one of the tooth supporting structures

1. PERIODONTAL LIGAMENT
BY- ANAMIKA SINGH
MDS 1 ST YEAR
DEPARTMENT OF PERIODONTOLOGY
INDERPRASTHA DENTAL COLLEGE &
HOSPITAL

2. CONTENTS
• Introduction
• Development of the PDL & principal
fibres
• PDL collagen fiber attachment to the
root surface
• PDL Homeostasis
• Cells
– Synthetic cells
– Resorptive cells
– Progenitor cells
– Relationship between cells
– Epithelial rests of Malassez
– Defence cells
• Extracellular substance
– Fibers
– Ground substance
• Structures present in connective
tissue
• Functions
• Age changes
• Clinical considerations

3.  PERIODONTIUM: The tissues that invest and support the teeth including the gingiva,
alveolar mucosa, cementum, periodontal ligament, and alveolar and supporting bone.
The PERIODONTAL LIGAMENT is composed of a complex vascular and highly cellular
connective tissue that surrounds the tooth root and connects it to the inner wall of the
alveolar bone.
The PERIODONTAL LIGAMENT is the soft, richly vascular and cellular connective tissue
which surrounds the roots of the teeth and joins the root cementum with the socket
wall.
The PERIODONTAL LIGAMENT occupies the periodontal space, which is located between
the cementum and the periodontal surface of the alveolar bone and extends coronally
to the most apical part of the lamina propria of the gingiva.
- Glossary of Periodontal Terms, 4th
edition
- Carranza's Clinical periodontology, 13th
edition
- Lindhe’s Clinical periodontology and Implant dentistry, 6th
edition
- Orban’s oral histology and embryology, 12th
edition

4. PERIODONTAL LIGAMENT;
TRANSVERSE SECTION

5. TERMS
Desmodont,
Gomphosis,
Pericementum,
Dental periosteum,
Alveolodental ligament,
Periodontal membrane.
• Because it is a complex soft
connective tissue providing
continuity between two
mineralized connective
tissues, the term
PERIODONTAL LIGAMENT
appears to be the most
appropriate.
Orban’s Oral Histology and Embryology, 12th edition

6. • Coronally, to the most apical part of
the lamina propria of the gingiva,
and demarcated by the alveolar
crest fibres.
• At the apical foramen, it is
continuous with the dental pulp.
• Ranges in width from 0.15 to 0.38
mm.

7. • An hour glass appearance, thinnest
around the middle third of the root.
• Shows a progressive decrease in
thickness with age.
• The ligament appears, as the
periodontal space of 0.4 to 1.5 mm
on radiographs.
• The periodontal spaces of the
permanent teeth are said to be
narrower than those of deciduous
teeth.
ACCORDING TO AGE :
 In young adults (11-16 yrs) – 0.21
mm.
 In mature adults (32-52 yrs) – 0.18
mm.
 In older adults (51-67 yrs) – 0.15
mm.
Orban’s Oral Histology and Embryology, 12th edition

8.  T h e d e v e l o p m e n t o f t h e p e r i o d o n t a l l i g a m e n t
b e g i n s w i t h r o o t f o r m a t i o n p r i o r t o t o o t h
e r u p t i o n .
 T h e c o n t i n u o u s p r o l i f e r a t i o n o f t h e i n n e r a n d
e x t e r n a l e n a m e l e p i t h e l i u m f o r m s t h e c e r v i c a l
l o o p o f t h e t o o t h b u d .
 T h i s s h e a t h o f e p i t h e l i a l c e l l s g r o w s a p i c a l l y, i n
t h e f o r m o f H e r t w i g ’ s e p i t h e l i a l r o o t s h e a t h ,
b e t w e e n t h e d e n t a l p a p i l l a a n d t h e d e n t a l
f o l l i c l e .
 A t t h i s s t a g e , t h e s h e a t h f o r m s a c i r c u m f e r e n t i a l
s t r u c t u r e e n c o m p a s s i n g d e n t a l p a p i l l a
s e p a r a t i n g i t e x t e r n a l l y f r o m d e n t a l f o l l i c l e
c e l l s .

9.  T h e d e n t a l f o l l i c l e c e l l s , l o c a t e d b e t we e n t h e
a lve o l a r b o n e a n d t h e e p i t h e l i a l ro o t s h e a t h , a re
c o m p o s e d o f t wo s u b p o p u l a t i o n s ;
Mesenchymal cells
of the dental
follicle proper
The perifollicular
mesenchyme
Dental
follicle cells

10.  T h e m e s e n c h y m a l c e l l s o f t h e p e r i f o l l i c u l a r
m e s e n c h y m e b o u n d e d b y t h e d e n t a l f o l l i c l e p r o p e r
a n d t h e d e v e l o p i n g a l v e o l a r b o n e a r e s t e l l a t e -
s h a p e d , s m a l l , a n d r a n d o m l y o r i e n t e d .
 I n c o n t r a s t t o t h e d e n t a l f o l l i c l e p r o p e r, t h e c e l l s o f
t h e p e r i f o l l i c u l a r m e s e n c h y m e a r e r a t h e r w i d e l y
s e p a r a t e d .
 U l t r a s t r u c t u r a l s t u d y o f t h e s e c e l l s i n d i c a t e s t h a t
t h e y c o n t a i n a n e u c h r o m a t i c n u c l e u s a n d s m a l l
c y t o p l a s m t h a t c o n t a i n s a s m a l l n u m b e r o f s h o r t
c i s t e r n a e o f r o u g h e n d o p l a s m i c r e t i c u l u m ,
m i t o c h o n d r i a , f r e e r i b o s o m e s , a n d a n i n a c t i v e G o l g i
a r e a .
 T h e s e c e l l s a l s o h a v e s e v e r a l l o n g a n d t h i n

11. As the root formation continues, cells in the
perifollicular area gain their polarity, increased
cellular volume and synthetic activity.
These cells become elongated and contain
increased numbers of rough endoplasmic reticulum
and mitochondria and an active Golgi complex.
As a result, they actively synthesize and deposit
collagen fibrils and glycoproteins in the developing
periodontal ligament.
Mostly type I collagen is secreted, which assembles
as collagen bundles extending from bone and
cementum surfaces.
Establish continuity across the ligament space and
thereby secure an attachment of the tooth to the
bone.

12. D
E
V
E
L
O
P
M
E
N
T
O
F
P
R
I
N
C
I
P
A
L
F
I
B
R
E
S
Immediately before tooth eruption, and for sometime
thereafter, active fibroblasts adjacent to cementum of the
coronal third of the root, appear to become aligned in an
oblique direction to the long axis of the tooth.
when the tooth erupts, the crest of the alveolar bone
is coronal to the CEJ and the developing fibers are
directed obliquely.
When the tooth moves during eruption, the level of the
alveolar crest coincides with the CEJ junction and the
oblique fibres become horizontally aligned.

13. The horizontal fibers termed as alveolar crest fibers have
become oblique once again but with the difference that
now the CEJ has reversed its relation to the alveolar
attachment and is positioned in a coronal direction.
Once the teeth come into function and the apical fiber
group is formed, the definitive periodontal ligament
architecture is established.
Alveolar crest fiber Initially oblique
Then
horizontal
Finally
again
oblique

14. • First, small, fine,
brush‐like fibrils are
detected arising from the
root cementum and
projecting into the
periodontal ligament
space.
• At this stage the surface
of the bone is covered by
osteoblasts.
• From the surface of the
bone only a small
number of radiating, thin
collagen fibrils can be
seen.
• Later on, the number and
thickness of fibers entering the
bone increase.
• These fibers radiate towards the
loose connective tissue in the
mid‐portion of the periodontal
ligament space, which contains
more or less randomly oriented
collagen fibrils.
• The fibers originating from the
cementum are still short, while
those entering the bone gradually
lengthen.
• The terminal portions of these
fibers carry finger‐like projections.
• The fibers originating from
the cementum
subsequently increase in
length and thickness and
fuse in the periodontal
ligament space with the
fibers originating from the
alveolar bone.
• When the tooth, following
eruption, reaches contact in
occlusion and starts to
function, the principal fibers
become organized into
bundles and run
continuously from the bone
to the cementum.
Lindhe’s
Clinical
periodontology
and
Implant
dentistry,
6
th
edition

15. PERIODONTAL LIGAMENT HOMEOSTASIS
 The periodontal ligament has the capacity to maintain its width more or less overtime
despite the fact, that it is squeezed in between two hard tissues.
 Studies indicate that the population of cells, within the periodontal ligament, both during
development and regeneration, secrete molecules that can regulate the extent of
mineralization and prevent ankylosis.
 Various molecules have been proposed, which play a role in maintaining an unmineralized
periodontal ligament :
Periodontal cells can inhibit mineralised bone nodule formation by bone stromal cells;
the inhibition may be dependant on prostaglandin production.
Msx2 prevents the osteogenic differentiation of periodontal ligament fibroblasts, by
repressing Runx2 transcriptional activity.
The balance between the activities of bone sialoprotein and osteopontin may also
contribute in maintaining an unmineralized periodontal ligament region.
Matrix ‘Gla’ protein, an inhibitor of mineralization; role in preserving the width of the

16. – Glycosaminoglycans or RGD-cementum attachment protein, a collagen
associated protein; role in maintaining the unmineralized state of the
periodontal ligament.
• Periodontal ligament has the capacity to adapt to functional changes;
When the functional demand
increases
When there is reduction in
function

18. CELLS
Synthetic cells
Progenitor
cells
Resorptive
cells
Epithelial rests
of Malassez
Defense
cells
Fibers
Ground
Substance
Fibroblast
Osteoblast
Cementoblast
Fibroblas
t
Osteoclast
Cementoclas
t
Macrophag
es
Mast cells
Eosinophil
s
Extracellular
substance
Blood
vessels,
nerves, and
lymphatics

21. C E L L S W I T H T H E S E M O R P H O LO G I C C H A R AC T E R I S T I C S ;

22.  T h e p r e d o m i n a n t c e l l i n t h e p e r i o d o n t a l
l i g a m e n t .
 V a r i e t y o f i t s c e l l p o p u l a t i o n s w i t h d i f f e r e n t
f u n c t i o n a l c h a r a c t e r i s t i c s ;
 fibroblasts on the bone side of the ligament show abundant
alkaline phosphatase activity than those on the tooth side.
 D e v e l o p m e n t a l d i f f e r e n c e s ;
a) Fibroblasts near cementum are derived from ectomesenchymal
cells of the investing layer of dental papilla, while
b) Fibroblasts near alveolar bone are derived from perivascular
mesenchyme.

23. Also have well
developed
cytoskeleton and show
adherens and gap
junctions.
MORPHOLOGY
• Flattened irregular disc like
• Large cells with extensive cytoplasm and abundant organelles, associated
with protein synthesis and secretion.
• Nucleus occupies a large volume of the cells with one or more prominent
nucleoli.
• Long and thin cytoplasmic extensions that form three-dimensional veils
that compartmentalize collagen fibrils into fibers.
• Have cilia ; associated with control of cell cycle or inhibition of centriolar
activity.

24.  R e g u l a r l y d i s t r i b u t e d t h r o u g h o u t t h e l i g a m e n t ;
o r i e n t e d w i t h t h e i r l o n g ax i s o f p a r a l l e l t o t h e
d i r e c t i o n o f c o l l a g e n f i b r i l s .
 G e n e r a t e a n o r g a n i z a t i o n a l p a t t e r n , a s t h e y h a v e
t h e a b i l i t y t o b o t h s y n t h e s i z e a n d s h a p e t h e
p r o t e i n s o f t h e e x t r a c e l l u l a r m a t r i x , i n w h i c h
c o l l a g e n f i b r i l s f o r m b u n d l e s , t h a t i n s e r t i n t o
t o o t h a n d b o n e a s S h a r p e y ’ s f i b e r s .
Characterized by rapid turnover of
extracellular matrix in particular collagen.

25.  R o l e o f f i b r o b l a s t s -
a. To produce the structural connective tissue proteins,
collagen and elastin,
b. As well as to produce glycoproteins and glycosaminoglycans
that comprise the periodontal ligament ground substance.
c. Also secrete an active collagenase and a family of enzymes
collectively known as matrix metalloproteinases (MMPs).
d. Responsible for the formation and remodeling of the
periodontal ligament fibers.
e. Maintain the width, by preventing encroachment of bone and
cementum into periodontal space.

26. • The osteoblasts covering the
periodontal surface of the alveolar
bone constitute a modified endosteum
and not a periosteum.
• A cellular layer, but not an outer
fibrous layer, is present on the
periodontal surface of the alveolar
bone.

27. • Cells contact one another through desmosomes
and tight junctions.
• Are also in contact with underlying osteocytes
through cytoplasmic processes.

28. These cells line the surfac
of cementum, but are not
regularly arranged as
osteoblasts.

29. • Cuboidal with a large vesicular
nucleus, with one or more nucleoli
and abundant cytoplasm.
• Organelles for protein synthesis and
secretion are present.
• Have abundant mitochondria and
less amounts of RER than
periodontal ligament fibroblasts.
Shows gap junctions and
desmosomes and has receptors for
growth hormone and epidermal
growth factor.
Cells actively depositing
cellular cementum;
• Exhibit abundant
basophilic cytoplasm
and cytoplasmic
processes
• The nuclei are folded
and irregularly shaped.
Cells depositing acellular
cementum do not have
prominent cytoplasmic
processes.
MORPHOLOGY

31. OSTEOCLASTS
• Cells that resorb bone.
• Tend to be large and
multinucleated but can also be
small and mononuclear.

32. • Eosinophilic cytoplasm.
• Appear to occupy bays in bone or surround the end of a
bone spicule.
• Exhibit numerous mitochondria and lysosomes
• Abundant Golgi saccules
• Free ribosomes but little RER.
• Part of the plasma membrane lying adjacent to bone that is
being resorbed is raised in characteristic folds and is
termed the ruffled or striated border.
• The ruffled border is separated from the rest of the plasma
membrane by a zone of specialized membrane that is closely
applied to the bone, the underlying cytoplasm of which
tends to be devoid of organelles and has been called the
clear zone.
• The bone related to the ruffled border can be seen undergoing
resorption.
• Exposed to highly acidic pH by virtue of the active pumping protons
by the osteoclasts into this environment.
O
S
T
E
O
C
L
A
S
T
S

33. FIBROBLASTS
• The cells show rapid degradation of collagen by fibroblast phagocytosis and that is
the basis of rapid turnover of collagen in periodontal ligament.
• The degradation of collagen may be expected to include both intracellular and
extracellular events.
• EXTRACELLULAR EVENTS –
– Degradation involve Collagenase (MMP-1); to cleave the triple helical portion of
molecules within the fibril.
– Together with MMP-IV, it leads to denaturation of collagen under physiological
conditions.
– The rest of the molecule undergoes further proteolysis by MMP-11 (gelatinase)
and MMP-V.
– Before any of these collagenase activities can occur, glycoproteins such as
fibronectin and proteoglycans on fibril surface, which mask the collagenase
binding site must be removed by stromelysin (MMP-III).

34. When a collagen fibril is phagocytosed by
the fibroblast, a banded fibril surrounded
by an electron-lucent zone is seen .
Subsequently, the banded fibrils are
surrounded by electron-dense
zone.
At this stage phagosome fuses with
primary lysosomes to form a
phagolysosome
At the terminal stage, fibrils show indistinct banding
and are surrounded by electron dense zone; the
fibril loses its characteristic structure by this point.

35. CEMENTOCLASTS
• Resembles osteoclasts and are occasionally found in
normal functioning periodontal ligament.
• Not remodelled in the fashion of alveolar bone and
periodontal ligament but that it undergoes
continual deposition during life.
• Resorption of cementum can occur under certain
circumstances; the mononuclear cementoclasts or
multinucleated giant cells, often located in
Howship’s lacunae, are found on the surface of the
cementum.
• Origin is unknown; conceivable that they arise in

37.  P r o g e n i t o r c e l l s a r e t h e c e l l s , w h i c h h a v e t h e c a p a c i t y
t o u n d e r g o m i t o t i c d i v i s i o n a n d r e p l a c e t h e
d i f f e r e n t i a t e d c e l l s d y i n g a t t h e e n d o f t h e i r l i f e o r a s a
r e s u l t o f t r a u m a .
 L o c a t e d i n p e r i v a s c u l a r r e g i o n , a n d e x h i b i t s o m e
c l a s s i c a l c y t o l o g i c a l f e a t u r e s o f s t e m c e l l s ;

38. • T h e r e a r e c e l l s w i t h c h a r a c t e r i s t i c s of
m e s e n c h y m a l s t e m c e l l s c a pa b l e of s u s t a i n e d
r e n e w a l a n d t i s s u e r e g e n e r a t i o n .
• T h e y r e m a i n w i t h i n t h e P D L a n d a r e r e s p o n s i b l e
f o r t i s s u e h o m e o s t a s i s , s e r v i n g a s a s o u r c e of
r e n e w a b l e p r o g e n i t o r c e l l s g e n e r a t i n g
c e m e n t o b l a s t s , o s t e o b l a s t s a n d f i b r o b l a s t s
t h r o u g h o u t a d u l t l i f e .
• I n t h e e v e n t of i n j u r y t o t h e p e r i o d o n t i u m , t h e s e
m e s e n c h y m a l s t e m c e l l s c o u l d b e a c t i va t e d
t o w a r d s t e r m i n a l d i f f e r e n t i a t i o n a n d t i s s u e r e p a i r

39. R E L AT I O N S H I P B E T W E E N C E L L S
 C e l l s of P D L f o r m a t h r e e - d i m e n s i o n a l n e t w o r k .
 A s s o c i a t e d w i t h b o n e , f i b r o u s C T, a n d c e m e n t u m
a r e s e p a r a t e d f r o m o n e a n o t h e r, b u t a d j a c e n t
c e l l s g e n e r a l l y a r e i n c o n t a c t w i t h t h e i r
n e i g h b o u r s , u s u a l l y t h r o u g h t h e i r p r o c e s s e s .
 T h e n a t u r e of j u n c t i o n s n o t c l e a r, a l t h o u g h
a p p e a r t o b e z o n u l a o c c l u d e n s , i n f a c t
c o n c e i va b l y g a p j u n c t i o n s .

41. • First described by MALASSEZ in 1884.
• Found close to the cementum.
• These are the remnants of the epithelium of Hertwig’s epithelial root
sheath.
• At the time of cementum formation, the continuous layer of epithelium that
covers the surface of the newly formed dentin breaks into lacelike strands.
• The epithelial rests persist as a network, strands, islands, or tubulelike
structures near and parallel to the surface of the root.
• In cross sections, they appear clusterlike; the arrangement appear like a duct
with the cells separated from the surrounding connective tissue by a basal
lamina.
• Abundantly located in the furcation areas.
• Could be involved in periodontal repair and regeneration.
• Less numerous in older individuals and more numerous in children.
• Upto the second decade, most commonly found in apical region, later mainly

42. HOW IT IS DIFFERENT FROM FIBROBLASTS??
 Close packing of their cuboidal cells.
 Nucleus stains more deeply and is prominent.
 Cytoplasm is scanty, and shows Tonofibrils that insert into the
desmosomes found between the cells and into the
hemidesmosomes between the cells and the basal lamina.
 Tight junctions are also seen.
 Mitochondria distributed throughout the cytoplasm.
 RER and Golgi apparatus are poorly developed, indicating
of protein synthesis.
 Epithelial cell rests attach to and spread rapidly on fibronectin,
vitronectin and type I collagen present in the extracellular
matrix.

44. MAST CELLS
• Relatively small, round or oval cell having a diameter of
about 12 to 15 µm.
• Often associated with blood vessels.
• Characterized by numerous cytoplasmic granules, which
frequently obscure small, round nucleus.
 0.5-1 µm in diameter.
 Positively stained by the periodic acid-Schiff
reaction.
 Dense, membrane-bound vesicles of varying
sizes.
 Contain heparin and histamine.
 Degranulates when stimulated.

45. • Cytoplasm contains free ribosomes, short profiles of granular and
endoplasmic reticulum, few round mitochondria, and a prominent Golgi
apparatus.
• Occasionally may be seen in the healthy periodontal ligament.
Role
• In the inflammatory reaction; degranulate in response to antigen-
antibody formation on their surface.
• Release of histamine causes proliferation of endothelial cells and
mesenchymal cells.
• Regulation of endothelial and fibroblast cell populations.

46. MACROPHAGES
• Found in the PDL predominately located adjacent
to blood vessels.
• Numerous microvilli, lysosomes,
and membrane bound vesicles.
• Paucity of RER and Golgi complex.
 Derived from blood monocytes.
 Horseshoe or kidney shaped
nucleus, generally of regular
contour, exhibits a dense uneven
layer of peripheral chromatin.
 Nucleoli are rarely seen.
 Cell surface is generally raised in
microvilli.
 Cytoplasm contains numerous free
ribosomes and lysosomes.
 RER is relatively sparse with widely
spaced polysomes that are
composed of only 2-4 ribosomes
each.
 Golgi apparatus is not well
developed
RESTING MACROPHAGES WANDERING MACROPHAGES

48. ROLE
 P h a g o c y t o s i n g d e a d c e l l s
 S e c r e t i n g g r o w t h f a c t o r s t h a t r e g u l a t e t h e
p r o l i f e r a t i o n of a d j a c e n t f i b r o b l a s t s .
 A l s o s y n t h e s i z e a r a n g e of m o l e c u l e s l i ke
i n t e r f e r o n s , p r o s t a g l a n d i n s a n d f a c t o r s t h a t
e n h a n c e t h e g r o w t h of f i b r o b l a s t s a n d
e n d o t h e l i a l c e l l s .

49. EOSINOPHILS
Occasionally seen in the
PDL.
Possess granules that
consist of one or more
crystalloid structures.
Capable of phagocytosis.

50. FIBERS-
• Collagen
• Elastic
• Reticular
• Secondary
• Indifferent fiber plexus
• Oxytalan
Ground substance-
• Proteoglycans
• Glycoproteins

51. FIBERS
• M a i n l y CO L L AG E N O U S .
• M a y b e s m a l l a m o u n t s of OX Y TA L A N A N D R E T I C U L I N
F I B E R S , a n d
• E L A S T I N F I B E R S i n s o m e s p e c i e s .

52. PRINCIPAL FIBERS
• The principal fibers are collagenous in nature.
• Composed of 3 polypeptide α-chain coiled around each other- Triple helix.
• Arranged in bundles approx. 5 µm in diameter.
• Follow a wavy course.
• Within each bundle, subunits present are called collagen fibrils; have transverse
striations with a characteristic periodicity of 64 nm.
• Primarily composed of type I & III collagen; more than 70% is type I and 20% is type III.
• Small amounts of type V and type VI collagens, and traces of type IV and type VII
collagen are also found in the ligament.
• Type IV and VII are associated with epithelial cell rests and blood vessels.

54. ALVEOLODENTAL
LIGAMENT
• The principal fiber group is the Alveolodental ligament.
• FIVE FIBER GROUPS;
 ALVEOLAR CREST
 HORIZONTAL
 OBLIQUE
 APICAL
* INTERRADICULAR GROUP
(In multirooted teeth)

55. • These fibers extend obliquely from
the cementum just beneath the
junctional epithelium to the alveolar
crest.
• Resist tilting, intrusive, extrusive, and
rotational forces.

56. HORIZONTAL
• Horizontal fibers extend at right angles
to the long axis of tooth from cementum
to alveolar bone.
• Parallel to the occlusal plane of the arch.
• These fibers are located immediately
apical to the level of alveolar crest fiber
group; limited to the coronal 1/4th of the
PDL.
• These fibers resists horizontal and
tipping forces.

57. OBLIQUE
• Nearly 2/3rd of the PDL.
• Inserted into the alveolar bone at a
position coronal to their attachment to
cementum; oblique orientation in the PDL
space.
• These fibers mainly resists the vertical and
intrusive forces.
• They bear the brunt of vertical masticatory
stresses and transfer them on to the
alveolar bone.

58. APICAL
• From the cementum to the root tip.
• Radiate through the PDL space to
become anchored into the fundus of
bony socket.
• Resist luxation forces, may prevent
tipping and probably protect delicate
blood and lymph vessels and nerves
traversing the PDL space at the apex.
• They do not occur on incompletely

59. • Inserted into the cementum from
the crest of interradicular septum in
multirooted teeth.
• Resist tooth tipping, torquing and
luxation.
• Total loss of these fibers in chronic
inflammatory periodontal disease.

60. SHARPEY’S FIBERS

62. ELASTIC FIBERS
E l a s t i c m e s h w o r k i n t h e P D L i s c o m p o s e d o f
m a n y e l a s t i n l a m e l l a e w i t h p e r i p h e r a l o x y t a l a n
f i b e r s a n d e l u a n i n f i b e r s .
THREE TYPES:
• EL ASTIN
• ELUANIN
• OXY TAL AN
MATURE ELASTIC FIBERS
IMMATURE ELASTIC FIBERS

63. ELASTIN
• Mature elastic fibers consist of a
microfibrillar component surrounding
an amorphous core of elastin.
• High %age of glycine, proline, and
hydrophobic residues, with little
hydroxyproline and no hydroxylysine.
• Observed only in walls of afferent
blood vessels

64. ELUANIN
• Bundles of microfibrils
embedded in a relatively small
amount of amorphous elastin.
• Found within the fibers of the
gingival ligament.

65. OXYTALAN
• Consists of microfibrillar component only.
• Approx. 0.5µm to 2.5µm in diameter.
• Orientation- tend to run in an axial direction,
from cementum or possibly bone eventually
embedding into the wall of the blood vessel.
• Within PDL proper, longitudinally orientated,
crossing the oblique fibers perpendicularly.
• Play a part in supporting the blood vessels of
the PDL
• May have a role in tooth support.

66. I
N
T
E
R
M
E
D
I
A
T
E
P
L
E
X
U
S
Earlier, it was
believed that the
fibers followed a
wavy course from
cementum to bone
and are joined in
the mid region of
the PDL space,
giving rise to a
zone of distinct
appearance, the so-
called intermediate
intermediate
plexus.
Research over past
years suggests that
cemental fibers meet
and fuse with osseous
fibers, no such plexus
remains.
Secondly, the entire
PDL is metabolically
active, not just the
middle or intermediate
intermediate zone.
(Thomas M. Hassel)
The recent
concept, fibers
cross the entire
width of PDL space,
but branch en
route and join
neighbouring
fibers to form a
complex three
dimensional
network.
* N o i n t e r m e d i a t e p l e x u s i s s e e n a c r o s s t h e P D L
s p a c e i n t e e t h o f n o n c o n t i n u o u s g r o w t h .

68. • Gel like matrix in which are embedded the cellular and fibrous components
such as collagen.
• Contain 70% water.
• Occupied by non collagenous proteins, which represent 10% of total
protein found in the PDL..
• Consists mainly of hyaluronate, GAGs, proteoglycans, and glycoproteins.
• All components of the ground substance are presumed to be secreted by
fibroblasts.
• Two proteoglycans identified in the PDL; proteodermatan sulfate and
chondroitin sulfate.
• GAGs are linear polymers of disaccharide repeat sequence; contains heparin

69. • Substrate adhesion molecules such as tenascin, osteonectin, laminin,
undulin, and fibronectin have also been identified.
– Fibronectin and osteonectin are uniformly distributed.
– Tenascin commonly found in the attachment zones located near the
cementum and alveolar bone; may act to transfer the forces of
mastication and the stresses of tooth support to specific protein
structures.
– Laminin has been found principally in the basement membrane of
the epithelial rests of Malassez.
– Undulin found to be associated with tightly packed major collagen
fibrils.

71. ARTERIAL SUPPLY
• Main blood supply is from superior and inferior
alveolar arteries. The blood vessels are derived from
the following:
– Branches from apical vessels supplying the
pulp.
– Branches from intra-alveolar vessels: Vessels
run horizontally and penetrate the alveolar bone
to enter into the periodontal ligament.
– Branches from gingival vessels: These enter
from the coronal direction.
• The arterioles and capillaries ramify and form a rich
network.

72. Arterioles range from a diameter of 15-50 µm with an avg. diameter of 20 µm.
The crevicular capillary loops arise from circular plexus of 1-4 intercommunicating
vessels of 6-30 µm diameter at the level of JE.
Blood supply increases from incisors to molars.
Single rooted teeth - gingival third > apical third > middle third.
In molars, gingival area > middle third = apical third.
Venous drainage -
 Accompanying the arterial counterparts.
 Larger in diameter with an average of 28 µm.
 Receive blood from the capillary network and also specialized shunts called
glomera in the PDL.

73. T h e f l o w i s v i a t h e a l v e o l a r l y m p h c h a n n e l s w h i c h
a r e j o i n e d b y t h e d e n t a l a n d i n t e r r a d i c u l a r l y m p h
c h a n n e l s .

84. injuries.

88. VI. ERUPTIVE
Provides space and acts as a medium for cellular
remodeling and hence continued eruption, and
approximal shift occurs.

93. CEMENTICLES
 Small calcified bodies.
 Remain free or fused into large calcified
mass or may be joined with the
cementum.
 When adherent with the cementum,
they form excementoses.
 Degenerated epithelial cells form the
nidus for their calcification.
 Old age

94. PERIAPICAL LESIONS

95. • 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.

96. TRAUMA
• The trauma can result from number of
ways:
Abnormal occlusal function, accidental
blows.
Premature contacts from high points in
restoration.
Excessive orthodontic forces.
• All of the above leads to pulpal injury
result in periapical changes.
 Over instrumentation during
RCT causes profuse periapical
haemorrhage and
dissemination of dentin debris
beyond the apical foramina.
 It result in edematous PDL,
intense neutrophil
inflammatory infiltrate.

97. • When there is very less damage to PDL –
Adjacent PDL proliferates.
 Inflammatory resorption : When there is
infection – inflammation of bone and PDL –
which is replaced by granulation tissue.
 Replacement resorption :
When there is severe
damage to PDL - resorption
of bone, cementum, PDL -
it is replaced by the bone.
Results in ankylosis of tooth

98. ORTHODONTIC TOOTH
MOVEMENT
• Depends on resorption and formation of
bone and periodontal ligament (i.e.
remodelling).
• When a orthodontic force is applied
through PDL to the tooth, there is an initial
compression of PDL on pressure side
followed by the bone-resorption, whereas
in tension side there is bone apposition.
• Application of large amount of force result
in necrosis and death of PDL