HIstology of Early Tooth Development

T/F Each tooth is considered an organ

true

define odontogenesis

tooth development

what are the 2 basic tissues required to start odontogenesis

oral epithelium and ectomesenchyme

what is oral epithelium derived from

the oral ectoderm

what does the oral epithelium form

the enamel organ

where is the ectomesenchyme coming from

the neural crest

what does the ectomesenchyme form

dentin and pulp in the crown and root

what is the neural crest

transient vertebrate embryonic cells

what is the first sign of tooth development

formation of dental lamina (initiation)

what occurs in the initiation step of tooth development

the formation of the dental lamina

when does the formation of the dental lamina occur

week 6 in utero

where can we see the dental lamina

looking down on developing arch in a jaw

the dental lamina is _________ into the ectomesenchyme

invaginating

the horseshoe shape describes how-

the oral epithelium is thickening to form the developing arch

pig dental lamina

circles show deep invaginations of dental lamina

what is the first tooth stage

the formation of the tooth bud

the formation of the dental placode is the start of what stage

the tooth bug stage

what is the dental placode made of

epithelial thickening (further thickening of the dental lamina)

what does epithelial thickening mean, cellularly

increased division of cells

how many dental placode points are made in EACH arch

10 for the 10 primary teeth on each arch

what shape does the tooth bud resemble

a boot (bulbous)

why does a concavity form in the tooth bud stage

MITOSIS takes place on the superior (top) surface and the distal tip

this forms the boot shape

is the dental lamina still connected to the oral epithelium in the bud stage

yes

at which stage do cells become functionally different

cap stage

what are all the functionally different areas in the cap stage

outer enamel epithelium

inner enamel epithelium

stallate reticulum

dental papilla

dental sac/follicle

cervical loop

what is the outer enamel epithelium made of

simple cuboidal epithelium

where is the outer enamel epithelium found

on the convexity of the cap (the sides that curve OUTWARD)

where it the inner enamel epithelium found

on the concavity of the cap (the side that curve inward)

what is the inner enamel epithelium made of

simple low columnar cells

where is the stellate reticulum found

INSIDE the cap

what is between the stellate shaped cells

glycosaminoglycans (GAGS)

why do stellate reticulum have a star shaped

the desmosomes pull on the cells to connect them

what does the space of the stellate reticulum give space for

the formation of the crown

what is the ectomesenchyme below the inner enamel epithelium called

dental papilla

what does the dental papilla eventually form

the dentin and pulp of the crown

what is the ectomesenchyme around the developing enamel organ and dental papilla called

dental sac/follicle

what does the dental sac/follicle form

the cementum, PDL, and alveolar process

what is the cervical loop in the cap stage

the junction of the outer and inner enamel epithelium

what is the cervical loop used to form

the root

what makes up the enamel epithelium

- outer enamel epithelium

- inner enamel epithelium

- stellate reticulum

define morphodifferentiation

significant changes in shape, ultimately determining the final shape and structure of the tooth crown

what stage can we see the shape of the tooth histologically

the bell stage

Define Histodifferentiation

cells differentiate into their final "phenotype" which determines what they make

what does the inner enamel epithelium differentiate into

ameloblasts

what does the dental papilla differentiate into

odontoblast layer under the inner epithelium

in what direction does differentiation move

cuspal tip to cervical area (neck)

is epithelial tissue vascular?

no

is the outer enamel epithelium vascular?

yes

what stage is the enamel knot found

the bell stage

why does the enamel knot form

the epithelial cells have been told that they need to differentiate into ameloblasts cells, SO they stop dividing

where can the enamel knot be found

near the tip of the inner enamel epithelium

which cells are the first to differentiate

the ones near the enamel knot

why do the sister cells near the enamel knot, not differentiate

they need to keep growing

what is the purpose of the enamel knot

orchestrate cuspal morphogenesis (by differentiating some, but not all cells into ameloblasts)

what stage is the stratum intermedium formed in

the bell stage

where can the stratum intermedium be found

on the inner layer of the inner enamel epithelium

what is the purpose of the stratum intermedium

nutritional multilayer for the formation of enamel (feed ameloblasts)

the remaining cells from the dental papilla that did not differentiate into odontoblasts, form what?

the dental pulp

what is the inner enamel epithelium constrained between

the cervical loop and cuspal tip

why does the cuspal outline form

differential proliferation (mitosis)

at each cusp, what is happening as far as cells

there is an enamel knot of cells that are being differentiated into ameloblasts

in what direction is the future cusp being pushed

up, towards the outer enamel epithelium

what type of tissue is ectomesenchyme

Connective tissue

how is the vestibular lamina formed

thickening of oral epithelium lateral (next to) to the dental lamina

which direction do cells grow in the vestibular lamina

downward (to invaginate the ectomesenchyme)

how is a cavity formed from the vestibular lamina

the cells degenerate (via apoptosis)

what is the vestibule forming

the space between the gingiva and the inside of the cheek

what is the successional lamina and what does it ultimately form

- it branches from the parent lamina that was used for the formation of the primary tooth

- it will ultimately form the successional tooth

how many teeth, IN TOTAL, does the the successional lamina create

20

does the permanent tooth use the same placode as the primary tooth

yes since they are coming from the same parent dental lamina

what is the lateral lamina

connects the developing primary tooth to the parent lamina

the extension of the dental lamina (successional lamina) is always _________ to the primary tooth

lingual

during which stage does the enamel organ lose its connection with the oral epithelium

the bell stage

how does the enamel organ lose its connection to the oral epithelium

the parent lamina degenerates (apoptosis)

when cells degenerate, what could be left behind

islands of epithelial cells (dental lamina) in the connective tissue (ectomesenchyme)

permanent molars are derived direction from the ________ portion of the ________ _________ without a primary tooth precursor

distal; dental lamina

where is the more mineralized enamel found

near the cuspal tip

how is enamel deposited by ameloblasts

in increments