Odontogenesis Flashcards
From what type of cells do tooth tissues derive from?
Stem cells originating in the ectoderm primary germ layer
When does odontogenesis occur?
6th embryonic week
What two tissues from the ectoderm are involved in odontogenesis?
Epithelium and mesenchyme
Dentinogenesis
Formation of dentin
Amelogenesis
Formation of enamel
Cemetogenesis
Formation fo cementum
What are the epithelial stages based on
Histological shapes of the epithelial tissue within a mesenchymal environment
What are the epithelial stages of tooth development?
Epithelial dental lamina stage
Epithelial bud stage
Epithelial cap stage
Epithelial bell stage
At what stage is the epithelium is arranged in 4 distinct cell layers
Epithelial bell stage
What happens during the tooth germ stage
Odontogenic epithelial and mesenchymal tissues are combined
Cells of each tissue is induced specifically to become fomative cells of dentin, enamel, cementum, and pulpal tissues
What tissue does the enamel organ derive from?
Epithelium
What tissue does the dental papilla drive from?
Mesenchyme
What tissue does the dental follicle derive from?
Mesenchyme
What occur during the primary dental lamina stage
Two epithelial invaginations appear in the lower anterior region of the lower jaw and later in the same week (6th) in the upper jaw
The invaginations descend into the underlying mesenchymal tissue (ectomesenchyme) and continue posteriorly within the mesenchyme as continuous epithelial bands
What are the 2 invaginations of the primary dental lamina stages?
Vestibular lamina
Primary dental lamina
Vestibular lamina
Facial band of invagination during primary dental lamina stage
Cell death will occur in the center of the vestibular lamina, leaving space known as the ‘vestibule’
Primary dental lamina
Lingual band of invagiation during primary dental lamina stage
Cells arising form the dental laminae (primary and secondary) become odontogenic epithelial part of tooth germ
Epithelial bud stage
Cells at the deep end of the dental lamina develop into epithelial knobs, known as ‘epithelial bud’
Each bud is surrounded by mesenchymal tissue, and bud cells are continuous with cells of the primary dental lamina
When do primary buds form?
6-8 weeks in utero
When do permanent buds form?
4 months in utero to 5 years postnatal
When do primary central incisor buds form?
6 weeks in utero
When do primary second molar buds form?
8 weeks in utero
When do first molar permanent buds form?
4 months in utero
When do permanent central incisor buds form?
5 months in utero
When do permanent second molar buds form?
10 months postnatally
When do permanent third molar buds form?
5 years postnatally
Epithelial cap stage
Odontogenic epithelial is in the shape of the cap
-this cap used to be the epithelial bud
Enamel knot
Concentration of epithelial cells in the epithelial cap
Signaling center to determine if the tooth will develop to become an anterior or posterior tooth
Epithelial bell stage
Epithelial cap undergoes growth and develops into a bell shaped epithelial structure called the ‘enamel organ’
Epithelium is in 4 distinct layers
What are the 4 cell layers of the epithelial bud stage?
Inner epithelial layer
Stratum intermedium epithelial layer
Stellate reticulum epithelial layer
Outer epithelial layer
What layer of the epithelial bell becomes the ameloblasts?
Inner epithelial layer
Secondary dental lamina
Lingual to the primary tooth germ
Arises from the primary dental lamina - not the oral epithelium
How many secondary lamina arise in each arch?
10 - one for each secondary tooth
Tooth germ stage
The epithelial enamel organ and a closely associated ectomesenchymal tissue that is continuous form around the epithelium to within the epithelium
-when combined, the enamel organa and ectomesenchyme are a tooth germ
What are the 3 parts of the tooth germ?
Enamel organ
Dental papilla
Dental follicle
Enamel organ
Avascular tissue from epithelium
inner epithlial cells differentiate into ameloblasts
After formation of the enamel is complete, ameloblasts, along with the other layers of the enamel organ come together to form what?
Reduced enamel epithelium
What is the purpose of the reduced enamel epthelium?
It is a protective structure over the surface of the enamel until the tooth enters the oral cavity
Dental papilla
Vascular tissue form mesenchyme
Stem cells become odontoblasts, fibroblasts, and reserve cells
Ultimately becomes the pulp of the tooth
Dental follicle
Vascular tissue from mesenchyme
Stem cells become cementoblasts, fibroblasts, osteoblasts, and reserve cells
Ultimately becomes the periodontal ligament of the periodontium
Where is the initial site of appearance of ameloblasts and odontoblasts?
Within the tooth germ along the area between the papilla and the inner cells of the enamel organ
Ameloblasts form what?
Enamel
Odontobalsts form what?
Dentin
What is the fate of enamel organ cells after completion of enamel?
The 4 cell layer come together to form the reduced enamel epithelium
Cervical loop
Rim of the epithelial bell
This is the site where the inner and outer cells merge
Fate of the cervical loop
Outer and inner layers come together to form a double epithelial layer called ‘Hertwig’s epithelial root sheath’
Hertwig’s epitheliual root sheath
Determines the root-dentin outline
Determines the number of root canals of the tooth
