Tooth development Flashcards
first sign of tooth development
6-7 weeks
in utero
when do descidusous teeth begin to calcify
13-20
weeks in utero
By_______weeks in utero all deciduous teeth
have begun to calcify
By 18-20 weeks in utero all deciduous teeth
have begun to calcify
Deciduous teeth erupt at
6-30 months
• First part of tooth to calcify is the
crown
stages of tooth development
I. Crown Formation: 1. Initiation 2. Bud Stage 3. Cap Stage 4. Bell Stage 5. Enamel and dentin formation
II. Root Formation
III. Supporting Structures
NC mesenchyme in tooth development
NCC will migrate to PA1, contributes to the mesenchyme of tooth development/ odontogenic epithelium btwn the maxillary and mandibular processes
where do the max incisors form
medial nasal process
Embryonic Oral Cavity: Internal Surface of Upper & Lower Jaw
what structure is here?
gives rise to?
Primary Epithelial Band
Horseshoe shaped
Correspond to future dental arches
Gives rise to
Dental lamina
Vestibular lamina
Early Patterning During Tooth Development, determines?
pattern of signaling molecules/ pathways will determine tooth morphology
Shh and PAX9 expression
Shh Is Expressed In The Epithelium And Pax9 In The Mesenchyme Where The Tooth
Bud Would Form
initiation stage
placode?
mesenchyme?
initial odontogenic potential? shifts?
Placode formation – Epithelial thickening.
Epithelial outgrowth into the mesenchyme
Initial odontogenic potential lies in the epithelium subsequently shifts to mesenchyme –the neural crest mesenchyme induces the oral ectoderm to become the dental lamina
how does the dental lamina form? what else forms
epithelium invaginates into the mesenchyme, vestibular lamina forms too
bud stage epithelial changes? signaling molecules of placode formation? mesenchyme at this time? cross talk? where is the odontogenic potential
Epithelial cells show no major changes
Shh, Lef-1 and Eda-Edar involved in placode formation (ectoderm thickening)
Mesenchyme beneath starts to condense by the factors secreted by the epithelium
Cross-talk between the epithelium and the mesenchyme
Odontogenic potential in the epithelium
Early Cap Stage
epithelium will? mesenchyme? looks like?
tooth germ forms what structures?
transition from bud stage regulated by?
Epithelium proliferates. Mesenchyme continue to condense. Looks like “Cap” sitting on a ball of
mesenchyme
Tooth germ forms:
Enamel organ – Enamel of the tooth
Dental papilla – Dentin (outer) and pulp (inner)
Bud to cap stage transition is regulated by signaling molecules and transcription factors
Cap Stage Enamel Knot formation/ dental follicle
Dental follicle or Dental Sac – Supporting structures (Cementum / Periodontium / alveolar bone
proper)
Enamel knot – It is a key signaling center consist of cluster of non-dividing cells determines cusp
formation. Primary and secondary enamel knot
Cap Stage Histodifferentiation
cells of enamel organ will synthesize? result?
epithelial cells become what populations?
Cells in the enamel organ synthesize glycosaminoglycans into the ECM. Hydrophilic and pull water into the enamel organ.
Increase in fluid volume force the cells apart leading to formation of star shaped stellate reticulum cells
Enamel organ epithelial cells form:
Inner enamel epithelium and Outer enamel epithelium
Cap Stage Enamel Knot Signaling Center
main molceule/ inhibitor?
SHH is main molecule to signal tooth formation, inhibited by SPRY2
bell stage
epthelium?
what layer forms?
crown?
- Under surface of the epithelium deepens and resemble a bell
- Stratum intermedium formation
- Crown attains full size and shape
Permanent Dentition Forms_____To The Deciduous Dentition
molecule involved?
Lingual
Osr2 inhibits BMP4 which stimulates Msx1 to allow this
bell stage morphodifferentiaition
cell shape/ layers?
junction of these?
- Low Cuboidal shaped outer enamel epithelium (OEE)
- Short columnar shaped inner enamel epithelium (IEE – will differentiate into ameloblasts)
- Junction of IEE and OEE is called cervical loop (CL) – also the future site of the CEJ
late bell stage dental lamina? IEE? folding due to? IEE causes mesenchyme to? IEE dif into? site of IEE dif determines?
Dental lamina breaks and the separates the tooth from oral epithelium
Inner enamel epithelium (IEE) completes folding forming the future crown pattern
Folding is due to differential rates of mitotic division in IEE
Under the influence of IEE mesenchymal cells differentiate into odontoblasts that makes
dentin
Subsequently IEE differentiate in to ameloblasts and make enamel
Site at which IEE differentiates determines future cusp formation
Amelogenesis
stages?
Ameloblasts are derived from inner enamel epithelium and the life cycle of ameloblasts
has following stages:
- Morphogenetic stage
- Histodifferentiation stage
- Initial secretory stage (no Tome’s process)
- Secretory stage (Tome’s process)
- Ruffle ended ameloblast of the maturation stage
- Smooth ended ameloblast of the maturation stage
- Protective stage
Secretory Stage Ameloblasts
activities?
forms?
secrete? contents?
Intense synthetic and secretory activity
Forms enamel rod (R) and inter-rod (IR)
Secrete granules on the newly formed mantle dentin.
Secretory products:
Proteins:
Amelogenin
Ameloblastin
Enamelin
Proteases
Enamelysin (MMP20)
Kallikrein
Under the influence of ______cells
__________ cells differentiate into
odontoblasts that make dentin
epithelial
mesenchymal
Types of Dentin
- Mantle dentin – First layer of dentin formed by the newly
differentiated odontoblasts, hypomineralized, and only in the
crown of the tooth (30-50um thick) - Primary dentin – Formed during tooth development (4um/day)
- Secondary dentin – Dentin formed after tooth eruption
(0. 4um/day) - Tertiary dentin – Dentin produced in response to injury to
protect the pulp
Enamel and Dentin Formation diagrammed
Root Formation
IEE/OEE?
odontoblasts?
IEE and OEE form the cervical loop proliferate downward to form double layered structure called Hertwig’s epithelial root sheath, also the site of the CEJ
Odontoblasts differentiation and dentin formation
Completion of root formation
Cementum Formation Fragmentation of Hertwigs? cementoblasts from? remnants of HERS? cementum cellularity?
Fragmentation of Hertwigs epithelial root sheath (HERS), mostly removed before cementum is
laid down
Differentiation of cementoblasts from HERS or dental follicle cells
Remnants of HERS are called epithelial rests of Malassez
Cementum: Acellular or Cellular
types of CEJ
overlapped
adjacent
no overlap
Periodontal Ligament Formation
occurs will root formation, several different kinds of fibers formed
epithelium development path
mesenchyme development path