Development of teeth Flashcards
when and where does the primary epithelial band appear
appears at 5-6 weeks of development in future maxilla and mandible and its a horseshoe shaped band of thickened epithelium in the position of future dental arches
what is the dental lamina and how does it develop
dental lamina is derived from the primary epithelial brand and around 7 weeks the epithelial band divides into
1-vestibular lamina( buccally forms vestibule)
2- dental lamina ( lingually forms teeth)
what are the main stages of tooth development
- bud stage
-cap stage - bell stage
-crown formation - dentinogenesis
-amelogensis - root formation
stages of tooth eruption include
- bud stage
-cap stage - bell stage
- crown stage
list the 3 process that overlap the stages of tooth development
-initiation: establish site of future teeth
- morphogenesis : determines shape of tooth
- histogenesis : differentiation of cells into specific types
where does tooth development occur
stomatodeum
what interactions are involved in tooth development
interactions between ectoderm and ectomesenchyme
what lines stomatodeum during tooth development
by thin epithelium derived from ectoderm
what is the significance of primary epithelial band in tooth development
its a superficial epithelial thickening in position of future dental arches and is crucial for initiation of tooth development
where do deciduous and permanent dentitions arise from
dental lamina
how does deciduous teeth develop
from initial development of dental lamina
when does the proliferation of epithelium for deciduous teeth occur
around 13 weeks in utero to initiate tooth formation
how do early tooth germs form in deciduous teeth
epithelium proliferates at 10 sites in each dental lamina forming early tooth germs
what initiates the formation of permanent incisors, canines, and premolars
results from further proliferation of dental lamina on lingual aspect of deciduous tooth germ
where does the proliferation of dental lamina occur
lingual aspect of deciduous tooth germ
what happens to the permanent tooth germ after its formed
it remains inactive for sometime after initial formation until the deciduous tooth is ready to be replaced
do permanent molar teeth have deciduous
no permanent teeth doesnβt have deciduous predecessors
how do permanent molar teeth develop
from the growth of dental lamina posteriorly so posterior extension
which layer initiates tooth development in the first 2 weeks of embryogenesis
epithelium from 1st branchial arch
how do neural crest cells and mandibular epithelium interact in tooth development
when the neural crest cells interact with mandibular epithelium they form tooth, bone, and cartilage
what happens when neural crest cells interact with limb epithelium instead of mandibular epithelium
they form only bone and cartilage
after initial stages of tooth development which structure takes over the process
ectomesenchyme takes over
which growth factor is involved in signaling gene expression in neural crest cells during tooth development
Fgf-8 growth factor from oral epithelium induces gene expression in neural crest cells
what genes are induced by Fgf-8 and expressed in the ectomesenchyme of 1st arch
Lhx-6 and Lhx-7 are induced by Fgf-8 and expressed early in the ectomesenchyme cells of 1st arch
which gene defines the exact sites where tooth germ appear
Pax-9 gene controls the positioning of teeth
how is the shape of teeth controlled before and after day 11 of development
before day 11= epithelium β ectodermβ controls shape of teeth
after day 11= ectomesenchyme cells determine shape using homeobox genes
what happens when molar epithelium is combined with incisor ectomesenchyme before and after day11
before day 11 = results in molar because the epithelium controls the shape of tooth
after day 11= results in incisor because the ectomesenchyme controls shape of tooth
how many genes have been identified in the initiation of tooth development
90 genes
ectomesenchyme can induce what
can induce tooth formation with oral epithelium and even non oral like foot epithelium
At what stage and week do individual epithelial buds appear on the dental lamina, and what happens to ectomesenchyme cells during this time
At the Bud Stage (~8 weeks in utero), individual epithelial buds (swellings) form on the deep surface of the dental lamina. Ectomesenchyme cells become closely packed around the epithelial bud.
Do epithelial cells change in shape or function during the bud stage
no, there is little to no change in the shape or function of epithelial cells during the bud stage
What characterizes the Cap Stage (~11 weeks in utero) of tooth development
the epithelial bud proliferates and invaginates, forming a cap shape, and there is **more condensation of ectomesenchyme cells.
How does morphogenesis occur in the enamel organ during the cap stage
Morphogenesis increases: the central cells of the enamel organ become spherical, while the **peripheral cells become cuboidal.
By what week does the late cap stage occur, and what happens to the enamel organ
by ~12 weeks in utero, the enamel organ cells differentiate into three layers: **Outer Enamel Epithelium (OEE), **Inner Enamel Epithelium (IEE), **Stellate Reticulum (SR).
Into what does the ectomesenchyme proliferate during the late cap stage
proliferates into the dental papilla (precursor to dentin and pulp) and dental follicle (sac) (precursor to cementum, periodontal ligament, and alveolar bone)
What are the three layers of the enamel organ during the late cap stage, and how do the cells differ in shape
-
Outer Enamel Epithelium (OEE): cuboidal cells.
- Inner Enamel Epithelium (IEE): columnar cells.
- Stellate Reticulum (SR): star-shaped cells connected by desmosomes with intercellular spaces
what does the enamel organ become in future
enamel
what does the dental papilla become in future
dentin and pulp
what does the dental follicle become in future
cementum
pdl
bone of tooth socket
what happens during bell stage of tooth development
tooth crown takes its final shape and enamel organ diff into 4 layers
list the 4 layers of the enamel organ in bell stage
inner enamel ep
stratum intermedium
stellate reticulum
outer enamel ep
inner enamel ep function in bell stage
responsible for enamel formation
made of columnar
determines shape of crown
stratum intermedium function in bell stage
consists of 2-3 layers of flat cells that help in supporting enamel formation by assisting IEE
stellate reticulum function in bell stage
star shaped cells that secrete intracellular fluid to protect inner enamel ep and dental papilla
outer enamel function in bell stage
consist of cuboidal
responsible for substance exchange with blood vessels in dental sac
what happens to dental lamina during bell stage
it breaks down separating tooth germ from oral ep and remnants may be present and calledβ epithelial pearlsβ
what is enamel niche
an artifact in histological sections caused by cutting through dental lamina
what is enamel knot
temporary structure seen in molar tooth development during cap stage and acts as reservoir of cells for the growing enamel organ and may influence crown formation
what is enamel cord
structure running from the enamel knot to outer enamel epithelium during early bell stage and help determine initial position of 1st cusp during crown pattern formation
What happens in the crown stage of tooth development
In the crown stage, dentine and enamel begin to form. The inner enamel epithelium cells differentiate into pre-ameloblasts, which induce the formation of odontoblasts from dental papilla. Dentine secretion triggers ameloblast differentiation, initiating enamel formation
