1. PERIODONTIUM
Oral mic anatomy and embyrology
BEE

2. PERIODONTIUM
Pulp cavity
Enamel
Cementum Dentin
PDL Gingiva
Alveolar bone
Sharpey's fibers
Cementum
Attachment
organ Periodontal
ligament
Root canal
Alveolar bone
Apical foramen
Alveolar vessels
& nerves

3. TEETH IN-SITU

4.  Four tissue supporting the tooth in the
jaw
◦ Cementum
◦ Periodontal ligament
◦ Alveolar bone
◦ Gingivae
Periodontium

5.  Thin layer of calcified tissue covering the
root in the human teeth
 Present in the crowns of some mammals
◦ Adaptation to herbivorous diet
 One of four tissues supporting the tooth
(periodontium)
 The least known of
◦ Periodontium tissues
◦ All mineralized tissues
Cementum

6. 1) It covers and protects the root dentin
(covers the opening of dentinal tubules)
2) It provides attachment of the periodontal
fibers
3) It reverses tooth resorption
Role of Cementum

7.  Varies in thickness
◦ Thick @ apex (50-200 µm) &
inter-radicular regions
◦ Thin cervically (10-15 µm)
 Contiguous with PDL
 Firmly adherent with root
dentine
 Highly responsive mineralized
tissue
◦ Maintenance of root integrity
◦ Maintenance of functional position
of tooth
◦ Tooth repair & regeneration
Cementum

8. Varies in thickness: thickest in the apex and
In the inter-radicular areas of multirooted
teeth, and thinnest in the cervical area
10 to 15 m in the cervical areas to
50 to 200 m (can exceed > 600 m) apically

9.  Slowly-formed throughout life
 Allowing continual reattachment of PDL
fibers
 Cementum can be regarded as a
mineralized component of PDL
 Precementum - a thin mineralized layer
on the surface of the cellular cementum
 Similar to bone, however -
◦ Avascular & not innervated
◦ Less rapidly resorbed – orthodontics
Cementum

10. Cement-
enamel
junction
 Pattern I
◦ Cementum overlaps enamel for a short distance
◦ Most predominant – 60% of sections
 Pattern II
◦ Enamel meet cementum at butt joint
◦ Occurs in 30% of sections
 Pattern III
◦ Enamel fails to meet cementum
◦ Dentine between them is exposed
◦ 10% of sections

11.  Pale yellow
 Softer than dentine
 Permeability
◦ Varies with age and type of cementum
◦ Decreases with age
◦ Cellular is more permeable
◦ More permeable than dentine
 Readily removed by abrasion after
gingival recession
Physical properties

12. Chemical properties
Inorganic Organic Water
By weight 65% 23% 12%
By volume 45% 33% 22%
 Hydroxyapatite crystals similar to those in bone
 More concentration of trace elements (F) at
surface
 F levels higher in acellular
 Collagenous organic matrix, primarily type I
 Molecules involved in PDL fiber reattachment
&/or mineralization
◦ Bone sialoprotein, osteopontin & cementum-specific
elements

13. Cellular and Acellular Cementum
Acellular cementum: covers the root
adjacent to dentin whereas cellular
cementum is found in the apical area
Cellular: apical area and overlying
acellular cementum. Also common in
interradicular areas
Cementum is more cellular as the
thickness increases in order to maintain
Viability
The thin cervical layer requires no cells
to maintain viability as the fluids bathe
its surface
A: Acellular cementum (primary cementum)
B: Cellular Cementum (secondary cementum)

14. A: Acellular cementum
B: Hyaline layer of Hopwell-Smith
C: Granular layer of Tomes
D: Root dentin
Cellular: Has cells
Acellular: No cells and has no structure
Cellular cementum usually overlies acellular cementum

15. Acellular
Cellular
Variations also noted where acellular and cellular reverse in position
and also alternate

16. CEMENTUM
Canaliculus
GT
Lacuna of cementocyte
Dentin
Acellular cementum
Cellular cementum
Hyaline layer
(of Hopewell Smith)
Granular layer of tomes
Dentin with tubules

17. Cementoblast and cementocyte
Cementocytes in lacunae and the channels that their processes extend are
called the canaliculi
Cementoid: Young matrix that becomes secondarily mineralized
Cementum is deposited in increments similar to bone and dentin

19. Are acellular and cellular cementum formed from two different
sources?
One theory is that the structural differences between acellular and cellular
cementum is related to the faster rate of matrix formation for cellular
cementum. Cementoblasts gets incorporated and embedded in the tissue
as cementocytes.
Different rates of cementum formation also reflected in more widely
spaced incremental lines in cellular cementum

20.  Presence or absence of cells
◦ Cellular cementum
◦ Acellular cementum
 Nature & origin of organic matrix
◦ Extrinsic fiber cementum
◦ Intrinsic fiber cementum
◦ Mixed fiber cementum
 Combinations
Classification of cementum

21.  Most common pattern- adjacent to
dentine
 Structureless
 Afibrillar cementum
◦ Exists between
 Acellular cementum
 Hyaline layer (of Hopewell-Smith)
◦ Mineralized GS
◦ Covers cervical enamel
◦ Results following loss of REE
Acellular cementum

22. •Fibres of
Periodontal
Ligament
•Epithelial •Cementum
Rests
Acellular cementum
•Root dentine

23.  Most common pattern
◦ Apical area
◦ Inter-radicular areas
◦ Overlying acellular dentine
 Cementocytes
◦ Inactive
◦ In lacunae – appear dark in GS
◦ Processes present in canaliculi
◦ Processes connected via gap junctions
Cellular cementum

24. Cellular cementum

25.  Organic fibrous framework, ground
substance, crystal type, development
 Lacunae
 Canaliculi
 Cellular component
 Incremental lines (also known as “resting”
lines; they are produced by continuous but
phasic, deposition of cementum)
Cementum simulates bone

26. Clinical Correlation
Cementum is more resistant to resorption: Important in permitting
orthodontic tooth movement

27. Cementocytes vs.
osteocytes
 Cementocytes
◦ More widely dispersed
◦ Randomly arranged
◦ Canaliculi oriented towards
PDL – nutrition
 Osteocytes
◦ Osteon – Haversian system
◦ Organized cells
◦ Circumferential lamellae

28.  More common pattern
◦ Acellular – cervically
◦ Acellular closer to dentine
◦ Cellular – apically
◦ Cellular covers acellular
 Less common patterns
◦ Alternating
◦ Acellular overlies cellular
Relationship between acellular
& cellular cementum

29.  Extrinsic fiber cementum
◦ Fibers derived from inserting Sharpy’s fibers of
PDL
 Intrinsic fiber cementum
◦ Run parallel to root surface at right angles to
extrinsic fibers
◦ Fibers derived from cementoblasts
Extrinsic & intrinsic fiber
cementum

30.  AEFC
 Over cervical half – 2/3s of the root
 Bulk of cementum in premolars
 First formed cementum - acellular
 Thickness of 15 µm
 All collagen are from Sharpy’s fibers
 Though GS from cementoblasts
 Fibers well-mineralized
Acellular extrinsic fiber
cementum

31.  CIFC
 Fibers deposited by cementoblasts
 Fibers run parallel to root surface
 No role of tooth attachment
 In apical 1/3 & inter-radicular areas
 May be
◦ Temporary – extrinsic fibers gain reattachment
◦ Permanent – without attaching fibers
Cellular intrinsic fiber cementum

32.  If cementum forms slowly in CIFC
Acellular intrinsic fiber cemetum

33.  Alternating AEFC with CIFC
 Root apex
 Furcation areas
Cellular mixed stratified
cementum

34.  Collagen fibers derived from
◦ Extrinsic fibers
◦ Intrinsic fibers
 Intrinsic fibers run between the extrinsic
fibers
 Two types – rate of formation
◦ Acellular mixed-fiber cementum
 Well mineralized fibers
◦ Cellular mixed-fiber cementum
 Less well mineralized fibers
Mixed-fiber cementum

35.  Irregular rhythm of deposition
 Not related to activity & quiescence
 Related to
◦ Difference in the degree of mineralization
◦ Composition of organic matrix
 Imprecise periodicity
 Acellular – closer, thinner & regular lines
 Cellular - farther apart, thicker & irregular
lines
Cemental incremental lines

36. Development of Cementum
Cementum formation occurs along the
entire tooth
Hertwig’s epithelial root sheath (HERS) –
Extension of the inner and outer dental
epithelium
HERS sends inductive signal to ectomesen-
chymal pulp cells to secrete predentin by
differentiating into odontoblasts
HERS becomes interrupted
Ectomesenchymal cells from the inner portion
of the dental follicle come in with predentin by
differentiating into cementoblasts
Cementoblasts lay down cementum

37. How cementoblasts get activated to lay down
cementum is not known
3 theories:
1. Infiltrating dental follicle cells receive reciprocal signal from
the dentin or the surrounding HERS cells and differentiate
into cementoblasts
2. HERS cells directly differentiate into cementoblasts
3. What are the function of epithelial cell rests of Malassez?

38.  Derive from dental follicle
 Transformation of epithelial cells
Cementoblasts

39. Incremental lines
 Cementum is formed rhythmically and can
be seen as being composed of layers

40.  Less susceptibility to resorption than bone
 Localized resorption areas occur
 Could be caused by microtrauma
 May continue to root dentine
 By multinucleated odontoclasts
 Resorption filled by mineralized tissue
(resembles cellular cementum)
 Reversal line
Resorption & repair of cementum

41.  Wider uncalcified zone
 Less mineralized
 Smaller crystals
 Calcific globules are present
Differences are related to
different speed of formation
Reparative cementum vs.
cementum

42.  Cemental callus
◦ Root fracture
◦ No remodeling to original dimensions of the
root
 Cementicles
◦ Free or attached pieces in PDL
◦ Microtrauma
◦ Apical & middle 1/3s of root
◦ Root furcation
Clinical considerations

43. Clinical considerations
 Supra-eruption of teeth
 Tooth wear
 Local hypercementosis
◦ Reaction to PA inflammation
◦ Difficulty in extraction
◦ Paget’s disease – multiple teeth
with hypercementosis
 Cementum narrowing root
canal and shifting the
junction between dental pulp
& PDL cervically
◦ Pulp removal in RCT up to that
point

45.  Dense fibrous connective tissue
 Occupies the area between the root of the
tooth and the walls of the alveolar socket
 Derived from the dental follicle
 Continuous with
◦ the connective tissue of the gingiva above the
alveolar crest
◦ The dental pulp at the apical foramen
Periodontal ligament PDL

46.  Variable in width,
average 0.2 mm
 looks hourglass in shape
 Reduced in unerupted &
non-functional teeth
 Increased in teeth
subjected to heavy
occlusal stress
Narrows slightly with
Periodontal ligament

age
space
 Narrower in permanent
teeth

47.  Attachment
 Has a role in tooth eruption
and support
 Its cells repair the alveolar
bone & cementum
 Neurological control of
mastication through its
Functions of PDL
mechanoreceptors

48.  Fibers
 Ground substance
 Cells
Components of PDL

49.  Collagen
◦ Type I (70% of fibers)
◦ Type III (20% of fibers)
 Found in the periphery of Sharpy’s fibers attachment into
alveolar bone
◦ Small amounts of type V, VI as well as basement
membrane collagen IV & VII associated with the epithelial
rests
◦ Highest turnover of collagen is in PDL
 Higher near apex
 Even across the width of PDL
 Rate could be related to the amount of occlusal stress
 Oxytalan (in humans) or elastin
Fibers of PDL
◦ Attached into cementum
◦ May have a role in tooth support

50.  Fibers exist as bundles
(principal fibers) running in
different orientations in
different regions
◦ Dentoalveolar crest fibers
◦ Horizontal fibers
◦ Oblique fibers
◦ Apical fibers
Principal fibers of PDL
◦ Interradicular fibers
 From crest of interradicular septum
to furcation

51. Principal fibers of PDL

52.  Principal fibers
embedded into
cementum and
bone
 More numerous
but smaller at
cemental end
 Mineralized and
Sharpy’s fibers
unmineralized
parts

53.  60% of PDL by volume
 Main components
◦ Hyaluronate GAGs
◦ Proteoglycans
◦ Glycoproteins
 Functions of GS
◦ Ion and water binding & exchange
◦ Control of collagen fibrillogenesis & fiber
Ground substance of
orientation
◦ Tooth support & eruption - high tissue fluid
PDL pressure

54.  Fibroblasts
◦ Fusiform cells with
many processes Cells of PDL
◦ Functions – secretion
and turnover of fibers
 Regeneration of tooth
support apparatus
 Adaptive responses to
mechanical loading
 Cementoblasts
◦ Cement-forming cells
lining cemental surface
◦ Cuboidal cells
 Osteoblasts
◦ Bone-forming cells
lining tooth socket
◦ Resemble
cementoblasts

55.  Cementoclasts & osteoclasts
◦ Resorbing cells
◦ Howship’s lacunae
 Epithelial rests cells
◦ Cuboidal cells that stain deeply
◦ Close to cemental surface
 Defence cells
◦ Macrophages
◦ Mast cells
Cells of PDL
◦ Eosinophils

56.  Separate from those entering pulp
 Some from alveolar bone through foramina
 Some from pulp through accessory canals
 Major vessels lie between principal fiber
bundle close to alveolar bone
 Capillary plexus around the tooth
 Crevicular plexus of capillary loops
 Veins do not follow arteries but drain into
intraalveolar venous networks
Blood vessels of PDL

57.  Sensory
◦ Nociception
◦ Mechanoreception
 Sensitivity to occlusal loads
 Guidance to intercuspation
 Autonomic
◦ Associated with blood vessels
Innervation of PDL

58.  The alveolar process develops during the
eruption of teeth
 Grows at a rapid rate at the free border
 Proliferates at the alveolar crest
 No distinct boundary exists between the
body of the maxilla or mandible and the
alveolar process
 If teeth are lost the alveolar bone
disappears
Alveolar process

59. Development of bony crypt
 Deciduous tooth &
permanent
successor initially
share crypt
 Bone subsequently
forms to encase
permanent tooth