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1. The Normal Periodontium
• INTRODUCTION: The Normal
Periodontium consists of Periodontium
the 4 parts
1) Gingiva
2) periodontal ligament
3) Alveolar bone
4) Cementum
These all 4 parts are the
investing & supporting
tissues of the tooth. Which
holds the tooth in its
position fixed to the socket.

2. PERIODONTAL LIGAMENT
• The Periodontal Fiber or Periodontal Ligament,
commonly abbreviated as the PDL ,is a group of the
specialized connective tissue fibers that essentially attach
a tooth to alveolar bone within which it sits. These fibers
help the tooth withstand the naturally
substantial compressive forces which occur
during mastication(chewing) and remain embedded in
the bone. It consists of bands of collagen fibers
connecting the cement of the tooth to both gingival and
alveolar bone and to the cement of adjacent teeth.
Interspersed among the collagen fibers are loose
connective tissue, blood vessels, lymphatic vessels, and
nerves.

3. PERIODONAL FIBERS
* The thickness of the
periodontal ligament varies
from tooth to tooth.
* The thinnest portion of the
PDL is near the middle of the
root.
* The width of the PDL shows a
progressive decrease with age.
* The most important thing to
consider about PDL that it is
always in a state of remodeling.

4. STRUCTURE OF PDL
• It consist of cells, and extracellular compartment
of fibers. The cells are fibroblast, epithelial,
undifferentiated mesenchymal cells, bone and
cementum cells. The extracellular compartment
consists of collagen fibers bundles embedded in
ground substance. The PDL substance has been
estimated to be 70% water and is thought to have
a significant effect on the tooth's ability to
withstand stress loads. The PDL is a part of the
periodontium that provide for the attachment of
the teeth to the surrounding alveolar bone by way
of the cementum.

5. PERIODONTAL FIBERS
• The PDL collagen fibers are categorized according to their
orientation and location along the tooth.
1. Transseptal fibers: extend interproximally over the alveolar
bone crest and are embedded in the cementum of adjacent
teeth; they form an interdental ligament. These fibers keep all the
teeth aligned. These fibers may be considered as belonging to the
gingiva because they don't have osseous attachment.
2. Alveolar crest fibers: extend obliquely from the cementum
just beneath the junctional epithelium to the alveolar crest.
These fibers prevent the extrusion of the tooth and resist lateral
tooth movements.
3. Horizontal fibers: attach to the cementum apical to the
alveolar crest fibers and run perpendicularly from the root of the
tooth to the alveolar bone.

6. PERIODONTAL FIBERS 4. Oblique Fibers: are the most
numerous fibers in the periodontal
ligament, running from cementum
in an oblique direction to insert
into bone coronally.
5. Apical Fibers: radiating from
cementum around the apex of the
root to the bone, forming base of
the socket.
6. Interradicular Fibers:
Interradicular fibers are only found
between the roots of multi-rooted
teeth, such as molars. They also
attach from the cementum and
insert to the nearby alveolar bone.

7. FUNCTIONS OF PDL
1. It provides a support mechanism for the tooth; it cushions teeth
against excessive occlusal forces, preventing damage to the blood
vessels and nerves at the root apex.
2. It maintains the functional position of a tooth by keeping the teeth
in contact and prevents the tooth from drifting or tilting.
3. The periodontal fibers undergo continuous change. Its cells form,
maintain and repair the alveolar bone and cementum.
4. Sensors in the periodontal ligament provide proprioceptive input,
detecting pressures on the tooth.
5. The periodontal ligament has a rich supply of blood, which
provides nutrients to the cementoblasts.

8. • The width of the periodontal ligament ranges from 0.15
to 0.21 mm.
• The part of the PDL fibers present in the cementum &
alveolar bone are called Sharpey’s Fibers.
• The fibroblasts, cementoblasts , osteoclast ,
undifferentiated mesenchymal cells, epithelial cells rest
of malassez and osteoblasts are the synthetic cells of the
PDL.
• The macrophages, mast cells and lymphocytes are the
defensive cells of the PDL.
• The blood supply is through the branches from gingival
vessels, intra-alveolar vessels & the apical vessels.
• The Age Changes include the decrease in vascularity,
cellularity and thickness. It may contain cementicles.

9. ALVEOLAR BONE
An alveolar bone is a specialized type of bone which is
designed to accommodate teeth. In humans, alveolar
bone is found in the mandible, or lower part of the jaw,
along with the maxilla, the upper part of the jaw.
Alveolar bone is especially thick and dense when
compared to other types of bone so that it can provide
adequate support for the teeth, along with attachment
points for muscles involved in the jaw and for the gums
which provide protection for teeth and bone. This bone is
also known as the “Alveolar Process”. It includes sockets
which are designed to accommodate the roots and lower
part of the teeth, with each socket separated from the
next by an interdental septum.

10. ALVEOLAR BONE
 The gums attach to the
alveolar process, and the
bone has accommodations
to allow blood vessels to
enter for the purpose of
supplying blood to the teeth.
Damage to the alveolar bone
can have serious
consequences, including the
risk of loss of teeth and
septicemia if the damage is
caused by an infection.

11. • ALVEOLAR SOCKET: It is also called dental alveolus.
These are the sockets in the jaws in which the roots of
teeth are held in the alveolar process with the
periodontal ligament.
• INTERDENTAL SEPTA: These are the plates of bone
that separate each individual sockets from one another.
• INTERTADICULAR SEPTA: These are the thin plates of
bone that separate the roots of multi-rooted teeth.
• CRIBRIFORM PLATE: Also called as bundle bone, is the
compact layer of bone lining the tooth socket.
• ALVEOLAR PROCESS: It is the thickened ridge of bone
that contains the tooth sockets on bones that bear
teeth.

12. cont’d alveolar bone
. If the teeth are lost, the alveolar process
disappears.
. It is composed of two parts: 1) Alveolar bone
proper & 2) Supporting bone.
* Alveolar bone proper is that part of the alveolar
bone that lines the socket. Radio graphically
alveolar bone proper is referred to as LAMINA
DURA.
* The remainder of alveolar process below the
alveolar bone proper is called Supporting bone. It
is attached to the alveolar bone proper. It includes
cortical plates and spongy bone.

13.  CORTICLE PLATES: This is also called Compact Supporting
Bone. The compact supporting bone of the alveolar process
extends from the alveolar crest to the lower border of the socket
on the outside surface of the maxilla & mandible.
 SPONGY BONE: This is also called Cancellous Bone. It is
located apically between the alveolar bone proper and the
cortical bone.
 Two types of bone are seen:
 1) INTERDENTAL BONE: The bone between the roots of
adjacent single-rooted or multi-rooted teeth is called Interdental
Bone
2) INTERRADICULAR BONE: The bone between the roots
of multi-rooted teeth is known as Interradicular Bone

14. AGE CHANGES IN ALVEOLAR
BONE
As people age, they often experience alveolar bone loss,
which can be seen on dental x-rays. Sometimes the bone
becomes thinner, and sometimes alveolar bone
resorption occurs. In this case, part of the bone is
reduced in volume. Resorption is often linked with
damage to the jaw or the loss of teeth, which is one
reason why extractions are avoided, if possible. Patients
with severe damage may require alveolar bone grafting
to replace missing bone or to promote bone growth to
repair areas of damage. The alveolar bone forms a ridge
around the neck of the tooth & holds properly in its
socket.

15. FUNCTIONS OF ALVEOLAR BONE
1) PROTECTION: Alveolar bone forms and
protects the sockets for the teeth.
2) ATTACHMENT: It gives the attachment to
the PDL fibers, which are the principle fibers.
These fibers which enter the bone are
regarded as Sharpey’s Fibers.
3) SUPPORT: It supports the tooth roots on
the facial & on the palatal/lingual sides.
4) SHOCK-ABSORBER: It helps absorb the
forces placed upon the tooth by disseminating
the force to underlying tissues.

16. VASCULAR SUPPLY
OF
ALVEOLAR BONE
1. ALVEOLAR PROCESS
OF THE MAXILLA:
Anterior & posterior
alveolar arteries (branch
from the maxilla & infra
orbital arteries)
2. ALVEOLAR PROCESS
OF THE MANDIBLE:
a)Inferior alveolar arteries
(internal)
b) Periosteal branches of
submental & buccal
arteries (external).

17. CEMENTUM
 Cementum is the calcified, avascular mesenchymal tissue
that forms the outer layer covering the anatomic root.
 2 Types of the cementum are there:
1) Acellular cementum
2) Cellular cementum
 Composition of the cementum is:
 Organic portion is 50%, composed of collageneous & non-
collageneous proteins while inorganic portion is 45-50%
composed of hydroxyapatite crystals.
 The collageneous composition of the organic portion is
type I (90%) & type III (5%).
 At cervical margin the thickness of cementum is 50um &
at apical margin the thickness progresses to 200um.

18. CEMENTUM  ACELLULAR
CEMENTUM: It is the first
cementum forms, covers
approximately cervical third
or half of the root & does
not contain cells.
 CELLULAR
CEMENTUM: It forms
after the tooth reaches the
occlusal plain. It is more
irregular and contain cells
(cementocytes) and in
individual spaces (lacunae)

19.  Cementum deposition is a
continuous process that
proceeds at varying rates.
 Cementum formation is most
rapid in the apical regions where
it compensates for the tooth
eruption.
 The term hypercementosis
refers to a prominent thickening
of the cementum.
 The terminal apical area of
cementum where it joins the
internal root canal dentine is
known as cemento-dentinal
junction.
 The point or area where
cementum joins the enamel is
called cemento-enamel junction.

20. AGE CHANGES IN
CEMENTUM
 Hypercementosis.
 Decrease permeability.
 Cementicles formation
(which are round or ovoid
calcified structures).
 Surface become rough.
 Cemental resorbtion
 More cemental
deposition may leads to the
closure of the apical
foramen.

21. DIFFERENT B/W ACELLULAR &
CELLULAR CEMENTUM
ACELLULAR CEMENTUM CELLULAR CEMENTUM
 First formed  Secondary formed
 Present on cervical 3rd or half  Mainly on apical 3rd of root
of the root  It contains cells called
 It doesn’t contain cells cementocytes in lacunae
 It is formed before the tooth  Formed after the tooth reaches
reaches the occlusal plane the occlusal plane
 More calcified  Less calcified
 Sharpey’s fibers are the main  Sharpey’s fibers occupy smaller
component and inserted at portion & are not the main
right angles onto the root component.
surface.