Histology: Tooth Development Flashcards
Name the 6 Stages of Tooth Development and the aproximate time table for when each stage occurs.
- Initiation Stage 6th-7th week of development
- Bud Stage 8th week
- Cap Stage 9th-10th week
- Bell Stage 11th-12th week
Terminal Differentiation
- Apposition Stage varies per tooth
- Maturation Stage varies per tooth
Dental lamina grows deep into the __________
ectomesenchyme
“Before birth, it is called ectomesenchyme. After birth, it is called epithelium”.
tooth development is reffered to as?
odontogenesis
vestibular lamina proliferates into _______, and then degenerates to form a ______.
mesenchyme
cleft=vestibule
Localized proliferations of the ____________ into the surrounding ____________ forms the intitial tooth buds.
dental lamina
mesenchyme
Describe the Bud Stage
- initial stage of definitive tooth development
- round localized cluster of oral epithelium of the dental lamina
Describe the Cap Stage
- beginning of morphogenesis
- oral epithelium forms a cap over a mesenchymal condensation forms the dental papilla
Describe the Bell Stage
- histodifferentiation
- epithelial cells differentiate into ameloblasts
- cells within the dental papilla differentiate into odontoblasts
- eventual shape of crown becomes distinct
dental lamina breaks up into discrete islands
developing tooth is now separate from the overlying oral epithelium
Describe the Termination (Crown) Phase
- final differentiation of odontoblasts and ameloblasts
- secretion of dentin and enamel in apposition
- Hard tissue formation of the teeth
- Dentinogenesis
- Amelogenesis (enamel formation)
- Dental follicle differentiates into alveolar bone forming around the tooth germ
Rooth Sheath development is intitiated in the _______
cervical loop region
Describe Root Formation
- Epithelial cells from the inner and outer dental epithelium proliferate from the cervical loop of the enamel organ to form Hertwig’s Epithelial Root Sheath.
- The root sheath extends down to encompass all but the basal portion of the pulp
- Ectomesenchymal cells of the pulp which face the root sheath differentiate to form odontoblasts
- The odontoblasts will eventually form root dentin.
Epithelial cells from the inner and outer dental epithelium proliferate from the cervical loop of the enamel organ to form ___________.
Hertwig’s Epithelial Root Sheath (HERS)
Root development begins after the enamel and dentin formation has reached the future _________.
cementoenamel junction
What determines the morphological characteristics of the root (number of roots, length, curvature etc)?
HERS (Hertwig’s Epithelial Root Sheath)
Ectomesenchymal cells of the pulp which face the root sheath differentiate to form _______
odontoblasts
Odontoblasts will form _______.
root dentin
The root sheath encompasses everything except the _________of the pulp.
basal portion of the pulp
The ________ differentiates into alveolar bone forming around the tooth germ.
dental follicle
The tooth originally develops from _______, a specialized region of ________?
dental lamina
oral ectoderm
Tooth development begins with the formation of a continuous band of thickened ______ called _______.
oral epithelium
Primary Epitheliual Band
Describe the primary epithelial band
- a continuous band of thickened oral epithelium
- tooth development begins with its formation
- formed by a change in the orientation of mitotic spindles and their increased proliferation activity.
- subdiivides into 2 areas that ingrow the underlying mesenchyme colonized by neural crest
- 1st- dental lamina
- 2nd- vestibular lamina
______ develops lateral to Dental Lamina and will become the ______.
Vestibular Lamina
oral vestibule
What is the oral vestibule and from which tissue does it develop?
- the cleft between the cheeks and the tooth-bearing area
- develops from the vestibular lamina
The dental lamina gives rise to ______by localized proliferation of the ________ into the surrounding _________, through a continuous process known as ______.
- teeth
- epithelium
- mesenchyme
- odontogenesis
Name the stage of odontogenesis and identify each number
Bud Stage
- Tooth bud
- Oral epithelium
- Ectomesenchyme
Describe which stage occurs during the 8th week of development
- Teeth begin to develop
- Formation of tooth bud.
- Cells proliferate.
- Neural crest cells migrate to 10 deciduous tooth sites along the future upper and lower jaws.
- These cells induce the overlying oral epithelium, or ectoderm, to become a tooth forming organ, the tooth bud.
Describe the stage of tooth development that occurs in the 9th week of development
- Early Cap Stage
- Each tooth bud undergoes a downward growth to form an epithelial structure called the enamel organ that is cap shaped.
- Histo-differentiation occurs.
- The tooth germ also begins to take on form – the start of morpho-differentiation.
Identify the Stage and the labeled aspects
Early Cap Stage 9th week
- enamel organ
- Dental Papilla
- Dental sac (dental follicle)
All 3 make up the Tooth Germ
Note: The tooth bud differentiates further to form the tooth germ.
Describe the Stage of Tooth Development that begins in the 10th week of development
Late Cap Stage
- Enamel organ produces future enamel.
- Dental papilla produces future dentin and pulp.
- Basement membrane separates enamel organ and dental papilla to form future DEJ
- Remaining ectomesenchyme around the enamel organ will form dental sac, cementum, PDL, alveolar bone.
Name the 2 cell types the tooth bud originates from
Ectoderm
Ectomesenchyme.
Name the 6 cell types the tooth germ originates from
The first 4 epithelium derived from the enamel organ
- Outer Enamel Epithelium (OEE) - forms the outer border
- Stellate Reticulum - forms the middle portion
- Stratum Intermedium - a border of cells between the Stellate Reticulum and Inner Enamel Epithelium.
- Inner Enamel Epithelium (IEE) - forms the inner border.
- DP: Dental papilla (dentinogenesis)
- DF: Dental follicle (sac) (periodontal ligament, alveolus, cementum)
Inner Enamel epithelium is composed of functional cells that will differentiate into __________ and make future _________.
ameleoblasts
enamel
Within the dental papilla, cells near the Inner Enamel Epithelium will differentiate into _______ to make future ______.
The remaining cells in the dental papilla will form ______.
odontoblasts
dentin
dental pulp
As we transition from Cap to Bell stage, which 2 newly formed cells can be identified.
Ameloblasts and Odontoblasts
Also start to see in the bell stage, the columnar shape of IEE to form Ameloblasts.
WHich 2 major events occur during the 11th week of development or early bell stage.
Defining feature of early bell stage= tooth germ assumes a bell-like shape
- Enamel Organ differentiates into 4 types of cells
- Inner dental epithelium-forms future ameloblasts
- Outer dental epithelium
- Stellate reticulum
- Stratum intermedium
- Dental papilla differentiates to 2 types of cells:
- Outer cells of the DP – forms future odontoblasts
- Central cells of the DP – forms future pulp
The entire dental organ is made of epithelial tissue and is avascular. Describe how it obtains nutrients to grow and develop into enamel.
The nutrients must come from the supporting cells.
Forming enamel requires a lot of energy, that is why Stellate Reticulum, Stratum Intermedium, and Outer Enamel Epithelium help supply nutrients to the developing Ameloblasts (from Inner Enamel/ Dental Epithelium).
- Stellate Reticulum has a large cytoplasm, where it stores nutrients and resources.
Also between the dental papila and the Inner Enamel Epithelium is a basement membrane (cell-free zone)
