tooth development Flashcards
all body tissues develop from 3 primary embryonic layers, what are they?
. ectoderm
. mesoderm
. endoderm
which primary embryonic layer does the enamel develop from?
ectoderm
which primary embryonic layer do all parts of the teeth and supporting structure other than the enamel develop from?
ectomesenchyme
what is ectomesenchyme derived from?
neural crest
what do teeth develop from?
tooth germs
what is neural crest tissue referred to?
ectomesenchyme
neural crest tissue migrates into what?
developing face and jaw
name the 5 stages of tooth development
initiation, bus stage, cap stage, bell stage, eruption
what occurs during the initiation stage of tooth development?
. oral epithelium proliferates into the ectomesenchymal cells situated below to form a primary epithelial band
. primary epithelial band differentiates into vestibular lamina and dental lamina containing tooth germs
at how many weeks does the primary epithelial band develop?
6
at how many weeks does the primary epithelial band differentiate into dental lamina and vestibular lamina?
7
what is the function of dental lamina?
structure from which tooth is formed
what is the function of vestibular lamina?
breaks down to from buccal suculus
when does the bud stage of tooth formation start?
8-10 weeks
what occurs during the bud stage of tooth development?
- dental lamina thickens into a bud stage enamel organ
- ectomesenchymal cells condense to form dental papilla
when does the cap stage of tooth formation start?
11 weeks
what occurs during the cap stage of tooth development?
tooth bud forms a cap over the papilla
the tooth bud is arranged into 3 parts, what are these?
enamel organ, detal papilla and dental follicle
at which stage are the internal and external enamel organ epithelium seen for the first time?
cap stage
where do the internal and external enamel epithelium meet?
cervical loop
when does the bell stage of tooth formation start?
14 weeks
what occurs during the bell stage of tooth development?
more cell layers differentiate and tooth shape is formed
how many layers are there during the bell sated of tooth development?
4
name the 4 layers present during bell stage of tooth formation
stellate reticulum, internal enamel epithelium, external enamel epithelium, stratum intermedium
what is the function of the stellate reticulum?
supporting tissue during enamel formation
where is the the stratum intermedium?
developing tooth layer between inner epithelium and stellate reticulum
the does the dental lamina for the permanent successor tooth appear?
week 12
what does the dental lamina of permanent successor tooth appear as?
an extension of the lingual side of dental lamina
what occurs during the late bell stage of tooth formation?
crown shape is well defined and enamel and dentin begin to from
during the formation of dentin, dental papilla cells adjacent to the internal enamel epithelium differentiate into which cells?
odontoblasts
what do odontoblasts do during dentin formation?
lay down dentin matrix which is later mineralised
after dentin formation has begun, intra enamel epithelium cells differentiate into what?
ameloblasts
what do dormant ectomesenchymal cells from?
tertiary dentin
what are the 2 stages of enamel formation?
protein matrix formation and mineralisation
name the 4 stages of the ameloblast lifecycle
differentiation, secretion, maturation, regression
what occurs during ameloblast differentiation?
. dentin induces IEE cells to differentiate into ameloblast
. ameloblasts elongate, nucleus migrates to basal end
what occurs during secretory phase of ameloblast lifecycle ?
. ameloblasts become secretory cells
. they synthesise and secrete enamel matrix proteins
what occurs during maturation phase of ameloblast lifecycle ?
. most matrix protein removed
. mineralised content of enamel increased
what occurs during protection phase of ameloblast lifecycle ?
. ameloblasts regress to form a protective layer
. form epithelial attatcmnent
what is the name for proliferation of epithelial cells located at the cervical loop of the enamel organ in a developing tooth?
henrtwigs epithelial tooth sheath
how many layers does henrtwigs epithelial root sheath have?
2
what happens to henrtwigs epithelial root sheath once the initial layer of root dentin is formed?
it breaks up
what does henrtwigs epithelial root sheath form?
root dentin
what do remains the remains of henrtwigs epithelial root sheath remain as?
debris of malassez
what may debris of malaise develop into?
cyst
how is the cementum formed from mesenchymal cells?
mesenchymal cells from the follicle contact the dentin and differentiate into cementoblasts
fibres from PDL are embedded in what structure?
cementum
what type is tissue is enamel organ?
epithelium
where does enamel organ originate?
ectoderm
what is the product of enamel organ?
enamel
what type of tissue is dental papilla?
ectomesenchyme
where does dental papilla originate?
neural crest
what parts of the tooth do dental papilla form?
dentine and pulp
what type of tissue is the dental follicle?
ectomesenchyme
where does the dental follicle originate?
neural crest
what structures does the dental follicle form?
cementum, PDL, alveolar bone
name some disorders associated with dental development
hypodontia, supernumerary, gemoiantion, fusion, dentinogenesis imperfecta
