Cementum is a hard, mineralized tissue found on the anatomical roots of teeth. It has several subtypes based on cellularity and collagen fiber organization. Cementum is composed of hydroxyapatite crystals and collagen fibers. It is formed by cementoblasts and cementocytes. Cementum provides attachment of periodontal ligament fibers to the tooth and continues growing throughout life. The main types are acellular and cellular cementum. Acellular cementum forms earlier and is less cellular while cellular cementum forms later and more rapidly to adapt to functional forces. Cementum plays an important role in tooth attachment and is involved in pathological processes like root resorption.

1. I AM A
STRONG
TOOTH

2. MOLECULAR BIOLOGY OF
CEMENTUM
AND
ALVEOLAR BONE
Dr. KRITIKA JANGID
MDS- Periodontics

4. Cementum

5. • Its name is derived from a Latin word,
“Caementum”, meaning quarried stone or
chips of stone used in making mortar.
• It was demonstrated in 1835.
Cementum

6. • It is a hard, mineralised, avascular connective
tissue found on the anatomic roots of the
teeth.

7. Uniqueness of Cementum
• Medium of attachment
• It is avascular and not innervated
• Does not undergo continuous remodelling like
bone, but continues to grow in thickness
throughout life.

8. Physical Characteristics
• Softer than Dentin (Selvig and Selvig 1962)
• It is light yellow in color.
• It is different from enamel by its lack of luster
and its darker hue.
• It is lighter than dentin.

9. Thickness of Cementum
 Coronal half 16 - 60µm
 Apical 20- 150µm
 Distal surface is thicker than mesial, probably
because of functional stimulation like mesial drift.

10. Composition
• Its content is
– 45–50% Inorganic:
• Ca, PO4 as Hydroxy-apatite.
• Numerous trace elements
• Highest fluoride content
– 50-55% Organic and Water:
• Collagen Type I
• Proteoglycans

11. Minerals:
• The mineral component is the same as in other calcified
tissues i.e. hydroxyapatite Ca10(PO4)6(OH)2
• with small amounts of amorphous calcium phosphates.

12. Minerals:
• Due to its lower crystallinity, cementum has a greater capacity
for adsorption of fluoride and other elements.
• Cementum has a high fluoride content compared to other
mineralized tissues (up to 0.9%), shows a general increase with
age and vary with fluoride supply to the individual.

13. • Cementum contains 0.5% magnesium, about half that in
dentin, and it is lower at the surface than in deeper layers of
cementum.
– Significance - composition of cementum is more similar to
bone tissue than to dentin.
• Cementum also contains 0.1-0.3% sulfur as a constituent of
the organic matrix.
• Trace elements may be present in concentrations detectable
by electron microprobe analysis, in particular Cu, Zn and Na.

14. Organic Components:
• The organic matrix of cementum is composed primarily of
collagen.
• Predominantly type I and type III (Birkedal and Hansen et al
1977)
• Type I collagen plays structural as well as morphogenic role
and provides scaffolding for mineral crystals
• It is the major component accounting for 90% of organic
components in cellular cementum.

15. • The type III collagen, which coats type I collagen
fibrils, accounts for only 5%. (Rao et al 1979, Wang et
al 1980)
• It is a less cross-linked collagen found in high
concentrations during development, repair and
regeneration of mineralized tissues

16. • Type XII collagen- A fibril associated collagen with interrupted triple
helices that binds to type 1 collagen and also to non collagenous
proteins
• Trace amounts of Type XIV are also found in extracts of mature
cementum, however these may be contaminants from periodontal
ligament.
• Based on immunostaining, the cementum does not appear to have
either Type V or Type VI collagen (Becker and Romanos et al 1991)

17. Non collagenous proteins:
– Bone sialoprotein (BSP)
– Osteopontin(OPN)
– Alkaline phosphatase
– Fibronectin
– Osteocalcin
– Osteonectin
– Proteoglycans
– Proteolipids
– Vitronectin
– Growth factors

18. • BSP and OPN are expressed in AEFC and AAFC.
• Both are phosphorylated and sulfated glycoproteins.
• They bind tightly to the collagenous matrices and
hydroxyapatite, and possess cell attachment properties
through the Arg-Gly-Asp sequence, that binds to integrins.

19. Bone Sialoprotein(BSP)
– Root surface cells express the BSP, and it is also
present in mature teeth.
– BSP is believed to have adhesion function to root
surface cells and participate in initiating
mineralization.
– It is chemotactic to pre-cementoblasts and promotes
their adhesion and differentiation.

20. Osteopontin
• OPN is present within the periodontal ligament region of the
mature teeth.
• Many cells express the OPN during periods of cementogenic
activity.
• It regulates cell migration, differentiation, and survival through
the interaction with integrins.
• Participates in inflammation by regulating monocyte-
macrophage activation, phagocytosis, and nitric oxide
production.
• It may regulate biomineralization by regulating bone cell
differentiation and matrix mineralization.

21. • Fibronectin
• Believed to bind cells to the extracellular matrix
• Tenascin
• Present in HERS during odontoblast differentiation.
• And later at the attachment site of periodontal ligament with the root
surface.
• Osteonectin
• Expressed by cementoblasts producing cellular extrinsic fiber
cementum and cellular intrinsic fiber cementum

22. • Osteocalcin:
– Appears to be involved in the mineralization process.
• Biochemical analysis of extracts of human
cementum have identified
– Chondroitin sulfate,
– Dermatan sulfate and
– Hyaluronic acid.

23. • Enzymes:
– Alkaline phosphatase is believed to participate in
cementum mineralization.
– The enzyme activity adjacent to cellular intrinsic fiber
cementum is higher than that to acellular extrinsic fiber
cementum.
• Growth factors
– BMP-2, 3 and 4, PDGF, α and β-FGFs, TGFβ, PTH and IGF-
1.

24. • Molecules unique to cementum have also been
described.
• One of these are an IGF-1, referred early as
Cementum Growth Factor (CGF).
• The second molecule is a collagenous protein
referred to as Cementum Attachment Protein (CAP).
CAP promotes the adhesion and spreading of
mesenchymal cells.
.

25. Cemento-Enamel Junction
60 – 65% Cementum overlaps the
enamel.

26.  Overlapping of cementum on enamel is due to
local degeneration of the reduced enamel
epithelium
 With the result that, the connective tissue
elements of the dental follicle enter and effect
cementogenic activity.

27. 30% - 35% there is an edge-to-edge butt joint.

28. 5 – 10 % the cementum and enamel fail to meet.

29. Cemento-Dentinal Junction
• It is relatively smooth in permanent teeth.
• Sometimes scalloped in deciduous teeth.
• Contains large quantities of collagen
associated with GAGs like chondroitin sulfate
and dermatin sulfate resulting in increases
water content and contributes to the stiffness.

31. • In histological sections, the cementum usually
stains more intensely than dentin.
• The cementum is more electron dense than
dentin.
• The collagen fibrils are in distinct bundles in
cementum where as
• The collagen fibrils are haphazard in dentin.

38. Current theories suggest
1. Infiltrating dental follicle cells recieve a reciprocal
inductive signal from the dentin or the surrounding
HERS and differentiate into cementoblasts.
2. HERS cells transform into cementoblasts.
• Evidence is increasing that ECRM are not simply
residual cells but may also participate in maintenance
and regeneration of periodontal tissues.
• Some HERS cells remain attached to the forming root
surface, they can produce focal deposits of enamel
like material called enamel pearls.

39. Cementoblasts
• Arise from the undifferentiated mesenchymal
cells
• Synthesise collagen and protein
polysaccharides- organic matrix of cementum.
• Mitochondrea, golgi, RER
• Inner cells of dental follicle: CIFC
• HERS- AEFC

41. Cementocytes
• In the apical 1/3rd,cementoblasts trapped in rapidly
calcifying cemental matrix, later, differentiate into
cementocytes.
• These locate in spaces termed lacunae & have
numerous cytoplasmic processes coursing in canaliculi,
that are preferentially directed towards the periodontal
ligament.
• This is how cementocytes derive their nutrition from
periodontal ligament & contribute to the vitality of this
mineralized tissue.
• While adjacent canaliculi of neighboring cells
communicate frequently, the processes remain
independent.
• Thus, the metabolites progress mostly by diffusion
through the canaliculi of cellular cementum.

42. Cementoclasts:
• They are multinucleated giant cells, which are
indistinguishable from osteoclasts.
• Responsible for root resorption that leads to
primary teeth exfoliation & also in the permanent
dentition in mesial surfaces in compliance with
mesial migration & may occur due to occlusal
trauma & orthodontic therapy.

44. GROWTH FACTORS
• BMPs- Members of TGFβ superfamily that act
through transmembrane serine/threonine
protein kinase receptors.
• BMP-2, BMP-4, BMP-7
• Known to promote differentiation of
preosteoblasts and cementoblasts precursor cells
• PDGF± IGF- Promote cementum formation by
altering cell cycle activities.
• FGF: Cell proliferation, migration and
vasculogenesis.

45. • BMPs have been used successfully to
induce periodontal regeneration in a
number of experimental models and
certain clinical situations.

46. EPITHELIAL FACTORS
• Dental epithlial
• Ectomesenchymal cells
• Enamel proteins
• PTH related protein
• Basal lamina constituents

47. ADHESION MOLECULES
• Contain cell adhesion motifs arginine-glycene-
aspartic acid
• Bone sialoprotein- Promotes mineralisation
• Osteopontin- Regulate the extent of mineral
growth.

48. COLLAGENS
• I
• III
• XII: Assist in maintaining the PDL space versus
continuous formation of cementum

49. Gla proteins
• Matrix/ Bone Gla proteins
• Contain γ- carboxyglutamic acid
• Matrix Gla protein: Inhibitor of mineralisation.
Significant role in preventing abnormal ectopic
calcification
• Osteocalcin: Marker for cells associated with
mineralisation (osteoblasts, cementoblasts,
odontoblasts) hence considered to be a
rgulator of crystal growth

50. TRANSCRIPTION FACTORS
• Runt-related transcription factor 2 (Core binding
factor alpha 1)
• Osterix
• Involved in cementoblast differentiation
• BMPs have been identified as factors promoting
Runx-2

51. SIGNALLING MOLCULES
• RANK
• RANKL
• OPG

52. Types of
Cementum
Embryologically Primary & Secondary
According to location
on teeth ( Kronfield
1928).
- Radicular cementum- found on root
surfaces.
- Coronal Cementum to Cementum that
forms on the enamel covering the crown.
On the basis of
cellularity (Gottlieb
1942).
- Acellular / Primary Cementum.
- Cellular / Secondary Cementum.
Schroder(1986)
classified cementum x 5
subtypes based on
cellularity &
organisation of collagen
fibres into
- Acellular afibrillar cementum.
- Acelluar extrinsic fiber cementum.
- Acellular intrinsic fiber cementum.
- Cellular intrinsic fiber cementum.
- Cellular mixed stratified cementum
Based on the origin of
the collagen matrix
- Extrinsic.
- Intrinsic.
- Mixed.
Depending on the
location & patterning
- Intermediate.
- Mixed stratified cementum.

53. Differences Between Acellular &
Cellular Cementum…..
Acellular
Cementum
Cellular
Cementum
Formation Forms before tooth reaches
occlusal plane
After tooth reaches occlusal
plane
Cells Does not contain any cells Contains cementocytes
Location Coronal portion of root Apical portion of root
Rate of
formation
Slow Rapid
Incremental
lines
More Sparse

54. Cont…..
Acellular
Cementum
Cellular
Cementum
Function Forms after regenerative
periodontal surgical procedure
Contributes to the
length of the root during
growth
Calcification More calcified Less calcified
Sharpey’s fibers More Less
Regularity of
fibers
Regular Irregular
Thickness 20 – 50µm near the cervical
region &150 – 200µm near the
apex.
Thickness of 1 – several
mm.

55. Acellular Afibrillar Cementum
(AFC):
• Contains neither cells, nor extrinsic / intrinsic
fibers, apart from a mineralized ground substance.
• It is a product of cementoblasts, found deposited
on the enamel over small areas of the dental
crown just coronal to the CEJ.
• Thickness is about 1 - 15 µm.

56. Acellular Extrinsic Fiber Cementum
(AEFC):-
Composed almost entirely of densely packed
bundle of Sharpey's fiber and no cells.
• A product of fibroblasts and cementoblasts,
• found on the cervical ⅓ of roots, but may
extend further apically..
• Cementoblasts that produce AEFC
differentiate in close proximity to the
advancing root edge.

57. • During root development, the first formed
cementoblasts align along the newly formed,
but not yet mineralized, mantle dentin surface
& exhibit fibroblastic characteristics.
• Deposit collagen fibrils within it so that dentin
& cementum fibers intermingle.

58. • Initially AEFC consists of mineralized layer
with a short fringe of collagen fibers implanted
perpendicular to the root surface.
• Cementoblasts then migrate away from the
surface but continue to deposit collagen so that
a fine fiber bundle lengthens & thickens.

59. • These cells also secrete non – collagenous matrix
proteins that fill in the spaces between the collagen
fibers.
• AEFC has the potential to adapt to functionally
dictated alterations such as mesial tooth drift.

60. Cellular Mixed Stratified Cementum
(CMSC):
• Contains both collagen fibers & calcified
matrix.
• It is the co – product of cementoblasts &
fibroblasts and consists of both extrinsic
& intrinsic fibers.

61. • Appears primarily in the apical third of the roots
& in furcation areas.
• Consists of AEFC and CIFC that alternate &
appear to be deposited in irregular sequence upon
one another.
- Schroeder, (1993).
• Deposited @ 0.1 – 0.5 µm / year.

62. Cellular Intrinsic Fiber Cementum
(CIFC):
• Contains cells but no extrinsic (Sharpey's)
fibers.
• Once the tooth is in occlusion, a more rapidly
formed & less mineralized variety of
cementum, (CIFC) is deposited on
unmineralized dentin surface near the
advancing root edge.

63. • Formed by cementoblasts & fills resorption
lacunae (resorptive cementum.)
• Can easily repair a resorptive defect of the root
due to its capacity to grow faster than any
other form of cementum.

64. Acellular Intrinsic Fiber Cementum
(AIFC):
• An acellular variant of cellular intrinsic fiber
cementum that is also deposited during adaptive
responses to external forces (i.e.,) slow deposition
rate so that cells are not engulfed in their matrix &
that forms without leaving cells behind.
- Bosshardt & Schroder, (1990)
.

65. • In the light microscope, CIFC is identified easily because of the
inclusion of cementocytes within lacunae with processes directed
towards the tooth surface, laminated structure & presence of
cementoid on its surface.
• Fine, densely packed intrinsic fibers running parallel to the root
surface & larger, haphazardly incorporated extrinsic fibers
running at right angles to the root surface.
• Cellular intrinsic fiber cementum is initially deposited on root
surface areas where no acellular extrinsic fiber cementum has
been laid down on the dentin (furcation and on the apical root
portions).

67. EXPOSURE TO ORAL
ENVIRONMENT:
• Cementum becomes exposed to oral environment
in gingival recession & as a result of loss of
attachment in pocket formation.
• Cementum is sufficiently permeable to be
penetrated by organic substances, inorganic ions
& bacteria, leading to hypersensitivity to thermal
changes / tactile stimulation, root caries, etc...
sometimes resulting in pulpal pathology.

68. Changes in the Periodontium During
Pocket Formation……….
• The changes may be grouped as
• Structural
• Chemical
• Cytotoxic

69. Structural Changes:
• Presence of pathologic granules, representing
areas of collagen degeneration / areas not fully
mineralized initially.
- Bass, (1951).

70. • Areas of Increased Mineralization: -
Selvig, (1966) as a result of exchange
on exposure to the oral cavity, of minerals &
organic component at the cementum saliva
interface.
• Areas of Demineralization:-
Exposure to oral fluids & bacterial
plaque results in proteolysis of the embedded
Sharpey’s fibres, leading to softening of the
cementum, which undergoes fragmentation &
cavitation (root caries) → Pulpal sensitivity /
severe pain.

71. Chemical Changes……
• Exposed cementum has an increased mineral
content (Selvig 1966)- Ca, Mg, P, F. & may be
resistant to decay.

72. Cytotoxic Changes:
• These include bacterial penetration into
cementum as deep as the CDJ.
• In addition, bacterial products such as
endotoxins are also found deep in the cemental
wall of the periodontal pocket.

73. Anomalies

74. Scurvy (Vit.C deficiency)
• It affects the deposition of bone, dentin and
cementum.
• It also produces atrophy of formative cells.
• This can lead to increase in bone resorption
leading to tooth loss.

75. Rickets
• The cementum is hypomineralized.
• The bone matrix also exhibits
hypomineralization.
Hypophospatasia
• There is a total absence of cementum.
• It is a rare hereditary disease with loosening
and premature loss of deciduous teeth.

76. Hypercementosis
• It is abnormal thickening of cementum.
• It may be diffuse or circumscribed.
• It may affect all teeth/ one tooth/ few
portions of a single tooth.
• It could be cemental hypertrophy or cemental
hyperplasia.

77. Cementicles
• These are calcified bodies appearing on/in
cementum and PDL.
• It is usually ovoid or round.
• It is classified as,
– Free
– Attached
– Embedded
• It forms as a response to local trauma or
hyperactivity.
• Its number increases with age.

78.  The nidus for the calcifying process are
 dead cells associated with epithelial rests of malassez,
 mineralized sharpeys fibres and
 phleboliths.
 A wall of Cementum of varying thickness form
around this with diameter ranging between 0.2-
0.3mm
• They may fuse into interstitial cementicles.

79. Resorption and Repair
• Cementum resists resorption under normal
conditions.
• But it can resorb after trauma or excessive occlusal
loads.
• If the original contour of the root surface is re-
established, it is called Anatomical repair.
• In Functional repair, only a thin layer is deposited
and a bay like recess remains. The outline is
followed by the alveolar bone.

80. Other Anomalies
• Cemental tears can occur.
• Transverse fractures of root may occur and it
heals by formation of new cementum.

83. Circumferential lamellae

84. Concentric lamellae

85. OSTEON

86. Interstitial lamellae

87. •outer "fibrous layer" and
• inner "cambium layer" (or "osteogenic layer").
P
E
R
I
O
S
T
E
U
M

88. Are responsible for formation, resorption and maintenance of
osteoarchitecture
• Osteogenic cells
• Osteoprogenitors
• Preosteoblasts
• Osteoblasts
• Osteocytes
• Bone lining cells
• Osteoclast
B
O
N
E
C
E
L
L
S

90. OSTEOBLASTS
• Mononucleated cell that synthesize
collagenous and non collagenous proteins of
the bone matrix proteins

92. • Exhibit high levels of alkaline phosphatase.
• Cleave organically bound phosphate.
• Liberated phosphate contributes to the
initiation and progressive growth of bone
mineral crystals.

93. • Plump
• Cuboidal (when active) or slightly flattened
• Primary role: Production of organic matrix of
bone
• Abundant RER, Golgi complexes, rich in secretory
granules
• Type 1 collagen dominant
• Type III collagen in small amounts
• Non- Collagenous proteins and PG also present

94. • Cytokines and growth factors
• BMP-2
• BMP-7
• Transforming growth factor β
• IGF-1
• IGF-2
• PDGF

95. • IGF-1 + PDGF: Increase the rapidity of bone
formation and bone repair
• Used in bone healing and bone growth after
periodontal surgical procedures.
• Enhance osseous integration after placement
of dental implants

96. Hormones
• PTH and Vit D: Enhance resorption at high
conc., bone formation at low conc.
• Calcitonin and estrogen: Inhibit resorption
• Glucocorticoids: Inhibit resorption and
formation

97. Leptin
• A circulating hormone
• Produced by adipocytes
• Regulates food intake and body weight;
control body mass
• Acts on hypothalamus
• Inhibit differentiation of osteoclasts
• Promote differentiation of osteoprogenitor
cells

98. Bone lining cells
• Last phenotype of osteoblast lineage prior to
activation of bone remodeling cycle
• Form sheets over bone. Estimated 80% of bone
surface is covered by lining cells
• Scarce organelles with less protein synthesizing
machinery
• Flattened cells that line the quiescent bone
surfaces
• These quiescent surface is the primary site of
mineral ion exchange between blood and bone.

99. OSTEOCYTES
• As osteoblasts produce bone, some cells get
entrapped in matrix they secrete , whether
mineralised or unmineralised.
• Smaller than osteoblasts

101. OSTEOCLASTS
• Large multinucleated cell

104. MORPHOLOGY(EM)
An active OCL occupies hollowed out
depressions called HOWSHIP’S LACUNAE

105. Secretory functions
• Cathepsins B,D,K have been localised in vacoules
near the ruffled border
• These degrade collagen at acidic Ph
• Express MMP1, MMP2,MMP3,MMP9,
• Digest collagen I,IV &V
• Cathepsins act first at low pH, followed by MMP’s

106. • Carbonic Anhydrase II in preosteoclasts &
osteoclasts
• This enzyme generates hydrogen ions, which
by proton pump is extruded in to sealed pit
via the ruffled border, creates an acidic
environment

108. Sequence of events
• Attachment of OCL to mineralised surfaces of
bone
• Creation of acidic environment, which
demineralises bone to expose matrix
• Degradation of exposed matrix by acid
phosphatase & Cathepsins
• Endocytosis of degradative products by ruffled
border
• Translocation & release of degradative products
at opposite border

109. MATRIX COMPONENTS

110. COLLAGEN
80- 90% of organic
component
TYPE
III & XII
TYPE I
TYPE
V(5%)

111. • Type I provides structural integrity
• Type III is present as mixed fibers with type I in
sharpey’s fibers
• Type XII is related to mechanical strain
I, V, XII
III &
Some
XII
OSTEOBLAST FIBROBLAST

112. NONCOLLAGENOUS PROTEINS
• Osteocalcin
• Osteonectin
• Osteopontin
• Bone Sialoprotein

113. OSTEOCALCIN
• Bone gla protein,15% of NC proteins
• Small/molecular mass of 6Kd
• 3 γ carboxy glutamic acid residues(gla groups)
• Dual role in bone
formation & resorption

114. • Expressed by osteoblasts and odontoblasts
• Secreted in to bone matrix at the time of
mineralisation (Boskey et al 1992)
• Carboxy terminal segment act as
chemottractant to OCL precursors

115. OSTEONECTIN
• SPARC(Specific Protein Acidic Rich in Cysteine
• 40Kd protein
• 20% of NC proteins
• Also known as endothelial ”culture shock”
protein, basement membrane protein (BM 40)

116. Four domains
• 1 - Calcium binding
• 2 - Cysteine rich domain
• 3 - α helical domain
• 4 - EF hand domain

117. OSTEOPONTIN
• Phosphoprotein with high content of serine,
asparagine & glutamate
• 55Kd low phosphorylated species produced by
preosteoblasts
• 44Kd highly phosphorylated species that binds
to HA(Sodek et al 1995)

118. • 8 α helices with RGD sequence in the middle
flanked by 2 segments of β sheet structures
• Amino terminus binds to calcium & HA

119. DUAL ROLE IN REMODELING
• Highest expression is seen in preosteoblasts
during bone formation and mature
osteoblasts during bone remodeling
• Through the RGD sequence , binds to α5β3 of
OCL, plays a role in remodeling

120. BONE SIALOPROTEIN
• Highly glycosated , acidic phosphoprotein with
high sialic acid content
• Highly expressed only in mineralised tissues
• RGD sequence, helps
in attachment of Ob to
mineralised tissues
• Glutamic acid domain
are sites for HA binding

121. • Implicated in nucleation of HA during de novo
bone formation & in initial mineralisation of
newly formed bone

122. PROTEOGLYCANS
• DECORIN
• 46Kd protein core
• Single c.sulfate chains at
amino terminus
• Binds to the gap region
of collagen fibrils
• Binds to TGF β
• Regulates fibrillogenesis
• BIGLYCAN
• 46Kd protein core
• Two c.sulfate chains at
amino terminus
• Binds to TGF β, collagen
• Regulates fibrillogenesis
Both comprise <10% of non collagenous proteins
& decreases with maturation of bone

123. OTHER PROTEINS
• Procollagen Peptides
• Thrombospondin
• Fibronectin
• Vironectin,
Modulate cell attachment

125. BONE COUPLING

126. REFERENCES
• Biology of the periodontal connective tissues by
Bartold and Sampath Narayan
• Molecular biology of periodontium by KV Arun
• Molecular and cellular biology of alveolar bone.
(Perio 2000)
• Targeting osteoclast-osteoblast communication
(nature.com)
• Ten cate’s oral histology
• Orbans oral histology and embryology
• Carranza 10th ed