Cementum Flashcards
what si cementum
mineralised tissue
etomesenhcymal (detail follicle origin)
tooth support
cover roots
what is the composition of cementum (mineral, matrix and water)
mineral - 65%
matrix - 23%
Water - 12%
how does cement differ from bone in respect to cells
cementum has <100Um live cells and >100Um dead cells
bone has all living cells
how does cementum differ to bone in respect of blood vessels and nerves
bone has blood vessels and nerves incorporated whilst cementum doesnt
what s of clinical importance of cementum vs bone remodelling
cementum is resistant to resorption but if late force will resorb
bone is easily remodelled imp in ortho
what cells are alive in cementum
cells close to surface (PDL) as near a blood supply as deeper they die
what ar the different ways a cementum can be around the cervical margin of a tooth
overlap 60%
but joint 30%
doesnt meet ervical margin (sensitivity) 10%
what si root development riven by
HERS
what des HERS actually do
apical dev of inner and outer enamel epi root morphology inductive proliferates disintegrate
what does HERS induce
root dentinogenesis
cementogenesis
where does HERS proliferate and disintegrate
proliferate - apically
disintegrates - cervically
how can some hers cells form cementobalast
epi/mesenchymal transformation
what are the 9 steps in cementum formtion
1 - HERS induces odontoblasts form
2 - predentine then dentine form HERS basal lamina breaks down
3 - Hers = enamel matrix P on to predentie
4 - EMP mineralise = hyaline layer
5 - Hers disintegrates
6 - induce follicle cells migrate to root surface and form cemetnoblasts
7 - cemnoblasts = cementum and retreat out
8 - cementum mineralise trap PDL
9 - cell rest malaise
where is the hyaline layer of hopewell smith
between dentine and cementum
is the hyaline layer mineralised
highly
how think is the hyaline layer
10 UM
what si the origin of the hyaline layer
matrix from
- epi cells - EMP
- ectomesenchymal cells
what is the role of the hyaline layer
induces cementoblast formtion
cements cementum onto tooth
what si the cementoblast origin
Dental follicle maybe hERS (from eli-mesenchymal transformation)
what does the cementoblasts do in cemeitogeneis
migrate out
depo matrix
mineralise
trap PDL fibres
what does he matrix consist of
collagen
ground sub
are there matrix vesicles in mineralisation of cementum
no
what are the classification of cells
cellular
acellular
what are the features of acellular cementum
no cells
slow depo
close incremental lines
narrow precememtun
what are the features of cellular components
cells in lacunae with canaliculi
rapid depo
incremental lines relatively far apart
wide precementum
what are the two diff types of fibres
intrinsic
extrinsic
mixed
afibrillar
what are the intrinsic fibres
fibres form cementoblasts
small
parallel to root surface
what are the extrinsic fibres
incorp PDL fibres
sharply fibres
perp or oblique to root surface
what is afibrillar
no fibres
what is primary cememtnum
first formed cement
acellular
what is secondary cementum
covers apical 2/3rd
what is acellular extrinsic fibre cememtnum
sharply fibres from PDL
attachment
thicker apically
cover 2/3 root
what is mixed fibre cementum
bulk cellular component cemtocytes incremental lines of salter extrinsic sharply and intrinsic acellular slow formed
what is cellular intrinsic fibre cementum
no attachment role
adaptive - apical and interradicular regios
what is acellular fibrillar cementum
on enamel surface local disrupt of REE DF cells contact with enamel mineralised GS imp REE no funcion
what is acellular intrinsic fibre cememtum
first formed cementum
collagen from cementoblast
slow formation
15-20 Um thick
Cementoblast line what
surface of cementum
where are cemetoblasts
between PDL fibre bundles
what des the presence of organelle reflect
activity
what happens to cementoblasts when cementum formed rapidly
get trapped in own secretions
in lacunae and cyto
whiter the little cell processes from cementocytes
canaliculi
project toward PDL
what is the function of primary/acellular cememtnunm
anchorage
what is the function of secondary/cellular cementum
adaptation
- cont eruption
- medial drift
rapidly laid down
where is the acellular and cellular cementum
acellular more near cervical margin
cellular at bottom apex
what is hypercemntosi
excess cementum
thicker at apex
hard to extract
EMP = ?
hyaline layer
hyaline layer = ?
induces cementoblast
diff from follicle = cementogeneis
what aids attachment
acellular compone
if REE breached what happens
follicle cells expo to epi prod induces follicle cells = cemetoblass = cementum
