oral histology by dr hesham dameer

1. By/ Dr. Hesham
Dameer

2. Cementum is part of the
peridontium

3. THE PERIODONTIUM
The peridontium consists of those tissues which surrounds ,
support the tooth and is composed of :
Gingiva
Periodontal ligament
Cementum
Alveolar bone
By/ Dr. Hesham
Dameer

5. Gingiva
The gingiva is that part of the oral
mucosa which surrounds the tooth and
cover the alveolar bone .
In light-skinned individuals the gingiva
(G) can be readily distinguished from the
adjacent dark red alveolar mucosa (AM)
by its lighter pink color. Its apical border,
that separates it from the adjacent
alveolar mucosa, is the mucogingival
junction (MGJ). A similar tissue
relationship can be seen on the lingual
aspect of the mandible

6. AM, alveolar mucosa .G, gingiva .MGJ, mucogingival junction

7. AM,alveolar mucosa .F, floor of the mouth .G, gingiva .MGJ, mucogingival junction

8. Periodontal ligament
Dense connective fibers that connect the
cementum covering the root of the tooth
with the alveolar bone of the socket wall .
Principal fibers of the periodontal
ligament :
The periodontal fibers of the periodontal
ligament are primarily composed of
bundles of type I collagen fibrils. They
have been classified into several groups
on the basis of their anatomic location:

9. The following constitute the principal fiber
groups of the periodontal ligament:
1. Alveolar crest group
2. Horizontal group
3. Oblique group
4. Periapical group
5. Interradicular group
By/ Dr. Hesham
Dameer

11. Cementum
By/ Dr. Hesham
Dameer

12. Cementum is a hard connective
tissue that covers the root of the
tooth to furnish a medium into
which the principle fibers of the
periodontal ligament are
terminally inserted .
By/ Dr. Hesham
Dameer

13. Cementum
It begins at the cervical portion of
the tooth at the cemento-
enamel junction and continues
to the apex.
Cementum furnishes a medium for
the attachment of collagen
fibers that bind the tooth to
surrounding structures.
By/ Dr. Hesham
Dameer

14. Physical Characteristics
1-Color
Light yellow
Lighter in color than dentin
2- Thickness
Acellular cementum (20-50 m)
Cellular cementum (150-200 m)
3- Permeability
Permeable from dentin and PDL sides.
Cellular C is more permeable than acellular C.

15. Chemical Composition
45-50 % Inorganic 50-55% Organic
substances substances
collagen
consists of
fibers protein
calcium
phosphate in the embedded
form of hydroxy- in a ground
apatite crystals substance . Polysaccharides
Cementum contains the greatest amount of
fluoride in all mineralized tissues
By/ Dr. Hesham
Dameer

16. Cementogenesis
• It takes place in two phases:
• Matrix formation
• Mineralization
There are 3 cell types responsible for the cementogenesis:
• Cementoblasts
• Cementocytes
• Fibroblasts
• All of these cells are derived from the ectomesenchymal
cells.
By/ Dr. Hesham
Dameer

17. Cementogenesis
Cementum formation in the developing tooth is preceded by
the deposition of dentin along the inner aspect of Hertwig‘s
sheath . Once dentin formation is underway breaks occur in
the epithelial root sheath allowing the newly formed dentin to
come in direct contact with the connective tissue of the
dental sac , the undifferentiated mesenchymal cells derived
from the dental sac differentiate into cementoblasts . These
cells have the ultrastructural characteristics typical of cells
actively synthesis protein and polysaccharide .
The main product of cementoblasts is collagen and ground
substances , both constitute the organic component of
cementum .
The inorganic material of cementum is calcium phosphate
Hydroxy apatite .

18. Cementogenesis
After degeneration of the
epithelial root sheath
ectomesenchymal cells from
the inner portion of the dental Odontoblast
follicle differentiate and
become cementoblasts
cementoblasts.
By/ Dr. Hesham
Dameer

22. Growth of cementum is a rhythmic process and as a new
cementoid is formed, the old one is calcified . A thin layer of
cementoid can be observed on cemental surface which is
covered by cementoblasts .
The mineralization begins after forming the first layer of
matrix.
The mineral crystals is deposited within and between the
collagen fibers, the long axes of the crystals are arranged
parallel to the long axis of the collagen fibers .
Sometimes crystals can be seen clustered into groups of
nucleation centers as found in bone.

23. Cementogenesis
cementoid
Cementodentinal junction
Cementoblasts

24. Cementoblast is a protein forming and secreting cell.
Maturation occur layer Collagen fibers +
by layer for the ground substance.
collagen fibers
D Cementum
Large open face nucleus
Cementoblasts
Cementoblast
RER
Cementoid layer
Golgi apparatus
Mitochondria
Secretory granules
Alkaline phosphatase

25. Cementogenesis
After reaching the full thickness the cementoblasts enter
a quiescent stage.
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. Those fibers are also called
perforating fibers.
.
By/ Dr. Hesham
Dameer

27. Remnants of the
Hertwig`s root
sheath, which
disintegrate into
the PDL are the
Malassez cells.
intermediate
cementum
By/ Dr. Hesham
Dameer

28. Histological structure :
cementum cover the root dentin from
cementoenamel junction to the root apex .
It is thinnest at this junction ( 20 – 50 μm ) but
becomes gradually thicker apicalward ranging
from 150 – 200 μm ) or more .
By/ Dr. Hesham
Dameer

29. Two forms of collagen are found in
cementum :
* collagen fibrils
* collagen bundles
The collagen fibrils are arranged in a very
complex fashion and constitute the main
bulk of the organic material of cementum.
The collagen bundles represent the
embedded portion of the principle fibers of
the periodontal ligament, that is Sharpey s
fibers .

30. Two types of cells are functionally concerned with
cementum :
* Cementoblasts
* Cementocytes
Cementoblasts line the root surface and when active,
they contain numerous mitochondria, well developed
Golgi complex, and open-faced nucleus. However, in
resting cementoblasts, these cytologic features
become less pronounced .
By/ Dr. Hesham
Dameer

31. While cementum is being deposited,
cementoblasts retreat leaving behind the
formed cementum matrix. Occasionally,
however, cementoblasts become
entrapped in the forming matrix and then
known cementocytes .

32. Cementocytes are seen located in lacunae in cementum
matrix and typically have numerous processes lying in
canaliculi . These processes may branch and
frequently anastomose with those of the adjacent
cementocytes . This indicates that these cells are not
functionally separated from each other . Because
cementum is avascular tissue, thus the processes of
the cementocytes are oriented toward the periodontal
ligament for nutrition .
As a result of continuous phasic deposition of
cementum, resting lines known Salter lines appear in
cementum .
By/ Dr. Hesham
Dameer

33. Cementocytes

34. Cementocyte lacuna

36. Cementocyte canaliculi
Cementocyte
Cementocyte process

38. Incremental Lines
• Incremental lines of Salter.
Incremental lines of Salter

39. Incremental lines of Salter
Dentin

40. Resting lines of Salter

41. Types of cementum :
I) Based on cellular connotation :
1- Cementum containing cells :
a. Cellular cementum
b. Intermediate cementum
2- Acellular cementum
II) Based on fibrillar connotation :
1. Intrinsic fibers cementum
2. Extrinsic fibers cementum
3. Mixed fibers cementum
4. Afibrillar cementum

42. I) Based on cellular connotation :
1- Cementum containing cells :
a. Cellular cementum is more frequently found on the
apical half of the root where cementum does contain
cementocytes in its matrix .
b. Intermediate cementum
Intermediate cementum is a thin, amorphous layer of hard tissue
approximately 10 micron thick.
Is more frequently seen in the apical two thirds of the roots of
posterior teeth but rarely in incisors or primary teeth .
This type of cementum does not exhibit the characteristic
features of either dentin or cementum, while in regard to its
location, it is found intermediate between cementum and dentin
.

43. In respect to the involved cells observed in
intermediate cementum, there is argument about there
derivation :
1- The cells of the epithelial root sheath of Hertwig are
proposed to become entrapped while dentin or
cementum is being rapidly deposited .
2- Other concept claims that odontoblasts are trapped
on the outer dentin surface at the commencement of
dentinogenesis which subsequently being enclosed by
the forming cementum .

44. Cementogenesis
intermediate cementum
Cementoblasts

45. Remnants of the
Hertwig`s root
sheath, which
disintegrate into
the PDL are the
Malassez cells.
intermediate
cementum
By/ Dr. Hesham
Dameer

46. 2- Acellular cementum :
The matrix of this type of cementum does not involve
cementocytes . However, cementoblasts present
on its outer surface and constitute an integral
component of acellular cementum .
Acellular cementum may cover the root dentin from the
cementoenamel junction to the root apex, but with
frequent absence on the apical third of the root .
II) Based on fibrillar connotation :
1. Intrinsic fibers cementum : the fibers are derived
from the synthetic and secretory activity of
cementoblasts .

47. 2. extrinsic fibers cementum : in this form, the extrinsic
fibers originate from the principal fibers of the
periodontal ligament that is Sharpey s fibers .
3. mixed fibers cementum : it contains both intrinsic and
extrinsic fibers .
4. Afibrillar cementum : as enamel is completely formed
and become fully calcified, it is seen covered by the
reduced enamel epithelium which is of paramount
importance in protecting enamel, however, the
reduced enamel epithelium may retract from the
cervical region of enamel . This allows for the adjacent
mesenchymal cells to invade and intervene between
enamel and its covering epithelium . The
mesenchymal cells differentiate into cementoblasts
and deposit a particular type of cementum, that is,
afibrillar cementum, on enamel surface .
By/ Dr. Hesham
Dameer

48. Cementoenamel Junction (CEJ)
• 3 patterns may be present
• 1) In approximately 60% of teeth cementum overlapping the cervical end of
enamel for a very narrow area at the CEJ . This occurs as a result of
premature degeneration or retraction of the reduced enamel epithelium at
the cervical region of enamel . This allows for the adjacent mesenchymal
cells to invade and intervene between enamel and its covering epithelium .
The mesenchymal cells differentiate into cementoblasts and deposit a
particular type of cementum, that is, afibrillar cementum, on enamel surface .
• 2) 30% of all teeth, cementum meets the cervical end of enamel in a knife
edge-to-edge pattern .
• 3) In approximately 10% of teeth, cementum does not meet enamel where a
zone of root dentin appears devoid of cementum . This can result in dental
hypersensitivity as the gingiva recedes exposing the underlying root dentin

49. Relation of Cementum to Enamel at the Cementoenamel Junction (CEJ)
In 60% of the teeth cementum Overlaps enamel
In 30% of the teeth cementum just Meets enamel
In 10% of the teeth there is a small Gap between cementum and enamel

50. Edge to edge 30%
By/ Dr. Hesham
Dameer

51. Cementum do not meet enamel 10%
By/ Dr. Hesham
Dameer

52. Cementum overlaps enamel 60%
By/ Dr. Hesham
Dameer

53. Cementodentinal junction
The dentin surface upon
Permanent teeth
which cementum is
deposited is relatively
smooth in permanent
teeth.
The cementodentinal junction
in deciduous teeth,
however, is sometimes
scalloped.
By/ Dr. Hesham Deciduous teeth
Dameer

54. Functions of cementum :
1. Cementum furnishes a medium for the incorporation of the
principal periodontal fibers, thereby securing the binding of the
tooth root to the alveolar bone proper .
2. Cementum serves as a reparative tissue in case of root
fracture or resorption .
3. Functional adaptation :
* When the superficial layer of cementum functionally ages,
a subsequent layer is deposited thus restoring the integrity of
the attachment apparatus .
* Another feature of functional adaptation is the excessive
formation of cementum on the apical root surface to
compensate for the occlusal and incisal wear and restore the
normal occlusion .
By/ Dr. Hesham
Dameer

55. Histological cross-section through a periodontal ligament . The periodontal
ligament fibers (F) originate from the cementum. and insert into bundle bone (BB),
so named because it contains numerous Sharpey's fibers (SF). Neurovascular
channels (NV) that house blood vessels, lymphatics and nerves in a loose
connective tissue sheath course throughout the periodontal ligament. The
ligament also contains cell rests of Malassez (M).
By/ Dr. Hesham
Dameer

56. Age changes of cementum
1) Hypercementosis:
It is an abnormal thickening of cementum, may be diffuse
or circumscribed.
It may affect all teeth of the dentition, be confined to a
single tooth, or even affect only Parts of one tooth.
If the overgrowth occurs in functional teeth and improves
the functional qualities of the cementum, it is termed
cementum hypertrophy.
If the overgrowth occurs in nonfunctional teeth, it is
termed cementum hyperplasia .
Hyperplastic cementum covering the enamel drops termed
excementosis

57. the enamel drops

58. Localized hypercementosis
Generalized hypercementosis

59. Age changes of cementum
In Localized hypertrophy prong like
extension of cementum may be
formed. This condition
frequently is found in teeth that
are exposed to great stress
(ortho) (compensatory
cementum). This extension of
cementum provide a larger
surface area for the attaching
fibers; thus a firmer anchorage
of the tooth to the surrounding
alveolar bone is assured.

60. Root resorption and
forming Reparatory
cementum

61. Root resorption – lost D. has been replaced by cellular
cementum, on the top of which acellular C. has formed

62. Hypercementosis
By/ Dr. Hesham
Dameer

63. 2) Decrease permeability : by aging the permeability of
cementum decreses gradually , the permiability from the
periodontal ligament side is lost except in the most recent
formed layers of cementum .
3) Cementicles : they are ovoid or round calcified structure
that exhibits by dystrophic calcification of the degenerated
periodontal tissue or the epithelial rests of Malssez . They
nidus favoring the deposition of concentric layers of
calcosherites around the degenerated or hemorrhagetic
areas .
Cementicles may be:
1. Free in the periodontal ligament.
2. Attached the cementum and form excementosis.
3. Embedded in the cementum during its growth by age.

64. Free Cementicles
Cementum
Bone
Periodontal ligament

65. Periodontal ligament
Free Cementicles Attached Cementicles

67. THE My best wishes
for you
END Dr. HESHAM
Dameer