Tooth Development Flashcards
What are the growth factors responsible for the shape of tooth?
SHH, FGFs, BMPs, and WNT
*and MSX2 (transcription factor)
extra enamel know express?
Fgf4
enamel organ is supported by?
basal lamina
outer enamel organ contents
- low cuboidal & high nuclear/cytoplasmic ratio
- free ribosomes, rER, mitochondria
- *few scattered TONOFILAMENTS
stellate reticulum are connected to?
**shape?
1) each other
2) OUTER enamel epithelim
3) stratum intermedium via desmosomes
* **STAR SHAPED
stratum intermedium connected to?
1) each other
2) INNER enamel epithelim
3) stellate reticulum via desmosomes
inner enamel epithelium contents?
- central nucleus
- *high glycogen content
- *poorly devel Gogli
- free ribosomes, rER, mitochondria, some TONOFILAMENTS
enamel organ derived from?
oral epithillum via dental lamina
enamel organ determines?
shape of crown
enamel organ induced the formation of?
dentin
enamel organ establishes the _____ juntion?
dentogingival
enamel organ FORMS?
enamel of tooth
Stellate reticulum cells secrete? what does this do?
Glycosaminoglycans (GAGs)
**GAGs draw water into enamel organ increasing its volume
Stratum intermedium adjacent to?
ssential for?
- adjacent to inner enamel epithelium
- Essential for enamel formation and mineralization – alkaline phosphatase!!!!
- *MUST be present or ameloblasts will not secret enamel
Inner enamel epithelium (IEE) differentiates into?
ameloblasts (enamel forming cells)
*Initiate dentin formation
during cap stage IEE/ameloblasts forms the?
enamel knot
what is hertwigs sheath?
place of contact between outer and inner enamel epithelium
*define the SHAPE and FORMATION OF THE ROOT
dentinogenesis
odontoblasts produce dentine toward inner ameloblasts
amelogenesis
inner ameloblasts produce organis substance of enamel against the dentine, formation of the crown
ameloblasts ____ off the layer of enamel
retreat off!!
the permenet dentition arises from?
dental lamina
The tooth germs that give rise to the permanent incisors, canines, and premolars form as a result of further proliferative activity within the??
dental lamina at its deepest extremity
increased proliferative activity at the dental lamina’s deepest extremity leads to?
formation of another tooth bud (permanent) on the lingual aspect of the deciduous tooth germ
do the molars of permanent dentition originate the same way as incisors, canines, and premolars?
NO! Bc they have no deciduous predecessors
When the jaws have grown long enough, the dental lamina burrows posterioly?
WHY?
posteriorly beneath the lining epithelium of the oral mucosa into the ectomesenchyme
**This backward extension gives off epithelial outgrowths that, with associated ectomesenchymal response, form the tooth germs of the 1, 2, and 3rd molars
the primary epithelial band divides into?
***
which one forms first?
1) outer thicker VESTIBULAR LAMINA that is repsonsible for separation of lips/cheeck (**forms second and is in front if DL)
2) inner smaller DENTAL LAMINA which gives rise to teeth!!!
asdental lamina grows in length, its penetrates deeper into the?
mesenchyme
- at front of mouth= shelf like
- back= more vertical
mesenchymal tissue surrounding the developing enamel gives rise to?
dental lamina (primitive pulp) and follicular sac for each tooth bud
What is the tooth germ?
the combination of enamel organ, dental papilla, and follicular sac
*ALL THREE
enamel organ in bud stage
- simple, spherical
* poorly morpho and histo differentiated
bud stage becomes concave on what side?
papillary surface/side
primary knot determines?
the position of the secondary enamel knots corresponding to the site of future CUSPS
what is the enamel cord?
**thought to be involved in what two events?
strand of cells seen at early bell stage
- it overlies the incial margin of a tooth or the apex of the first cusp to develop
- ***thought to be involved in cap to bell process OR the focus for the origin of stellate reticulum cells
are permanent molars regarded as part of deciduous series?
Yes, but they arise so differently that it is questioned if that is true
what is the cervical loop?
where the inner and outer layers of the bell stage curve and MEET
**the ACTIVE SITE of cellular proliferation until the ENTIRE TOOTH is mapped out
the vestibular lamina band growth occurs
at the same time as dental lamina
*around CAP stage the vertical cleft establishes vertical band and thus separates lips
what is Pax9?
one of the earliest mesenchymal genes that define the localization of the tooth germs
*expressed at bud stage mesenchyme
Pax9 induced by?
Fgf-8 which has some tooth positioning role (represented by bone morphogenetic proteins BMP-2 and BMP-4)
Fgf-8, Bmp-2, and Bmp-4 are expressed in?
Pax9 expressed in?
non-overlapping areas
*Pax9 is expressed at sites where Fgf-8 but not BMPs are
What if you have no Msx genes?
may have no premolars
3 stages of tooth develoment?
bud, cap, bell
AND THEN crown stage (dentinogenesis and amelogenesis), root formation, tooth eruption
1) Histodifferentiation
2) initiation
3) Morphogenesis
1) differentiation of primitive cells into tooth germ population
2) site of future teeth established
3) shape of the tooth determined
Is the epithelium or the mesenchyme responsible for tooth morphology?
early= epithelium directs patterning late= mesenchyme directs patterning (Reciprocal Signaling)
dental papilla
- undifferenciated mesenchyma cells
* MAKES PULP
dental follicle
- MAKE CEMENTUM AND ROOT
* distinguishable from dental papilla bc it has many more collagen fibrils
ameloblastoma
is an EXAMPLE of the severel types of odontogenic cysts/tumors that can arise from developing tooth structures (like epithelium, cell rests, enamel organ)
blood enters dental papilla during what stage?
cap
- the # of vessels increases until the bell stage when matrix is deposited
- enamel organ is avascular but has vessels ajacent to OEE
- vessels cluster in groups in papilla where the ROOTS will form
nerve fibers approach developing tooth during? when do they penetrate?
nerve growthfactors?
bud to cap stage
- pentrate pulp when dentinogenesis begins
- neurotrophin, glial cell line derived growth factor, semaphorin
