PERIODONTAL LIGAMENT

PERIODONTAL
LIGAMENT
Dr. SUSHMITHA SHANKAR
POST GRADUATE STUDENT
DEPARTMENT OF PERIODONTOLOGY

CONTENTS
1. Introduction
2. Definitions
3. Synonyms
4. Development
5. Development of periodontal fibres
6. Extent And Shape
7. Average Width
8. Periodontal Ligament Homeostasis
9. Blood Supply
10. Nerve Supply
11. Lymphatics
12. Functions of PDL
13. Age changes in PDL
14. Clinical considerations
15. Conclusion
16. References

INTRODUCTION
The term
Periodontium arises
from Greek word
“Peri’’ meaning
around and “odont”
meaning tooth.
Tissues that invests
and support the
teeth are
collectively termed
Periodontium.
Periodontium
Gingiva
PDL
Alveolar
bone
Cementum

According to Carranza & Bernard,
“The periodontal ligament is the connective tissue that surrounds the root and connects it to
the bone. It is continuous with the connective tissue of gingiva and communicates with marrow spaces through
vascular channels in the bone’’
According to Orbans,
“The periodontal ligament occupies the periodontal space which is located between the
cementum and the periodontal surface of alveolar bone and extends coronally the most apical part of the lamina
propria of the gingiva’’
According to GPT,
“The periodontal ligament is the connective tissue that surrounds and attaches roots of teeth to
alveolar bone ’’
DEFINITIONS

SYNONYMS
 Periodontal membrane
 Alveolodental ligament
 Desmondont
 Pericementum
 Dental Periosteum
 Gomphosis

 The continuous proliferation of the internal and the external enamel epithelium forms the cervical loop
of the tooth bud
 This sheath of epithelial cells grows apically, in the form of Hertwig’s epithelial root sheath, between
the dental papilla and the dental follicle.
 The dental follicle cells located between the alveolar bone and the epithelial root sheath are
composed of two cells :
 Mesenchymal cells of the dental follicle proper.
 Mesenchymal cells of perifollicular mesenchyme.
DEVELOPMENT

As the root formation continues, cells in the
perifollicular mesenchyme gain their
polarity, cellular volume & synthetic activity
increases
They Actively synthesize and deposit collagen
fibrils and glycoproteins in the developing PDL
The developing pdl differentiates into osteoblast
,fibroblast and cementoblast.
Type 1 collagen is secreted
Assembles as collagen bundles on the bone and
cementum surface
Establish continuity across the ligament space
DEVELOPMENT

Immediately before tooth eruption, active fibroblasts
adjacent to cementum, lay down the alveolar crest fiber
bundle group
Brush like fibres from cementum and developing
alveolar process elongate, interwine and fuse as covalent
bonding and cross linking of individual collagen
molecule
First occlusal contact of tooth with its antagonist,
principle fibers around coronal third of root, horizontal
fibres are almost completely developed.
DEVELOPMENT OF PRINCIPLE FIBERS

The oblique fibers in middle third of the root are still being formed
As eruption continues, and definite occlusion is established, there
is progressive apical maturation of oblique fibre bundles.
With the formation of apical fiber group ,the definitive
periodontal ligament architecture is established.
DEVELOPMENT OF PRINCIPAL FIBERS

ORGANIZATION OF PDL
As the teeth begins to erupt, the orientation of ligament fiber changes
according to the stage of eruption (Grant and Bernick 1972)

EXTENT
 It extends coronally to the most apical part of the lamina propria of the gingiva, which is
continuous with the dental pulp at the apical foramen.
 It ranges in width from 0.15mm to 0.38mm (AR Tencate)
Depending on age Width According to functional state of tissue Width
11-16 yrs 0.21mm time of eruption 0.1-0.5mm
32-51 yrs 0.18mm at function 0.2-0.35mm
52-67 yrs 0.15mm hypofunction 0.1-0.15mm

 It is thinnest around the middle third of the root with an hour glass appearance.
 The ligament appears as a radiolucent area of 0.4-1.5mm between the radio opaque lamina dura of the
alveolar bone and cementum.
SHAPE

PERIODONTAL LIGAMENT HOMEOSTASIS
 A remarkable capacity of the PDL is that it maintains its width more or less overtime despite the fact, that
it is squeezed in between two hard tissues.
 Studies indicate that cells of PDL, both during development and regeneration, secrete molecules that can
regulate the extent of mineralization and prevent ankylosis.
 PDL also has the capacity to adapt to functional changes.
•Functional demand increases
•Width of PDL can increase by
as much as 50%
•Fibre bundle increases in
thickness
•Functional demand decreases
•Narrowing of the ligament.
•Decrease in number and
thickness of the fiber bundles.

PDL
EXTRACELLULAR
SUBSTANCE
FIBERS
1. Collagen
2. Elastic-Oxytalan
3. Reticular
4. Secondary
5. Indifferent fiber plexus
GROUND SUBSTANCE
• Glycosaminoglycans
• Proteoglycans
• Glycoproteins
1.SYNTHETIC CELLS
Fibroblasts
Osteoblasts
Cementoblasts
2.RESORPTIVE CELLS
Osteoclasts
Fibroblasts
Cementoclasts
3.PROGENITOR CELLS
4.EPITHELIAL RESTS OF
MALASSEZ
5.DEFENSE CELLS
Mast cells
Macrophages
Eosinophils
CELLS
PDL STRUCTURE

Characteristic of synthetic cell
1.Should be actively synthesizing ribosomes.
2.Increase in the complement of RER and Golgi apparatus.
3.Large open face or vesicular nucleus containing prominent nucleoli.
4.Large numbers of mitochondria.
5.abundant cytoplasm
1) SYNTHETIC CELLS

Fibroblasts- most common cells in PDL.
65% -total cellular population.
Elongated cells with pseudopodia like process.
Synthesize higher quantities-chondroitin sulphate & lesser quantities-
heparan sulphate and hyaluronic acid
The fibroblast is stellate shaped cell which produces:
1. COLLAGEN FIBERS
2. RETICULIN FIBERS
3. OXYTALAN FIBERS
4. ELASTIC FIBRES
FIBROBLASTS
 SHARPEYS FIBRES.

FUNCTIONS OF FIBROBLASTS
• The role of fibroblast is to produce the structural connective tissue protiens, collagen and elastin, as
well as PDL ground substance.
• Secretes an active collagenase and a family of enzymes collectively known as MMPs
• Characterized by the rapid turnover of extra cellular matrix
• Organize fibrous network and generate force for tooth eruption.
• Has capacity to give rise to cementoblasts and osteoblasts.
• Maintains normal width of PDL.
• Regulate fast collagen turnover by phagocytosing old collagen fibers.

• They are bone forming cells lining the tooth socket and are cuboidal in
shape with a prominent round nucleus at the basal end of the cell.
• Microfilaments are prominent beneath the cell membrane at the
secreting surface
• The cells contact one another through desmosomes and tight junctions
OSTEOBLASTS

• These cells line the surface of cementum.
• They are cuboidal with a large vesicular nucleus ,with one or more nucleoli and abundant
cytoplasm.
• All the intracytoplasmic organelles required for protein synthesis and secretion are present.
CEMENTOBLASTS

2) RESORPTIVE CELLS
OSTEOCLASTS
• These resorb bone and tend to be large and multinucleated but can also
be small and mononuclear.
• Multinucleated Osteoclasts are formed by fusion of precursor cells
similar to circulating monocytes
• The part of the plasma membrane lying adjacent to bone that is being
resorbed is raised into characteristic folds and is termed the Ruffled or
Striated border.
• The Clear Zone.
• Howship’s lacunae

 Cementoclasts resemble osteoclasts and are occasionally found in normal functioning ligament.
 These cells occur in certain pathologic conditions, during resorption of deciduous teeth and when
regressive forces are applied on a tooth such as orthodontic therapy.
CEMENTOCLASTS

• All connective tissues including PDL contain progenitors cells that have the capacity to
undergo mitotic division and replace the differentiated cells dying at the end of their
lifespan.
• When stimulated appropriately, these cells undergo mitotic division and can differentiate
into fibroblasts, osteoblasts or cementoblasts.
3. PROGENITOR CELLS

4. EPITHELIAL CELL RESTS OF MALASSEZ
• These were first described by Malassez in 1884 and are
the remnants of the Hertwig’s epithelial root sheath.
• They lie about 25 μm from the cementum surface.
• They persist as network, strands, islands or tubule-like
structures near and parallel to the surface of the root.

5. DEFENSE CELLS
MAST CELLS
• These are relatively round or oval cell having a diameter
of about 12 to 15 um.
• Mast cell histamine plays a role in the inflammatory
reaction and have been shown to degranulate in
response to antigen – antibody reaction on their surface
.
• The release of histamine into the extracellular
environment causes proliferation of endothelial cells and
mesenchymal cells.

MACROPHAGES
• These are also found in the ligament and are predominantly located adjacent to blood vessels .
• Has a characteristic ultrastructure that permits it to be readily distinguished from fibroblasts.
• In the periodontal ligament macrophages may play a dual role:
Phagocytosing dead cells
Secreting growth factors that regulate the proliferation of adjacent fibroblasts.

EOSINOPHILS
• These are occasionally seen in the periodontal ligament.
• They posses granules that consist of one or more crystalloid structures.
• These cells are capable of phagocytosis.

EXTRACELLULAR SUBSTANCES
FIBERS
 Collagen
 Elastic- oxytalan
 Reticular
 Secondary
 Indifferent fiber
plexus
GROUND
SUBSTANCE
 Glycosaminoglycans
 Proteoglycans
 Glycoproteins

 The collagen is gathered to form bundles approximately 5 um in diameter.
 These bundles are termed as PRINCIPAL FIBERS
COLLAGEN FIBRES

 The main types of collagen in the PDL are Type I (70%) and Type III(20%).
 Type III collagen, is involved with collagen turnover, tooth mobility
 Small amounts of Type V and Type VI collagens and traces of Type IV and VII are also found in the
ligament, IV and VII are associated with epithelial cell rests and blood vessels.
 Type XII collagen occur only when the ligament is fully functional.

PRINCIPAL FIBERS
 The principal fiber group is the Alveolodental ligament, which consists of six fibers
groups

ALVEOLAR CRESAL GROUP Extend obliquely from the cementum just beneath the junctional
epithelium to the alveolar bone. Functions: Oppose lateral forces. Prevents extrusion & intrusion of tooth.
Protects deeper periodontal ligament structures.
HORIZONTAL GROUP They extend from rc to ab in horizontal direction at right angles to long axis of
tooth. Limited to the coronal 1/4
th
of the PDL space.
Function: Resist horizontal and tipping forces.
OBLIQUE GROUP Largest group of PDL fibres.Occupy 2/3rd of the ligament. Extend from cementum
in a coronal direction obliquely to the bone. Function: Resist vertical and intrusive forces.
APICAL GROUP : radiate in irregular fashion from cementum to the apical region of the socket. not
seen on incompletely formed roots. Functions:Prevent tooth tipping Resist luxation Protect blood, lymph
vessels and nerves
INTERRADICULAR GROUP: Th inserted into the cementum from the crest of interradicular
septum in multirooted teeth. Resists tooth tipping, torquing and luxation.
TRANSSEPTAL FIBRE GROUPextend interproximally over the alveolar bone crest and are embedded
in cementum of adjacent teeth.

SHARPEYS FIBERS
• The collagen bundles of the periodontal ligament embedded into
cementum and alveolar bone – are called as Sharpey’s fibers
• Sharpey’s fibers in Acellular cementum are fully mineralized.
• Those in Cellular cementum and bone are partially mineralized.
• Few Sharpey’s fibers pass uninterruptedly through bone of
the alveolar process, termed as Transalveolar fibers.

ELASTIC FIBERS
3 Types of elastic fibres, which are
ELASTIN FIBRES
(MATURE)
ELAUNIN
FIBERS
IMMATURE
OXYTALAN
FIBRES

ELASTIN FIBRES: Consist of microfibrillar component surrounding an amorphous core of elastin
protein. observed -in the walls of the afferent blood vessels.
ELUANIN- seen as bundles of microfibrils embedded in a relatively small amount of
amorphous elastin.
Functions :Regulate vascular flow Role in tooth support Facilitate fibroblast attachment and migration
OXYTALIN – Consist of microfibrillar component only ;
type IV collagen Role in tooth support

 These are fine immature collagen fibers with argyrophilic staining properties
 They are related to basement membrane of blood vessels and epithelial cells which lie within the periodontal
ligament.
RETICULAR FIBERS

• Located between and among the principal fibers.
• These are relatively non-directional and randomly oriented.
• Appear to transverse the periodontal ligament space corono-apically and are often associated with
paths of vasculature and nervous elements.
SECONDARY FIBERS

 These are small collagen fibers associated with the large principal collagen fibers.
 These fibres run in all directions, forming a plexus called indifferent fiber plexus.
 Once the tooth has erupted into clinical occlusion such intermediate plexus is no longer demonstrable.
INDIFFERENT FIBRE PLEXUS

 The ground substance is the gel like matrix synthesized by the fibroblast family & fills the space
between the fibers and cells.
GROUND SUBSTANCE

COMPOSITION
Consists of a biochemically complex, highly hydrated, semisolid gel.
Water content of 70%.
Consists mainly of Glycosaminoglycans, proteoglycans, glycoproteins.

STRUCTURES PRESENT IN CONNECTIVE TISSUE
Following discrete structures are present
BLOOD
VESSELS
NERVES
LYMPHATICS CEMENTICLES

BLOOD VESSELS
 Branches in the
PDL from apical
vessels that supply
the dental pulp
 Branches from
intra-alveolar
vessel, runs
horizontally,
penetrating the
alveolar bone to
enter the PDL.
 Branches from
gingival vessels,
enter the PDL from
the coronal
direction.

 The blood supply increases in the PDL from incisors to molars.
 The single rooted teeth have more supply at the gingival third followed by apical third and least in the
middle third.
 In molars it is equal in middle and apical areas but is greater at the gingival area.
FUNCTIONAL VARIATIONS AT DIFFERENT SITES.

NERVE SUPPLY
2 Types of nerve fibers
1) Sensory
2) Autonomic.
4 types of nerve transmissions:
1. Free endings with tree like ramifications :
Located at regular intervals along the length of the root.
Nociceptors and mechanoreceptors

 Found around the root apex.
 Appear to be dendritic and end in terminal expansions among the PDL fiber
bundles.
 Are mechanoreceptors.
Meissner's corpuscles :
 coiled endings
 Found in mid region of PDL
 for tactile perception
Encapsulated spindle type :
 Temperature receptor
 associated with root apex.
Ruffini’s corpuscles

• The lymph from the periodontal tissues drains into the lymph nodes of head and neck.
• It may course apically to pass through the fundus of the socket or they may pass through the cribriform
plate to empty into larger channels pursuing intra osseous paths.
• The flow is via the alveolar lymph channels which are joined by the dental and inter radicular lymph
channels
LYMPHATIC DRAINAGE

 Calcified bodies sometimes found in the PDL.
 These bodies are seen in older individuals, and they may remain free in the connective
tissue and may fuse into large calcified masses, or they may be joined with the
cementum.
 When they are adherent to the cementum, they form excementoses.
CEMENTICLES

FUNCTIONS OF PDL
SUPPORTIVE PHYSICAL
FORMATIVE &
REMODELLING
SENSORY
HOMEOSTATIC NUTRITIVE

SUPPORTIVE FUNCTION
 When a force is applied on the tooth either by mastication or orthodontic tooth movement there is
compression of PDL on one side and widening of PDL on the other side.
 Load on the PDL is dissipated to alveolar bone through the oblique principle fibers of PDL, when
placed in tension and on release, an elastic recoil of tissue enables the tooth recovery to its original
position.
 The compressed PDL provides support for the loaded tooth, water molecules and other molecules
bound to collagen act as cushion for displaced tooth. The pressure of blood vessels also provides a
hydraulic cushion for the support of the teeth.

PHYSICAL FUNCTION
 Provides soft tissue ‘casing’ in order to protect the vessels and nerves from injury due to mechanical
forces.
 Transmit the occlusal forces to the bone.
 Attaches the teeth to the bone.
 Maintains the gingival tissues in their proper relationship to the teeth.
 Shock absorption resists the impact of occlusal forces.

MECHANISM OF TOOTH SUPPORT
3 theories have been proposed
States that the principal fibers of PDL are the major factors
in supporting the tooth and transmitting the forces to the
bones.
States that the displacement of tooth is largely controlled by
fluid movement, with fibers having only a secondary role.
TENSIONAL
THEORY
VISCOELASTIC
THEORY

FORMATIVE AND REMODELING FUNCTION
• Cells of the PDL participate in the formation and resorption of cementum and
bone, which occur during physiologic tooth movement,
• accommodation of the periodontium to occlusal forces
• in the repair of injuries.
• Old cells & fibers are broken down & replaced by new ones, & mitotic activity
can be observed in the fibroblasts & endothelial cells

NUTRITIONAL & SENSORY FUNCTION
• Since PDL has a rich vascular supply it provides nutrition to the cementum, bone, and
gingiva.
• The PDL is abundantly supplied with sensory nerve fibers that are capable of transmitting
tactile, pressure and pain sensations via the trigeminal pathway.
• Nerve bundles pass into the PDL from the periapical area and through channels from the
alveolar bone that follow the course of the blood vessels.

• PDL adapts to the rapidly changing applied force and it has a capacity to maintain its width at
constant dimensions throughout its lifetime.
• It is evident that the cells of PDL have the ability to resorb and synthesize the extracellular substance
of the connective tissue of the ligament , alveolar bone and cementum.
HOMEOSTATIC

• One of the prominent changes seen in the calcified tissues of periodontium
• With aging the activity of the PDL tissue decreases because of restricted diets and therefore
normal functional stimulation of the tissue is diminished.
• Any loss of the gingival height related to gingival and periodontal disease promotes
destructive changes in the pdl.
AGE CHANGES IN PDL
Cell number and their activity
Collagen turnover
Elastic fibers
PDL width due to masticatory load

• The primary role of the periodontal ligament is to support the tooth in the bony socket.
• Its thickness varies in different individuals, in different teeth in the same person, and in
different locations on the same tooth .
CLINICAL CONSIDERATION

1) Acute trauma to the periodontal ligament, accidental blows or rapid mechanical separation may produce
pathologic changes such as
• fractures or resorption of the cementum,
• tears of fiber bundles
• hemorrhage
• necrosis.
• The adjacent alveolar bone is resorbed, the PDL is widened, and the tooth becomes loose.
• When trauma is eliminated, repair usually takes place.

2)Orthodontic tooth movement depends on resorption and formation of both bone and periodontal
ligament.
These activities can be stimulated by properly regulated pressure and tension.

• If the movement of teeth is within physiologic limits, the initial compression of PDL on
the pressure side results in bone resorption whereas on the tension side bone apposition
is seen.
• Application of large forces results in necrosis of PDL and alveolar bone on the pressure
side
• Movement of the tooth will occur only after the necrotic bone has been resorbed by
osteoclasts located on its endosteal surface.

3) Inflammatory diseases of the pulp progress to the apical periodontal ligament and replace its fiber
bundles with granulation tissue .
• This lesion , called a periapical granuloma may contain epithelial cells that undergo proliferation and
produce a cyst

4) Chronic inflammatory periodontal disease is the commonest
pathology related to PDL .
The toxins released from the bacteria in the dental plaque and
metabolites of the host’s defense mechanism destroy the PDL and
the adjacent bone very frequently.
This leads to tooth mobility and further loss of tooth.

5) Fusion of alveolar bone and cementum with obliteration of the periodontal ligament is termed
Ankylosis.
Occurs in teeth with cemental resorption which suggests that it may represent a form of abnormal repair.
May also develop after chronic periapical inflammation , tooth implantation and occlusal trauma around
embedded teeth.

• Osseo integration is an intimate bone to implant contact without presence of PDL in between.
• So this is not the ideal substitute for natural tooth replacement.
• Future studies will be directed to regenerate PDL fibers as an interface between bone and implant.
• Some fiber bundles are present which have a cuff like circular orientation.
• The role of these fibers remains unknown but it appears that their presence helps to create a soft – tissue
seal around the implant .

GUIDED TISSUE REGENERATION
The periodontal ligament is unique among the periodontal tissues, in that it
contains precursor cells for the production of the entire attachment
apparatus of the tooth, i.e. cementum, periodontal ligament and bone.
By using biologically compatible barriers, the therapist is able to promote
the ingrowth of these cells into damaged sites where a new periodontal
attachment is needed.
This therapeutic principle is known as guided tissue regeneration.

RECENT ADVANCES IN PERIODONTAL REGENERATION: A
BIOMATERIAL PERSPECTIVE
Yongxi Lianga, Xianghong Luanb, Xiaohua Liua,
Periodontal disease (PD) is one of the most common inflammatory oral diseases, affecting approximately 47% of adults aged
30 years or older in the United States. If not treated properly, PD leads to degradation of periodontal tissues, causing tooth
movement, and eventually tooth loss.
Conventional clinical therapy for PD aims at eliminating infectious sources, and reducing inflammation to arrest disease
progression, which cannot achieve the regeneration of lost periodontal tissues. Over the past two decades, various
regenerative periodontal therapies, such as guided tissue regeneration (GTR), enamel matrix derivative, bone grafts,
growth factor delivery, and the combination of cells and growth factors with matrix-based scaffolds have been
developed to target the restoration of lost tooth-supporting tissues, including periodontal ligament, alveolar bone, and
cementum. This review discusses recent progresses of periodontal regeneration using tissue-engineering and regenerative
medicine approaches.
Specifically, we focus on the advances of biomaterials and controlled drug delivery for periodontal regeneration in recent
years. Special attention is given to the development of advanced bio-inspired scaffolding biomaterials and
temporospatial control of multi-drug delivery for the regeneration of cementum-periodontal ligament-alveolar bone
complex. Challenges and future perspectives are presented to provide inspiration for the design and development of
innovative biomaterials and delivery system for new regenerative periodontal therapy.

STEM CELLS FOR PERIODONTAL REGENERATION
Pejcic , Kojovic , Mirkovic , Minic
Periodontal regeneration is considered to be biologically possible but clinically unpredictable.
In periodontitis, inflammation manifests clinically as loss of supporting periodontal tissues and regeneration
of damaged tissue is the main goal of treatment. For decades, periodontists have sought to repair the damage
through a variety of surgical procedures, and use of grafting materials and growth factors, and of barrier
membranes. Reports have emerged that demonstrate which populations of adult stem cells reside in the
periodontal ligaments of humans and other animals. This opens the way for new cell-based therapies for
perio-dontal regeneration.
Mesenchymal stem cells can effectively regenerate destroyed periodontal tissue.
Mesenchymal progenitor cells, isolated from the dental follicle of human third-molar teeth can generate perio-
dontal ligament-like tissue implying that they may be a useful for regenerative periodontal therapy.
Differentiation Potential of Periodontal Ligament Stem Cells. Previous studies have demonstrated that periodontal
ligament stem cells can build a typical cementum-periodontal ligament-like structure.
This review provides an overview of adult human stem cells and their potential use in perio-dontal regeneration.

1. Newman’s and Carranza’s Clinical Periodontology-13th Edition
2. Clinical Periodontology and Implant dentistry- Jan Lindhe, 4th edition
3. Orban’s Oral Histology and Embryology - 13th edition
4. Development and general structures of the periodontium. Periodontol 2000;24,2000;9-22
5. Role of physical forces in regulating the form and function of the periodontal ligament.
Periodontology 2000;vol24;56-72
6. Recent advances in periodontal regeneration: a biomaterial perspective yongxi lianga, xianghong
luanb, xiaohua liua
7. Stem cells for periodontal regeneration pejcic, kojovic, mirkovic, minic
References

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