preameloblasts become enamel matrix secreting cells
Preameloblasts become odontoblasts
Odontoblasts begin dentinogenesis
Dentinogenesis
The formation of dentin
How does ameloblasts form?
Basement membrane disappears
Preameloblasts can then contact predentin
This contact cause preameloblasts to become ameloblasts
Amelogenesis begins
Enamel matrix is secreted by tomes process
Basement membrane mineralized forming DEJ
amelogenesis
Formation of enamel
What causes the formation of the DEJ
When the basement membrane mineralizes
What is the job of tomes process?
To secrete the enamel matrix
Enamel matrix formation
Odontoblasts leave attachments in the predentin called odontoblastic processes
What houses the odontoblastic processes?
Dentinal tubules
What does the cervical loop develop?
The root which consists of the IEE and OEE
How does root development occur?
1. Cervical loop grows deep into ectomesenchyme to move away from the crown area
2. Hertwig epithelial sheath is formed.
What is the job of HERS?
To shape the root and induces dentin formation in the root area.
Why is enamel not located in the roots?
Because HERS can not induce into ameloblasts. It can only induce odontoblastic differentiation.
What happens when root dentin formation is completed?
Basement membrane goes away and so does entire HERS
What occurs after those two things disappear?
Cells become epithelial rests of Malassez (ERM)
Cementogenesis
Laying down of cementum
How does cementum form?
1. Mesenchymal cells become cementoblasts
2. Cementoblasts lay down cementoid
3. Cementoblasts become trapped and then mature to cementocytes
4. Cementoid calcifies to become cementum
concrescence
Excess cementum formation
Multirooted teeth
1. Start as single root
2. Root trunk divides into tooth branches
3. HERS divides root trunk into 2-3 roots
4. Cervical loop elongates into extensions or roots
Which teeth take a shorter amount of time to develop?
Primary teeth
When do primary crowns mineralize?
Before birth
When do permanent teeth begin to form?
After birth
Dilaceration
Distorted root angulations (dancing root) due to injury to HERS