5. Defensive macrophage, lymphocytes and
cells mast cells
epithelial cells remnants of the epithelial
root sheath of Hertwig
6. Extracellular
substances
The fibers of the periodontal ligament are
. mainly collagen
:They are divided into
.A) The principal fibers
.B) The accessory fibers
.C) The oxytalan ( elastic ) fibers
7. .a) Gingival fibers
.b) Transseptal or interdental ligament
c) Alveolodental ligament which is subdivided into the
:following five groups
. Alveolar crest group- 1
. Horizontal group- 2
. Oblique group- 3
. Apical group- 4
. Interradicular group- 5
8. 1- Dentogingival group : extend
from the cervical cementum
into the lamina propria of the
gingival.
2- Alveologingival group:
extends from the alveolar
crest into the lamina propria.
3- Circular group: a small group
of fibers that encircles the
tooth and interlaces with the
outer fibers . bone.
4- Dentoperiosteal fibers: they
extend from the cementum
direct over the crest and then
incline apically between the
periosteum of the alveolar
bone to the lamina propria of
the gingiva.
9. Functions of the gingival fibers
They hold the marginal gingiva against the tooth .
They provide the marginal gingiva with enough
rigidity to withstand the forces of mastication
without distorting .
10. *It connects two adjacent teeth.
*The ligament runs from the
Denti
cementum of one tooth over the
n
crest of the alveolus to the
cementum of the adjacent tooth.
Bone
Dentin
11.
12.
13. 1-Alveolar crest group:
radiate from the crest of
the alveolar process and
attach to the cervical part of
the cementum.
2-Horizontal group: Bone Dentin
The fiber bundles run from the
cementum to the bone at
right angle to the long axis
of the tooth.
14. 3- Oblique group:
The fiber bundles run obliquely.
Their attachment in the bone is
somewhat coronal than the
attachment in the cementum.
It is the greatest number of bone
fiber bundles found in this
group. dentin
They perform the main support
of the tooth against
masticatory force.
15. 4- Apical group: denti
n
The bundles radiate from the
apical region of the root to
the surrounding bone. bone
5- Interradicular group:
The bundles radiate from the
interradicular septum to the denti
furcation of the multirooted n
tooth.
bone
16. It is collagenous in nature and run from bone to
cementum in different planes, more tangentially
to prevent rotation of the tooth and found in
the region of the horizontal group.
17. Oxytalan Fibers
Immature elastic fibers.
Run in axial or oblique direction.
One end being embedded in cementum or
bone and the other end in the wall of b.v.
The function of the oxytalan fibers has been
suggested that they play a part in supporting
the blood vessels of the periodontal ligament
during mastication i.e., it prevents the sudden
closure of the blood vessels under masticatory
forces.
18. Some of the b.vs.,
lymphatics, and nerves of
the PDL are surrounded
by loose C.T. These areas
have termed interstitial
tissue.
Fibroblasts histiocytes,
UMC, and lymphocytes
are also found in
interstitial tissue.
Biological significance:
unknown.
19. The arterial blood supply of the periodontal
:ligament is derived from 3 sources
1- Branches from the gingival vessels.
2- Branches from the intra-
alveolar vessels, these branches
run horizontally and these
constitue the main blood supply.
3- Branches from the apical vessels that supply
the dental pulp.
20. The nerve supply of periodontal ligament
comes from either the inferior or superior
dental nerves.
1- Bundles of nerve fibers run from the apical
region of the root towards the gingival margin.
2- Nerves enter the ligament horizontally through
multiple formatina in the bone.
Small fibers pain sensation
mechanoreceptors
large fibers touch & pressure
21. 1- Supportive:
*periodontal ligament permits the teeth to withstand
the considerable forces of mastication.
*As the force is applied on the teeth, the wavy course
of the collagen fibers gradually straightening out
*Also periodontal fibers being non elastic prevent the
tooth from being moved too far.
22. The periodontal ligament having the
mechanoreceptor contributes to the
sensation of touch and pressure on the
teeth.
3- Nutritive:
The blood vessels in the periodontal
ligament provide nutrient supply
required by the cells of the ligament and
to the cementocytes and the most
superficial osteocytes.
23. 4- Formative:
The fibroblasts are responsible for the
formation of new periodontal ligament fibers
and dissolution of the old fibers
Cementoblasts and osteoblasts are essential in
building up cementum and bone.
24. The protective function of the periodontal ligament is
achieved by:
a- The principal fibers.
b- The blood vessels.
c- The nerves.
a- The principal fibers:
The arrangement of the fiber bundles in the different
groups is well adapted to fulfill the functions of the
periodontal ligament.
The alveolodental ligament transforms the masticatory
pressure exerted on the tooth into tension or traction
on the cementum and bone.
If the exerted force on a tooth is transmitted as
pressure this will lead to differentiation of
osteoclasts in the pressure area and resorption of
bone.
25. b- The blood vessels:
The capillaries form a rich network, they are
arranged in form of a coil and attached to bone
and cementum through the oxytalan fibers.
This arrangement makes it possible when pressure is
exerted on the tooth, the blood does not escape
immediately from the capillaries and thus
buffering the pressure action before it reaches the
bone.
c- The nerves:
By its mechanoreceptors nerves.
26. *The periodontal ligament through aging shows
Vascularity
Cellularity
Thickness
*It may contain cementicles.
27. The cementicles appear near the
surface of cementum may be free
, attached or embedded in the
cementum.
They have nidus favoring the
deposition of concentric layers of
calcosphrite as degenerated cells,
area of hemorrhage and epithelial
rest's of Malassez.
Cementicles are usually seen in
periodontal ligament by aging
but in some cases they may be
seen in a younger person after
local trauma.
