HISTOLOGY OF CEMENTUM FOR 1ST BDS STUDENTS.

1. CEMENTUM

2. CEMENTUM
It is calcified avascular
mesenchymal tissue that
forms the outer covering of
anatomic root

3. 1.Acellular( primary)
2.cellular(secondary)
Types

4. Acellular cementum – first
cementum formed before tooth reaches
occlusal pane
Covers cervical third or half of the root.
Doesnot contain cells.
Thickness – 30 to 230 u
sharpey’s fibres abundant and arranged
irregularly or parallel to the surface

6. Cellular cementum – formed after
tooth reaches occlusal plane
More irregular
Contains cementocytes in lacunae which
communicates through canaliculi
Sharpey’s fibres occupy smaller portion
Less calcified

8. Rest periods – both acellular and
cellular cementum are arranged in
lamellae separated by incremental lines
parallel to long axis of tooth
More mineralized than adjacent cementum

9. According to schroeder, cementum
can be classified as –
Acellular afibrillar cementum :
No cells
No intrinsic or extrinsic collagen fibers
Mineralised ground substances
Product of cementoblasts
Found in coronal cementum
Thickness 1 -15 u

10. Acellular extrinsic fiber cementum
No cells
Densely packed bundles of sharpey’s
fibers
Product of cementoblasts and fibroblasts
Found in cervical third of roots
Thickness – 30 to 230 u

11. Cellular mixed stratified cementum
Contains cells
Both intrinsic and extrinsic fibres present
Co product of cementoblasts and
fibroblasts
Present in apical third, apices and
furcation areas
Thickness – 100 to 1000u

12. Cellular intrinsic fiber cementum
Contains cells
No extrinsic fibers
Formed by cementiblasts
Fills resorption lacunae

13. Intermediate cementum
Poorly defined zone near cementodentinal
junction
Contains cellular remnants of root sheath

14. Composition
Organic content - 50 to 55 %
Type I collagen – 90 %
Type III collagen – 5 %
Sources of collagen include sharpey’s
fibers (extrinsic ) and those belonging to
cementum produced by cementoblasts
(intrinsic)

15. Inorganic content – 45 to 50 %
Consist of calcium and phosphorous in the
form of hydroxyapatite
Trace elements in varying amounts
Contains highest fluoride content

16. Cementoenamel junction
Cementum at and immediately
subjacent to cementoenamel
junction is of great interest in root
planing

17. three types of relationships
exist
In approx. 30% of all teeth cementum
meets the cervical end of enamel
In 10% cases enamel and cementum
donot meet which can cause accentuated
sensitivity because of exposed dentin
In about 60% cases cementum overlaps
the cervical end of enamel

19. Cementodentinal junction
Definition – the terminal apical area of
cementum where it joins the internal root
dentin is called cementodentinal junction
or CDJ
The obturating material should be at CDJ
during root canal treatment
Width of CDJ is 2 to 3u and remains
relatively stable

20. Thickness of cementum
Formation of cementum is continuous
process and its rate varies throughout the
life.
It is most rapid at apical regions.
At apical third it varies from 150 – 200u
At coronal portion it varies from 16 – 60u
It is thicker on distal surfaces than mesial
because of following mesial migration

21. Between 11 and 70 years of age the
thickness increases three fold and is more
on apical region
At the age of 20 years the average
thickness is 95u and at 60 years it is 215u

22. Abnormalities of cementum
includes
Cemental aplasia or hypoplasia –
absence or paucity of cellular cementum
Cemental hyperplasia or hypercementosis –
excessive deposition of cementum

23. It can be –
Localised
Generalised – with nodular enlargement
called cemental spikes

24. It may be assosciated with situations like –
A. teeth without antagonist
B. teeth with pulpal and periapical
infections
Hypercementosis of entire dentition may
be seen in patients with paget’s disease.
Other systemic disturbances include
acromegaly,calcinosis,thyroid goitre etc.

25. Cementum resorption and
repair
Causes of cementum resorption are –
1.local causes –a.trauma from occlusion
B. orthodontic movement
C. pressure from erupting teeth
D. cyst and tumours
E. Teeth without functional antagonist

26. 2.systemic causes – A.calcium deficiency
B. hereditary fibrous osteodystrophy
C. hypothyroidism
d,. Paget’s disease
Resorption occurs most commonly in
apical third then middle third followed
by gingival third
3. idiopathic

28. Microscopically, 1.bay like concavities
seen in root surfaces.
2. presence of multinuclear giant cells and
large mononuclear macrophages.
3. several sites coalesce to form large
areas of destruction
It may extend into even to pulp and is
painlees.

29. Cementum resorption may alternate with
repair and deposition of new cementum.
Newly formed cementum is demarcated
from the root by an irregular deep staining
line called reversal line.
Remodelling requires the presence of
viable connective tissue and may occur
even in non vital teeth.

30. ANKYLOSIS
Definition – fusion of cementum and
alveolar bone and obliteration of the
periodontal ligament is called ankylosis.
This condition is uncommmon.
Occurs in teetgh with cemental resorption.
It represents a form of abnormal repair.
Can also occur after
- chronic periapical infection

31. - tooth reimplantation
- occlusal trauma
- around embedded teeth.
More common in primary dentition
Results in resorption of root and its
replacement by bone tissue.

32. Propriception is lost because pressure
receptors in periodontal ligament are
altered or donot function correctly.
Physiologic drifting and eruption cannot
occur.

33. Clinically ,
1.lack of physiologic mobility which is
Diagnostic sign of ankylotic resorption.
2.Teeth have special metallic percussion sound.
3. If the process continues teeth will be in
infraocclusion.

34. Radiographically,
Resorption lacunae are filled with bone.
periodontal ligament space is missing.

35. Treatment-
Treatment ranges from conservative
approach such as restorative intervention
to surgical extraction of tooth

36. Exposure of cementum to
oral environment
Occurs in case of gingival recession and
loss of attachment in pocket formation.
Becomes permeable to bacteria, organic
substances, and inorganic ions resulting in
cemental caries.

37. FUNCTIONS OF CEMENTUM
1. it is medium for attachment of collagen
fibres that bind the tooth to alveolar bone.
2. serves as a reparative tissue for root
surfaces.
Damage to roots such as resorption and
fractures can be repaired by depsition of
new cementum.

38. –3. Makes functional adaptation of teeth
possible.
–Deposition in apical region can
compensate for tooth loss from occlusal
wear.

40. Definition
 It is that portion of the maxilla and mandible
that forms and supports the tooth sockets
(alveoli).
 It forms when the tooth erupts to provide
the osseous attachment to the forming
periodontal ligament; it disappears
gradually after the tooth is lost.

41.  Since the alveolar processes develop &
undergo remodeling with the tooth formation and
eruption, they are tooth dependent bony structures

42.  Therefore, the size, shape, location & function of
the teeth determine their morphology.
 Although the growth and development of the bones
of the teeth, a certain degree of repositioning of
teeth can be accomplished through occlusal forces
& in response to orthodontic procedure that rely on
the adaptability of the alveolar bone & associated
periodontal tissues.

43. PARTS OF ALVEOLAR PROCESS
1. An external plate of cortical bone formed by
haversian bone & compacted bone lamellae.
2. Inner socket of thin, compact bone called
alveolar bone proper. Histologically, it
contains a series of openings (cribriform
plate) through which neurovascular bundles
link the periodontal ligament with the central
component of alveolar bone, cancellous bone.

44. Shape of roots and surrounding bone distribution
in transverse section in maxilla and mandible at
mid root level.

45. 3. Cancellous Trabeculae between these 2
compact layers, which acts as supporting
alveolar bone. The interdental septum
consists of cancellous supporting bone
enclosed within a compact border.

46. 4. In addition, bones of jaw include basal bone which is the
portion of jaw located apically, but unrelated to teeth.
5. Most of the facial & lingual portions of the sockets are formed
by compact bone alone
The dotted line indicates separation between
the basal bone and alveolar bone.

47. COMPOSITION OF ALVEOLAR BONE
It has 2 basic constituents:
a)The cells consist of
•osteoblasts,
•osteoclasts
• osteocytes
b)Extra cellular matrix consists of
•65% inorganic
• 35% organic matrix.

48. CELLS:-
 Osteoblasts differentiate from pleuripotent
follicle cells.
 Alveolar bone is formed during fetal growth by
intra membranous ossification and consists
of a calcified matrix with osteocytes enclosed
within spaces called lacunae.
 Osteocytes extend processes into canaliculi
that radiate from the lacunae.

49.  The canaliculi form an anastomizing system
through the intercellular matrix of the bone,
which brings oxygen and nutrients to the
osteocytes and removes metabolic waste
products.
 Bone growth occurs by apposition of an
organic matrix that is deposited by
osteoblasts.

50.  Haversian systems (osteons) are the internal
mechanisms that bring a vascular supply to
bones too thick to be supplied only by surface
vessels.
 These are found primarily in the outer cortical
plates & alveolar bone proper.

51. Extra Cellular Matrix
– It consists of:
2/3rd inorganic matter
1/3rd organic matter.
Inorganic matter is composed of minerals
- Calcium & Phosphate
- Hydroxyl
- Carbonate
- Citrate

52.  Trace amounts of other ions like sodium,
magnesium and fluorine.
 Mineral salts are in the form of hydroxyapatite
crystals and constitute 2/3rd of bone structure.
 The organic matrix consists mainly of
collagen type-I (90%) and small amounts of
noncollagenous proteins such as
- Osteonectin
- Bone morphogenetic protein
- Phosphoproteins
- Proteoglycans

53.  Osteopontin and bone sialoprotein are cell
adhesion proteins which are important for
adhesion of osteoclasts and osteoblasts.
 In addition factors including
- Cytokines
- Chemokines
- Growth factors are also found

54. REMODELLING AND RESORPTION
 Although, alveolar bone tissue is constantly
changing in its internal organisation, it retains
approximately the same form from childhood
through adult life.
 Bone deposition by osteoblasts is balanced by
resorption by osteoclasts during tissue remodelling
and renewal.
Remodelling
 Is major pathway of bony changes in shape ,
resistance to forces, repair of wounds and
calcium & phosphate homeostasis in the body.

55.  It involves the coordination of activities of cells
from 2 distinct lineages – osteoblasts and
osteoclasts, which form & resorb the mineralised
connective tissue of the bone.
 Regulation of bone remodelling is a complex process
involving hormones and local factors on the
generation and activity of differentiated bone cells.
 Bone contains 90% of body’s calcium & is thus the
major source for calcium release when blood calcium
levels decrease, this is monitored by parathyroid
glands.

56.  This interdependency of osteoclasts & osteoblasts is
called coupling.
 Bone matrix that is laid down by osteoblasts is non-
mineralised osteoid.
 While new osteoid is being deposited, older osteoid
located below the surface becomes mineralized
as the mineralization front advances.
 Bone resorption is a complex process
morphologically related to the appearance of eroded
bone surfaces & large, multinucleated cells.

57. Ten Cate described the following sequence of events
during bone resorption.
1. Attachment of osteoclasts to the mineralised
surface of the bone.
2. Creation of a sealed acidic environment which
demineralises the bone and exposes the organic
matrix.
3. Degradation of exposed organic matrix by the
action of enzymes like acid phosphatase and
cathepsin.
4. Sequestering of mineral ions & amino acids within
the osteoclasts.

58. SOCKET WALL
 Socket wall consists of dense,lamellated
bone, some of which is arranged in
haversian systems & bundle bone.
 Bundle bone is the term given to a bone
adjacent to the periodontal ligament that
contains a great no. of sharpey’s fibers.

59.  It is characterised by thin lamellae arranged
in layers parallel to the root.
Socket Wall

60.  The cancellous portion of the alveolar bone
consists of trabeculae that enclose
irregularly shaped marrow spaces lined
with a layer of thin, flattened endosteal cells
 Cancellous bone is found predominantly in
the inter-radicular and interdental spaces
and in limited amounts facially or lingually,
except in the palate in the adult human,
more cancellous bone exists in the maxilla
than in the mandible.

61. BONE MARROW
 In the embryo and newborn the cavities of
all bones are occupied by red
hematopoietic marrow.
 Red marrow gradually undergoes a
physiologic change to the fatty or yellow
inactive type of marrow.
 In the adult the marrow of the jaw is
normally of latter type & red marrow is
found only in the ribs, sternum, vertebrae,
skull and humerus.

62.  The foci of red bone marrow are occasionally
seen in the jaws, often accompanied by
resorption of bony trabeculae.
 Common locations are the maxillary
tuberosity, maxillary and mandibular molar
and premolar areas and the mandibular
symphysis and ramus angle, which will be
visible radiographically as zones of
radiolucency.

63. PERIOSTEUM & ENDOSTEUM
 Layers of differentiated osteogenic connective
tissue cover all the bone surfaces.
 The tissue covering the outer surface of bone
is termed periosteum.
 The periosteum consists of an inner layer
composed of osteoblasts surrounded by
osteoprogenitor cells, which have the potential
to differentiate into osteoblasts and an outer
layer rich in blood vessels and nerves and
composed of collagen fibres and fibroblasts.

64.  Bundles of periosteal collagen fibres penetrate
the bone, binding the periosteum to the bone.
 The endosteum is composed of a single layer
of osteoblasts and sometimes a small amount
of connective tissue.
 Cellular events at the periosteum modulate
bone size throughout an individual’s life span
and change in bone size is probably the result
of the balance between periosteal osteoblastic
and osteoclastic activities.

65. INTERDENTAL SEPTUM
 The interdental septum consists of cancellous
bone bordered by the socket wall cribriform
plates (lamina dura or alveolar bone proper) of
approximating teeth and the facial and lingual
cortical plates.
 If the interdental space is narrow, the septum
may consist of only the cribriform plate.

66.  If roots are too close together, an irregular
“window” can appear in the bone between
adjacent roots.
Boneless window between adjoining
close roots of molars

67.  The mesiodistal and faciolingual dimensions &
shape of the interdental septum are governed
by the size and convexity of the crowns of the
approximating teeth, as well as by the position
of the teeth in and their degree of eruption.

68. OSSEOUS TOPOGRAPHY
 The bone contour normally conforms to the
prominence of the roots, with intervening
vertical depressions that taper toward the
margin.
 Alveolar bone anatomy varies among patients.
 The height & thickness of the facial and lingual
bony plates are affected by the alignment of the
teeth, angulations of the root to the bone and
occlusal forces.

69.  On teeth in labial version, the margin
of the labial bone is located farther
apically than on teeth in proper
alignment.
 The bone margin is thinned to a
knife-edge and presents an
accentuated arc in the direction of the
apex.
 On teeth in lingual version, the facial
bony plate is thicker than normal.

70.  The margin is blunt, rounded and horizontal
than accurate.
 The cervical portion of the alveolar plate is
sometimes considerably thickened on the
facial surface, apparently as reinforcement
against occlusal forces.
A B
Variation in the cervical portion of buccal alveolar
plate:
A:- Shelf like conformation
B:- Comparatively thin buccal plate

71. FENESTRATIONS AND DEHISCENCE
 Isolated areas in which the root is denuded of
bone and the root surface is covered only by
periosteum and the overlying gingiva are
termed as fenestrations.
 In these areas marginal bone is intact.
Fenestrations

72. FENESTRATION &
DEHISCENCE
Dehiscence
Fenestration

73. When the denuded areas extend through the
marginal bone, the defect is called dehiscence.
 Such defects occur on approximately 20% of
the teeth.
 They occur more often on the facial bone than
on the lingual bone.
 They are more common on anterior teeth than
on posterior.
 The cause of these defects is not clear.
Dehiscence

74. PREDISPOSING FACTORS
Prominent root contour
Malposition
Labial protrusion of the root combined
with a thin bony plate.
Fenestrations and dehiscence are important
as the my complicate the outcome of
periodontal surgery.

75. REMODELLING OF ALVEOLAR BONE
oIn contrast to its apparent rigidity,alveolar bone
is the least stable of the periodontal tissues
because its structure is in a constant state of flux.
o A considerable amount of internal remodelling
takes place by means of resorption and
formation, which is regulated by local and
systemic factors.

76. Local influences include
• Functional requirements on the tooth
•Age related changes in bone cells
Systemic influences
-Calcitonin
-Vit D3
The remodeling of alveolar bone affects its
- Height - Contour
- Density
& this is manifested in the following 3 areas.

77.  Adjacent to periodontal ligament
 In relation to the periosteum of the facial and
lingual plates.
 and along the endosteal surface of the
marrow spaces.

78. Age changes in the alveolar bone
 Osteoporosis
 Decreased vascularity
 Reduction in metabolic rate and healing
capacity.
 Resorption activity is increased and the rate of
bone formation is decreased.
 Greater irregularity in the surface of alveolar
bone.

79. PERIODONTAL
LIGAMENT

80. INTRODUCTION
Periodontal ligament is an integral part of
periodontium. The periodontium is an
attachment apparatus of the teeth. It is a
connective tissue organ, which is covered
by epithelium on top surface. Teeth are
attached to the bone of the jaws by
periodontium.

81. It consists of 4 connective tissues:-
Cementum
Periodontal ligament
Alveolar bone
Deeper part of
gingiva

82. Two of these tissues are mineralized and two are
fibrous. The cementum and alveolar alone are
mineralized tissue while the periodontal ligament
and part of gingiva are fibrous tissues. On one side,
the periodontium is attached to the dentine of root
of teeth by cementum while on other side it is
attached to the bone of jaws by alveolar bone.

83. Definition
 The periodontal ligament is a soft, fibrous
specialized connective tissue which is present in
the periodontal space, which is situated between
the cementum of root of the tooth and the bone
forming the socket wall.
 The periodontal ligament extends coronally up to
the most apical part of connective tissue of
gingiva.
 Because the collagen fibers are attached to the
cementum and alveolar bone, the ligament
provides soft tissue continuity between the
mineralized connective tissues of periodontium.

84. Other terms which were previously used
for periodontal ligament are:-
1. Desmondont
2. Gomphosis
3. Pericementum
4. Dental Periosteum
5. Alveolodental ligament
6. Periodontal membrane

85. “Periodontal ligament” and “Periodontal
membrane” are the terms that are now most
commonly used. Neither term describes structure nor
function adequately. It is neither a typical membrane
nor a typical ligament. However, because it is a
complex connective tissue providing continuity
between two mineralized connective tissues, the term
“periodontal ligament” appears to be more
appropriate.

86. DEVELOPMENT
Shortly after the beginning of root formation and formation of out dentinal
layer of root, the periodontal ligament is formed. The external and internal
dental epithelia proliferate from the cervical loop of dental organ to form
“Hertwigs Epithelial root sheath” This sheath is double layered. Because of
growth changes, the root sheath is stretched and then it fragments to form
the discrete cluster of epithelial cells called as “epithelial cell rests of
malassez”.

87. Now the periodontal ligament formation
occurs. The enamel organ and hertwig
epithelial root sheath are surrounded by
dental sac that is formed by condensed cells.
A thin layer of these cells lie adjacent to
dental organ. This is known as “Dental
Follicle”.

88. The cells of Dental Follicle divide and
differentiate into:
 Fibroblasts
 Cementoblasts
 Osteoclasts

89. STRUCTURE
The periodontal ligament has the shape of an
“HOUR GLASS” and is narrowest at the midroot
level. The width of periodontal ligament is
approximately 0.15-0.38mm.
CELLULAR COMPOSITION
The cells of periodontal ligament are
categorised as:
1. Synthetic Cells
a) Osteoblasts

90. b) Fibroblasts
c) Cementoblasts
2) Resorptive Cells
a) Osteoclasts
b) Cementoclasts
c) Fibroblasts
3) Progenitor Cells
4) Epithelial Cell rests of malassez
5) Connective Tissue cells
i) Mast cells
ii) Macrophages

91. SYNTHETIC CELLS
The characteristic of synthetic cells are:
1. Should be actively synthesizing ribosomes.
2. Increase in the complement rough endoplasmic
reticulum and golgi apparatus.
3. Large open faced or vesicular nucleus with
prominent nucleoli.

92. The osteoblasts covers the periodontal surface of
alveolar bone. Alveolar bone constitute a modified
endosteum and not a periosteum. A periosteum
comprises at least two distinct layers:
1. An Inner – CELLULAR LAYER
2. An Outer – FIBROUS LAYER
A cellular, but not an outer fibrous layer is present on
the periodontal surface of alveolar bone.
A) OSTEOBLASTS

93. Function:
Osteoblasts help in the synthesis of alveolar bone.

94.  Fibroblasts are the most common cells in
periodontal ligament. They constitute about
65% of total population.
 They appear as ovoid or elongated cells with
psuedopodia like process.
 They consist of subtypes with distinct phenotypes
and found to synthesize higher quantities of
chondroitin sulphate and lesser quantities of heparin
sulphate and hyaluronic acid.
 The main function of fibroblasts is the production
of various types of fibers and is also instrumental
in the synthesis of connective tissue matrix.
B) FIBROBLASTS

96.  The fibroblast is stellate shaped cell which produces:
1. COLLAGEN FIBERS
2. RETICLUIN FIBERS
3. OXYTALAN FIBERS
Various stages in the production of collagen fibers are
as follows:
 The first molecule released by fibroblasts is
tropocollagen which contains three polypeptide
chains intertwined to form helix. Tropocollagen
molecules are aggregated longitudinally to form
protofibrils, which are subsequently laterally arranged
parallel to form collagen fibrils.

97. Collagan fibers are bundle of collagen fibrils. Because of
exceptionally high turnover of collagen in the ligament, any inter
reference with fibroblats function by disease may produce a loss
of supporting tissue of the tooth.
Importantly in inflammatory situations such as those
associated with periodontal diseases, an increased expression of
matrix metalloproteinase's occurs that aggressively destroys
collagen. Thus attractive therapies for controlling tissue
destruction may include host-modulators that have the capacity to
inhibit metalloproteinases.
The damaged periodontal fibers are replaced and
remodeled by newly formed fibers. The “RENEWAL
CAPABILITY” is an important characteristic of periodontal
ligament.

98. FUNCTIONS
 Cementoblasts synthesize collagen and protein
polysaccharides, which make up the organic matrix of
cementum.
 After some cementum has been laid down, its
mineralization begins with the help of calcium and
phosphate ions
 Connective tissue fibers from the periodontal ligament
pass between cementoblasts into the cementum. These
fibers are embedded in the cementum and serve to attach
the tooth to the surrounding bone and are known as
“Sharpey’s Fibers”. Each “Sharpey’s fibers” is composed
of numerous collagen fibrils.
C) CEMENTOBLASTS

99. a) OSTEOCLASTS
RESORPTIVE CELLS
FUNCTIONS
 Multinucleated osteoclasts are the cells which resorb bone.
 The surface of an ostoclasts which is in contact with bone
has a ruffled border.
 Resportion occurs in two stages
- The mineral is removed at bone margins and then
exposed organic matrix disintegrates. The
osteoclasts demineralise the inorganic part as well
as disintegrates the organic matrix.

101. b) FIBROBLASTS
 Fibroblasts are capable of both synthesis and resorption.
 They exhibit lysosomes, which contain collagen
fragments undergoing digestion.
 The presence of collagen resorbing fibroblasts in a
normal functioning periodontal ligament indicates
resorption of fibers occurring during remodeling of
periodontal ligament.
C) CEMENTOCLASTS
 Cementoclasts are found in periodontal ligament but
not remodeled like alveolar bone and periodontal
ligament.
 These are found on the surface of cementum.

102. PROGENITOR CELLS
FUNCTION
 Progenitor cells are the undifferentiated mesenchymal
cells, which have the capacity to undergo mitotic division
and replace the differentiated cells dying at the end of their
life span.
 These cells are located in perivascular region and have
a small close faced nucleus and little cytoplasm.
 When cell division occurs, one of the daughter cells
differentiate into functional type of connective tissue
cells. The other remaining cells retain their capacity to
divide.

103.  These cells are the remnants of the epithelium of
Hertwig’s Epithelial Root Sheath and are found close to
cementum.
 These cells exhibit monofilaments and are attached to
each other by desmosomes.
 The epithelia cells are isolated from connective tissue
by a basal lamina.
FUNCTION
 The physiologic role of these cells is not known but
cells of epithelial rests can undergoe rapid
proliferation and can produce a variety of cysts and
tumors when certain pathologic conditions are present.
EPITHELIAL CELL RESTS OF MALASSEZ

104. Periodontal ligament showing
epithelial cell rests of malassez,
indicated by arrows.

105.  Mast cells are small round or oval. These cells
are characterized by numerous cytoplasm,
which mask its small, indistinct nucleus.
 The diameter of mast cells is about 12 to 15
microns.
MAST CELLS

106.  The granules contain heparin and histamine.
The release of histamine into the extracellular
compartment causes proliferation of the
endothelial and mesenchymal cells.
FUNCTION
 Mast cells play an important role in regulating
the endothelial and fibroblasts cell populations.
These cells degranulate in response to antigen-
antibody formation on their surface.

107.  Macrophages are derived from blood monocytes and are
present near the blood vessels.
 These cells have a horse-shoe shaped or kidney shaped
nucleus with peripheral chromatin and cytoplasm
contain phagocytosed material.
FUNCTION
 Macrophages help in phagocytosing dead cells and
secreting growth factor, which help to regulate the
proliferation of adjacent fibroblasts.
MACROPHAGES

108. Extra cellular substance comprises the following:
1. Fibers
a) Collagen b) Oxytalan
2. Ground Substance
a) Proteoglycans b) Glycoprotein's
PERIODONTAL FIBRES
The most important element of periodontal ligament
has principal fibres, the principal are fibres are
collagenous in nature and a arranged in bundles and
follow a wavy course.
- Collagen is a high molecular weight protein.
EXTRA CELLULAR SUBSTANCE

109.  Collagen macromolecules are rod like and are arranged in
form of fibrils. Fibrils are packed side by side to form
fibers.
 Vitamin C help in formation and repair of collagen.
 Half life of collagen fibers is between 3 to 23 days and
collagen imparts a unique combination of flexibility and
strength to tissue.

110. The principal fibers of periodontal ligament are
arranged in six particular groups. These are:
Development of principal fibers of periodontal ligament

111. 1. TRANSEPTAL GROUP
These fibers extend interproximally over alveolar bone
crest and are embedded in the cementum of adjacent
teeth.
- They are reconstructed even after the destruction
of alveolar bone resulting from periodontal disease.
- These fibers may be considered as belonging to the
gingiva because they do not have osseous
attachment.

112. 2. ALVEOLAR CREST GROUP
These fibers extend obliquely from the cementum just
beneath the junctional epithelium to alveolar crest.
- Fibers also run from the cementum over the
alveolar crest and to fibrous layer of periosteum
covering alveolar bone.
- The alveolar crest fibers prevent extrusion of tooth
and resist lateral tooth movements.
- The incision of these fibers during periodontal
surgery does not increase tooth mobility unless
significant attachment loss has occurred.

113. 3. HORIZONTAL GROUP
Horizontal fibers extend at right angles to long axis of
tooth from the cementum to alveolar bone.
4. OBLIQUE GROUP
Oblique fibers, the largest group in periodontal ligament,
extend from cementum in a coronal direction obliquely to
bone. They bear the brunt of vertical masticatory stresses
and transfer them into tension on the alveolar bone.
5. APICAL GROUP
The apical fibers radiate in a rather irregular manner from
the cementum to bone at apical region of the socket. They
do not occur on incompletely formed roots.

114. 6. INTERRADICULAR FIBERS
The interradicular fibers fan out from the
cementum to the tooth in furcation areas of multirooted
teeth.
Some fibers arising from the cementum and bone
are joined in the mid-region of periodontal space. This
gives rise to a distinct zone called as “intermediate
plexus”. The remodeling of fibers take place in
intermediate plexus. This allows adjustments in the
ligament, which accommodate small movements of
tooth.

115. OXYTALAN
These are immature elastic fibers restricted to
walls of blood vessels and are oriented in an axial
direction.
- The function is to support the bloods vessels in
the periodontal ligament.

116. GROUND SUBSTANCE
Ground substance is present between cells and
fibers of periodontal ligament.
 The cell surface proteoglycans participate in
several biologic functions including cell-adhesion,
cell-cell and cell-matrix interactions, binding to
various growth factors as co-receptors and cell
repair.
 A fibronectin, glycoprotein occur in filamentous
form in periodontal ligament. It contain a chemical
group that gets attached to surface of the
fibroblast, to the collagen, proteoglycans and fibrin.

117.  The ground substance has 70% water in
periodontal ligament.
 The function of ground substance is transporting
the food to cells and waste products from cells to
blood vessels.

118. STRUCTURES PRESENT IN THE
CONNECTIVE TISSUE
1. BLOOD VESSELS
Main blood supply is form superior and inferior
alveolar arteries. The blood vessels are derived
from the following:
 Branches from apical vessels
Vessels supplying the pulp
 Branches from intra-alveolar vessels
Vessels run horizontally and penetrate the alveolar
bone to enter into the periodontal ligament.

119.  Branches from gingival vessels
The arterioles and capillaries ramify and form a
rich network. Rich vascular plexus is found at the
apex and in cervical part of ligament.

120. 2. LYMPHATICS
Lymphatic drainage is from the ligament to
alveolar bone.
 Lymphatic vessel network follows the path of blood
vessels.
3. NERVES
Nerves found in ligament pass through foramina in
alveolar bone.
 The nerves are the branches of second and third
division of fifth cranial nerve (trigeminal nerve)
and follow same path as blood vessels.
 These nerve fibers provide sense of touch, pressure,
pain and proprioception during mastication.

121. 4. CEMENTICLES
Cementicles are small calcified bodies present in
the periodontal ligament.
 They may form into large calcified bodies and fuse
within cementum or remain free. These are found
in old age.
 The degenerated epithelial cells form a nidus for
calcification.

122. FUNCTIONS
The periodontal ligament has many functions,
important among them are as follows:
1. PHYSICAL FUNCTION
A) Provision of soft tissue ‘casing” in order to protect
the vessels and nerves from injury due to
mechanical forces.
B) Transmission of occlusal forces to bone
 Depending on type of force applied, axial force
when applied causes stretching of oblique fibers of
periodontal ligament.

123.  Transmission of this tensional force to alveolar
bone encourages bone formation rather then bone
resorption.
 But when horizontal or tipping force is applied,
the tooth rotates around the axis.
 When a greater force is applied, displacement of
facial and lingual plates may occur.
 The axis of rotation in a single rooted tooth is
located in area between the apical and middle third
of root.
 In multirooted tooth, axis of rotations is located
at furcation area.

124. C) Attaches the teeth to the bone.
D) Maintains the gingival tissues in their proper
relationship to the teeth.
E) “Shock absorption” resists the impact of occlusal
surfaces. Due to its property of shock absorption
the teeth are slightly more mobile in early morning
than in evening.

125. A. The periodontal ligament fibers
are compressed in areas of pressure
(a) and stretched in area of tension
(b) . B. Same tooth in a resting state.

126. 2 Theories have been explained for mechanism of
tooth support.
A. TENSIONAL THEORY
B. VISCOELASTIC THEORY
According to it, principal fibers play a major role in
supporting tooth and transmitting forces to bone.
When forces are applied to tooth, principal fibers
unfold and straighten and then transmit the forces to
alveolar bone, causing elastic deformation of socket.
A. TENSIONAL THEORY

127. According to it, the fluid movement largely controls the
displacement of the tooth, with fibers playing a
secondary role.
- When forces are transmitted to the tooth, the
extracellular fluid is pushed from periodontal
ligament into marrow spaces through the cribriform
plate. After depletion of tissue fluids, the bundle fibers
absorb the shock and tighten. This leads to blood vessel
stenosis – arterial lack pressure – ballooning of vessels
– tissue replenishes with fluids.
B. VISCOELASTIC THEORY

128. FORMATIVE AND REMODELING FUNCTION
 Cells of the periodontal ligament have the capacity
to control the synthesis and resorption of
cementum, ligament and alveolar bone.
 Periodontal ligament undergoes constant
remodeling, old cells and fibers are broken down
and replaced by new ones.

129. NUTRITIONAL FUNCTION
 Blood vessels of periodontal ligament provide
nutrition to the cells of periodontium, because they
contain various anabolites and other substances,
which are required by cells of ligament.
 Compression of blood vessels (due to heavy
forces applied on tooth) leads to necrosis of cells.
Blood vessels also remove catabolites.

130. SENSORY FUNCTION
The nerve bundles found in periodontal ligament, divide into
single myelinated nerve, which later on lose their myelin
sheath and end in one of the four types of nerve termination.
 Free endings, carry pain sensations.
 Ruffini like mechanoreceptors located in the apical
area.
 Meissener’s corpuscles are also mechanoreceptors
located primarily in mid-root region.
 Spindle like pressure endings, located mainly in
apex.
- Pain sensation is transmitted by small diameter
nerves, temperature by intermediate type;
pressure by large myelinated fibers.

131. HOMEOSTATIC MECHANISM
 The resportion and synthesis are controlled
procedures. If there is a long term damage of
periodontal ligament, which is not repaired, the
bone is deposited in the periodontal space. This
results in obliteration of space and ankylosis
between bone and the tooth.
 The quality of tissue changes if balance between
synthesis and resorption is disturbed.

132. If there is deprivation of Vit C which are essential for
collagen synthesis, resorption of collagen will
continue. So there is progressive destruction and loss
of extra cellular substance of ligament. This occurs
more on bone side of ligament. Hence, loss of
attachment between bone and tooth and at last, loss of
tooth. The connective tissue cells of the periodontal
ligament are turned over and old cells are replaced by
new ones that are provided by cell division of
progenitor cells.

133. CLINICAL CONSIDERATION
The primary role of periodontal ligament is to support
the tooth in the bony socket.
 The width of periodontal ligament varies from
0.15 to 0.38mm. The average width is:
- 0.21mm at 11 to 16 years of age.
- 0.18mm at 32 to 50 years of age
- 0.15 mm at 51 to 67 years of age
So, the width of periodontal ligament decreases as
age advances.

134.  In the periodontal ligament, aging results in more
number of elastic fibers and decrease in vascularity,
mitotic activity, fibroplasia and in the number of collagen
fibers and mucopolysaccharides.
 If gingivitis is not cured and supporting structure become
involved, the disease is termed as periodontitis.

135.  There are few coccal cells and more motile rods and
spirochetes in the diseased site than in the healthy site. The
bacteria consists of gram-positive facultative rods and
cocci in healthy site while in diseased site, gram-negative
rods and anaerobes are more in number.
 Trauma to the ligament due to mechanical separation
can produce pathologic changes such as fracture or
resorption of cementum, tear of fiber bundles,
haemorrhage and necrosis. These result in resorption of
bone and periodontal ligament is widened, so that the
teeth become loose. If trauma is eliminated, repair will
take place.

136.  Resorption and formation of both bone and periodontal
ligament play an important role in orthodontic tooth
movement. If tooth movement takes place, the
compression of PL is compensated by bone resorption
whereas on tension side, apposition takes place.
 Periapcial area of the tooth is the main pathologic site.
Inflammation of the pulp reached to the apical
periodontal ligament and replaces its fiber bundles with
granulation tissue called as granuloma, which then
progresses into apical cyst.

137.  Chronic periodontal disease can lead to infusion of
microorganisms into the blood stream.
 The pressure receptors in ligament have a protective
role. Apical blood vessels are protected from excessive
compression by sensory apparatus of the teeth.
 The rate of mesial drift of tooth is related to health,
dietary factor and age. It varies from 0.05 to 0.7mm per
year.

138. AGING OF LIGAMENT
Aging occurs in all tissues of body including all
ligaments. If general and dental health is good,
periodontium may remain healthy even in advanced
age.
So, always motivate the patients to maintain good
oral hygiene and to have regular dental visits to have
life long good oral health.