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PRESENTED BY:PRESENTED BY:
DR SHILPA SHIVDR SHILPA SHIV
I MDSI MDS
DEPT OF PERIODONTOLOGYDEPT OF PERIODONTOLOGY
 Introduction
 Definition
 Extent and shape
 Average width
 Evolution of PDL
 Development
 Orientation of PDL fibe...
 Collagen
 Ground substance
 Functions of PDL
 Blood supply
 Venous drainage
 Lymphatic
 Nerve supply
 Age change...
 The normal periodontium is a unique and a complex
dynamic structure; each of its components having distinct
functions t...
 Periodontal ligament is composed of soft complex vascular and
highly cellular connective tissue that surrounds the toot...

 Soft, richly vascular and cellular connective tissue which
surrounds the roots of the teeth and joins the root
cementu...

 In the coronal direction it is continuous with lamina
propria of gingiva & is demarcated by the alveolar crest
fibers....

 Depending on age
11-16 yrs - 0.21mm
32-52 yrs - 0.18mm
51-67 yrs - 0.15mm
 According to functional state of the tissu...

 The evolutionary step from reptile to mammal included a
series of coordinated changes in the jaws.
 The central point...

 In mammals-
 Fate of dentary- Forms the mandible
 Others were lost or changed into middle ear ossicles
Articulare- m...
 Change from many boned to single boned mandible brings in a
radical change in mode of growth.
 Reptiles –Sutural
 Mam...

 Begins with root formation
(Tencate et al.,1972)
& prior to tooth eruption.
 Varies among species, tooth families
& b...

 The periodontal tissues are derived from dental follicle which
in turn originates from dental papilla.
 It has also b...

-

 Closely related to root formation
Development of principal fibersDevelopment of principal fibers

Development….
Fig 2Fig 1 Fig 3

 Terminal portions of principal fibers that insert into
cementum and bone are termed as Sharpey’s fibers.
 The princip...

Orientation of PDLOrientation of PDL
 Mature PDL can be sub divided into 3 regions:
-Bone related region- rich in cells
-Cementum related region- dense and o...

 CELLULAR ELEMENTS
a. Connective tissue cells
Synthetic Resorptive
-Fibroblasts - Fibroblasts
-Cementoblasts - Cementoc...


Basic properties
 Increased transcription of RNA and production of
ribosomes which is reflected by a large open faced o...
 Most common cells in PDL
 Occupies about 30% of the volume of the periodontal
ligament space in rodents (Beertsen W, B...
 Phenotypically distinct & functionally different sub
populations of fibroblasts exist in adult PDL.
 They may have dif...

 The PDL fibroblasts are large cells with an extensive
cytoplasm containing in abundance, all organelles
associated wit...

 The migratory and contractile activity of fibroblast
is because of the presence of contractile protein actin
and myosi...
 Chemo attractants produced locally or by the hard tissues
bordering the ligament may have a role in this process.
 Dir...

 Although technically situated within the PDL, bone
and cementum cells are properly associated with the
hard tissues th...

 Fibroblasts :
- Exhibit lysosomes that contain fragments of
collagen that appear to be undergoing digestion.
- Dual ac...

 Cell division ---- daughter cell
---- undifferentiated progenitor
CHARACTERISTICS
 Small cells
 Close faced nucleus
...

 Mallassez – 1884
 Remnants of HERS and are formed close to cementum
 Most numerous in the apical area & cervical are...

ELECTRON MICROSCOPIC STRUCTURE
 Attached to one another by desmosomes
 Exhibit tonofilaments
 Isolated from CT cells ...

Fig. shows the presence of clusters of epithelial cells (ER) in the
periodontal ligament. These cells, called the epithe...
 Include neutrophils, lymphocytes, macrophages,&
eosinophil's.
MAST CELLS
 Small round or oval cell; Diameter 12-15µm.
...
CHARACTERISTICS
 Found adjacent to the blood vessels
 Nucleus has a regular contour and may be horse shoe or
kidney sha...

CementiclesCementicles
 Calcified masses, adherent to or
detached from the root surfaces
(O.J. Mikola, Wm.H. Bauer,1949...

 Too small to be seen on IOPA, seldom being larger than
0.2-0.3 mm. in diameter.
 No clinical significance.
 Actually...

 Small spicules of cementum torn from the root
surface or fragments of bone detached from the
alveolar plate (Bosshardt...
PRINCIPAL FIBRES
 The most important elements of PDL are the principal
fibers which are collagenous and follow a wavy pa...

 The adult human PDL fibers are slightly thicker than other
mammalian species and measure about 54-59 nm in diameter.
...

 Is derived from the French word collagene to
designate connective tissue constituents that
produce glue.
 Collagen mo...

STRUCTURE
 All collagens are composed of 3 polypeptide chains
coiled around each other to form the typical triple
helix...

 Made up of 3 polypeptide chains
 α chains that are left handed chains assembled into a triple
helix with a right hand...

 The amount of collagen in a tissue is determined by its
hydroxy proline content.
 There are at least 19 recognized co...

 Type I, III, V, XII – Periodontal Ligament
 Type VI, II – cartilage
 Type IV - Basement membrane
 Type VI – Ligamen...

 The ligament fibers and Sharpey’s fibers are composed of
interstitial collagen type III and I
 Collagen V is associat...

 Synthesized by - Fibroblasts, chondroblasts,
osteoblasts, odontoblasts and other cells.
 The steps involved in biosyn...
Shortened collagen molecules align as 5-unit, quater staggered microfibrils,
which assemble in parallel fashion giving ris...
Collagen microfibrils, fibrils, fibers, and bundles

Collagen RegulationCollagen Regulation
 A variety of growth factors and cytokines regulate collagen
production
 The co...
1. Intracellular degradation - Selective ingestion of collagen
fibrils by fibroblasts.
2. Extracellular degradation - Deg...

Principal fibers of PDLPrincipal fibers of PDL
 Trans septal
 Alveolar crest group
 Horizontal
 Oblique
 Apical
 I...

 Extend Inter proximally over the alveolar bone crest
and are embedded in the cementum of adjacent
tooth.
 Are a remar...

 Extend obliquely from the cementum just beneath
the junctional epithelium to the alveolar crest.
 Fibers also run fro...

HORIZONTAL GROUP (10-15%)
 Extend at right angles to the long axis of tooth from
cementum to the alveolar bone.
OBLIQUE...
APICAL GROUP
 Radiate in a rather irregular fashion from the cementum to
the bone at the apical region of the socket .
...
 The terminal portion of principal fibers of periodontal
ligament, that are inserted into cementum and alveolar
bone are...

Elastin FibersElastin Fibers
 Restricted to walls of blood vessels in humans
 PDL fibers do not contain mature elastin...

Oxytalan FibersOxytalan Fibers
 Are micro fibrils
 Run in apico-coronal direction to bend and attach at
cervical third...
 Are immature elastic fibers consisting of micro fibrils
within small quantity of elastin
 An elastic meshwork has been...

 Small Collagen fibers in association with the larger
principal collagen fiber
 Run in all directions forming a plexus...
 Fills the space between the fibers and cells
 Overlooked possibly because difficult to investigate and
not recognized ...
 Large group of anionic macromolecules that consists of a
protein core to which are attached hexose amine
containing pol...
 The primary function of these molecules is to bind cells to
extracellular elements.
 Most widely studied is FIBRONECTI...

 TENASCIN is an adhesive glycoprotein synthesized
at specific times and location during embryogenesis.
 In adult its d...

1. Physical
2. Formative and Remodeling
3. Nutritive
4. Sensory
5. Regulation of periodontal ligament width
Functions Of...

1. Provision for a soft tissue ‘CASING’ to protect the vessels
and nerves from injury by mechanical forces .
2. Transmis...
Tensional TheoryTensional Theory Ascribes the principal fibers of PDL the major responsibility in
supporting the tooth an...
Viscoelastic TheoryViscoelastic Theory According to this, the displacement of tooth is largely
controlled by fluid moveme...

Transmission Of OcclusalTransmission Of Occlusal
Forces to boneForces to bone
 Arrangement is like suspension bridge or...
Distribution of faciolingual forces (arrow) around the axis of rotation (black
circle on root) in a mandibular premolar. T...

 The apical portion of the root moves in a direction
opposite to the coronal portion.
 Areas of tension→ Principal fib...

FORMATIVE &FORMATIVE &
REMODELLINGREMODELLING
 Cells have the capacity to resorb & synthesize the
extracellular substan...

 Sodek (1977) has demonstrated that the periodontal
ligament incorporates proline at least 5 times faster
than gingiva ...

 Sodek ,1977 found collagen synthesis in PDL of adult rat
to be
- two fold greater than that of gingiva,
- four fold gr...

 Half-life for collagen turnover: in ligament – 1 day,
in bone – 6 days
in gingiva - 5 days,
in skin - 15 days
 Accord...

 PDL supplies nutrients to the cementum , bone, and
gingiva by way of blood vessels and provides
lymphatic drainage.
 ...

 Periodontal ligament provides the most efficient
proprioceptive mechanism
 4 types of neural terminations are seen
1....

 The extracellular signal-regulated kinase 1 and 2
(ERK-1/2) have been implicated in the inflammation
dependent sensiti...
 Actin binding protein-280 plays an important role in
mechano protection by:
1. Reinforcing the membrane cortex thereby ...

 An important measure of periodontal ligament
homeostasis.
 The ability of periodontal ligament cells to synthesize
an...
 Transforming growth factor-β isoforms -synthesized by
periodontal ligament cells can dose-dependently down-
regulate os...
 Pro-inflammatory cytokine interleukin-1 (Shimizu N et al
1995) and one of the isoenzymes responsible for
prostaglandin ...

Blood SupplyBlood Supply
 Inferior & superior
alveolar arteries to the
mandible & maxilla -
reaches the PDL from 3
sour...
Blood supply….
 Branches of the intraseptal
vessels – perforate the lamina
dura & enter the ligament.
After entering th...

 Perforating channels are more abundant in the
maxilla than in the mandible, & more in the posterior
than in the anteri...

 Specialized feature of the PDL
 Fenestrated capillary beds differ from continuous
capillary beds in that the diffusio...

 Frohlich (1964) - diagonal symmetry of the
periodontal vessels
 If there is abundant vascularity palatally at the api...

Nerve SupplyNerve Supply
 The nerve follow
almost the same
course as the blood
vessels.
 Nerve bundle divide
→ myelina...

1.Free nerve endings
- terminal arborization of thick/fine myelinated fibers
- 0.2-1 um in diameter
- fine, nonmyelinate...
 development of a new technique in which the axons can
be radioactively labeled & visualized by
radioautography
 The PD...

 The vast majority of the nerve endings –
unencapsulated, Ruffini-like mechanoreceptors &
free nerve endings.
 In expe...

Absence of PDL aroundAbsence of PDL around
implantimplant
 important clinical consequences
 No resilient connection ex...

 Accompany the arterial supply.
 Venules receive the blood through the abundant
capillary network. Also, arterio-venou...

 Lymph vessels - originate as cul-de-sac in PDL
 course apically - pass through the fundus of the
socket or they may p...
 The cell number and cell activity decreases with aging.
 One of the prominent changes seen in the calcified tissues
of...

 With aging the activity of the PDL tissue decreases
because of restricted diets and therefore normal
functional stimul...

 The primary role of the periodontal socket is to support
the tooth in the bony socket .
 Its thickness varies in diff...
 The adjacent alveolar bone is resorbed the PDL is
widened and tooth becomes loose .When trauma is
eliminated repair usu...
 Application of large forces results in necrosis of PDL and
alveolar bone on the pressure side and movement of the
tooth...
 Chronic inflammatory disease is common pathology
related to PDL .
 The toxins released from the bacteria in the dental...
 Various surgical techniques like Guided Tissue
regeneration are being used for correction of Periodontal
destruction .
...
 Fusion of alveolar bone and cementum with obliteration
of the periodontal ligament is termed Ankylosis.
 Occurs in tee...

 Osseo integration is an intimate bone to implant contact
without presence of PDL in between.
 So this is not the idea...
 Within physiologic limits, the PDL can accommodate
increased function with
- an increase in width,
- a thickening of it...

 To have any chance of success , it is essential to maintain the
viability of PDL .
 Avoid dehydration of PDL.
 Avoid...
 Cemento-ossifying fibroma – Middle age, mandible
(midbody), Women Predilection (slight) & Blacks, Well
Circumscribed
 ...
 Nishimura et al, 1998 - PDL cells - susceptible to hyper &
hypoglycemia & effects - mediated via the integrin system.
...

 Thin radiolucent line interposed between the root &
lamina dura.
 Occlusal Trauma → widened PDL space or funneling
of...
 Gestrelium et al, 1997 studied effects of EMD on periodontal
ligament cell migration, attachment, proliferation,
biosyn...

PROGRESSIVE SYSTEMIC SCLEROSIS
Radio graphically ---- PDL widening up to 3mm
thickening
Collagen ---- dense, mature & ...
LATHYRISM
 Condition caused by drugs that inhibit cross linking in
collagen & elastin (cystamine)
 Fragile collagen fib...
FOOD TEXTURE
Little correlation between the advent of soft, fiber deficient
diet & dental health.
Significant factor in...
CARBOHYDRATES
 Refined carbohydrates in the diet influence the severity of
PDL disease in humans (Holloway et. Al 1963)
...
PROTEINS
 Deficiency of protein might be expected to produce
changes within it.
 Reduction in PDL transseptal fibers (S...
REGENERATION is the reproduction or reconstitution of a
lost or injured part.
REPAIR is the healing of a wound by tissue ...

 NEW ATTACHMENT is defined as the union of
connective tissue or epithelium with a root surface
that has been deprived o...
 Carranza’s Clinical Periodontology, 10th
Edition
 Clinical Periodontology and Implantology by Jan Lindhe, 5th
edition
...

 Bartold PM, Walsh LJ, Sampath Narayan A. Molecular and cell
biology of gingiva. Periodontol 2000, Vol. 24, 2000, 28–55...

 Xiong J, Gronthos S, Bartold PM. Role of the epithelial cell
rests of Malassez in the development, maintenance and
reg...
PDL, PERIODONTAL LIGAMENT.
PDL, PERIODONTAL LIGAMENT.
PDL, PERIODONTAL LIGAMENT.
PDL, PERIODONTAL LIGAMENT.
PDL, PERIODONTAL LIGAMENT.
PDL, PERIODONTAL LIGAMENT.
PDL, PERIODONTAL LIGAMENT.
PDL, PERIODONTAL LIGAMENT.
PDL, PERIODONTAL LIGAMENT.
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PDL, PERIODONTAL LIGAMENT.

  1. 1. PRESENTED BY:PRESENTED BY: DR SHILPA SHIVDR SHILPA SHIV I MDSI MDS DEPT OF PERIODONTOLOGYDEPT OF PERIODONTOLOGY
  2. 2.  Introduction  Definition  Extent and shape  Average width  Evolution of PDL  Development  Orientation of PDL fibers  Structure  Biochemical composition  Cellular elements  Periodontal fibers ContentsContents
  3. 3.  Collagen  Ground substance  Functions of PDL  Blood supply  Venous drainage  Lymphatic  Nerve supply  Age changes & Clinical considerations  Healing after periodontal surgery  Conclusion  References
  4. 4.  The normal periodontium is a unique and a complex dynamic structure; each of its components having distinct functions that are capable of adaptation during the life of the structure.  PDL is the soft, richly vascular and cellular connective tissue which surrounds the roots of teeth and joins the root cementum with the socket wall.  Synonyms: Desmodont, Gomphosis, Pericementum, Dental –periosteum, Alveolodental ligament, Periodontal membrane. IntroductionIntroduction
  5. 5.  Periodontal ligament is composed of soft complex vascular and highly cellular connective tissue that surrounds the tooth roots and connects to the inner wall of the alveolar bone (Mc Culloch CA, Lekic P, Mc Kee MD Periodontol 2000 24:56,2000)  It is that soft, specialized CT situated between the cementum covering the root of the tooth and bone forming the socket wall. (A.R.Tencate 1971)  It is a narrow and highly cellular CT that forms the interface between alveolar bone and cementum. (Periodontol 2000,vol.3,1993) DefinitionDefinition
  6. 6.   Soft, richly vascular and cellular connective tissue which surrounds the roots of the teeth and joins the root cementum with the socket wall. (Jan Lindhe 5th ed)  The periodontal ligament occupies the periodontal space, which is located between the cementum and the periodontal surface of alveolar bone and extends coronally to the most apical part of the lamina propria of the gingiva. (Orban’s)
  7. 7.   In the coronal direction it is continuous with lamina propria of gingiva & is demarcated by the alveolar crest fibers.  At the root apex it merges with the dental pulp.  PDL has the shape of an hour glass and is narrowest at the mid root level.  It ranges in width from 0.15-0.38mm. Extent & shapeExtent & shape
  8. 8.   Depending on age 11-16 yrs - 0.21mm 32-52 yrs - 0.18mm 51-67 yrs - 0.15mm  According to functional state of the tissues Time of eruption - 0.1- 0.5mm At function - 0.2-0.35mm Hypo function - 0.1-0.15mm Average widthAverage width
  9. 9.   The evolutionary step from reptile to mammal included a series of coordinated changes in the jaws.  The central point is the radical reconstruction of the mandible  In reptiles mandible consists of- Dentary Mandibular articulation - Articulare and Quadratum EvolutionEvolution
  10. 10.   In mammals-  Fate of dentary- Forms the mandible  Others were lost or changed into middle ear ossicles Articulare- malleus Quadratum- incus  Dentary developed a condylar process which formed the new temporomandibular joint, that for some time functioned with old articulare-quadratum joint- Double jointed forms
  11. 11.  Change from many boned to single boned mandible brings in a radical change in mode of growth.  Reptiles –Sutural  Mammals- Cartilage of condyle  Growth of mandibular body height  Tooth movement during eruption. Teeth move as unit independent of bones, by remodeling of periodontium. Growth changesGrowth changes
  12. 12.   Begins with root formation (Tencate et al.,1972) & prior to tooth eruption.  Varies among species, tooth families & between primary & secondary teeth. DevelopmentDevelopment
  13. 13.   The periodontal tissues are derived from dental follicle which in turn originates from dental papilla.  It has also been proposed that the mesenchyme deriving periodontium may have two differentiation compartments a. Alveolar clade --- Fibroblasts & osteoblasts b. Cementum clade --- fibroblasts & cementoblasts  The term dental follicle has been used by different authors to mean different things. Development….
  14. 14.  -
  15. 15.   Closely related to root formation Development of principal fibersDevelopment of principal fibers
  16. 16.  Development…. Fig 2Fig 1 Fig 3
  17. 17.   Terminal portions of principal fibers that insert into cementum and bone are termed as Sharpey’s fibers.  The principal fibers embedded in the cementum have a small diameter but are more numerous than those embedded in the alveolar bone proper.  In addition to these fiber types, small collagen fibers associated with larger principal fibers have been called as “Indifferent fiber plexus of Shefforfold” Development…
  18. 18.  Orientation of PDLOrientation of PDL
  19. 19.  Mature PDL can be sub divided into 3 regions: -Bone related region- rich in cells -Cementum related region- dense and ordered collagen fibers -Middle zone- few cells & thinner collagen fibrils
  20. 20.   CELLULAR ELEMENTS a. Connective tissue cells Synthetic Resorptive -Fibroblasts - Fibroblasts -Cementoblasts - Cementoclasts -Osteoblasts - Osteoclasts b. Epithelial cell rests c. Immune system cells d. Neuro-vascular elements • PERIODONTAL FIBERS • GROUND SUBSTANCE StructureStructure
  21. 21.
  22. 22.  Basic properties  Increased transcription of RNA and production of ribosomes which is reflected by a large open faced or vesicular nucleus containing prominent nucleoli.  Development of large quantities of RER covered by ribosomes.  Large amounts of golgi saccules and vesicles (seen as clear unstained areas in light microscope).  Large numbers of mitochondria.  Abundant cytoplasm. Cellular elementsCellular elements
  23. 23.  Most common cells in PDL  Occupies about 30% of the volume of the periodontal ligament space in rodents (Beertsen W, Brekelmans M, Everts V. 1978)  Appear as ovoid or elongated cells oriented along the principal fibers, exhibiting pseudopodia like processes.  In cross section, they may exhibit a stellate appearance with cytoplasmic process segregating individual fiber bundles of collagen fiber. FibroblastsFibroblasts
  24. 24.  Phenotypically distinct & functionally different sub populations of fibroblasts exist in adult PDL.  They may have different functions like secretion of different collagen types & production of collagenase.  Importantly in inflammatory situations, an increased expression of MMP occurs that aggressively destroys collagen.  Thus attractive therapies for controlling this may include host modulators to inhibit MMP. Fibroblasts…
  25. 25.   The PDL fibroblasts are large cells with an extensive cytoplasm containing in abundance, all organelles associated with protein synthesis and secretion.  They also have well developed cytoskeleton with a particularly prominent actin network. ATTACHMENTS  The fibroblasts of PDL are interconnected by gap junctions or adherence type of junctions.  The cells may attach to collagen via a fibro nexus type of attachment plaque and are likely to have the capacity to orient extracellular matrix. Fibroblasts…
  26. 26.   The migratory and contractile activity of fibroblast is because of the presence of contractile protein actin and myosin in their cytoskeleton.  It may:  Remain stationary and pull on adjacent structures  Crawl and cause the environment in which it lies to wrinkle. Fibroblasts…
  27. 27.  Chemo attractants produced locally or by the hard tissues bordering the ligament may have a role in this process.  Directed migration of cells is associated with polarity of organelles, the nucleus usually in the trailing portion of cell and golgi apparatus and centrioles are towards the leading edge of the cells.  They appear to be rich in alkaline phosphatase activity- an enzyme along outer plasma membrane that plays a key role in phosphate metabolism, probably in the mineralization process and in Acellular cementum formation. Fibroblasts…
  28. 28.   Although technically situated within the PDL, bone and cementum cells are properly associated with the hard tissues they form.  Osteoblasts line the bone surface of the ligament and may be either functional or resting, depending on the functional state of the ligament.  Cementoblasts are responsible for formation of cellular cementum. Osteoblasts & cementoblastsOsteoblasts & cementoblasts
  29. 29.   Fibroblasts : - Exhibit lysosomes that contain fragments of collagen that appear to be undergoing digestion. - Dual action  Osteoclasts & Cementoclasts: - Osteoclast cells resorb bone and tend to be large and multinucleated. - Cementoclasts resemble osteoclasts and are occasionally found in normal functioning PDL. Resorptive cellsResorptive cells
  30. 30.   Cell division ---- daughter cell ---- undifferentiated progenitor CHARACTERISTICS  Small cells  Close faced nucleus  Very little cytoplasm  Highest concentrations' close to blood vessels  Burst of mitosis occurs when pressure is applied Progenitor cellsProgenitor cells
  31. 31.   Mallassez – 1884  Remnants of HERS and are formed close to cementum  Most numerous in the apical area & cervical area. (Xiong J, Gronthos S, Bartold PM )  Form a lattice work and appear as either isolated cluster of cells or interlacing strands. They diminish in number with age and may undergo calcification to form cementicles. Epithelial rests of MallassezEpithelial rests of Mallassez
  32. 32.  ELECTRON MICROSCOPIC STRUCTURE  Attached to one another by desmosomes  Exhibit tonofilaments  Isolated from CT cells by basal lamina & inter connected by hemidesmosomes.  Contain keratinocyte growth factors.  Can proliferate and participate in formation of peri apical cysts and lateral root cysts.
  33. 33.  Fig. shows the presence of clusters of epithelial cells (ER) in the periodontal ligament. These cells, called the epithelial cell rests ofepithelial cell rests of MallassezMallassez, represent remnants of the Hertwig's epithelial root sheathHertwig's epithelial root sheath. The epithelial cell rests are situated in the periodontal ligament at a distance of 15-75 μm from the cementum (C) on the root surface. A group of such epithelial cell rests is seen in a higher magnification.
  34. 34.  Include neutrophils, lymphocytes, macrophages,& eosinophil's. MAST CELLS  Small round or oval cell; Diameter 12-15µm.  Contain numerous cytoplasmic granules(0.5-1 µm) that stain metachromatically with dyes like azure A and positively by PAS reaction.  Contain heparin & histamine.  Role of heparin is not clear. Histamine plays a role in inflammatory reaction. Occasionally seen in healthy PDL. It may cause proliferation of endothelial & mesenchymal cells. Defense CellsDefense Cells
  35. 35. CHARACTERISTICS  Found adjacent to the blood vessels  Nucleus has a regular contour and may be horse shoe or kidney shaped with a dense peripheral layer of chromatin.  Surface may be raised in microvilli.  Sparse RER with widely spaced polysomes.  Golgi apparatus is not well developed. DUAL ROLE 1. Phagocytosing dead cells 2. Secreting growth factors that regulate the proliferation of adjacent fibroblasts MacrophagesMacrophages
  36. 36.  CementiclesCementicles  Calcified masses, adherent to or detached from the root surfaces (O.J. Mikola, Wm.H. Bauer,1949)  Represent dystrophic calcification (example of regressive or degenerative change)  Develop from: calcified epithelial rests, calcified Sharpey’s fibers, Calcified, thrombosed vessels within the PDL, around small spicules of cementum or alveolar bone traumatically displaced into the PDL
  37. 37.   Too small to be seen on IOPA, seldom being larger than 0.2-0.3 mm. in diameter.  No clinical significance.  Actually a variety of calcified bodies may occur in the PDL, not all of which have the morphologic characteristics of cementum. Nevertheless, they have all been commonly known as cementicles.  The pattern of calcification often gives the appearance of a circular lamellated structure. Cementicles…
  38. 38.   Small spicules of cementum torn from the root surface or fragments of bone detached from the alveolar plate (Bosshardt DD, Selvig KA 1977)  If lying free in the PDL may resemble cementicles, particularly after they have undergone some remodeling through resorption & subsequent repair. Cemental Tears
  39. 39. PRINCIPAL FIBRES  The most important elements of PDL are the principal fibers which are collagenous and follow a wavy pattern when viewed in longitudinal section.  They are associated with abundant non collagenous proteins typically found in bone and cementum like osteopontin and bone sialoprotein.  They are thought to contribute to the regulation of mineralization and to tissue cohesion at sites of increased biomechanical strain. (Mc Kee MD, Zalzal S, Nanci A 1996) Periodontal fibersPeriodontal fibers
  40. 40.   The adult human PDL fibers are slightly thicker than other mammalian species and measure about 54-59 nm in diameter.  This relatively small diameter reflects the short half-life of ligament collagen, meaning that there is little time for continuous assembly.
  41. 41.   Is derived from the French word collagene to designate connective tissue constituents that produce glue.  Collagen molecule is rigid and resists stretching. Therefore it is utilized in tissues where mechanical forces should be transmitted without loss.  Organization of collagen depends upon the specific functional requirements in various CollagenCollagen
  42. 42.  STRUCTURE  All collagens are composed of 3 polypeptide chains coiled around each other to form the typical triple helix configuration. Variations are brought about by  Differences in assembly of the basic polypeptide chains  Different lengths of helix  Various interruptions in helix  Differences in the terminations of the helical mains Collagen…
  43. 43.   Made up of 3 polypeptide chains  α chains that are left handed chains assembled into a triple helix with a right handed twist. May be a homo-trimer or hetero-trimer.  Has a repeating gly-X-Y amino acid sequence in which X and Y are usually amino acid other than glycine.  Contain 2 unique amino acid hydroxy proline and hydroxy lysine along with glycine & proline (Carneiro J, Fava de Moraes F , 1955)  Collagen molecules are covalently linked through lysine derived intra and inter chain crosslink.  It is synthesized by fibroblasts, chondroblasts, osteoblasts UNIQUE STRUCTURAL PROPERTIESUNIQUE STRUCTURAL PROPERTIES THAT DISTINGUISH COLLAGENTHAT DISTINGUISH COLLAGEN FROM OTHER PROTEINSFROM OTHER PROTEINS
  44. 44.   The amount of collagen in a tissue is determined by its hydroxy proline content.  There are at least 19 recognized collagen species encoded by at least 25 separate genes, dispersed among 12 chromosomes (Embery et al 2000) Collagen classes a. Interstitial collagens ---- Type I,II,III b. Basement membrane type ---- Type IV,VI,VII c. Short chain collagens ---- Type IX,X Collagen…
  45. 45.   Type I, III, V, XII – Periodontal Ligament  Type VI, II – cartilage  Type IV - Basement membrane  Type VI – Ligaments, skin, bone  Type VII - Anchoring fibrils of basement membrane  Type IX - Cartilage  Type X, XI - Cartilage, Bone  Type XIII - Epidermis Cartilage Collagen…
  46. 46.   The ligament fibers and Sharpey’s fibers are composed of interstitial collagen type III and I  Collagen V is associated with these fibrils and is either buried within these fibrils or is found in the spaces between the fiber bundles.  Type VI - microfibrillar component associated with oxytalan fiber system.  Type XII contribute to the construction of 3-dimensional fibril arrangement- hence closely associated with regeneration of PDL. Collagen…
  47. 47.   Synthesized by - Fibroblasts, chondroblasts, osteoblasts, odontoblasts and other cells.  The steps involved in biosynthesis of collagen fiber involve - Intra cellular pro collagen synthesis - Extra cellular collagen biosynthesis & fibril/fiber formation. Formation of collagenFormation of collagen
  48. 48. Shortened collagen molecules align as 5-unit, quater staggered microfibrils, which assemble in parallel fashion giving rise to a regular series of gaps or holes within the fibril The C-terminal extension and part of N-terminal ones are removed by action of C- and N- proteinases in the secretory granules Secretory granules containing procollagen molecules formed at the transface of golgi complex Transported to the golgi complex where glycosylation takes place to the O-linked galactose residues
  49. 49. Collagen microfibrils, fibrils, fibers, and bundles
  50. 50.  Collagen RegulationCollagen Regulation  A variety of growth factors and cytokines regulate collagen production  The collagen mRNA levels may increase or decrease due to change in either the rate of collagen gene transcription or in mRNA stability.  TGF-β is an important mediator as it enhances the synthesis of collagen and other matrix components.  Interferon-γ suppress collagen gene expression.  During inflammation and wound healing, these substances are secreted by platelets, macrophages and other inflammatory cells.
  51. 51. 1. Intracellular degradation - Selective ingestion of collagen fibrils by fibroblasts. 2. Extracellular degradation - Degradation by enzymes secreted by cells  Cleaving of polypeptide chain occurs at gly-iso-leucin and gly-leu bonds in α1 and α2 chains respectively by enzymes collagenases.  These peptide bonds are located at approximately 1/4th of the length from C-terminal, thus fragments of 3/4th and 1/4th sizes are released.  These fragments are denatured and further degraded by other common tissue proteinases Collagen DegradationCollagen Degradation
  52. 52.  Principal fibers of PDLPrincipal fibers of PDL  Trans septal  Alveolar crest group  Horizontal  Oblique  Apical  Inter – radicular
  53. 53.   Extend Inter proximally over the alveolar bone crest and are embedded in the cementum of adjacent tooth.  Are a remarkably constant finding and are reconstructed even after destruction of the alveolar bone has occurred in periodontal disease.  Considered as belonging to the gingiva because they do not have osseous attachment. Transseptal GroupTransseptal Group
  54. 54.   Extend obliquely from the cementum just beneath the junctional epithelium to the alveolar crest.  Fibers also run from the cementum over the alveolar crest and to the fibrous layer of the periodontium covering alveolar bone  Functions – 1. Prevent extrusion of tooth (Carranza, 1956) 2. Resist lateral tooth movement Alveolar Crest GroupAlveolar Crest Group
  55. 55.  HORIZONTAL GROUP (10-15%)  Extend at right angles to the long axis of tooth from cementum to the alveolar bone. OBLIQUE GROUP (80-85%)  Largest group in the PDL. Extend from the cementum in a coronal directing obliquely to the bone.  Function - Bear the brunt of vertical masticatory stresses and transform them into tension on the alveolar bone.
  56. 56. APICAL GROUP  Radiate in a rather irregular fashion from the cementum to the bone at the apical region of the socket .  Do not occur on incompletely formed roots.  Resist forces of luxation, may prevent tooth tipping and protect the delicate blood vessels, nerves and lymphs at the apex. INTER RADICULAR FIBERS  Fan out from cementum to the tooth in the furcation areas of multi rooted teeth.  Other well formed fiber bundles inter digitate at right
  57. 57.  The terminal portion of principal fibers of periodontal ligament, that are inserted into cementum and alveolar bone are called Sharpey’s fibers.  The number and size of sharpey’s fibers varies with functional status of the tooth. Sharpey’s FibersSharpey’s Fibers Functional stage Pre-eruptive, eruptive stagePre-eruptive, eruptive stage Normal functionNormal function Completely embeddedCompletely embedded Fixed bridge abutmentFixed bridge abutment Density/100µ2 Diameter(µm) 53.453.4 3.03.0 2828 4.04.0 2.12.1 4.14.1 21.321.3 4.64.6
  58. 58.  Elastin FibersElastin Fibers  Restricted to walls of blood vessels in humans  PDL fibers do not contain mature elastin but two immature forms are found oxytalan and eulanin.
  59. 59.  Oxytalan FibersOxytalan Fibers  Are micro fibrils  Run in apico-coronal direction to bend and attach at cervical third of root (Fulmer et al. 1974)  Diameter – 0.5-2.5mm  Volume – 3%  No cross banding seen  Function - regulate vascular flow - play a role in tooth support - guides cell migration
  60. 60.  Are immature elastic fibers consisting of micro fibrils within small quantity of elastin  An elastic meshwork has been described in the PDL as being composed of many elastin lamellae with peripheral oxytalan & eulanin fibers  Functions - Regulate vascular flow - Role in tooth support - Facilitate fibroblast attachment and migration Eulanin FibersEulanin Fibers
  61. 61.   Small Collagen fibers in association with the larger principal collagen fiber  Run in all directions forming a plexus  Described by Shackleford, 1971  Once the tooth has erupted into clinical occlusion such an intermediate plexus is no longer demonstrable  Intermediate plexus has been reinterpreted by Sloan as representing merely an optical effect explained entirely by the arrangement of middle layer collagen into sheets rather than bundles. Indifferent Fiber PlexusIndifferent Fiber Plexus
  62. 62.  Fills the space between the fibers and cells  Overlooked possibly because difficult to investigate and not recognized in routine methods COMPOSITION  Consists of a biochemically complex, highly hydrated, semisolid gel.  Water content of 70%  Glycosaminoglycan's – hyaluronic acid, proteoglycans( versican , decorin )  Glycoproteins -- fibronectin , laminin , vibronectin , tenascin Ground SubstanceGround Substance
  63. 63.  Large group of anionic macromolecules that consists of a protein core to which are attached hexose amine containing polysaccharide called gag chains.  Distribution in PDL is similar to gingival tissue. FUNCTIONS a. Cell adhesion b. Cell-cell & cell- matrix adhesion c. Cell repair d. Binding to various growth factors ProteoglycansProteoglycans
  64. 64.  The primary function of these molecules is to bind cells to extracellular elements.  Most widely studied is FIBRONECTIN  Exists in one form as an insoluble connective tissue matrix protein which promotes the attachment and subsequent spreading of cells that bind to a fibronectin – collagen complex.  The attachment and spreading of cells within the PDL collagen matrix is a pre requisite for both alignment of collagen fibers and for cell migration. GlycoproteinGlycoprotein
  65. 65.   TENASCIN is an adhesive glycoprotein synthesized at specific times and location during embryogenesis.  In adult its distribution is specific and restricted.  It binds to fibronectin and to proteoglycans.  Its blocks the binding capacity of syndecan and thereby enables the cell to move freely Glycoproteins….
  66. 66.  1. Physical 2. Formative and Remodeling 3. Nutritive 4. Sensory 5. Regulation of periodontal ligament width Functions Of PDLFunctions Of PDL
  67. 67.  1. Provision for a soft tissue ‘CASING’ to protect the vessels and nerves from injury by mechanical forces . 2. Transmission of occlusal forces to the bone 3. Attachment of teeth to bone. 4. Maintenance of gingival tissues in their proper relationship to the teeth. 5. Resistance to impact of occlusal forces  SHOCK ABSORPTION : Tensional theory & Viscoelastic theory Physical FunctionsPhysical Functions
  68. 68. Tensional TheoryTensional Theory Ascribes the principal fibers of PDL the major responsibility in supporting the tooth and transmitting the forces to the bone. Force is applied to the tooth Principal fibers first unfold and straighten Transmit force to the alveolar bone causing elastic deformation of the socket. When alveolar bone has reached its limit, the force is transferred to underlying basal bone  Many investigators find this theory insufficient to explain available experimental evidence.
  69. 69. Viscoelastic TheoryViscoelastic Theory According to this, the displacement of tooth is largely controlled by fluid movement, with fibers having only secondary role (Bien SM, 1966 and Birn H, 1966) Force applied on tooth Extra-cellular fluid from PDL escapes to marrow spaces Depletion of fluid, Fibers absorb slack and tighten Blood vessels stenosis Arterial back pressure created Ballooning of vessels Passage of blood ultra filtrates Lost fluid replenished
  70. 70.  Transmission Of OcclusalTransmission Of Occlusal Forces to boneForces to bone  Arrangement is like suspension bridge or hammock.  The oblique fibers alter their wavy pattern and sustain the major part of the axial force AXIS OF ROTATION  Single rooted tooth at junction of middle and apical 3rd of the root.  Multirooted tooth in the bone between the roots below furcation.
  71. 71. Distribution of faciolingual forces (arrow) around the axis of rotation (black circle on root) in a mandibular premolar. The periodontal ligament fibers are compressed in areas of pressure
  72. 72.   The apical portion of the root moves in a direction opposite to the coronal portion.  Areas of tension→ Principal fiber bundles are taut rather than wavy.  Areas of pressure→ fibers are compressed, the tooth is displaced & a corresponding distortion of bone exists in a direction of root movement (Picton DC, 1967)
  73. 73.  FORMATIVE &FORMATIVE & REMODELLINGREMODELLING  Cells have the capacity to resorb & synthesize the extracellular substance of the CT ligament, alveolar bone & cementum.  Participate in physiologic tooth movement & in repair of injuries.  PDL is constantly undergoing remodeling old cells and fibers are broken down and replaced by new ones.  Radio autographic studies indicate a very high turnover rate of collagen in PDL. A rapid turnover of sulfated GAGs in the cells and amorphous ground substances also occur.
  74. 74.   Sodek (1977) has demonstrated that the periodontal ligament incorporates proline at least 5 times faster than gingiva or alveolar bone and that the biological half-life of mature collagen was 20% and 17% less than found in gingiva and alveolar bone, respectively.  The PDL is constantly undergoing remodeling. Old cells & fibers are broken down & replaced by new ones, & mitotic activity can be observed in the fibroblasts & endothelial cells (Muhlemann; 1954)
  75. 75.   Sodek ,1977 found collagen synthesis in PDL of adult rat to be - two fold greater than that of gingiva, - four fold greater than that of skin, & - six fold greater than that of bone.  Almost all the newly synthesized collagen in the ligament was converted to mature cross linked collagen, whereas much less was converted in the gingiva & skin. Collagen Turn Over RateCollagen Turn Over Rate
  76. 76.   Half-life for collagen turnover: in ligament – 1 day, in bone – 6 days in gingiva - 5 days, in skin - 15 days  According to Rippin: half life in the apical areas 2.45 days, in the crestal areas 6.42days, fibers in mid-root region 5.7 days, transseptal fibers 8.4 days for dentogingival fibers 25 days.
  77. 77.   PDL supplies nutrients to the cementum , bone, and gingiva by way of blood vessels and provides lymphatic drainage.  Rich vascular plexus at apex & in the cervical part of the ligament  Rich network of arcades are more evident in the PDL space adjacent to the bone than to cementum NutritionalNutritional
  78. 78.   Periodontal ligament provides the most efficient proprioceptive mechanism  4 types of neural terminations are seen 1. Free nerve endings -pain 2. Ruffini like mechanoreceptors (apical area) 3. Meissner’s corpuscles - mechanoreceptors (middle 3rd ) 4. Spindle like pressure and vibration endings (apex) SensorySensory
  79. 79.   The extracellular signal-regulated kinase 1 and 2 (ERK-1/2) have been implicated in the inflammation dependent sensitization of nociceptors.  It is responsible for the neural regulation of blood vessels in the PDL (Korkmaz et al ,2009)  PDL contains calcitonin gene related peptide (CGRP) in nociceptors (Silverman JD, Kruger, 1987) and calretinin in mechanoreceptors (Maeda T et al , 1999)
  80. 80.  Actin binding protein-280 plays an important role in mechano protection by: 1. Reinforcing the membrane cortex thereby preventing force- induced membrane disruption 2. Increasing the strength of cytoskeletal links to the extracellular matrix 3. Desensitizing stretch activated ion channel activity.
  81. 81.   An important measure of periodontal ligament homeostasis.  The ability of periodontal ligament cells to synthesize and secrete a wide range of regulatory molecules is essential in accurately maintaining the width of the periodontal ligament in spite of high-amplitude physical forces during mastication and despite the presence of osteogenic cells within the whole width of the periodontal ligament. (McCulloch, 1983) Regulation of PDL widthRegulation of PDL width
  82. 82.  Transforming growth factor-β isoforms -synthesized by periodontal ligament cells can dose-dependently down- regulate osteoblastic differentiation of periodontal ligament cells (Brady TA et al. 1998)  Prostaglandins - also produced by periodontal ligament cells, can inhibit mineralized bone nodule formation and prevent mineralization by periodontal ligament cells in vitro (Ogiso B, Hughes FJ, et al. 1991,1992)  Paracrine factors - inhibit bone resorption (Ginger MS, et al 1991)
  83. 83.  Pro-inflammatory cytokine interleukin-1 (Shimizu N et al 1995) and one of the isoenzymes responsible for prostaglandin synthesis (cyclooxygenase 2 - Shimizu N et al 1998) are induced by applied mechanical force on periodontal ligament cells in vitro.  As prostaglandins and interleukin-1 can strongly induce matrix degradation, there is evidently an important relationship between mechanical forces, cytokine production and regulation of the periodontal ligament space.
  84. 84.  Blood SupplyBlood Supply  Inferior & superior alveolar arteries to the mandible & maxilla - reaches the PDL from 3 sources: 1. Apical vessels (Dental artery) 2. Transalveolar vessels (rami perforantes-penetrating vessels from alveolar bone) 3. Intraseptal vessels (anastomosing vessels from the gingiva)
  85. 85. Blood supply….  Branches of the intraseptal vessels – perforate the lamina dura & enter the ligament. After entering the PDL, perforating rami anastomose & form a polyhedral network which surrounds the root like a stocking.
  86. 86.   Perforating channels are more abundant in the maxilla than in the mandible, & more in the posterior than in the anterior teeth.  This dual supply allows the ligament to survive following removal of the root apex during certain endodontic procedures  Arteriole in PDL – diameter – 15 to 50 µm. Blood supply….
  87. 87.   Specialized feature of the PDL  Fenestrated capillary beds differ from continuous capillary beds in that the diffusion & filtration capabilities are greatly increased  Capillary fenestrations are related to the high metabolic requirements of the PDL & its high turnover rate. Fenestrated CapillariesFenestrated Capillaries
  88. 88.   Frohlich (1964) - diagonal symmetry of the periodontal vessels  If there is abundant vascularity palatally at the apical area, there will be a similar abundance labially in the coronal area of the PDL.  This causes minute (0.5 µm) labiopalatal pulsation of teeth with each heart beat. Palatolabial discrepanciesPalatolabial discrepancies in vascularityin vascularity
  89. 89.  Nerve SupplyNerve Supply  The nerve follow almost the same course as the blood vessels.  Nerve bundle divide → myelinated fibers → lose their myelin sheath → end in one of the 4 types of neural termination
  90. 90.  1.Free nerve endings - terminal arborization of thick/fine myelinated fibers - 0.2-1 um in diameter - fine, nonmyelinated fibers only type of ending in tooth pulp → classic model of pure nociception. 2. Ruffini - like→ apical area 3. Meissner's corpuscles → mid-root, for tactile perception 4. Spindle shaped (Krause type end bulbs) → temperature receptor, present at apex of the tooth
  91. 91.  development of a new technique in which the axons can be radioactively labeled & visualized by radioautography  The PDL has double innervation:  Axons arising both from the mesencephalic nucleus - Unconscious reflex pathways & proprioceptors – position control of the mandible  Axons from the trigeminal ganglion - Conscious sensation of touch, pain & temperature
  92. 92.   The vast majority of the nerve endings – unencapsulated, Ruffini-like mechanoreceptors & free nerve endings.  In experimental animals, innervation from the trigeminal ganglion is very dense – tooth apex, circular & interdental ligaments.  Innervation from mesencephalic nucleus – most dense – subapical region, especially for the canines & incisors, with no innervation in the zone of the circular & interdental ligaments.
  93. 93.  Absence of PDL aroundAbsence of PDL around implantimplant  important clinical consequences  No resilient connection exists between teeth & jaw bone - any occlusal disharmony - repercussions at the bone-to-implant interface.  No intrusion or migration of teeth can compensate for the eventual presence of a premature contact.  Because the principal proprioception of the natural dentition comes from the pdl, its absence in implants reduces tactile sensitivity & reflex function.
  94. 94.   Accompany the arterial supply.  Venules receive the blood through the abundant capillary network. Also, arterio-venous anastomosis bypass the capillaries; these are seen most frequently in the apical & inter-radicular regions, & there significance is unknown.  They are somewhat larger in diameter – 28 µm (mean). Venous drainageVenous drainage
  95. 95.   Lymph vessels - originate as cul-de-sac in PDL  course apically - pass through the fundus of the socket or they may pass through the cribriform plate to empty into larger channels pursuing intraosseous paths. Lymphatics
  96. 96.  The cell number and cell activity decreases with aging.  One of the prominent changes seen in the calcified tissues of periodontium , the bone and the cementum is scalloping and the PDL fibers are attached to the peaks of these scallops than over the entire surface as seen in a younger periodontium.  This remarkable changes affect the supporting structures of the teeth. Age changes in PDLAge changes in PDL
  97. 97.   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 gingival height and periodontal disease promotes destructive changes in the PDL
  98. 98.   The primary role of the periodontal socket 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 .  Acute trauma to the periodontal ligament, accidental blows or rapid mechanical destruction may produce pathologic changes such as fractures or resorption of the cementum tears of fiber bundles , hemorrhage and necrosis . Clinical considerationsClinical considerations
  99. 99.  The adjacent alveolar bone is resorbed the PDL is widened and tooth becomes loose .When trauma is eliminated repair usually takes place.  Orthodontic tooth movement depends on resorption and formation of tooth bone and periodontal ligament .  These activities can be stimulated by properly regulated pressure and tension.  If the movement of teeth is within phsysiologic limits the initial compression of PDL on the pressure side is compensated for by bone resorption whereas on the tension side bone apposition is seen. Clinical considerations…Clinical considerations…
  100. 100.  Application of large forces results in necrosis of PDL and alveolar bone on the pressure side and movement of the tooth will occur after the necrotic bone has been resorbed by osteoclasts located on its endosteal surface.  Inflammatory diseases of the pulp progress to the apical periodontal ligament and replace its fiber bundles with granulation tissue .  This lesion is called a periapical granuloma may contain epithelial cells that undergo proliferation and produce a cyst . ClinicalClinical considerations…considerations…
  101. 101.  Chronic inflammatory disease is common 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.  To repair the existing destruction of PDL can be quite challenging .  It involves limiting the disease process and to regenerate the host tissues to their original form in such a way that reattachment of PDL to bone becomes possible ClinicalClinical considerations…considerations…
  102. 102.  Various surgical techniques like Guided Tissue regeneration are being used for correction of Periodontal destruction .  Guided Tissue regeneration is based on principle that specific cells contribute to formation of specific tissues.  Important cells responsible for periodontal regeneration are derived from PDL.  Exclusion of the faster growing epithelium and connective tissue from a periodontal wound for 6 to 8 weeks allows the slower growing tissues to occupy the space adjacent to the tooth. ClinicalClinical considerations…considerations…
  103. 103.  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 and around embedded teeth.  Clinically ankylosed tooth sounds DULL or WOODY on percussion.  Before extraction such tooth require X-ray to facilitate surgical extraction. ClinicalClinical considerations…considerations…
  104. 104.   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 there presence helps to create a soft – tissue seal around the implant . ClinicalClinical considerations…considerations…
  105. 105.  Within physiologic limits, the PDL can accommodate increased function with - an increase in width, - a thickening of its fiber bundles, and - an increase in diameter & number of Sharpey’s fibers  Forces that exceed the adaptive capacity of the periodontium produce injury called trauma from occlusion.  Slight excessive pressure: resorption of bone, widening of PDL space  Slight excessive tension: elongation of PDL fibers & apposition of bone External forces & PDLExternal forces & PDL
  106. 106.   To have any chance of success , it is essential to maintain the viability of PDL .  Avoid dehydration of PDL.  Avoid loss of viability of its cell rests. Transplantation  Best results when unerupted tooth with partially formed roots as there is less damage to PDL. Replantation &Replantation & transplantationtransplantation
  107. 107.  Cemento-ossifying fibroma – Middle age, mandible (midbody), Women Predilection (slight) & Blacks, Well Circumscribed  Reactive fibro-cemento-osseous lesions of PDL origin: 1.Periapical cemento-osseous dysplasia (PCD) – young- middle age, black female, apical area of anterior mandibular teeth. 2. Focal cemento-osseous dysplasia – women predilection, poster mandible. 3. Florid cemento-osseous dysplasia – Middle-elderly black women. Neoplasms arising fromNeoplasms arising from PDLPDL
  108. 108.  Nishimura et al, 1998 - PDL cells - susceptible to hyper & hypoglycemia & effects - mediated via the integrin system.  Hyperglycemia – increased expression of fibronectin receptor → results in reduced cellular adhesion & motility → probable tissue impairment.  Hypoglycemia – decreased expression of fibronectin receptor → lowers the viability & ultimately results in cell death & hence tissue impairment Effect of hyper & hypoEffect of hyper & hypo glycaemia on PDLglycaemia on PDL
  109. 109.   Thin radiolucent line interposed between the root & lamina dura.  Occlusal Trauma → widened PDL space or funneling of coronal aspect of PDL space.  It can also widened in case of vertical fractures & progressive systemic sclerosis (Scleroderma). PDL space RG appearancePDL space RG appearance
  110. 110.  Gestrelium et al, 1997 studied effects of EMD on periodontal ligament cell migration, attachment, proliferation, biosynthetic activity mineral nodule formation & ability to absorb a large range of polypeptide growth factors & cytokine.  In culture, EMD formed protein aggregates which appeared to provide ideal conditions for cell-matrix interactions.  Under these conditions EMD enhanced the proliferation of PDL cells, increased protein & collagen production of PDL cells & promoted mineral nodule formation by these cells.  However, no effect on migration, attachment & spreading of these cells nor did they absorb any of the growth factor or cytokine that were tested. EMD & PDLEMD & PDL
  111. 111.  PROGRESSIVE SYSTEMIC SCLEROSIS Radio graphically ---- PDL widening up to 3mm thickening Collagen ---- dense, mature & more hyalinized than normal Oxytalan fibers increased. Soft CT disorders & PDLSoft CT disorders & PDL
  112. 112. LATHYRISM  Condition caused by drugs that inhibit cross linking in collagen & elastin (cystamine)  Fragile collagen fibers  Retard eruption DISUSE ATROPHY  Narrowing of PDL & reduction in no. of principal fibers.  Fibers oriented parallel to the long. Axis of root & PDL shows reduced rate of collagen turn over.
  113. 113. FOOD TEXTURE Little correlation between the advent of soft, fiber deficient diet & dental health. Significant factor in chronic inflammatory periodontal disease is loss of natural masticatory function, leading to accumulation of dental plaque. Influences pattern of mastication & hence the mode of support offered by the PDL. Nutrition & PDLNutrition & PDL
  114. 114. CARBOHYDRATES  Refined carbohydrates in the diet influence the severity of PDL disease in humans (Holloway et. Al 1963)  No direct evidence showing the direct effect of carbohydrates per se on PDL , though in some circumstances there could be an influence as a result of modifying the diet consistency.
  115. 115. PROTEINS  Deficiency of protein might be expected to produce changes within it.  Reduction in PDL transseptal fibers (Stien & Ziskin 1949; Ten Cate et al 1976)  Reduction in cementoblasts, fibroblasts  Occlusal trauma exacerbates these effects (Chawla & Glickman 1951)  Healing is delayed in rats fed on protein deficient diet.
  116. 116. REGENERATION is the reproduction or reconstitution of a lost or injured part. REPAIR is the healing of a wound by tissue that does not fully restore the architecture or the function of the part. PERIODONTAL REGENERATION is defined histologically as regeneration of the tooth’s supporting tissues, including alveolar bone, periodontal ligament, and cementum over a previously diseased root surface. Healing after periodontalHealing after periodontal therapytherapy
  117. 117.   NEW ATTACHMENT is defined as the union of connective tissue or epithelium with a root surface that has been deprived of its original attachment apparatus. This new attachment may be epithelial adhesion and/or connective tissue adaptation or attachment and may include new cementum.
  118. 118.  Carranza’s Clinical Periodontology, 10th Edition  Clinical Periodontology and Implantology by Jan Lindhe, 5th edition  Oral Histology and Embryology by Orban, 11th edition  Tencate oral histology, 5th edition  Fundamentals of Periodontics, 2nd Edition, by Thomas G. Wilson, Kennath S. Kornman  Hassel TM. Tissues and cells of periodontium. Periodontol 2000, Vol. 3, 1993, 9-38.  The Periodontium - Hubert E Schroeder ReferencesReferences
  119. 119.   Bartold PM, Walsh LJ, Sampath Narayan A. Molecular and cell biology of gingiva. Periodontol 2000, Vol. 24, 2000, 28–55.  Cho MI, Garant PR. Development and general structure of the periodontium, Periodontol 2000, Vol. 24, 2000, 9–27.  Ertsenc W, Mcculloc HG , Sodek HJ. The periodontal ligament: a unique, multifunctional connective tissue. Periodontol 2000. Vol. 13, 1997, 20-40.  Wright JM. Reactive, dysplastic and neoplastic conditions of periodontal ligament origin. Periodontol 2000, Vol. 21, 1999, 7-15.
  120. 120.   Xiong J, Gronthos S, Bartold PM. Role of the epithelial cell rests of Malassez in the development, maintenance and regeneration of periodontal ligament tissues. Periodontol 2000, Vol. 63, 2013, 217–233.  Bosshardt DD, Selvig KA.Dental cementum: the dynamic tissue covering of the root. Periodontol 2000 1997;13:41-75.

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