Explains about Periodontal Ligament

1. PERIODONTIUM II
CEMENTUM AND PERIODONTAL
LIGAMENT
DR KRISHNA PRIYA.B

2. CEMENTUM
• Calcified, avascular
mesenchymal tissue
that forms the outer
covering of the
anatomic root.
• Begins at cervical
portion of the tooth at
the cementoenamel
junction & continues to
the apex.

3. Cemento enamel junction

5. Types
• Acellular
• Cellular

7. Role of Cementum
• The main function of cementum is to provide
attachment to the collagen fibres present in the
periodontal ligament. This helps maintain the
integrity of the root and its position in the gum and
bone.
• Cementum is also deeply involved in the repair
and regeneration of teeth.

8. THICKNESS OF
CEMENTUM
• At coronal half may be 20-50
µm thick
• Attains greatest thickness at
apical third and furcation areas
may be 150-200 µm
• It is thicker in distal surfaces
than in mesial surfaces
because of mesial drift over
time.

9. COMPOSITION OF CEMENTUM
45-50% inorganic substance
• The inorganic portion consists calcium and
phosphate in the form of
• Hydroxyapatite.
• It is less than that of
bone(65%)
enamel(97%)
dentin(70%)

10. 50-55% organic material and water
• The organic portion of the cementum is
composed primarily of type I (90%) and type III
(about 5%) collagens.
• Sharpey’s fibers, which constitute the major
portion of cementum are composed of mainly
collagen type I.

11. TYPES OF FIBERS
EXTRINSIC
INTRINCIC

12. CLASSIFICATION OF CEMENTUM
1. By location:
Radicular cementum: The cementum that is found on
the root surface.
Coronal cementum: The cementum that forms on the
enamel covering the crown.

13. 2. By cellularity:
Cellular cementum: Cementum containing
cementocytes in lacunae
that communicate with each other through a system of
anastomosing canaliculi. It is less calcified. Sharpey’s
fibers occupy a small portion.
Acellular cementum: Cementum without any cells
in its matrix. It covers approximately the cervical third
or half of the root. Sharpey’s fibers make up most of
the structure and is completely calcified, with the
mineral crystals oriented parallel to the fibrils.

14. 3.By the presence of collagen fibrils in the
matrix:
• Fibrillar cementum: Cementum with a matrix that contains well-
defined fibrils of type I collagen.
•Afibrillar cementum: Cementum that has a matrix devoid/ absence of
type I collagen fibrils.
4.Based on the time of formation :
•Primary Cementum: It is formed before the tooth reaches the
occlusal plane.
•Secondary cementum : it forms after the tooth reaches the occlusal
plane.

15. 5. By the origin of the matrix fibers :
• Extrinsic fiber cementum: Cementum that
contains primarily extrinsic fibers, i.e. Sharpey's fibers
that are continuous with the principal fibers of the
periodontal ligament. Since the fibers were originally
produced by periodontal ligament fibroblasts, they are
considered "extrinsic" to the cementum
• . These fibers are orientated more or less
perpendicularly to the cementum surface and play a
major role in tooth anchorage.

16. • Intrinsic fiber cementum: Cementum that
contains primarily intrinsic fibers, i.e. fibers
produced by cementoblasts and that are orientated
more or less parallel to the cementum surface. This
form of cementum is located predominantly at sites
undergoing repair, following surface resorption. It
plays no role in tooth anchorage.
• Mixed fiber cementum: Cementum that
contains a mixture of extrinsic and intrinsic fiber
cementum.

17. • By Schroeder
1. Acellular, afibrillar cementeum- No cells & no
fibers
2. Acellular, extrinsic fiber cementum- no cells &
extrinsic fibers
3. Cellular, intrinsic fiber cementum-
Cementoblast & intrinsic fibers
4. Cellular, mixed fiber cementum-
cementoblasts, intrinsic fibers & extrinsic fibers

18. CELLS IN CEMENTUM
• The following are the major cell types associated
with cementum:
• Cementoblasts
Cementocytes
Periodontal ligament fibroblasts
Cementoclasts

19. ⚫CEMENTOBLAST
⚫Soon after Hertwig’s sheath breaks up,
undifferentiated mesenchymal cells from
adjacent connective tissue differentiate into
cementoblasts.
⚫Synthesize collagen & protein
polysaccharides which make up the organic
matrix of cementum.
⚫Have numerous mitochondria, a well-formed golgi
apparatus, & large amounts of granular endoplasmic
reticulum.

20. • Cementocytes
• During periods of rapid cementogenesis,
cementoblasts may become trapped as cementocytes
within lacunae.
• Cytoplasmic processes extend toward cementum
surface through canaliculi in the cementum.

22. • Periodontal fibroblasts: Although technically
part of the periodontal ligament, they produce
collagen fibers that become mineralized, as they
become incorporated into cementum. Therefore,
periodontal ligament fibroblasts contribute to
cementogenesis and are considered as cementum
cells.
• Cementoclasts: These multinucleated giant
cells play an active role in cemental resorption.

23. CEMENTODENTINAL JUNCTION
⚫Smooth in permanent teeth.
⚫Scalloped in deciduous teeth.

24. ⚫Dentin is separated from cementum by a zone
known as the intermediate cementum layer.
⚫This layer is predominantly seen in apical two-
thirds of roots of molars & premolars.

25. CEMENTOENAMEL JUNCTION
⚫In 60% of the teeth, cementum overlaps the
cervical end of enamel for a short distance.
⚫In 30% of all teeth, cementum meets the cervical
end of enamel in a relatively sharp line.
⚫In 10% of the teeth, enamel & cementum do not
meet.

28. CLINICAL CONSIDERATIONS
⚫Cementum is more resistant to
resorption than is bone, & it is for this reason
that orthodontic tooth movement is made
possible.
⚫It is because bone is richly vascularized, whereas
cementum is avascular.
⚫Cementum resorption can occur after
trauma or excessive occlusal forces.

29. ⚫HYPERCEMENTOSIS: Is an
abnormal thickening of
cementum

30. • Scaling produces no pain, but if cementum is
removed, dentin is exposed causes sensitivity.
• Thinness at the cervical portion means that
cementum is readily removed by the abrasion when
gingival recession occurs when exposed the root
surface to the oral environment.
Fusion of the cementum & alveolar bone with
obliteration of the periodntal ligament is c/d
ANKYLOSIS

31. Periodontal Ligament
• The periodontal ligament is composed of a
complex vascular and highly cellular connective
tissue that surrounds the tooth root and
connects it to the inner wall of the alveolar bone

32. Synonyms
• Periodontal membrane
• Alveolo- dental ligament
• Gomphosis
• Pericementum

33. • The periodontal ligament is a soft, fibrous
specialized connective tissue which is present in the
periodontal space, which is situated between the
cementum of root of the tooth and the bone forming
the socket wall.
• The periodontal ligament extends coronally up to
the most apical part of connective tissue of gingiva.

35. CELLULAR COMPOSITION
The cells of periodontal ligament are categorized as:
1. Synthetic Cells a) Osteoblasts b) Fibroblasts c)
Cementoblasts
2. Resorptive Cells a) Osteoclasts b) Cementoclasts
c) Fibroblasts
3. Progenitor Cells
4. Epithelial Cell rests of malassez
5. Connective Tissue cells a) Mast cells b)
Macrophages

36. EXTRACELLULAR SUBSTANCE
• Extra cellular substance comprises the following
• Fibers a) Collagen b) Oxytalan, C)Elastic,
d)Reticular
• Ground Substance a) Proteoglycans
(b) Glycoproteins

37. • The most important elements of the periodontal
ligament are the principal fibers.
• The principal fibers of the periodontal ligament
are arranged in six groups that develop
sequentially in the developing root:
• Transseptal
• Alveolar crest
• Horizontal
• Oblique
• Apical
• Interradicular fibers

38. FIBERS OF THE PERIODONTAL LIGAMENT

39. The principal fibers of the PDL are
arranged in five groups:

40. BLOOD SUPPLY
• Blood supply is derived mainly from : Inferior
and superior alveolar arteries to mand & max
respectively .

41. NERVE SUPPLY
• Nerves found in ligament pass through foramina
in alveolar bone.
• The nerves are the branches of second and third
division of of fifth cranial nerve (trigeminal
nerve) and follow same path as blood vessels.

42. CEMENTICLES
• Cementicles are small calcified bodies present in
periodontal ligament.
• They may form into large calcified bodies and
fuse within cementum or remain in pdl

43. • Functions of Periodontal Ligament
• The functions of the periodontal ligament are
categorized as
• Physical
• Formative and remodeling
• Nutritional
• Sensory

44. Physical Functions
• The physical functions of the periodontal ligament
entail the following:
• 1. Provision of 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 the teeth to the bone
• 4. Maintenance of the gingival tissues in their
proper relationship to the teeth
• 5. Resistance to the impact of occlusal forces (i.e.,
shock absorption)

45. Formative and Remodeling Function
• Periodontal ligament cells are exposed to physical
forces in response to mastication, parafunction,
speech, and orthodontic tooth movement.
• Cells of the periodontal ligament participate in the
formation and resorption of cementum and bone,
which occur during physiologic tooth movement,
during the accommodation of the periodontium to
occlusal forces, and during the repair of injuries.

47. Nutritional and Sensory Functions
• The periodontal ligament supplies nutrients to
the cementum, bone, and gingiva by way of the
blood vessels, and it also provides lymphatic
drainage

48. SENSORY FUNCTION
• 1. Free endings, carry pain sensations.
• 2. Ruffini like mechanoreceptors located in the
apical area.
• 3. Meissener’s corpuscles are also
mechanoreceptors located primarily in mid-root
region.
• 4. Spindle like pressure endings, located mainly
in apex. Pain sensation is transmitted by small
diameter nerves, temperature by intermediate
type; pressure by large myelinated fibers.

49. •
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