5. Once dentin formation is
underway
break occurs in the
epithelial root sheath
allowing newly formed
dentin
come in direct contact
with Connective tissue of
dental follicle.
8
6. 6
1.PRIMARY CEMENTUM FORMATION
ultrastructural level
break down of HERS
degeneration or loss of its basal lamina on cemental side
Appearance of collagen fibrils and cementoblasts
migrate away from the hyaline layer
9
7. continue to deposit collagen bundles
thicken to form the fibrous matrix of acellular
cementum.
cells develops relatively slowly
covers atleast the coronal third of the root. 10
8. 1
8
2.SECONDARY CEMENTUM FORMATION
when tooth is in occlusion,
cementum deposited - the apical third of the root.
cementoblasts lay down initially an organic matrix
secretory activity declines
becomes cementocytes
11
9. 9
3.CORONAL CEMENTUM
completion of cementogenesis,
enamel surface remains lined with an epithelial covering
During pre-eruption period, portion of REE covers the
cervical half of the crown.
deposition of thin layers of coronal cementum over the
exposed enamel surface.
afibrillar and acellular - organic matrix devoid of collagen
fibrils.
12
10. 10
4.RADICULAR CEMENTUM
root formation proceeds,
HERS becomes perforated by ectomesenchymal cells of the
dental follicle
cells lay down a collagenous matrix, enlarges the
perforations of the sheath
gradually displaces it away from the dentin surface.
13
11. HERS eventually breaks up into a network of more or less
interconnected epithelial strands
epithelial remnants are known as the Epithelial cell
rests of Malassez.
14
12. composition
Organic(50%-55%)
• Type I Collagen fibers
• Protein
polysaccharides
Inorganic(40%-45%)
• Calcium
• Phosphorous
• Traces of Magnesium
• Fluoride
• Water
13. Collagen Fibers
• The two sources of collagen fibers in
cementum are;
• Sharpey's (extrinsic) fibers, which are the
embedded portion of the principal fibers of
the periodontal ligament and are formed
by the fibroblasts, and
• fibers that belong to the cementum matrix
per se (intrinsic) and are produced by the
cementoblasts.
14. Physical Properties
• It is yellowish in color but lighter than
dentin.
• It is less harder than dentin.(70 KHN)
• Cementum is permeable, but decreases as
age advances
15. Types of Cementum
Acc to location;
a) Coronal Cementum.
b) Radicular Cementum.
Acc to Presence or absence of cells;
a) Acellular (primary) cementum.
b) Cellular (secondary) cementum.
Both consist of a calcified interfibrillar
matrix and collagen fibrils
16. Classification
• Acc to content of fibrils;
a) Fibrillar Cementum.
b) Afibrillar Cementum.
Acc to Schroeder et .al;
• Acellular afibrillar cementum (AAC)
• Acellular extrinsic fiber cementum (AEFC)
• Cellular mixed stratified cementum (CMSC)
• Cellular intrinsic fiber cementum (CIFC)
• Intermediate cementum
17. Differences between
Acellular & Cellular cementum
Acellular (primary) cementum
• First formed cementum
• Formed before reaches occlusal
surface.
• Covers cervical third or half of the
tooth.
• No cells.
• More calcified.
• Sharpeys fibers make up most of
the structure.
I) Inserted perpendicular to tooth
surface.
II)size,No.,distribution increases
with function.
III) Completely calcified.
Cellular (secondary) cementum
Formed after acellular
cementum
Formed after tooth reaches
occlusal surface.
Covers apical third of root.
Contains cells (cementocyte).
Less calcified.
Sharpeys fibers occupy a
smaller portion.
I) Arranged parallel to root
surface.
II) May be completely or partially
be calcified.
19. Afibrillar type of cementum
• In addition, loss of the cervical part of the
reduced enamel epithelium at the time of tooth
eruption may place portions of mature enamel in
contact with the connective tissue, which then
will deposit over it an acellular afibrillar type of
cementum
20. Acellular afibrillar cementum (AAC)
• It contains neither cells nor extrinsic or
intrinsic collagen fibers, apart from a
mineralized ground substance.
• It is a product of cementoblasts
• It is found as coronal cementum in humans,
with a thickness of 1 to 15μ.
21. Acellular extrinsic fiber cementum
(AEFC)
• It is composed almost entirely of densely
packed bundles of Sharpey's fibers and lacks
cells.
• It is a product of fibroblasts and
cementoblasts
• It is found in the cervical third of roots.
• Its thickness is between 30 and 230microns.
23. Cellular mixed stratified cementum
(CMSC)
• It is composed of extrinsic (Sharpey's) and
intrinsic fibers and may contain cells.
• It is a co-product of fibroblasts and
cementoblasts,
• It appears primarily in the apical third of the
roots and apices and in furcation areas.
• Its thickness ranges from 100 to 1000 nm.
24. Cellular intrinsic fiber cementum
(CIFC)
• It contains cells but no extrinsic collagen
fibers.
• It is formed by cementoblasts,
• It fills the resorption lacunae.
25. Permeability of Cementum
• In very young animals, cellular and acellular
cementum are very permeable and permit the
diffusion of dyes from the pulp and external root
surface.
• In cellular cementum, the canaliculi in some
areas are contiguous with the dentinal tubuli.
• The permeability of cementum diminishes with
age
27. Cementoenamel Junction
• Three types of relationships involving the
cementum may exist at the cementoenarnel
junction.
• In about 60% to 65% of cases, cementum
overlaps the enamel.
• In about 30% an edge-to-edge butt joint
exists; and
• In 5% to 10% the cementum and enamel fail
to meet.
• In the last instance, gingival recession may
result in accentuated sensitivity because the
dentin is exposed.
29. Thickness of Cementum
• The thickness of cementum on the coronal half
of the root varies from 16 to 60micron, or about
the thickness of a hair.
• It attains its greatest thickness (up to 150 to
200μ) in the apical third and in the furcation
areas.
• It is thicker in distal surfaces than in mesial
surfaces, probably because of functional
stimulation from mesial drift over time.
30. Thickness of Cementum
• Between the ages of 11 and 70, the average
thickness of the cementum increases threefold,
with the greatest increase in the apical region.
• Average thicknesses of 95μ at age 20 and 215μ
at age 60 have been reported.
32. Functions of Cementum.
• Primary function is to furnish a medium for
attachment of collagen fibers that bind to alveolar
bone.
• Continuous deposition helps to keep the
attachment apparatus intact.
• Root fracture or resorption can be repaired by new
cementum deposition
• Make functional adaptation of tooth possible. (i,e-
deposition of cementum apically can compensate
for loss of tooth substance from occlusal wear&help
maintain vertical dimension.)
34. 1. CEMENTOBLASTS
synthesize collagen and
protein polysaccharides
Active cementoblasts –
round, plump cells ,
basophilic cytoplasm,
extensive RER
and open face nuclei.
34
35. Cementoblasts contains more
mitochondria then PDL fibroblasts.
[YAMASAKI et al 1987]
35
Resting cementoblasts –
closed nucleus
and little cytoplasm.
36. 2.CEMENTOCYTES
cells incorporated into cellular
cementum - cementocytes.
similar to osteocytes.
located within lacunae and
numerous cytoplasmic processes
occurring in canaliculli
36
1.Cementocyte lacunae
2.Cementocyte canaliculi
37. In deeper layers very few organelles, dilated
- ER, and sparse mitochondria.
37
A-cementoblasts
B-precementium
C-cementocytes in cellular
cementum
D-Sharpey fiber
cytoplasmic volume and density of cytoplasmic
organelles is reduced .
40. Develpmental Anomalies
with Cementum.
Enamel Projections;
If amelogenesis does not stop before the start
of root formation,enamel may continue to form
overportions normally covered by cementum.
Enamel Pearls;
This consists of globules of enamel on the root
surface in cervical region.(act as plaque retentive
areas)
42. Hypercementosis
• The term hypercementosis (cementum
hyperplasia) refers to a prominent
thickening of the cementum.
• It may be localized to one tooth or affect
the entire dentition.
• Hypercementosis occurs as a generalized
thickening of the cementum, with nodular
enlargement of the apical third of the root.
43. Hypercementosis
The etiology of hypercementosis
• The spikelike type of hypercementosis generally
results from excessive tension from orthodontic
appliances or occlusal forces.
• The generalized type occurs in a variety of
circumstances. In teeth without antagonists,
hypercementosis is interpreted as an effort to
keep pace with excessive tooth eruption.
45. Cementicle
• Cementicle
Globular masses of acellular cementum
which form with in the periodontal ligament
Types;
Free-Lies within the PDL space.
Attached-Lies fused to radicular
cementum.
Interstitial-Incorporated in the cementum.
47. Cementoma
Cementoma
These are masses of cementum generally
situated apical to the teeth, to which they may
or may not be attached.
They are regarded as either odontogenic
neoplasms or developmental malformations.
48. Cementum Resorption and
Repair
• Permanent teeth do not undergo physiologic
resorption as do primary teeth.
However, the cementum of erupted as well
as unerupted teeth is subject to resorptive
changes that may be of microscopic proportion
or sufficiently extensive to present a
radiographically detectable alteration in the root
contour.
49. Cementum Resorption and
Repair
• Cementum resorption may be caused by
local or systemic causes or may occur without
apparent etiology (i.e., idiopathic).
• Among the local conditions in which it occurs
are
trauma from occlusion.
orthodontic movement
pressure from malaligned erupting teeth,
50. Cementum Resorption
• cysts, and tumors;‘
• teeth without functional antagonists;
• embedded teeth; replanted and transplanted
teeth;
• periapical disease; and periodontal disease.
51. Cementum Resorption
• Among the systemic conditions mentioned as
predisposing to or inducing cemental resorption
are
• calcium deficiency,
• hypothyroidism,
• hereditary fibrous osteodystrophy, and
• Paget's disease.
52. Cementum Resorption and
Repair
• Cementum resorption appears microscopically as
baylike concavities in the root surface (Fig. 2-16).
• Multi-nucleated giant cells and large mononuclear
macrophages are generally found adjacent to
cementum undergoing active resorption (Fig. 2-17).
• Several sites of resorption may coalesce to form a
large area of destruction.
• The resorptive process may extend into the
underlying dentin and even into the pulp, but it is
usually painless
53. Cementum Resorption and
Repair
• Cementum resorption is not necessarily
continuous and may alternate with periods of
repair and the deposition of new cementum.
• The newly formed cementum is demarcated
from the root by a deeply staining irregular line,
termed a reversal line, which delineates the
border of the previous resorption
54. Cementum Resorption and
Repair
• Embedded fibers of the periodontal ligament
reestablish a functional relationship in the new
cementum.
• Cementum repair requires the presence of viable
connective tissue.
• If epithelium proliferates into an area of
resorption, repair will not take place. Cementum
repair can occur in devitalized as well as in vital
teeth.
57. Ankylosis
• Fusion of the cementum and alveolar bone with
obliteration of the periodontal ligament is termed
ankylosis.
• Ankylosis occurs in teeth with cemental
resorption, which suggests that it may represent
a form of abnormal repair.
• Ankylosis also may develop after chronic
periapical inflammation, tooth replantation, and
occlusal trauma and around embedded teeth.
58. Exposure of Cementum to the
Oral Environment
• CLINICAL SIGNIFICANCE
• Cementum becomes exposed to the oral
environment in cases of gingival recession and
as a consequence of loss of attachment in pocket
formation.
• The cementum is sufficiently permeable to be
penetrated in these cases by organic substances,
inorganic ions, and bacteria.
• Bacterial invasion of the cementum occurs
commonly in periodontal disease .
• Caries of the cementum also can develop
