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The
periodontal
 Ligament
Periodontium:
    Is the investing and supporting attachment system of the
    teeth.
                          :It consists of

     Two soft tissues                  Two hard tissues

 Gingiva -1                           Cementum -1
That part covers the neck of the
tooth and part of the alveolar        covers the anatomical root
.bone                                 Alveolar Bone -2
                                      The bone of the jaw that
 Periodontal Ligament -2             surrounds the root of the tooth
 Strong ligament that attaches
the tooth to the alveolar bone
   Definition: The periodontal
    ligament is the dense fibrous
    connective tissue that occupies
    the periodontal space between
    the root of the tooth and the
    alveolus.
•Inflammation from the dental pulp
and gingiva could spread to involve
the PDL and other apical supporting
tissues.
Width of the periodontal ligament:
It ranges from 0.15-0.21 mm.
The narrowest area is at the mid-root ( Fulcrum ).
The region at the alveolar crest is the widest area
followed by the apical region.
                        The width generally reduced in:
                        •Non-functional teeth.
                        •Un-erupted teeth.
                        While increased in:
    Bone   Dentin
                        *Teeth subjected to an occlusal stress
                        within the physiological limits .
                        *Deciduous teeth
The periodontal ligament resembles
immature, fetal-like connective tissues in
the following features:

1- High rate of turnover.
2- Large volume of ground substance.
3- The presence of oxytalan fibers.
4- High cellularity.
5- Similar biomechanical propereties.
Knocked out tooth
The length of time before a tooth is reimplanted (within half an
hour) and how it is transported to the dentist (in saline) are
critical in successfully saving and re-implanting the tooth.




The periodontal ligament will regenerate and revascularize.
A tooth that is replaced within half an hour has a 90% chance of
  successful re-implantation.
Development
     Of PDL:
  •Dental follicle consists of
1-Dense fibrous and cellular
tissues immediately
encapsulate the developing
tooth

        (Cementum)

2-Perifollicular mesenchyme

   (PDL ,Alveolar bone)
Histological structure
The periodontal ligament is formed of :

                      Intercellular
  cells                substances
Synthetic                Fibers,

Resorptive
                      ground substances
Progenitor
                        blood vessels,
Defensive            nerves & lymphatics.
A- The principal fibers:
 They are formed of collagen bundles, which
 are wavy in course and are arranged in three
                   groups.
a) Gingival fibers.
b) Transseptal or interdental ligament.
c) Alveolodental ligament which is subdivided
     into the following five groups:
      1- Alveolar crest group.
      2- Horizontal group.
      3- Oblique group.
      4-Apical group.
      5- Interradicular group.
A- The principal fibers:
   a- The gingival fibers:
1- Dento-gingival fibers: extend from
   the cervical cementum into the          Dento-
   gingiva.                                gingival
                                                                   Alveolo-
2- Alveolo-gingival group: extends                                 gingival
   from the alveolar crest into the
   gingiva.                               Circular
                                          fibers
3- Circular group: a small group of
   fibers that encircles the tooth and
   interlaces with the outer fibers.
4- Dento-periosteal fibers: they           Dento-
   extend from the cementum directed       periosteal
   over the bone crest and then incline                 Alveolar
   apically between the periosteum of                   bone
   the alveolar bone and the gingiva.
Function of gingival fibers:
They form a rigid cuff around the
tooth that can add stability and resist
gingival displacement.
b- The transseptal ligament:
*It connects two adjacent
  teeth.
                            Dentin
*The ligament runs from the
  cementum of one tooth
  over the crest of the
  alveolus to the cementum
  of the adjacent tooth.
                                 Bone
*Function:                              Dentin
Resists mesial and distal
tooth separation.
c- The alveolodental ligament:
1-Alveolar crest group:
 radiate from the crest of the
   alveolar process and attach
   themselves to the cervical
   part of the cementum.
Function: resists vertical and
intrusive forces.              Bone   Dentin
2-Horizontal group:
The fiber bundles run from the
cementum to the bone at right
angle to the long axis of the
tooth.
Function: resists horizontal
   and tipping forces.
3- Oblique group:
The fiber bundles run obliquely.
Their attachment in the bone is
somewhat coronal (higher)
than the attachment in the
cementum.                          bone

The greatest number of fiber              dentin
bundles are found in this group.
Function:
*Performs the main support
of the tooth against masticatory
forces.
*Resists vertical and intrusive
  forces.
4- Apical group:
The bundles radiate from the          dentin
apical region of the root to
the surrounding bone
                               bone
Function: resists vertical
force.
5- Interradicular group:
                                  dentin
The bundles radiate from the
interradicular septum to the
furcation of the multirooted
tooth.                            bone

Function: resists vertical
   and lateral forces.
1  periodontal ligament future
1  periodontal ligament future
B- Accessory fibers:
They are 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.
2- Oxytalan fibers
These are immature elastic (pre-
elastic) fibers.

They need special stains to be
demonstrated.

They tend to run in an axial
direction, one end being embedded
in bone or cementum and the
other in the wall of blood vessels.

At the apical region they form a
complex network.
The functions of oxytalan fibers:
1-Support nerves.
   2- Support blood vessels.
3- Help fibroblasts migration.
Histological structure
The periodontal ligament is formed of :

  cells               Intercellular
                       substances
Synthetic
                          Fibers,
Resorptive
                      ground substances
Progenitor
                        blood vessels,
Defensive            nerves & lymphatics.
The cells
 Synthetic
             fibroblasts, osteoblasts and cementoblasts.
   cells


Resorptive
           cementoclasts , osteoclasts and fibroclasts.
   cells
           Note that fibroblasts perform both
           synthetic and resorptive activities.
Progenitor undifferentiated mesenchymal
   cells   cells                             Epithelial cells
                                 remnants of the epithelial
Defensive macrophage, lymphocytes root sheath of Hertwig
  cells   and mast cells
Synthetic Cells of PDL
   Fibroblasts

   Cementoblasts

   Osteoblasts
PDL Fibroblasts




              • Oriented parallel to collagen fibers
              •Are motile due to contractile properties
              •Show numerous microtubules &
                microfilaments
              •Assembles procollagen molecules
              •Perform fibroclastic function
              •Ingestion collagen fibers
              •Contains intracellular collagen profiles
                & vacoules
              •Contains lysosomal system
Cementoblasts                Osteoblasts




Both are rich in alkaline phosphatase activity.
Resorptive Cells of PDL

• osteoclasts
• cementoclasts
Both are rich in acid phosphatase
activity.
Progenitor cells
                     .U. M. C
• Can undergo mitotic
  devision
• Can differentiate to
  different types of cells
• Have small, closed-
  face nucleus
• Little amount of
  cytoplasm
• Found close to blood
  vessels
Defensive Cells of PDL
Macrophages              Mast cells




lymphocytes

           Note: There are no plasma cells.
Epithelial Cells: remnants of the epithelial
 .root sheath of Hertwig




•They are separated from the
surrounding connective tissue by a
basal lamina.
•They show low cells turnover,
although they may proliferate to form
cysts or tumors.
1  periodontal ligament future
Histological structure
The periodontal ligament is formed of :

  cells               Intercellular
                       substances
Synthetic
                          Fibers,
Resorptive
                      ground substances
Progenitor
                        blood vessels,
Defensive            nerves & lymphatics.
Interstitial tissues
*They are found between the
fibers of the periodontal
ligament.
*They are areas that
contain some of the blood
vessels, lymphatic and
nerves.
*They are surrounded
by loose connective tissue.
Blood supply
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 constitute the
 main blood supply.

  3- Branches from the apical vessels that supply the dental pulp.
Nerve supply:
   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
   foramina in the bone.
Are responsible for
Small nerve fibers                              pain sensation


                        Are responsible for
Large nerve fibers                            touch & pressure
   (mechanoreceptors)

•Stimulation of the mechanoreceptors initiates a reflex jaw
opening.

•This reflex is a protective mechanism to prevent forces
applied to the teeth from reaching damaging levels.
Functions of the periodontal
              ligament:
1- Supportive: Through the collagen fibers and the blood vessels.
                      [




*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 and
  then acting as inelastic strings.
 *Also periodontal fibers being non elastic prevent the
  tooth from being moved too far.
*Blood vessels and all the components of the
ligament act together as a hydraulic damper
or shock absorber with the ground
substance and the tissue fluid.
Dental implants lack periodontal ligament fibers
and they have a rigid connection to bone
(Osseointegration).
Periimplant tissues

                 Titanium implant

                 Sulcular epithelium

                 Juunctional epithelium

                 Connective tissue




                 Bone
2- Sensory:
The periodontal ligament having the mechanoreceptors
 contributes to the sensation of touch and pressure on
the teeth.
                  proprioceptive reflex
sudden overload                           inhibition of the activity
                                          of the masticatory muscles



                                          Opening the mouth
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.

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.
5- Protective
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.
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.
The behavior of the blood in the capillaries may be simulated
  to a hydraulic brake.

c- The nerves:
By its mechanoreceptors nerves.
The Age Changes of periodontal
                ligament

*The periodontal ligament through aging shows
  Vasuclarity
  Cellularity
  Thickness
*It may contain cementicles.
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.
Thank you
   &
good luck

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1 periodontal ligament future

  • 2. Periodontium: Is the investing and supporting attachment system of the teeth. :It consists of Two soft tissues Two hard tissues Gingiva -1 Cementum -1 That part covers the neck of the tooth and part of the alveolar covers the anatomical root .bone Alveolar Bone -2 The bone of the jaw that Periodontal Ligament -2 surrounds the root of the tooth Strong ligament that attaches the tooth to the alveolar bone
  • 3. Definition: The periodontal ligament is the dense fibrous connective tissue that occupies the periodontal space between the root of the tooth and the alveolus. •Inflammation from the dental pulp and gingiva could spread to involve the PDL and other apical supporting tissues.
  • 4. Width of the periodontal ligament: It ranges from 0.15-0.21 mm. The narrowest area is at the mid-root ( Fulcrum ). The region at the alveolar crest is the widest area followed by the apical region. The width generally reduced in: •Non-functional teeth. •Un-erupted teeth. While increased in: Bone Dentin *Teeth subjected to an occlusal stress within the physiological limits . *Deciduous teeth
  • 5. The periodontal ligament resembles immature, fetal-like connective tissues in the following features: 1- High rate of turnover. 2- Large volume of ground substance. 3- The presence of oxytalan fibers. 4- High cellularity. 5- Similar biomechanical propereties.
  • 6. Knocked out tooth The length of time before a tooth is reimplanted (within half an hour) and how it is transported to the dentist (in saline) are critical in successfully saving and re-implanting the tooth. The periodontal ligament will regenerate and revascularize. A tooth that is replaced within half an hour has a 90% chance of successful re-implantation.
  • 7. Development Of PDL: •Dental follicle consists of 1-Dense fibrous and cellular tissues immediately encapsulate the developing tooth (Cementum) 2-Perifollicular mesenchyme (PDL ,Alveolar bone)
  • 8. Histological structure The periodontal ligament is formed of : Intercellular cells substances Synthetic Fibers, Resorptive ground substances Progenitor blood vessels, Defensive nerves & lymphatics.
  • 9. A- The principal fibers: They are formed of collagen bundles, which are wavy in course and are arranged in three groups. a) Gingival fibers. b) Transseptal or interdental ligament. c) Alveolodental ligament which is subdivided into the following five groups: 1- Alveolar crest group. 2- Horizontal group. 3- Oblique group. 4-Apical group. 5- Interradicular group.
  • 10. A- The principal fibers: a- The gingival fibers: 1- Dento-gingival fibers: extend from the cervical cementum into the Dento- gingiva. gingival Alveolo- 2- Alveolo-gingival group: extends gingival from the alveolar crest into the gingiva. Circular fibers 3- Circular group: a small group of fibers that encircles the tooth and interlaces with the outer fibers. 4- Dento-periosteal fibers: they Dento- extend from the cementum directed periosteal over the bone crest and then incline Alveolar apically between the periosteum of bone the alveolar bone and the gingiva.
  • 11. Function of gingival fibers: They form a rigid cuff around the tooth that can add stability and resist gingival displacement.
  • 12. b- The transseptal ligament: *It connects two adjacent teeth. Dentin *The ligament runs from the cementum of one tooth over the crest of the alveolus to the cementum of the adjacent tooth. Bone *Function: Dentin Resists mesial and distal tooth separation.
  • 13. c- The alveolodental ligament: 1-Alveolar crest group: radiate from the crest of the alveolar process and attach themselves to the cervical part of the cementum. Function: resists vertical and intrusive forces. Bone Dentin 2-Horizontal group: The fiber bundles run from the cementum to the bone at right angle to the long axis of the tooth. Function: resists horizontal and tipping forces.
  • 14. 3- Oblique group: The fiber bundles run obliquely. Their attachment in the bone is somewhat coronal (higher) than the attachment in the cementum. bone The greatest number of fiber dentin bundles are found in this group. Function: *Performs the main support of the tooth against masticatory forces. *Resists vertical and intrusive forces.
  • 15. 4- Apical group: The bundles radiate from the dentin apical region of the root to the surrounding bone bone Function: resists vertical force. 5- Interradicular group: dentin The bundles radiate from the interradicular septum to the furcation of the multirooted tooth. bone Function: resists vertical and lateral forces.
  • 18. B- Accessory fibers: They are 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.
  • 19. 2- Oxytalan fibers These are immature elastic (pre- elastic) fibers. They need special stains to be demonstrated. They tend to run in an axial direction, one end being embedded in bone or cementum and the other in the wall of blood vessels. At the apical region they form a complex network.
  • 20. The functions of oxytalan fibers: 1-Support nerves. 2- Support blood vessels. 3- Help fibroblasts migration.
  • 21. Histological structure The periodontal ligament is formed of : cells Intercellular substances Synthetic Fibers, Resorptive ground substances Progenitor blood vessels, Defensive nerves & lymphatics.
  • 22. The cells Synthetic fibroblasts, osteoblasts and cementoblasts. cells Resorptive cementoclasts , osteoclasts and fibroclasts. cells Note that fibroblasts perform both synthetic and resorptive activities. Progenitor undifferentiated mesenchymal cells cells Epithelial cells remnants of the epithelial Defensive macrophage, lymphocytes root sheath of Hertwig cells and mast cells
  • 23. Synthetic Cells of PDL  Fibroblasts  Cementoblasts  Osteoblasts
  • 24. PDL Fibroblasts • Oriented parallel to collagen fibers •Are motile due to contractile properties •Show numerous microtubules & microfilaments •Assembles procollagen molecules •Perform fibroclastic function •Ingestion collagen fibers •Contains intracellular collagen profiles & vacoules •Contains lysosomal system
  • 25. Cementoblasts Osteoblasts Both are rich in alkaline phosphatase activity.
  • 26. Resorptive Cells of PDL • osteoclasts • cementoclasts Both are rich in acid phosphatase activity.
  • 27. Progenitor cells .U. M. C • Can undergo mitotic devision • Can differentiate to different types of cells • Have small, closed- face nucleus • Little amount of cytoplasm • Found close to blood vessels
  • 28. Defensive Cells of PDL Macrophages Mast cells lymphocytes Note: There are no plasma cells.
  • 29. Epithelial Cells: remnants of the epithelial .root sheath of Hertwig •They are separated from the surrounding connective tissue by a basal lamina. •They show low cells turnover, although they may proliferate to form cysts or tumors.
  • 31. Histological structure The periodontal ligament is formed of : cells Intercellular substances Synthetic Fibers, Resorptive ground substances Progenitor blood vessels, Defensive nerves & lymphatics.
  • 32. Interstitial tissues *They are found between the fibers of the periodontal ligament. *They are areas that contain some of the blood vessels, lymphatic and nerves. *They are surrounded by loose connective tissue.
  • 33. Blood supply 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 constitute the main blood supply. 3- Branches from the apical vessels that supply the dental pulp.
  • 34. Nerve supply: 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 foramina in the bone.
  • 35. Are responsible for Small nerve fibers pain sensation Are responsible for Large nerve fibers touch & pressure (mechanoreceptors) •Stimulation of the mechanoreceptors initiates a reflex jaw opening. •This reflex is a protective mechanism to prevent forces applied to the teeth from reaching damaging levels.
  • 36. Functions of the periodontal ligament: 1- Supportive: Through the collagen fibers and the blood vessels. [ *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 and then acting as inelastic strings. *Also periodontal fibers being non elastic prevent the tooth from being moved too far.
  • 37. *Blood vessels and all the components of the ligament act together as a hydraulic damper or shock absorber with the ground substance and the tissue fluid.
  • 38. Dental implants lack periodontal ligament fibers and they have a rigid connection to bone (Osseointegration).
  • 39. Periimplant tissues Titanium implant Sulcular epithelium Juunctional epithelium Connective tissue Bone
  • 40. 2- Sensory: The periodontal ligament having the mechanoreceptors contributes to the sensation of touch and pressure on the teeth. proprioceptive reflex sudden overload inhibition of the activity of the masticatory muscles Opening the mouth
  • 41. 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. 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.
  • 42. 5- Protective 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.
  • 43. 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. The behavior of the blood in the capillaries may be simulated to a hydraulic brake. c- The nerves: By its mechanoreceptors nerves.
  • 44. The Age Changes of periodontal ligament *The periodontal ligament through aging shows Vasuclarity Cellularity Thickness *It may contain cementicles.
  • 45. 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.
  • 46. Thank you & good luck