Understanding Cementum: A Guide to its Development, Composition and Function

C NTENT
 Introduction
 Definition
 Development of tooth
 Cementogenesis
 Histology of cementum
 Classification.
 Compositions

 Physical characteristics
 Function.
 Clinical consideration.
 Mesodermal tumours of odontogenic origin
related to cementum in the jaws.
 Future direction on cementum.
 Referrences.

Introduction
The periodontium consist of :
 Cementum
 the periodontal ligament
 bone lining the alveolus
 part of the gingiva facing the tooth.

 Cementum is the mineralised dental tissue covering the
anatomic roots of human teeth.
Extent:
Begins at the cervical
portion of the tooth
at the CEJ upto
the apical foramen.
Definition

 The word cementum is derived from latin word
CAEMENTUM which means Quarried stone
i.e chips of stone used in making mortar.

 It was first demonstrated microscopically in
1835 by two pupils of purkinje.
 It furnishes a medium for attachment of collagen
fibres that binds the tooth to surrounding structures.
Òrbans oral histology and embryology 13th edition

 It is a specialised connective tissue that shares some
physical,chemical properties and structural
characteristics with compact bone.
 Cementum thickness varies in different teeth and in
the same teeth in different regions.

The apical foramen is surrounded by
cementum
Sometimes cementum extends into the
innerwall of the dentin for a short distance,
and so a lining of the root canal is formed.
Like dentin, cementum can form throughout
the life of a tooth.

Development of tooth
 Two or three weeks after the
rupture of the buccopharyngeal
membrane,when the embryo
is about 6 weeks old,certain
areas of basal cells of the oral
ectoderm proliferate more
rapidly than do the cells of
the adjacent area

 This leads to the formation of the primary epithelial
band which is the band of the epithelium that has
invaded the underlying ectomesenchyme along each
of the horse-shoe shaped future dental arches.
 At about 7th week the primary epithelium divides into
an inner (lingual)process called dental lamina and an
outer (buccal) process called vestibular lamina.

Bud stage
Oral ectoderm
Dental lamina
Enamel organ
Central polyhedral cells
Peripheral columnar cells
Condensation of
ectomesenchyme
Developing bone

Oral ectoderm
Dental lamina
outer enamel
epithelium
Dental follicle
Stellate reticulum
Inner enamel
epithelium
Dental papilla
Cap stage

Outer enamel epithelium
Stellate reticulum
Dental follicle
Stratum intermedium
Inner enamel epithelium
Odontoblasts
Dental papilla
Early bell stage

Collapsed stellate reticulum
Ameloblasta
Enamel
Dentin
Outer enamel epithelium
Dental sac
Odontoblats
Developing pulp
Advanced bell stage

Stages of Cementum formation
 Phase I : Laying down of Cementoid tissue
(matrix formation)
 Phase II : Mineralization

matrix formation
 Formation of cementum
occurs over an extended
period of time.
 Occurs over a period of
31/2 to almost 8 years

 Deposition of acellular cementum occurs at a slow but a
constant rate of about 3µm/year on a single rooted teeth
 However, the rate varies with tooth type and root surface
area.

 As the epithelial root sheath begins to break up and
move away from the predentin surface
 Cells with the appearance of fibroblasts originating
from the dental follicel,migrate in between the
epithelial cells and differentiate to cementoblasts.

 The expression of bone morphogenic protien
(BMP-3) by dental follicle cells,and later by cells lining
the root surface,has been linked to differentiation of
cementoblasts.
These newly differentiated cementoblasts begin to
deposit collagen fibrils oriented perpendicular to the
root surface

 This fringe of collagen fibers intermingle with the
collagen fibrils of the predentin,forming a firm
attachment at dentin-cementum junction.
 Mineralization of the mantle dentin begins internally
and proceeds in the peripheral direction,surrounding
the dentin-cementum junction and spreading into the
cementum.

 The cementoblast on the root surface continue to
deposit collagen,lenghtening the fiber fringe,and
also secrete ,non collagenous protien around the
fibrils .
 When the initial layer of cementum achieves a
thickness of 15-20µm, at about that time cusp tip
penetrates the oral mucosa,the fiber fringe connects
with the principal fiber bundles of the developing
PDL.

 Acellular cementum thus serves as the main site for
the attachment of PDL collagen fibers.
 These fibers , inserting roughly perpendicular into
the cementum,are visible in the histologic sections are
called sharpey’s fibers.

mineralization
 After some cementum matrix is laid down,its
mineralization begins.
 The uncalcified cementum is called cementoid
 Calcium and phosphate ions present in tissue fluid are
deposited into the matrix and are arranged as unit
cells of hydroxyapatite

 Gla protien osteocalcin and osteonectin act as
nucleator for mineralization,due to their strong
affinity for calcium.
 BSP and alkaline phosphatase promote mineralization
 osteopontin promote growth of apatite crystals
 Insulin like growth factor(IGF)-present in developing
and matured cementum monitors mineralization and
controls cell differentiation

Cellular cementum
Forms 30 times faster than acellular cementum

 Mineralization of the predentin extends across the
dentin cementum junction into newly formed
cementum.
 An irregular layer of unmineralized cementum
precementum or cementoid is present between the
cementoblasts and the mineralization cementum
matrix.

 Newly differentiated cementoblasts
cover the root predentin in the apical and furcation region
and begin to deposit initial matrix of cementum with
collagen fibrils intermingling with those of the predentin.

 Cementoblasts secrete matrix componenet
completely around themselves ,resulting in their
entrapment in the lacunae.
 Collagen fibrils of cellular cementum are mainly
oriented parallel to the root surface running in
circular direction around the tooth.
 Cellular cementum is mainly deposited as an
adaptive tissue, in response to functional demands
and to repair resorptive defects.

 Sharpeys fibers are fewer in number and more
irregularly spaced in cellular cementum than in
acellular cementum
 Minerlization of cementum is similar to that of the
bone.
 Cementoblasts regulate the level of the
mineralization inhibitor inorganic pyrophosphate in
order to control the amount of cementum
deposition.

 Cementum mineralization is a very slow process
 The width of the unmineralized precemetum layer is
3-5µm.
 Mineral crystals achieve their mature size between 1-
4µm deep to the mineralization front.

Physical characteristics
Light yellow in colour
Permeable to variety of materials
Thickness-variable,thinnest at CEJ (20-50µm) and thickest at
apex(150-200µm).

 cementum is thicker in distal surface then mesial
surface probably because of the fuctional
stimulation from mesial drift.


Inorganic substances
45-50%
Organic substances
50-55%
Chemical composition
 Calcium
 Phosphate
 fluoride
 Collagen
(I,III,V,VI,XII)
 Dentin matrix
protien
 Bone sialoprotien
 Osteopontin
 Proteoglycan
 CAP

Cells associated with cementum
A.R.TENCATES 4TH EDITION
cementocyte
cementoblasts
cementoclasts

Cementoblasts
Characteristics:
 Numerous mitochondria
 Well formed golgi apparatus
 Large number of granular
endoplasmic reticulum

 Synthesize collagen and protien polysaccharides
which make up the organic matrix of cementum.
 Once the cementum is laid down,its mineralization
begins.
 The cells are found lining the root surface

Cementocytes
 Spider shaped cells and
are characteristics feature
of cellular cementum.
 During the formation of
cellular cementum,
cementoblast
becomes entrapped within
their own matrix due to
rapid deposition and are
called cementocytes.

 Similar to osteocytes and they lie in spaces known as
lacunae.
 Haphazardly arranged and widely dispersed.
 Canalicular processes branch and frequently
anastomose with those of neighboring cell.

 Processes are directed towards the PDL for
nutrition.
 Deeper layers of cementum (60µm from
nutrition)cementocytes shows definite signs of
degeneration such as cytoplasmic
clumping,vesiculations and sometimes empty
lacunae.

Cementoclasts
 Found in Howships lacunae.
 unilocular/multilocular cells.
 function-resorption of cementocytes.
 Major role-resorption and repair.

Cementoidtissue
 Uncalcified matrix is called
Cementoid
 Growth of cementum is a
rhythmic process,and as a
new layer of cementoid is
formed the old one
calcifies.
A
B
C
D
E
F
A-dentin B-cementum
C-cementoid tissue D-cementoblats
E-PDL F-cementoblasts

Incremental lines of cementum
 Referred to as “Incremental lines of salter”
 Represent rhythmic periodic deposition of cementum.
 Appear dark lines running parallel to root surface.

 Seen in both acellular and cellular cementum but
more prominent in acelluar cementum.
 Best seen in decalcified section under light
microscopy.
 Highly mineralized areas with less collagen and more
ground substances.

Intermediate Cementum /
Hyaline layer of Hopewell Smith
 In 1927, Bencze first used
the term intermediate
cementum to indicate a
narrow part containing
a cellular elements or
lacunae between dentin
and cellular mixed
stratified cementum
Yamamoto en et al Jpn dental science Rev 2016 aug,52(3);63-74

 Hopewell smith found a homogeneous layer
between acellular extrinsic fiber cementum and the
granular layer of tomes.The homogeneous layer is
now referred to as Hyaline layer of Hopewell smith
Yamamoto en et al Jpn dental science Rev 2016 aug,52(3);63-74

Cementodentinal junction
 Interface between dentin and cementum:
 permanent teeth-smooth
 deciduous teeth-scalloped

 It is the region where dentin and cementum are
united,the point at which cemental surface
terminates at or near the apex of the tooth.
 It is not necessary that CDJ always coincide with the
apical constriction.
 Location of CDJ ranges from 0.5-3mm short of
anatomic apex
 Areas of dentin adjacent to Cementodentinal
junction appear granular in cross section due to
coalescing and looping of terminal portion of
dentinal tubules and is called Tomes granular layer.

 Narrowest diameter of the canal identified not at the
site of the exiting of canal
 He referred to the position as minor diameter.
 Major diameter is at the site of the exit of the canal
 Distance between major and minor diameter
Kutler Study:

 Age 18-25yrs - 0.524mm
 Age 55yrs or more-0.659mm
 Using kutlers method is the most scientific method for
calculation of working length.

Cementoenamel Junction
 The relationship between cementum and enamel at
the cervical region of the teeth is variable
 Cementum overlaps the cervical end of enamel-60%
cases
 Cementum meets enamel at the cervical region of the
teeth in sharp line- 30% cases
 Enamel and cementum does not meet-10% cases

Types of Cementum
By location:-
 Radicular cementum
 Coronal cementum
By cellularity
 Cellular cementum
 Acellular cementum

By the presence of collagen fibrils in the matrix
 Fibrillar cementum
 Afibrillar cementum
By the orgin of the matrix fibers
 Extrinsic fibres
 Intrinsic fibres
 Mixed fibres

Schroders classification
Acellular afibrillar cementum
Acellular extrinsic fiber cementum
Acellular intrinsic fiber cementum
Cellular mixed fiber cementum’
Cellular mixed stratified cementum
Cellular intrinsic fiber cementum

ACELLULAR CEMENTUM CELLULAR CEMENTUM
Embedded cementocytes are absent Embedded cementocytes are present
Deposition rate is slower Deposition rate is faster
It is the first formed layer Formed after acellular cementum
Width is more or less constant Width can be highly variable
Found more at cervical third of root Mainly seen at apical third and interradicular
Area though a thin layer is present all over the
root
Also called as primary cementum Also called as secondary cementum
Sharpey’s fibers are well mineralised Sharpey’s fibers are partially mineralised
Incremental lines are regular and closely placed Incremental lines are irregular and placed wide
apart with variable thickness between them

Acellular extrinsic fiber cementum
 Extends from cervical
margin to apical 1/3rd.
 Only type of cementum
seen in single rooted teeth
 60%-90% of total root
length is covered –single
rooted teeth

 Cervical half to 1/3rd –Multi rooted teeth.
 Covers cervical root surface in both permanent and
deciduous teeth.
 It contains collagen fibers and non collagenous
protiens as organic matrices both of which are fully
mineralised

 This type of cementum forms slowly and regularly hence
Incremental lines are placed parallel to the surface and
closer together.
 The incremental lines are highly mineralized
also know as “resting lines.”
 The main function of this type of cementum is Anchorage
in single rooted teeth.

AcellularAfibrillar Cementum
 Consist of mineralized
matrix containing neither
collagen fibers nor
cementocytes.
 It is found on the most
cervical part of acellular
extrinsic fiber cementum
on enamel just coronal
to the CEJ.
 Function and origin –not determined

Cellular intrinsic fiber cementum
Cellular mixed fiber cementum
Cellular mixed stratified cementum

Cellular Intrinsic Fiber Cementum (CIFC)
 Contains cells
but no collagen fibers.
 Fibers are secreted
by the cementoblasts
 Formed on the root
Surface and in cases
of repair.

Cellular Mixed Fiber Cementum
 Formed faster with less mineralized fibers.
 Collagen fibers derived from PDL fibroblasts and the
cementoblasts.
 The intrinsic fibers and extrinsic fibers run between
each other at right angles.
 The fiber bundles originating from fibroblasts are
bigger then those originating from cementoblasts

Cellular Mixed Stratified Cementum.
 Cellular intrinsic fiber
cementum alternates
with acellular extrinsic
fiber cementum.
 Formed by cementoblasts
and fibroblasts
 Present on the apical third
of the root and furcation
areas.

 thickness-100-1000µm
 The cells present-cementocytes

Anchorage
 The primary function of the cementum is to furnish a
medium for attachment of collagen fibres that bind the
tooth to alveolar bone.
 Since collagen fibres of the PDL cannot be incorporated
into the dentin, a connective tissue attachment to the
tooth is impossible without cementum.
 These are seen in the cases of hypophosphotasia

Adaptation
 Cementum may also be viewed as the tissue that
makes functional adaptation of teeth possible.
 for example,deposition of cementum in an apical
area can compensate for loss of tooth substance
from occlusal wear.

 In contrast to the alternating resorption and new
formation of bone, cementum is not resorbed under
normal conditions.
 As the most superficial layer of cementum ages, a
new layer of cementum must be deposited to keep the
attachment apparatus intact

Repair
 cementum serves as the major reparitive tissue
for root surfaces.
 Damage to roots such as fractures and resorption
can be repaired by the deposition of new
cementum.
 Cementum formed during repair resembles
cellular cementum because it forms faster but it
has wider cementoid zone and the apatite
crystals are smaller
Òrbans oral histology and embryology 13th editions

Hypercementosis:
 It is an abnormal thickening
of cementum.
 it may be diffuse or
circumscribed.
It may affect all teeth of the dentition,
be confined to a single tooth,or even
affect part of only one tooth.

hypercementosis
Functional
cusp
Non
functional
cusp
Increased number
of sharpeys fibers
Decreased number
of sharpeys fibers
Cementum
hypertrophy
Cementum
hyperplasia

 Hyperplastic cementum covering the enamel drops is
termed as excementosis.
Appearance :
Occurs as generalised
thickening of cementum,
with nodular attachment
of the apical third of the root.

It is due to inborn error of metabolism.
the basic disorder is a deficiency of enzyme alkaline
phosphatase in serum or tissues
Hypophosphatasia

 This is characterised by loosening and
premature exfoliation of deciduous
teeth,mainly anteriors.
 Exfoliated teeth microscopically shows complete
absense of cementum or isolated areas of abnormally
formed cementum.

 The detachment of a
fragment of cementum
is described as a cemental
tear.
 Cemental tears have been
reported in the literature
associated with localized,
rapid periodontal breakdown
Cemental tear

Ankylosis
 Fusion of cementum and alveolar bone and
obliteration of the PDL is called ankylosis

 Results in resorption of root and its replacement by
bone tissue.
 This condition is uncommon.
 Occurs in teeth with cemental resorption.
 It represents a form of abnormal repair.

Clinically
 Lack of phsiologic mobility
which is a diagnostic sign
of ankylotic resorption
 As the PDL is replaced with
bone in ankylosis,propioception
is lost because pressure receptors
in PDL are deleted or do not
function correctly

Cementicles
 They are small globular
masses of the cementum
found in approximately
35% of human roots.
 May not always be
attached to tooth surface
but may be located free
in the PDL

If some HERS remain attached
to remaining tooth
surface, they can produce
focal deposits of enamel
like structures called
ENAMEL PEARLS.
Enamel pearls

Enamelprojection
 Most commonly seen in the
mandibular furcation areas,
when amelogenesis does not
cease before the formation
of root,there enamel projection
may form over the portion of root

 This is a form of fusion
which occurs after root
formation has been
completed
Concrescence

 Teeth are united by cementum only,as a result of
traumatic injury or crowding of teeth with
resumptions of the interdental bone so that these 2
roots are in contact and become fused by deposition
of cementum between them.
 It occurs before or after teeth have erupted and
distally involve two teeth.

Osteitis deformans
 Pagets disease of bone.
 Generalised skeletal disease characterised by
deposition of excessive amount of secondary
cementum on the roots of the teeth and by the
apparent disappearance of lamina dura of the teeth,as
well as by other features related to the bone itself.
 Excessive amount of cellular cementum is found
deposited over the thin layer of primary acellular
cementum.
Shafers textbook of oral pathology 7th edition

Papillon-lefevre syndrome
 Autosomal recessive disorder
 It consist of:
juvenile periodontitis
palmar plantar keratotis
calcification of falx cerebri

Injuries to cementum
Vertical fracture –
 Poor prognosis
 Cannot be repaired by
cementum.

 Variable prognosis
depending on age and
location
Horizontal fracture

Cementum and Endodontics
Hypercementosis
External root resorption
Treatment of immature apex

Hypersensitivity
Class II cavity
subgingival margins
Cementum and Operative Dentistry

Root caries
Gingival recession

MesodermalTumours
related toCementum

Cementoma
 It is a lesion of rather common occurrence.
 Not considered a neoplasm
 Etiology-due to mild
chronic trauma

Benign cementoblastoma
 True neoplasm of functional
cementoblastoma
 Tumour mass attached to tooth
root appears as a well circumscribed
dense radioopaque mass often
surrounded by a thin uniform
radiolucent line

Cementopathia
In 1923,gottlieb reported a patient with fatal
cases of influenza and disease called diffuse
atrophy of bone.

 Characterized by loss of collagen fibers in PDL and
their replacement by loose connective tissue and
extensive bone resorption resulting in the widened
PDL space
 Gottlieb attributed this condition to inhibition of
continuous cementum formation which he considered
essential for maintainace of PDL fibers .he then
termed the disease as cementopathia

Cementum in forensic odontology
 Age estimation in adults by Gustafsons method.
 1950,Gosta Gustafsons proposed a method for age
estimation based on morphological and histologic
changes of teeth.

 The method assesed regressive changes such as
attrition secondary dentin deposition,loss of
periodontal attachment.
 cementum apposition at the root apex.
 Root resorption at the apex and dentin translucency

Future directions on cementum
 It is indicated that tooth cementum annulation(TCA) may
be used more reliably than any other morphological or
histological traits of the adult skeleton ,for age estimation
journal of forensic dental science2009;1(2):82-8
 it is indicated that MTA is a potential root end filling
material and root ends filled with MTA had a complete
layer of cementum over the filling
journal of endodontics 1997;20(4);225-226

conclusion
 Cementum, a unique avascular mineralised tissue
covering the root surface that forms the interface
between root dentin and periodontal ligament.
 Being a unique tissue that is avascular and non-
innervated, it continues to grow through out life.
 There is still much to study about cementum
regeneration and researches are being carried out.

References
 Orbans oral histology and embryology 13th edition
 Orbans oral histology and embryology 11th edition
 A.R TEN CATE 4th edition
 Maji Jose-manual of oral histology and oral
pathology
 Shafer’s textbook of oral pathology 7th edition
 Yamomoto en et al Jpn dental science rev:2016
aug,52(3);63-74.

Understanding Cementum: A Guide to its Development, Composition and Function

Understanding Cementum: A Guide to its Development, Composition and Function

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