enamel development and function :) Flashcards
what is enamel derived from
ectodermal enamel organ
what does enamel form
surface layer of anatomical crown
minerlisation of enamel
96%
what cells form enamel
ameloblasts
what do ameloblasts come from
differentiate from the interla dental epithelium starting from the uppermost part
what causes a signal to be sent to the IDE to differentiate into ameloblasts
dental papillary cells form odontoblasts
secrete dentine and signal is sent
what forms first dentine or enamel
dentien
what induces the differentiaion of IDE into emeloblasts
BMPs
secreted by odontoblasts into dentine matrix
how do ameloblasts deposit enamel
from secretory end
move in an S shape
absorb protiens from enamel as it is mineralised
phases of enamel formation
secretory
transition
maturation
what % is mineralised when it is first secreted
30%
what happens in the maturation phase
organic material is removed
what happens in the transition phase
increased mineral content from30 to 96%
secretion of amelogenin
how is the enamel deposited initially
prismatic
adjacent to the ADJ
what happens during secretion of enamel steps
ameloblasts produce a pyrmatidal tomes process
HAP crystals are laid down at right angles to the cell surface (from to apex)
where are rod boundaries
coincide with tomes process apex
how do rod boundaries happen
HAP crystals are laid down at right angles to the cell surface so either side is opposite rods
enamel maturaltion
crystals get thicker as the enamel becomes more mineralised
enamel structure
keyhole shape - interlock to strength enamel
rods run parallel in layers
what does the enamel structure have
shallow sinusoidal curvature
what occurs during enamel formation
amelogenins are withdrawn and destroyed by enamelysins
enamelins left
space vacated is replaced by water
HAP grow in thickness displacing water
what does fluoride to
strengthen enamel
what can protein do to enamel if not removed
developmental defect
protein inhibit mineralisation by preventing crystal crystal fusion
what is the reduced enamel epithelium
amelobalsts and EDE?
protects the enamel and forms part of the gingiva
what are examples of defects of enamel development
hypoplasia hypominerlisation amelogensis imperfecta fluoride induced opacity intrinsic discolouration
what is hypoplasia
thinner layer of enamel on crown
what is hypominerlisation
less mineralised
occurs in maturation stage
what is amelogensis imperfect
abnormalities in genes involved in enamel formation
what does too much fluoride cause
less mineralisation as it affects protein degredation
what cannot be presribed to pregnant women
tetracyclines
caused discoloured enamel to foetus
what are optical artefacts of enamel
interference and diffraction(interaction and bending)
reflection and refraction(speed changes)
where do enamel rods run
from ADJ to outer surface
in adjacent layers offset abut 2degress from eahc other
what desgin features of enamel give strength
offset of enamel rods
keyhole shape
what is enamel supported by
dentine and PDL
what does the PDL do
absorbs masticatory loads
properties of dentine
high tensile and compressional strenght
how does enamel form
in increments
brown striae and dailty incrememtal lines
what is the neonatal line
exaggerated incremental line in teeth mineralising at birhtas ameloblasts pause their activity
what teeth have the neonatal line
the developing teeth at birth ie 6’s
what are enamle spindles
at ADJ
odontoblasts get trapped within the enamel
what are enamel tufts
found at ADJ in transverse section
areas of hypomineralised rods
what are enamel lamallae
cracks that run through enamel following lines of prism orientation
may cause the tooth to fracture
what happens once enamel is fomed
it cannot be reparied as the ameloblasts die
how can remineralisation occur
saliva contains calcium and phosphate (ion exchange)
how do carious lesions appear initially
white spots
what is topical fluride
exchange of fluride for hydroxl ions in apatite crystals
what type of surface will restorative materials adhere to and how is this done
roughened surface
‘acid etch’
applying acid to enamel surface and then washing off
what does fluride do to calcified material
will decrease its acid solubility
how can fluide be appliec
topically
systemically
what can be seen in ground sections
brown striae(like tree trunk circle lines) light interfernece lines
what forms the reduced enamel epithelium
the enamel organ reduces in thickness and forms the REE
what provides nutrients for amelobalsts
stellate reticulum
what is the matrix of enamel in the secretory phase
matrix consists of amelogenin and enamelin proteins ratio 20:1
