Dr. Mona Denewar

1. CementumCementum
Dr. Mona Denewar
Lecturer of oral biology departmentLecturer of oral biology department
Mansoura UniversityMansoura University

4. Contents:Contents:
• Definition.
• Physical and chemical properties.
• Development of Cementum.
• Classification of Cementum.
• Cells of Cementum.
• Incremental lines of Salter
• Age changes of Cementum.
• Clinical considerations.

5. PeriodontiumPeriodontium

6. • Cementum is the
mineralized dental tissue
covering the anatomic
roots.
• It begins at the CEJ and
continues to the apex.
Definition:Definition:

7. • It furnishes a medium for
the attachment of collagen
fibers that bind the tooth to
surrounding structures
(Sharpey’s fibers).
Definition:Definition:

8. Physical properties:Physical properties:
Cementum shares some physical, chemical and structural
characteristics with compact bone except that human
cementum is avascular and with no nerve supply.

9. Physical properties:Physical properties: Color: pale yellow in color.pale yellow in color.
It can be distinguished fromIt can be distinguished from
enamelenamel by its lack of lusterby its lack of luster
and darker hue.and darker hue.
Thickness: the thicknessthe thickness
of cementum at theof cementum at the
cervical areacervical area is about (is about (20-20-
50µm50µm) and it gradually) and it gradually
increases in thickness tillincreases in thickness till
it reaches its maximumit reaches its maximum
about (about (150-200150-200µmµm) at the) at the
apexapex and at theand at the bifurcationbifurcation
of the root.of the root.
Thickness: the thicknessthe thickness
of cementum at theof cementum at the
cervical areacervical area is about (is about (20-20-
50µm50µm) and it gradually) and it gradually
increases in thickness tillincreases in thickness till
it reaches its maximumit reaches its maximum
about (about (150-200150-200µmµm) at the) at the
apexapex and at theand at the bifurcationbifurcation
of the root.of the root.
A
B

10. From
periodontal
side
From dentin
side
Permeability: it isit is
permeable from bothpermeable from both
thethe dentindentin and theand the
periodontal ligamentperiodontal ligament
side.side.
Physical properties:Physical properties:

11. Hardness of fully mineralized cementum is less than dentin

12. The inorganic substances consist mainly of
calcium and phosphate in the form of
hydroxyapatite.
The organic portion consists mainly of collagen
and non-collagenous protein forming the ground
substance.
Chemical compositionChemical composition

13. CementogenesisCementogenesis

14. CementogenesisCementogenesis
Cementum development has been
subdivided into:
A) Prefunctional stage:
- Matrix formation
- Mineralization
B) Functional stage:

15. There are 3 cell types responsible for the
cementogenesis:
 Cementoblasts
 Cementocytes
 Fibroblasts
CementogenesisCementogenesis
By/ Dr. Hesham Dameer
All of these cells are
derived from the
ectomesenchymal cells.

16. • The development of the root begins after the crown is
formed.
• The outer and inner dental epithelium forms the
Hertwig's epithelial root sheath.
Matrix formation:Matrix formation:

17. The inner dental
epithelium will induce
the neighboring cells
of the dental papilla to
differentiate into
odontoblasts.
Matrix formation:Matrix formation:

18.  Once the dentin
formation is started,
the Hertwig's epithelial
root sheath will lose its
continuity and its cells
became the epithelial
rests of Malassez.
Matrix formation:Matrix formation:

19. Matrix formation:Matrix formation:

20. By/ Dr. Hesham Dameer
Remnants of the
Hertwig`s root sheath,
which disintegrate into
the PDL are the Malassez
cells.
Matrix formation:Matrix formation:

21.  Direct contact of the
cells of the dental sac
with the root dentin
resulted in cementoblast
differentiation.
Matrix formation:Matrix formation:

22.  These newly formed
cementoblasts extend
numerous tiny cytoplasmic
processes into the loosely
arranged and not
mineralized dentinal matrix.
Matrix formation:Matrix formation:

23. Cementoblasts lay down
cementum matrix (cementoid)
leading to an intimate
integration of the two different
fibril populations forming the
dentinocemental junction.
Matrix formation:Matrix formation:

24.  It is not distinctive, because
the Fibers of dentin and
cementum intermingle at the
interface
C
D
Cementodentinal junctionCementodentinal junction

25. Derived from Two sources
Matrix formation:Matrix formation:

26. Matrix formation:Matrix formation:

27. Extrinsic fibers Intrinsic fibers
Derived from PDL Derived from cementum.
Formed by fibroblast Formed by cementoblast
Run in same direction of the PDL
principal fibers i.e. perpendicular or
oblique to the root surface.
Run parallel to the root surface
and at right angles to the extrinsic
fibers.
Mixed fiberMixed fiber
Found at the area where
both types of cells produce
fibers.

28. During matrix formation fibroblasts form collagen fibers
(sharpey`s fibers), which become embedded in the matrix
to provide attachment of the root to the surrounding bone
Matrix formation:Matrix formation:

29. Some cementoblasts deposit cementum matrix
at various locations around themselves,
resulting in their entrapment into the cement
matrix converting them into cementocytes.

30.  First layer of cementum is actually formed by the inner
cells of the Hertwig's epithelial root sheath and is
deposited on the root’s surface was called intermediate
cementum.
 Deposition occurs
before the HERS
disintegrates.
 Situated between the
granular dentin layer of
Tomes and the
secondary cementum
that is formed by the
cementoblasts.
A-acellular cementum. B-hyaline layer. C-
granular layer of Tomes. D-dentine

31. The term intermediate cementum recently found to be
named as Hyaline layer of Hopewell-Smith and is
considered as an inductive influence for beginning of
cementum formation.
Matrix formation:Matrix formation:

32.  The role of this layer
is to seals of the
dentinal tubules
before the Hertwig's
epithelial root sheath
disintegrates.
Matrix formation:Matrix formation:

33. CementogenesisCementogenesis
Cementum development has been
subdivided into:
A) Prefunctional stage:
- Matrix formation
- Mineralization
B) Functional stage:

34. Mineralization:Mineralization:
 It begins in the depth of the cementum matrix
(cementoid tissue), where, fine hydroxyapatite crystals
are deposited between and within the collagen fibrils.
 Mineralization of the outermost layer of the dentin
matrix (mantle dentin), appears to be delayed until the
implantation of the cementum matrix is established
and the dentinal matrix is completely covered with the
collagen fibrils of cementum.

35. Cementum
Cementoid layer
Cementoblast
Maturation occur
layer by layer for
the collagen
fibers
Mineralization:Mineralization:

36. CementogenesisCementogenesis
Cementum development has been
subdivided into:
A) Prefunctional stage:
- Matrix formation
- Mineralization
B) Functional stage:

37. Functional stage:Functional stage:
This started when the tooth is in
occlusion and continues throughout life.
It is an adaptive role in response to tooth
wear and movement and is associated with
repair and regeneration of periodontal
tissues.

38. Cementum deposition apically
compensate for the attrition.
Functional stage:Functional stage:

39. Classification of cementumClassification of cementum
I. According to the development:
• Primary cementum (prefunctional).
• Secondary cementum (functional).
II. According to its cellularity:
• Acellular cementum
• Cellular cementum
III. According to the origin of the collagenous matrix:
• Extrinsic fiber cementum.
• Intrinsic fiber cementum.
• Mixed fiber cementum.
• Afibrillar cementum.

40. Under the light microscope two types of
cementum can be differentiated:
Acellular cementum
cellular cementum
The difference between the two types is the
presence or absence of the cells (cementocytes)

41. Acellular cementum Cellular cementum
The difference between the two types is the
presence or absence of the cells (cementocytes)

42. Classification of cementum:Classification of cementum:

43. Acellular cementum Cellular cementum
Present on the cervical third or
half of root.
Present mainly on apical third of
root.
Does not contain cells. Contain cells called cementocytes
in individual spaces lacunae.
Formed before the tooth reaches
the occlusal plane.
Formed after the tooth reaches the
occlusal plane.
Sharpey’s fibers are main
component which inserted at
approximately right angles onto
the root surface. (extrinsic fibers)
Sharpey’s fibers occupy smaller
portion & occupy other fibers that
are arranged parallel to the root
surface. (intrinsic fibers)
Rate of development is slow . faster .
Incremental lines are wide apart. Closer.
Classification of cementum:Classification of cementum:

44. A B
Sharpey’s fibers in cementum (arrowed)
A = unminralized T. , B = mineralized T.
The increase in thickness of
cementum does not
enhance the strength of
attachment of the individual
fibers, because the deeper
portion of the fibers is
calcified and the attachment
proper is confined to the
superficial layer of
Note that....Note that....

45. Classification of cementumClassification of cementum
I. According to the development:
• Primary cementum (prefunctional).
• Secondary cementum (functional).
II. According to its cellularity:
• Acellular cementum
• Cellular cementum
III. According to the origin of the collagenous matrix:
• Extrinsic fiber cementum.
• Intrinsic fiber cementum.
• Mixed fiber cementum.
• Afibrillar cementum.

46. The enamel at cervical
area not covered by
reduced dental
epithelium before tooth
eruption
The connective tissue of the
dental sac lay down
cementum on the exposed
enamel
Afibrillar cementumAfibrillar cementum

47. Cells of cementumCells of cementum

48. •Large cuboidal cells
•Found on the surface of both
celular and acellular
cementum.
•They produce collagen fibers
(intrinsic fibers) and ground
substance of cementum.
CementoblastsCementoblasts

49. Cementoblasts:Cementoblasts:

50. Cementoblast is aCementoblast is a protein formingprotein forming
and secreting cell:and secreting cell:
Large open face nucleus
R E R
Golgi apparatus
Mitochondria
Alkaline phosphatase
Secretory granules

51.  They are incorporated in
cellular cementum
 They have numerrous
irregular processes.
 Most processes are
directed towards PDL.
CementocytesCementocytes
Dentin PDL

52.  The cell body is located in a space called lacuna and
their processes are present in canaliculi.
 Cementocytes in deeper layers of cementum undergo
degeneration and gradually lose their organelles and
die.
Dentin PDL

53. In ground section,
cementocytes spaces
appear as dark spaces
Cementocytes:Cementocytes:

54. CementocyteCementocyte Cementocyte canaliculiCementocyte canaliculi
Cementocyte processCementocyte process

55. Both cellular and acellular cementum is separated
by incremental lines into layers which indicate
periodic formation.
Incremental lines of Salter:Incremental lines of Salter:

56. In acellular C, less
distance between IL
In cellular C,more
distance between IL
 Incremental lines run parallel to the root surface.
 They are hypermineralized area with less collagen
fibers and more ground substance.
Incremental lines of Salter:Incremental lines of Salter:

57. Cemento-enamel junctionCemento-enamel junction
 It is the relation
between the enamel
and cementum edges
at the cervix of the
tooth.
 This relation is found
to be either one of
three forms:

58. Edge to edge:
Incidence: 30%.
Cause: proper development.
Description: the cementum
edge of the tooth meets the
enamel edge in a sharp line
all around.
Cemento-enamel junction:Cemento-enamel junction:

59. Denuded area of dentin:
Incidence: 10%.
Cause: when the Hertwig's
epithelial root sheath delayed in
its separation from the dentin, a
zone of the root dentin became
devoid of cementum.
Description: a pare dentin area
found to be so sensitive at the
cervix of the tooth especially if
there is a gingival recession.
Cemento-enamel junction:Cemento-enamel junction:

60. Cement overlap enamel:
Incidence: 60%.
Cause: local disruption of the
reduced dental epithelium at its end
(cervix of the tooth) that permits
follicular cells to come into contact
with the enamel surface and
differentiate into cementoblasts.
Description: histologically, it may
appear as an island of afibrillar
cementum on the cervical enamel
surface.
Cemento-enamel junction:Cemento-enamel junction:

61. Functions of cementumFunctions of cementum
 Cementum furnishes
a medium for the
attachment of the
collagen fibers of the
periodontal ligament
to the alveolar bone.

62. Functions of cementumFunctions of cementum
 Compensation of
the lost tooth
structure with
wearing or fracture
by deposition of
new cementum at
the apical part of
the root.

63. FunctionFunction of cementum:of cementum:
Repair any
damaged area of the
root resulted from
resorption.

64. External resorption
(8 ws. After trauma) Obturation
Repair after 1 yr.
(new PDL space)

65. Age changesAge changes

66. 1. Smooth surface becomes irregular due to
calcification of ligament fiber bundles where
they are attached to cementum.
2. Continues deposition of
cementum occurs with age in
the apical area.
(maintains tooth length while
obstructs the apical foramen) .
Age changes:Age changes:

67. 3.Cementum resorption: it
is active for a period of
time and then stops for
cementum deposition
creating reversal lines.
Age changes:Age changes:

68. 4. Resorption of root dentin occurs with aging which
is covered by cemental repair.
Age changes:Age changes:

69. 5. Permeability decreases gradually :
From periodontal
side, but remain
at the superficial
recently formed
layers
From dentin
side remains
at apical area
ONLY

70. • Calcified ovoid or rounded nodule.
• Found in the periodontal ligament.
• Single or multiple near the cemental surface.
• It could be free, attached or embedded in cementum.
6. Cementicles :
Periodontal ligament
Cementum
Bone
Free Cementicles

71. HypercementosisHypercementosis
• 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.

72. Localized
hypercementosis Generalized
hypercementosis
HypercementosisHypercementosis

73. HypercementosisHypercementosis
 Cementum hypertrophy:Cementum hypertrophy:
It is physiologic thickening of the cementum found in
the good functioning teeth as a response to increase the
function of the tooth to improve the functional quality
through increase the root surface area and thus
permitting more periodontal fibers to be attached to the
tooth.
Cementum hyperplasia:Cementum hyperplasia:
It is overgrowth of the cementum in a non-functioning or
embedded tooth. It is characterized by the absence of
Sharpey's fibers.

74. Hypercementosis
hyperplasia
Hypercementosis
hypertrophy
Increase number of
Sharpey’s fibers
Decrease number of
Sharpey’s fibers
Types Of HypercementosisTypes Of Hypercementosis

75.  Cementum is similar to
bone but has no nerves.
Therefore it is non-
sensitive to pain.
 Scaling produces no
pain, but if cementum is
removed, dentin is
exposed causes
sensitivity.
Clinical considerationsClinical considerations

76. Clinical considerationsClinical considerations
 Cementum is more resistant to resorption than is
bone, & it is for this reason that orthodontic tooth
movement is made possible.

77. Any questions ???