Odontogenesis #2 Flashcards
What is the definition of Odontogenesis?
Formation of tooth tissues from stem cells originating in the ectoderm primary germ layer.
When does Odontogenesis begin?
6th embryonic week
What are the two basic tissues that arise from the ectoderm primary germ layer in tooth development?
Epithelium & Mesenchyme
What is Dentogenesis?
formation of dentin tissue
What is Amelogenesis?
Formation of Enamel tissue
What is Cementogenesis?
Formation of cementum
What is the first stage of Odontogenesis?
Epithelial stages: based of histological SHAPES of the epithelial tissue.
- epithelial dental lamia stage
- Epithelial bud stage
- epithelial Cap stage
- Epithelial Bell stage *at this stage the epithelium is arranged in 4 distinct layers.
What is the second stage of Odontogenesis?
Tooth germ stage: Ondotogenic epithelial and mesenchymal tissue combined: cells of each tissue induced specifically to become formative cells of dentin, enamel, cementum and pulp tissues.
What are the three parts of tooth germ?
- Enamel organ (bell) epithelium
- Dental Papilla (Mesenchyme)
- Dental follicle (Mesenchyme)
Briefly describe when and what occurs during the primary dental lamina stage….
- Occurs during 6th embryonic week
Two epithelial invaginations appear in the lower anterior region of the lower jaw and later in the same week in the upper jaw.
These two invaginations descend into the underlying mesenchyme tissue and continue posteriorly within the mesenchyme as continuous epithelial bands.
** Facial band = vestibular lamina
** Lingual band = Primary dental lamina
What is the fate of the vestibular lamina (Facial band)?
Cell death will occur in the center of it, leaving a space called a vestibule.
What is the fate of the Primary dental lamina (Lingual band)?
cells will become the odontogenic epithelial part of a tooth germ.
What occurs during the Epithelial Bud stage?
Cells at the deep end of the dental lamina, (Where tooth is destine to form) will develop into epithelial knobs, each known as “epithelial bud”. *Each epithelial bud is surrounded by mesenchymal tissue:
Vestibular lamina band lies _____ to developing tooth site.
Facial
Epithelial bud cells are _____ withe the cells of the PDL.
Continous
When do Primary (teeth) buds form?
6-8 weeks in utero
- Central incisors = 6 weeks
- Second molars = 8 weeks in utero
When do permeant (teeth) buds form?
4 months in utero - 5 years postnatal
- First molar = 4 months in utero
- Central incisor = 5 months in utero
- Second molar = 10 months in utero
- third molar = 5 years postnatal
What occurs in the Cap stage?
Odontogenic epithelial tissue is in the shape of a cap.
* Note: Site of enamel knot (concerntraion of epithelial cells in cap) is a signaling center that determines if tooth will develop to become ant. or post. tooth!
What occurs in the Epithelial Bell Stage?
Epithelial cap undergoes growth and develops into a bell shaped epithelia structure called an “enamel organ).
* At this point the epithelium is arranged into 4 distinct layers; given names according to position within the bell and the cell morphology.
Where do ameloblasts come from?
Enamel organ
Where does secondary dental lamina arise from?
Primary dental lamina!
What happens in the Enamel organ?
- Avascular
Inner epithelial cells differentiate into ameloblasts.
*After formation of enamel, ameloblasts come together over surface of enamel and form a protective structure called reduced enamel epithelium.
What happens in the Dental papilla?
* Vascular Undifferentiated cells (stem cells) become odontoblasts, fibroblasts, reserve cells and ultimately becomes the pulp of tooth.
What happens in the Dental follicle?
- Vascular
Its stem cells become cementoblasts, fibroblasts, osteoblasts and reserve cells. Ultimately forms the periodontal ligaments.
