Transcript
Cem.per.
Cementum is a hard, avascular, connectivetissue, that covers the root of the teeth.
Root cementum is a hard non-vascularized, and
non-innervated tissue covering the tooth root.
It does not have ongoing remodeling like bone but
continues to grow with age.
It originates from the third element of the dental
germ - the dental follicle after stimulation by
Hertwig's epithelial root sheath.
Cementum formation involves two tissues - the
mesenchyme of the tooth follicle and the ectoderm
of the Hertwig`s root sheath.
DEVELOPMENT OF
CEMENTUM
CEMENTUM FORMATION IS CALLED
CEMENTOGENESIS.
CEMENTOBLASTS ARE THE CELLS RESPONSIBLE FOR
CEMENTOGENESIS.
Cementogenesis
It’s occur right after the enamel was completely formed;
The outer and inner enamel epithelia together form the epithelial root sheath of Hertwig which is responsible for determining the shape of the root;
The growth of sheath does not occur downward into jaws but that proliferation in cells of sheath causes an upward movement of developing tooth.
These two epithelial layers, which are separated by stratum
intermedium and stellate reticulum, are connecting in the area of
the future enamel-cementum junction and form the cervical loop.
Stratum intermedium and stellate reticulum are pushed and a
double layer of outer and inner enamel epithelium is obtained.
The following step is a proliferation in-depth to the dental follicle. The
name of this proliferation is Hertwig`s epithelial root sheath.
Its function is to stimulate mesenchymal cells of the dental follicle to
differentiate.
Three layers of cells of the dental follicle are formed. The innermost
differentiates to cementoblasts that will build the cementum, the
outermost differentiate to osteoblasts that build the alveolar bone,
and the middle differentiates to the fibroblasts that build the
periodontal ligaments.
Cervical loop These two epithelial layers which are
separated by stratum intermedium and
stellate reticulum become continous in
the area of the future enamel-
cementum junction;
Hertwig’s epithelial root
sheath
The Hertwig's epithelial root sheath
(HERS) is a proliferation of epithelial
cells located at the cervical loop
of the enamel organ in a
developing tooth.
Hertwig's epithelial root sheath
initiates the formation of dentin in
the root of a tooth by causing the
differentiation of odontoblasts
from the dental papilla.
The root sheath eventually
disintegrates, but residual pieces
that do not completely disappear
are seen as epithelial cell rests of
Malassez (ERM).
Epithelial root sheath(diaphragm);
Both epithelial layers merged apically into one;
At the bottom form 4-5 cells -guides that are not divided;
Cervically begins disintegration of epithelial sheat and beginspenetration into mesenchymalcells.
The first stimulation of the Hertwig's epithelial root
sheath initiates the formation of root dentin by
differentiation of odontoblasts from the dental papilla.
Both epithelial layers merged apically into one.
At its end are forming 4-5 cells, without proliferation.
They do not divide, only direct the proliferation of the
Hertwig`s epithelial root sheath in order to control the
length, thickness, curves, and number of roots.
Cervically begins disintegration of epithelial sheet and begins penetration into mesenchymal cells.
The root sheath eventually disintegrates, but residual pieces that
do not completely disappear are seen as epithelial cell rests of
Malassez (ERM).
Hertwig`s epithelial root sheath stimulated the differentiation of
cementoblasts.
At the same time, they deposit a thin acellular cementum over the
root dentin, called intermediate cementum.
It plugs up the dentinal tubules and isolates and protects the
dentin.
This first layer of cement serves as the basis for building the cement.
Immediately afterward, the disintegration of
the Hertwig's epithelial root sheath begins.
The epithelial cells are grouped into clusters of
3-4 cells, which are quickly removed from the
root surface.
It separates the organic matrix secreted by
the cement regions.
Cementoblasts are cuboidal cells. They are
arranged on the outer surface of a hyaline layer
that covers the dentine.
Cementoblasts start to secrete an organic matrix of
cementum. It consists of proteoglycan and intrinsic
collagen fibers.
After that, cementoblasts are involved in
mineralization of the organic matrix.
Cementogenesis occurs when Hertwig`s root
sheath disintegrates.
This disintegration of the sheath allows the
undifferentiated cells of the dental sac to come into
contact with the newly formed surface of root dentin.
This contact induces differentiation of the cells to
immature cementoblasts.
They turn into oblong cells arranged along the
developing root and are preparing for protein
synthesis and secretion.
The cementoblasts are producing fibers, are
synthesizing of an amorphous organic matrix, and
mineralize it.
The organic matrix of cementum is produced by
fibroblasts in the middle layer of the Hertwig's
epithelial root sheath.
It starts the production of thick collagen fibers
incorporated into the cementum organic matrix,
which are perpendicular to the root surface.
They remain part of the cementum.
They are called Sharpe's collagen fibers.
They are coming out of the cementum lick a part
of periodontal ligaments.
Cells including in cementogenesis
There are two types of differentiated cells included
in cementogenesis:
Cementoblasts are situated directly over the dentin;
Subcementoblasts (fibroblasts) are located just below cementoblasts. They are producing Sharpe's
collagen fibers.
Stages of cementogenesis
Cementogenesis has two stages;
In the first, an organic matrix is formed,
and in the second, it is mineralized.
Organic matrix formation has
two phases:
In the first, the fibrillar scaffold is formed,
and in the second, amorphous organic and
inorganic matter is deposited on it.
The organic matrix is made up
of two groups of fibers.
The first group is produced by subcementoblasts and is named Sharpey's fibers.
They are perpendicular to the root.
The second group is formed by cementoblasts. It is composed of thin fibers.
They are perpendicular to the Sharpey's fibers and are parallel to the longitudinal axis of the root.
When the fibril matrix is ready, the cementoblasts synthesize and deposit an amorphous organic matter over them.
A noncollagenous matrix is deposited on the collagen network, which masks the fibers.
Amorphous organic matter is consist of bone sialoprotein and osteocalcin. Amorphous inrganic matter is deposited in parallel with organic matter. It consists of calcium and phosphate ions.
The next step is the mineralization of the matrix.
When the thin layer of cementum matrix has formed, mineral ions
come from tissue fluid. Calcium and phosphate ions will be deposited
as hydroxyapatite crystal along axes of collagen fibers.
As cementum continues to increase in thickness, more follicular
(extrinsic) fibers become included in cementum, known as Sharpey’s
fibers.
After the formation of the first layer, cementoblasts move away and
free up a new space for matrix deposition and its mineralization. The process is repeated until the root is forming. While the root is
developing, the process occurs in an apical direction.
The first formed cementum does not contain cells. Cementoblasts will
be included in the next layers of the cementum. The enclosed
cementoblasts are known as cementocytes and found in lacunae.
Cementogenesis
The differentiation of
odontoblasts from
ectomesenchymal cells;
The fragmentation of
Hertwig`s epithelial root
sheath;
The ensuing differentiation of
cementoblasts from Hertwig`s
sheath cells or follicle cells.
Cementum is made
by cementoblasts
Derived from
undifferentiated
mesenchyme through
intermediate
precemntoblast stage in
cuboidal cell’s form;
They are arranged on outer
surface of hyaline layer that
covers the dentine.
Cementoblasts are responsible for
deposition of organic matrix of
cementum which consist
proteoglycan and intrinsic
collagen fibers.
Also they are responsible for
subsequent mineralization of
organic matrix (cementoid or
precementum).
A. HERS did not show any signs of
fenestration at this stage;
Single cells (arrowheads) were
positioned between ameloblasts
(amel) and the beginning of HERS.
(B). Tooth mineralization was significantly advanced .
The bilayered unit of HERS was still distinguishable at the apex
(hers) but had lost its continuity with
the ameloblast layer (amel). Instead,
bundles of mesenchymal cells (mes,
between arrowheads) as well as
fibrous structures (fib) were occupying
the developing root surface.
Isolated epithelial cells (ep) were localized between mesenchymal
tissues and HERS.
Note the clear separation between ameloblast cell layer (amel,
upper row of arrowheads) and mesenchymal cells (mes) covering
the developing root surface.
The fragmentation of Hertwig`s epithelial
root sheat:
With residual portion formingthe epithelial rests of Malassez
The ensuing differentiation of cementoblasts;
The follicle contribution to theformation of the fiber bundlesof the periodontal ligament.
A1 and A2. Note how tubular cells from adjacent to the ameloblast cell layer (arrowheads) were interrupting the
continuity of the ameloblast cell layer (amel).
B1 and B2. The enamel layer (en) and the ameloblast cell layer
(amel) clearly demarked the cervical margin of the developing
tooth
crown. A membrane (arrowheads) separated the ameloblast
cell layer (amel) from the mesenchymal cells (mes) occupying
the developing root surface. There
were only a few epithelial cells (ep) in immediate proximity to the root dentin surface (de)..
Cementogenesis
Cementogenesis occurs when
Hertwig`s root sheath
disintegrates;
This disintegration of the sheath
allows the undifferentiated cells
of the dental sac to come into
contact with the newly formed
surface of root dentin;
This contact of the dental sac
cells with the dentin surface
induces these cells to become
immature cementoblasts.
Periodontal ligament and
alveolar bone development
As the crown and root
develop, the surrounding
supporting tissues of the
tooth are also
developing. The
mesenchyme from the
dental sac begins to
form the periodontal
ligament (PDL) adjacent to the newly formed
cementum.
The mesenchyme of the dental sac
also begins to mineralize to form the
tooth sockets or alveoli of the alveolar
bone surrounding PDL.
This process involves forming collagen
fibers that are immediately organized
into the fiber bundles of the PDL. The
ends of these fibers insert into the outer
portion of the cementum and the
surrounding alveolar bone to support
the tooth.
Hertwig`s epithelial root sheat
Thedifferentiation of thecementoblasts;;
The begining of thedesintegration of Hertwig`s sheat.
The begining of
cementogenesis
Dodge the cementoblastsfrom the dentin;
Secretion of matrix of cementum;
Disintegration of cervical cells of the sheat.
Differentiation of dental
follicle cells
The cementoblasts –directly over the dentin
They are involved in the secretion of the
organic matrix of cement and its mineralization;
Subcementoblasts(fibroblasts)-just below
them
They produce fibers that enter into the
matrix.
There are two types of differentiated cells:
Desintegration of the Hertwig`s root sheat endformation of cementum end periodontal ligaments
(1)Hertwig`s sheat;
(2)Epithelial rests of
Malassez;
(3)The cells of the dental
follicle;
(4) Cementoblasts;
(5)Priodontal ligaments;
(6) Osteoblasts;
(7) Alveolar bone;
(8) Odontoblasts.
Cementogenesis
СВ - cementoblasts;
D - Dentin;
ECR -Epithelial rests of Malassez;
DF - Dental folicle.
Mineralization occurs :
When the thin layer of cementoid has formed, mineral salt comes from tissue fluid;
Calcium and phosphate ions will deposited as hydroxyapatite crystal along axes of collagen fibers.
As cementum continues to increase in thinkness, more follicular (extrinsic) fibers become included in cementum, known as Sharpey’s fibers right after periodontal ligament become established.
During the root is developing, those
process occurred on apical direction
:
Proliferation of cells of epithelial root sheath of Hertwigs;
Dentine formation;
Fragmentation of older part of sheath;
Differentiation of new cementoblasts;
Formation of cementum.
Cementum
A. Haversian bone ;
B. Bundle bone (A & B make up alveolar bone proper);
C. Reversal line;
D. Osteoid ;
E. Endosteum, composed of osteoblasts ;
F. Cementoid (the organic matrix of cementum) ;
G. Pericementum, composed of cementoblasts.
(A) the position of pulp (pulp), dental follicle (df), mineralized dentin (md), periodontal ligament
(lig), Hertwig’s epithelial root sheath (hers)
epithelial diaphragm (epd), predentin (pd),
dentin (dent), and several blood vessels (bv),
(B) Note the position of epithelial and
mesenchymal tissues on the predentin surface at
the apical tip of the root. At the apical margin of
the root dentin the periodontal ligament (lig) was
in direct contact with the non-mineralized
predentin (pd).
Hertwig’s root sheath (hers) was separated from
the root surface by a periodontal ligament cell
layer measuring at least 10 cell layers in thickness.
The nude predentin surface (pd) was not
covered by mineralized dentin or cementum.
At this stage, mesenchymal
cells of the ligament (lig) had
direct access to the root
surface. Due to their spatial
separation, HERS cells had lost
their opportunity to deposit
cementum on the root dentin
prior to their departure from the
root surface
Before tooth erupts :- Extrinsic fiber are incorporated in cementum and lie parallel
to the root structure.
After tooth erupts :
The fiber become oblique.
It is known as the precursor
of periondontal ligament
fibers.
Extrinsic fiber
Cementum which is formed first:
Does not contain any closed cells, but
cementoblast are included in later cementum;
These enclosed cementoblast are known as
cementocytes and found in lacunae;
Multi-rooted teeth – the formation of root
diaphragm
Multi-rooted
teeth:
Like anterior teeth, multi-rooted
premolars and molars originate as a
single root on the base of the crown;
This portion on these posterior teeth is
called the root trunk;
The root of a posterior tooth divides
from the root trunk into the correct
number of root branches for its type;
During the formation of the enamel
organ on a multi rooted tooth, elongation of its cervical loop occurs
in such a way that long, tongue like
horizontal epithelial extensions or
flaps develop within.
In teeth with more than one root
The initial single primary apical
foramen, formed by the epithelial
diaphragm of root sheath
Hertwig’s, become divided into two
or more secondary apical foramina
by tongues of epithelial tissue from
diaphragm.
These fuse in future
furcation area of the roots.
The number of secondary
apical foramina is
determined by the
presence of groups of
blood vessels which enter
the dental papilla.
Two types of cementum form:
Cellular and Acellular
Acellular cementum forms first. The
cementoblasts differentiate from follicular
cells, which can only reach the surface of
the tooth's root once Hertwig's Epithelial
Root Sheath (HERS) has begun to
desentigrate;
The cementoblasts secrete fine collagen
fibrils along the root surface at right angles
before migrating away from the tooth;
As the cementoblasts move, more collagen is deposited to lengthen
and thicken the bundles of fibers;
Noncollagenous proteins, such as bone sialoprotein and
osteocalcin, are also secreted;
Acellular cementum contains a secreted matrix of proteins and
fibers;
As mineralization takes place, the cementoblasts move away from
the cementum, and the fibers left along the surface eventually join
the forming periodontal ligaments
Cellular cementum
Develops after most of the tooth formation is complete
and after the tooth occludes (in contact) with a tooth in
the opposite arch. This type of cementum forms around
the fiber bundles of the periodontal ligaments;
The cementoblasts forming cellular cementum become
trapped in the cementum they produce;
The origin of the formative cementoblasts is believed to
be different for cellular cementum and acellularcementum;
One of the major current hypotheses is that cells
producing cellular cementum migrate from the
adjacent area of bone, while cells producing
acellular cementum arise from the dental follicle;
Nonetheless, it is known that cellular cementum is
usually not found in teeth with one root;
In premolars and molars, cellular cementum is
found only in the part of the root closest to the apex
and in interradicular areas between multiple roots.
The fate of Hertwig`s
epithelial toot root sheath
With the progressive formation of cementum and shaping the root, the Hertwig`s sheat undergoes complete disintegration;
Cementogenesis is completed with the construction of the root apex closure;
During toot root maturation, cellswithin fragmented root sheath formdiscrete masses surrounded by a basement membrane, known asepithelial cell rests of Malassez.
Cementum Varieties
Cemento enamel junction
In 30% the cementum andenamel meet as a buttjoint, forming a distinctcementoenamel junctionat the cervical margin –edge to edge;
In 60% the cementumoverlaps the enamel;
In 10% have a gap between the cementum and enamel – it lead to sensitivity at this site.
Cementum may be classified in
the following ways:
By location:
Radicular cementum: The
cementum that is found on the root
surface.
Coronal cementum: The cementum
that forms on the enamel covering
the crown.
By cellularity:
Cellular cementum:
Cementum containing
cementocytes in lacunae
within the cementum matrix.
Acellular cementum:
Cementum without any cells
in its matrix.
By the presence of collagen fibrils in the matrix:
Fibrillarcementum: Cementum with a matrix that contains well-defined fibrils of type I collagen.
Afibrillarcementum: Cementum that has a matrix devoid of detectable type I collagen fibrils. Instead, the matrix tends to have a fine, granular consistency.
Extrinsic fiber cementum: Cementum that contains
primarily extrinsic fibers, i.e. Sharpey's fibers that are
continuous with the principal fibers of the periodontal
ligament.
Since the fibers were originally produced by periodontal ligament fibroblasts, they are considered "extrinsic" to the
cementum.
These fibers are orientated more or less perpendicularly to
the cementum surface and play a major role in tooth anchorage.
By the origin of the matrix fibers (applies only to fibrillar
forms of collagen
Intrinsic fiber cementum: Cementum that contains
primarily intrinsic fibers, i.e. fibers produced by
cementoblasts and that are orientated more or less
parallel to the cementum surface. This form of
cementum is located predominantly at sites
undergoing repair, following surface resorption. It
plays no role in tooth anchorage.
Mixed fiber cementum: Cementum that contains
a mixture of extrinsic and intrinsic fiber cementum.
The description of
the classes of
cementum
Cementum Varieties
AEFC – acellular extrinsic fiber cementum;
CIFC –cellular intrinsic fiber cementum;
MC – mixed (alternating layers of acellularand cellular) cementum;
IC – Intermediate cementum.
AAC - Acellular afibrillar (prymary)
cementum
1. Acellular, afibrillar cementum
This cementum is mostly composed of mineralized matrix,
without detectable collagen fibrils or cementocytes. It is
produced exclusively by cementoblasts. It is typically found
as coronal cementum on human teeth over enamel and dentin in proximity to the cementoenamel junction
Cervical portion of cementum
A –deposition of cementum on the enamel in the cervical area;
Internal basal lamina and hemidesmosomesattached to the reduced enamel epithelium;
2. Acellular, extrinsic fiber cementum
This type of cementum has a matrix of well-defined, type I collagen
fibrils;
The fibrils are part of the, densely packed Sharpey's fibers, that are
continuous with the principal fibers of the periodontal ligament;
Because of their dense packing, the individual Sharpey's fibers that
form the bulk of the matrix may no longer be identifiable as individual
fibers within the cementum layer;
This cementum, which is acellular, is located in the cervical two-
thirds of the root of human teeth;
It plays a major role in tooth anchorage.
Acellular Extrinsic Fiber Cementum
A: Tightly packed Sharpey´sfibers.
B: Sharpey´s fibers are with central pitting;
Acellular Extrinsic Fiber Cementum
(Primary cementum)
It is mainly found on cervical and middle root portions, covering 40% to 70% of the root surface;
It serves the exclusive function of anchoring the root to periodontal ligament;
The acellular extrinsic fiber cementum matrix consists of a densefringe of short collagenous fibers that are implanted into the dentinal matrix (glycosaminoglycans) and are oriented about perpendicularly to the root surface;
When they become elongated and eventually continuous with theprincipal periodontal ligament fibers they are called Sharpey´s fibers.
Intermingling of collagen fiber bundles
with those at the unmineralized dentin.
The final connection between the
collagen fiber bundels of acellular
cementum and dentin surgace are
shown.They are perpendicular to the dentin and
penetrates between the cementoblasts.
Cross section of the cementum
Acellular cementum
Cellular cementum
Cementocytes
Lines indicate apposition, a period of rest in the deposition of the cement
3. Cellular, intrinsic
fiber cementum
This cementum contains cementocytes in a matrix composed almost exclusively of intrinsic fiber cementum;
It is located at sites of cementum repair.; It plays no part in tooth anchorage.; However, it may be covered over by
extrinsic or mixed fiber cementum, both of which are able to provide new anchorage;
Once the tooth is in occlusion, a more
rapidly formed and less mineralized
variety of cementum, cellular intrinsic
fiber cementum, is deposited;
Differentiating cementoblast extend cell
processes and deposit the collagen
fibrils;
As cementum deposition progresses, cementoblasts become entrapped in the extracellular matrix they secrete;
These entraped cells, with reduced secretory activity, are called cementocytes, and the space they occupy is the osteocytic lacuna.
Cementocytes
Cementocyteshave processes that lodge in canaliculi that communicate but do not form a syncytium that extends all the way to the surface’
As cementum deposition progresses, cementoblasts become
entrapped in the extracellular matrix they secrete.
These entrapped cells have reduced secretory activity.
They are called cementocytes, and the space they occupy is the
osteocytic lacuna.
Cementocyte's processes are in canaliculi. They communicate but do
not form a syncytium.
They are always directed to the surface of the cementum.
The nourishment of the cells is believed to occur essentially by
diffusion, and cementocytes in deeper layers may not be vital.
Collagen fibrils in the CIFC are deposited haphazardly during the rapid
phase. However, subsequently the bulk of fibrils organize as bundles
oriented parallel to the root surface.
Nourishment of the cells is believed to occur
essentially by diffusion, and cementocytes in
deeper layers may not be vital.
Collagen fibrils in the CIFC
They are deposited haphazardly during the rapid
phase;
Hawever, subsequently the bulk of fibrils organize as
bundles oriented parallel to the root surface.
Acellular and Cellular cementum
А –Acellularcementum
В –cellularcementum in:
•Periapical region.
4. Cellular, mixed fiber cementum
It is found on the apical third of the root and in furcations (i.e.
between roots);
In these locations, the rate of cementum formation is usually
more rapid than in the cervical region;
The mineralized, extrinsic collagen fibers (Sharpey's fibers) run a
more irregular course than in acellular, extrinsic fiber cementum;
Intrinsic fibers are found interspersed among the extrinsic fibers
of the cementum matrix, so that individual Sharpey’s fibers are
more readily identifiable than in extrinsic fiber cementum;
Cementoblasts are trapped in hollow chambers (or lacunae)
where they become cementocytes.
Cellular Mixed Fibrils Cementum
Cellular Mixed FibrilsCementum(CMFC) andperiodontal ligaments (PDL);
Sharpey´s fibers (SF);
Cementoblasts (CB);
Cementocytes (СС).
Cellular Mixed Fibrils Cementum
When the PDL becom organized, cellular cementum continues to be
deposited around the ligament fiber bundles, wich become
incorporated into the cementum and partially mineralized, thereby
creating cellular mixed fiber cementum;
It has:
Inclusion of cementocytes;
It has laminated structure;
The presence of cementoid on its surface;
Distinguishing between the fine-fibered, densely packed intrinsic fibers
running parallel to the root surface and incorporated extrinsic fibers
running at right angles to the root.
5. Intermediate Cementum
IC is a thin. noncellular, amorphous layer of hardtissue approximately 10µm thick;
It is deposited by the inner layer of the epithelial cellls of the root sheath;
Deposition occurs immediately before the epithelial root cells disintegrate as a sheet and migrate away from the root into the periodontal tissue;
It is the first layer of hard tissue deposited, and itseals the tubules of dentin;
IC is composed of enamel protein rather thancollagen
Longitudinal section of cementum
Sharpey`s fibers
Incremental lines
Periodontalligaments
Cross section of the toot roots –
incremental lines of cementum
Different layers in the cementum
Cimenticles
A cymenticle is a calcified ovoid
or round nudule found in the
periodontal ligaments;
Single or in a group they are
near the surface of the
cementum;
Their origin may be a nidus of
epithelial cells that are
composed of calcium
phosphate and collagen in the
same amounts as cementum.
Composition of the Cementum
Since cementum is not a uniform, mineralized
connective tissue, differences in the proportional
composition of the chemical constituents exist
between the cementum varieties.
Thus, the percentages of its chemical components
may vary from sample to sample, particularly in
different species.
Cementum has a similar composition to bone -
to about equal parts per volume, cementum is
composed of water, organic matrix and
mineral.
About 50% of the dry mass is inorganic, and
consists of hydroxyapatite crystals.
The remaining organic matrix contains largely
collagens, glycoproteins and proteoglycans.
Mineral composition
Cementum is generally less mineralized than root
dentin;
Acellular extrinsic fiber cementum appears more
highly mineralized than cellular intrinsic fiber
cementum and cellular mixed stratified cementum;
The mineral component is the same as in other
calcified tissues, that is, hydroxyapatite -
Ca10(PO4)6(OH)2, with small amounts of
amorphous calcium phosphates present;
As in other hard tissues, the hydroxyapatite of
cementum is not pure, but contains other
elements (ions) incorporated into mineral phase
during mineralization;
Thus, cementum contains 0.5-0.9%;
Have a high fluoride content compared to other
mineralized tissues (up to 0.9% as weight);
Cementum also contains 0.1-0.3% sulfur, in
particular Cu+2, Zn+2 and Na+.
Organic composition
The organic matrix of cementum is
composed primarily of collagens type I
and III collagen;
Cementum contains two major non-
collagenous proteins:
bone sialoprotein (BSP);
and osteopontin (OPN).
Both are phosphorilated and sulfated
glycoproteins.;
These proteins,which are prominently expressed
in acellular extrinsic fiber cementum and
acellular afibrillar cementum, bind tightly to the
collagenous matrices and hydroxyapatite, and
they possess cell attachment properties.
Comparison of the composition of the
enamel, dentin, cementum, and bone
% Enamel Dentin Cementum Bone
Mineral 95 70 61 45
Organic
composition 1 20 27 30
Water 4 10 12 25
Cement Repair
Cement repair is a protective function of
cementoblasts after resorption of rooth dentin
and cementum;
These cells are programmed to maintain a
smooth surface of the root;
Loss of cementum is accompanied by loss of
attachment fibers;
When this occurs, repair cementum may be
deposited by cementoblasts in the defect.
The functions of the cementum
Roofing function;
Function to attach the periodontal ligaments;
Protective function:
Adaptive function.
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