ultrastructure and function of cementum seminar

1. ULTRASTRUCTURE
AND FUNCTION OF
CEMENTUM
BY
DR.AYUSHI SINGH
MDS 1ST YEAR

2. CONTENTS
• Introduction
• Physical properties
• Chemical composition
• Histology of cementum
• Classification
• Development of cementum
• Cemento-dentinal junction
• Cemento-enamel junction
• Cementum resorption and repair

3. CONTENTS
• Functions
• Effects of ageing on cementum
• Cementum in oral environment
• Role of cementum in periodontal disease
• Developmental anomalies
• Conclusion
• References

4. CEMENTUM
• Cementum furnishes a
medium for the attachment
of collagen fibers that bind
the tooth to surrounding
structures.1

5. DEFINITION
• The cementum is the part of the
periodontium that attaches the teeth to
the alveolar bone by anchoring
the periodontal ligament.- GPT
• Cementum is the calcified, avascular
mesenchymal tissue that forms the outer
covering of the anatomic root. Orbans 2

6. 1
2
3
The cementum is the
surface layer of the tooth
root. Rather than being a
passive entity like paint on
a wall, cementum is a
dynamic entity within the
periodontium.1
In fully formed and functioning teeth,
1. Cementum is firmly attached to the radicular dentin.
2. Covers the entire surface of the root.
3. Increases in thickness towards the apex and may
extend partially into the apical foramen1

7. PHYSICAL CHARACTERISTICS
• Hardness: less than dentin2
• Color: Light yellow with dull surface and lighter than dentin2
• Thickness: Variable, thinnest at CEJ and thickest at at apex. Apical
foramen is surrounded by cementum2
• Its permeable, (as age progresses permeability of cementum
diminishes)

8. CHEMICAL CHARACTERISTICS
On dry weight basis, cementum of fully formed teeth contains:
• Inorganic substances- 45-50% 2
• Organic substances and water- 50-55% 2

9. INORGANIC PORTION
• Hydroxyapatite- calcium and Phosphate1
• Trace elements like
- Copper
- Fluorine
- Iron
- Lead
- Potassium
- Silica
• Cementum has highest fluorine content among mineralized tissues

10. ORGANIC PORTION 2
• Collagen: Type I predominant (90%), others include type III (5%), V,
XII, XIV 1
• Matrix proteins2
• Proteoglycans
• Osteonectin
• Osteopontin
• Osteocalcin
• Fibronectin
• Bone sialoprotein

11. HISTOLOGYOF CEMENTUM
• Histology section of cementum shows:
• A) Cells, fibers, ground substance
• B) Cemento-enamel junction
• C) Cemento-dentinal junction
Cells of cementum
• The cells are:2
• Cementoblast
• Cementocytes
• Cementoclasts

12. CEMENTOBLASTS 1
• Numerous mitochondria
• Well defined golgi apparatus
• Large number of granular endoplasmic reticulum
• Synthesize collagen and protein polysaccharide, which make up the
organic matrix of cementum
• After some cementum is laid down, its mineralization begins
• The cells are found lining the root

13. CEMENTOCYTES 1
• Spider shaped cells, characteristic feature of cellular cementum
• During the formation of cellular cementum, cementoblasts become
entrapped within their own matrix due to rapid deposition and are called
cementocytes
• Similar to osteocytes, they lie in spaces called as lacunae
• Haphazardly arranged and widely dispersed
• In deeper layers of cementum, cementocytes shows definite signs of
degeneration such as cytoplasmic clumping, empty lacunae, vesiculation

14. • CEMENTOCLASTS 1
• Found in howship’s lacunae
• Unilocular /multilocular cells
• Function: resorption of cementocytes
• Major role: resorption and repair

15. INCREMENTAL LINES OF CEMENTUM 2
• Referred to as incremental lines of salter
• Represent rhythmic periodic deposition of cementum
• Appears as dark lines running parallel to root surface
• Seen in both cellular and acellular cementum but more prominent in
acellular cementum
• Best seen in decalcified sections under light microscope
• Highly mineralized areas with less collagen and more ground
substance

16. CLASSIFICATION1
BASED ON LOCATION
BASED ON TIME OF FORMATION
CORONAL
RADICULAR
PRIMARY SECONDARY

17. BASED ON
CELLULARITY
BASED ON THE PRESENCE OR ABSENCE OF
COLLAGENOUS FIBRILS
1. FIBRILLAR
2. AFIBRILLAR
• It lacks embedded cells.
• Covers the root adjacent to
dentin near crown
ACELLULAR
• Cells are located within
the mineralized matrix.
• Seen at apical area and
overlying acellular
cementum. Also common in
interradicular areas
CELLULAR

18. BASED ON THE ORIGIN OF COLLAGENOUS FIBRILS
INTRINSIC FIBERS -
Which are formed due to
cementoblasts activity.
Are found between the
Sharpey's fibers. Arranged
either randomly or parallel
to the surface of the
cementum1
EXTRINSIC FIBERS - The
first group is made up of the
embedded parts of the principal
fibers of the periodontal
ligament which are known as
Sharpey's fibers (extrinsic
group).1
They are formed by the
fibroblasts of the periodontal
ligament.

19. SCHRODER & PAGE
CLASSIFICATION (1968,1991)
1.ACELLULAR AFIBRILLAR
CEMENTUM
2.ACELLULAR EXTRINSIC
FIBRE CEMENTUM
3.CELLULAR MIXED FIBRE
CEMENTUM
4.CELLULAR INTRINSIC
FIBRE CEMENTUM
5.INTERMEDIATE
CEMENTUM

21. ACELLULARAFIBRILLAR
CEMENTUM 1
• Found deposited on mature
enamel surfaces (1-15um) as
coronal cementum.
• It may be deposited during tooth
formation, during tooth eruption
or after it.
• This type of cementum is
probably of little significance as it
is not involved in fiber insertion
and tooth anchorage.
• Contains neither cells nor
extrinsic or intrinsic collagen
fibers, except for a mineralized
ground substance.
•.

22. ACELLULAR EXTRINSIC FIBER
CEMENTUM 1
• Is composed almost entirely of densely packed bundles of Sharpey
fibers and lacks cells.
• Acellular extrinsic fiber cementum is a product of fibroblasts and
cementoblasts.
• It is found in the cervical third of roots in humans, but it may extend
farther apically.
• Its thickness is between 30 and 230 µm.

23. (PLOS ONE | DOI:10.1371/journal.pone.0167316 December 9, 2016)
The results highlighted five main points –
1. The AEFC is mainly composed of carbonated hydroxyapatite and
collagen type I, with a Raman spectrum response similar to that of bone
and dentin.
2. The spatial distribution of peak and ratio intensities reproduced the
alternating bright and dark incremental lines observed in polarized
microscopy.

24. The alternating pattern of AEFC could thus be partly related to
the mineral/organic composition, with higher mineral/ organic
ratio in dark lines compared to bright lines.
3. The collagen fibers seemed to be better aligned in dark lines
(the dark lines correspond to smaller, more mineralized and
better organized incremental layers produced during a winter
rest period. )
4. Mineral crystals were always parallel to collagen fibrils.
5. Based on the results of Raman polarized acquisitions, they
proposed an organization of the AEFC consisting of orthogonal
or radial fibers in the continuity of periodontal ligament
Sharpey’s fibers and “non-orthogonal” fibers (occasionally
mistakenly called intrinsic fibers), which in turn may consist of
branching and bending radial fibers.

25. CELLULAR MIXED STRATIFIED
CEMENTUM 1
• Composed of extrinsic & intrinsic fibers & contains cells.
• Forms the bulk of the Secondary Cementum.
• Co-product of cementoblasts & fibroblasts.
• Location: Apical interradicular regions.
• Thickness ranges from 100-1000um.
• Primary function is adaptation.

26. • It has a lower mineral content than Acellular Extrinsic Fiber
Cementum.
• This difference can in part be accounted for by:
• the non mineralized structures present in Cellular Intrinsic Fiber
Cementum.
• The Sharpey’s fibers present in it generally retain an
unmineralized core as these fibers have a coating of type 3
collagen, which may prevent mineralization of the type I collagen
in the core.

27. CELLULAR INTRINSIC FIBER
CEMENTUM 1
• Location: Found in middle and apical
third
• Contains cells but no extrinsic collagen
fibers.
• Formed by Cementoblasts.
• Only it can repair a resorptive defect of
the root in a reasonable time due to its
capacity to grow much faster than any
other known cementum type.
• It has a major role in adaptation and
repair
• its formation on the developing root
commences in closest proximity to the
advancing root edge.

28. INTERMEDIATE CEMENTUM LAYER
• It does not exhibit characterstics of either DENTIN OR CEMENTUM
• It is structureless
• It mainly observed in apical 2/3rd of molars and premolars , rarely seen
in incisors or deciduous teeth.
• In this layers hertwig’s epithelial sheath become trapped in rapidly
deposited dentin or cementum matrix.1
• It contains no tubules but wide range spaces which are thought to be
enlarged terminals of dentinal tubules
• Sometimes it found as a continuous layer or in isolated areas
• Seen at zone near CDJ

29. CEMENTOGENESIS
(Development of Cementum)2
Deposition of
dentin along the
inner aspect of
HERS
Disintegration of
HERS allowing
newly formed dentin
to come in contact
with cells of dental
follicle
Differentiation of
cementoblast
along the external
surface of the
root
Protein secretion by
cementoblast mainly
collagen &
proteoglycans which
form organic matrix of
cementum
Phase of matrix
maturation which
subsequently
mineralizes to form
cementum.

30. FORMATION OFCEMENTOBLASTS
• CEMENTOBLASTS FORMATION RESULTS IN 2 WAYS2
FROM HERTWIG’S
EPITHELIAL ROOT
SHEATH
FROM DENTAL
FOLLICLE
 Soon after Hertwig’s root sheath
breaks down
Epithelial cells of hertwig’s root
sheath undergo epithelial
mesenchymal transformation
CEMENTOBLASTS
Ecto- mesenchymal in origin

31. • These cells are rich in numerous Mitochondria ,well formed
Golgi apparatus, and larger amounts of Granular Endoplasmic
Reticulum
Electron microscopically
cementoblasts show
Mitochondria and
Endoplasmic reticulum

32. • Cementoblasts synthesize collagen and protein polyasaccharides.
• Cementoblasts derived from dental follicle have similar phenotype to
osteoblasts ,it is shown to be involed in formation of Cellular Intrinsic
fiber Cementum.2
• Cementoblasts derived from HERS has different phenotype than
osteoblasts and are shown to be involved in Acellular Intrinsic Fiber
Cementum.2
• In the differentiation of cementoblasts, growth factors belonging to the
TGF beta including BMP, MOLECULE EPIDERMAL GROWTH
FACTOR etc. are involved .

33. CEMENTO-DENTINALJUNCTION
• The terminal apical area of cementum where it joins internal root canal
dentin is known as cemento-dentinal junction.
• Interface between cementum and dentine
• In deciduous teeth- scalloped
• In permanent teeth- smooth
• Areas of dentine adjacent to CDJ appears granular in ground section due to
colaescing and looping of terminal portion of dentinal tubules and is called
TOMES GRANULAR LAYER
• During RCT obturating material must end near CDJ
• No increase or decrease in width with age(2-3 micrometer)1

34. CEMENTO-ENAMELJUNCTION 1
It is defined as the area of union of cementum and enamel at the
cervical region of the tooth.

35. CEMENTUM RESORPTIONAND
REPAIR 1
• Permanent teeth doesn’t undergo the process of physiologic resorption as
does the counterpart
• However the cementum of erupted as well as unerupted teeth is subject to
resorptive changes that may be of microscopic proportion or sufficiently
extensive to present a radiographically detectable alteration in the root
contour
• Local conditions1
• 1) Trauma from occlusion
• 2) Orthodontic movement
• 3) Cysts and Tumors
• 4) Pressure from mal-aligned erupted teeth
• 5) Peri-apical disease and Periodontal disease

36. Systemic Conditions1
1) Paget’s disease
2) Hypothyroidism
3) Heredity fibrous osteodystrophy
4) Calcium deficiency
• Cementum resorption appear microscopically as bay like
concavities in the root surface1
• Multi-nucleated giant cells and large mononuclear macrophages
are generally found adjacent to cementum undergoing active
resorption1
• Several sites of resorption coalesce to form a larger area of
destruction1
• Resorptive process may extend into underlying dentin and even
into pulp, but its usually painless

37. • Cementum resorption is not necessarily continuous and may
alternate with periods of repair and deposition of new cementum1
• The newly formed cementum is demarcated from the root by a
deep stained irregular line, termed as reversal line, which
delineates the border of the previous resorption1

38. • Repair of cementum is a process to heal the damage caused by
resorption or cemental fracture
• Cementum repair requires the presence of viable connective
tissue
• If epithelium proliferates in the area of resorption then repair will
not take place
• Repair can occur in both vital and non-vital teeth
• Repair can be
Anatomical Functional

39. Anatomic Repair: The root outline is re-established as it was before
cemental resorption. It generally occurs when the degree of destruction
is low.
Cementum resorption is repaired by cellular and acellular cementum.
Functional Repair: in cases of large cemental resorption or
destruction, repair doesn’t re-establish the same contour as before.
To maintain the width of PDL, the adjacent alveolar bone grows and
takes the shape of defect, this is done to improve the function of tooth,
hence called functional repair.

40. FUNCTIONS OF CEMENTUM 2
• ANCHORAGE:
Primary function of cementum is to furnish a medium for the
attachment of collagen fibers that bind the tooth to alveolar bone.
• ADAPTATION:
The continuous deposition of cementum is of considerable functional
importance.
As the superficial layer of cementum ages, a new layer of cementum is
deposited to keep the attachment apparatus intact.
• REPAIR:
Cementum serves as the major reparative tissue for root surfaces.
Damage to roots such as fractures and resorption can be repaired by
the deposition of new cementum

41. AGE CHANGES IN CEMENTUM 5
• Cementum formation continues throughout life
• It appears that cementum is deposited at a linear rate
• There is tendency for cementum to reduce root surface concavities .
Thus, its thicker layers are found in root surface grooves and furcation
areas
• Tooth position may exert temporal and spatial variation in pressure and
tension on root surface and these stimuli influence the rate as well as
pattern of cementum formation
• Non- functioning impacted teeth have thicker cementum
• Sharpey’s fibers may nearly completely absent

43. (2018 International Journal of Oral Health Sciences)
The relationship between chronological age and estimated age using light
microscope, phase contrast and polarized microscope showed stronger
correlation while stereo microscope showed a weaker correlation.
The aim of this study was to examine the correlation between chronologic age and
estimated age and to find the most accurate method of calculating cemental
annulations using different types of microscopes (light microscope, phase contrast
microscope, polarized, and stereomicroscope).

44. EXPOSURE OF CEMENTUM TO
ORALENVIRONMENT 5
• Cementum becomes exposed to oral cavity in cases of gingival
recession and a consequence of loss of attachment in pocket formation
• Cementum is sufficiently permeable to be penetrated by micro-
organisms, organic and inorganic substances in such cases
• Bacterial invasion of the cementum occurs commonly in periodontal
disease
• Caries of cementum can also develop.

45. (Journal of Indian Society of Periodontology - Vol 18, Issue 5, Sep-Oct 2014)
The results of this study indicated that the hardness and modulus of elasticity of
the cervical third cementum decreases significantly in chronic periodontitis.
This study aims to analyze the nanomechanical properties of the cervical third of
the cementum (transverse section) in health and chronic periodontitis
Twenty teeth (10 healthy and 10 periodontally diseased) were collected and the
nanomechanical properties of the transverse section of the cervical third cementum
were evaluated

46. CHANGES IN CEMENTUMASSOCIATED
WITH PERIODONTALDISEASE
• Structural Changes
• Partial demineralization
• Decrease or loss of cross banding of collagen
• Sub-surface condensation of organic material of exogenous origin
• Chemical Changes
• Increase in calcium and phosphate levels
• Increase in fluoride content
• Decrease in sodium levels

47. • Cytotoxic changes
• Effects on cell proliferation
• Hatfield and Bomhammers- inhibitory substance penetrates the exposed
cementum that prevents growth of epithelial cells in tissue cultures
• Presence of endotoxins - limits fibroblast proliferation – detrimental to the
arrest of disease
• Cementum bound endotoxins – 50 times more toxic
• Destructive physical changes – cavitation, partial demineralization
• Effect on cell attachment
• Cultured human gingival fibroblasts do not attach to diseased tooth (Aleo
et al 1975)

48. Inhibitory principle of matrix- Morris (1975)
• Disease inhibited development of implanted marrow whereas
demineralized healthy tooth did not
• Demineralized diseased roots showed more inhibition-toxins must
have seeped into root matrix during pocket formation and
demineralization removed the toxin allowing development of marrow
• According to inhibitory principle of matrix-phenol extraction usually
required to remove toxins from bacterial cell wall is not necessary to
make diseased cementum receptive cell attachment

49. • In early and moderate periodontitis- acellular cementum is affected
(coronal half of the root)
• Damage extends to cellular cementum in most advanced periodontal
conditions and furcally positioned lesions
• These surfaces are almost always covered by cellular cementum
during successful regeneration, whether this is adequate is unclear
(McNeil and Sommerman-1999)

50. DEVELOPMENTALANOMALIES
OF CEMENTUM
Enamel Projections
If amelogenesis does not stop before the start of
root formation, enamel may continue to form over
portions normally covered by cementum3
Enamel Pearls
This consist of globules of enamel on root
surface in cervical regeneration (act as
plaque retentive areas)3

51. Hypercementosis
• Refers to prominent thickening of cementum
• It may be localised to one tooth or may involve the entire dentition3
(Paget’s disease)
• Occurs as generalised thickening of the cementum, with nodular
enlargement of cementum in apical third of root
• Etiology of Hypercementosis
Spike-like type of Hypercementosis : results from excessive forces from
orthodontic appliances or occlusal forces
Generalised type-occurs in teeth without antagonist

52. (2015 Journal of Indian Academy of Oral Medicine and Radiology)
A very unusual case of mammoth, dumbbell-shaped hypercementosis
in a 49-year-old male patient is reported. Literature on hypercementosis
is reviewed. Etiology, radiographic appearances, and differential
diagnosis are discussed. Importance of pre-extraction radiographs in all
cases is stressed.

53. Cementoblastoma
• Only neoplasm of cementum
• Cementum like tissue is deposited around the roots
of teeth as irregular or rounded mass
• Age less than 25
• Involves commonly- mandibular molars and pre-
molars
• Tooth usually as vital pulp
• Attached to roots and causes its resorption,
involves pulp canal and also causes slow
expansion of cortical plate
• Enlargement produced is usually asymptomatic

54. Cementicles
• Are small, globular masses of cementum found in approx 35% of
human roots.
• May not be always attached to the cementum surface but may be
located free in Pdl.
• These may result from microtrauma, when extra stress on sharpey’s
fibers causes a tear in the cementum. 3
• Are more commonly found in apical & middle third of root and in
root furcation areas

55. • May develop from calcified epithelial rests; around small spicules of
cementum or alveolar bone traumatically displaced into the
periodontal ligament; from calcified Sharpey's fibers; and from
calcified, thrombossed vessels within the periodontal ligament

56. Cementoma
• Benign cementoblastoma /cemental
dysplasia2
• Represents an unusual reaction of bone
• Caused due to occlusal trauma
• Present usually at apex of mandibular
incisor
• Almost exclusively found in black persons
• Age-20 to 40 years
• Causes expansion of jaw

57. Concrescence
• Form of fusion which occurs root formation has been completed
• Thought to arise as a result of crowding or traumatic injury of the
teeth with resorption of interdental bone so that the two roots are in
approximate contact and fused by deposition of cementum between
them2
• May occur before or after tooth has erupted

58. Hypophosphatasia
• This is a hereditary disease characterized by total absence of
cementum
• It results in early loss of teeth
• It occurs due to deficiency of enzyme ALP in serum and tissues
Acromegaly
• The tooth crowns are usually longer in size and the roots often
enlarge as a result of secondary cemental hyperplasia.
• This hypercementosis may be the result of functional and
structural demands on teeth.

59. Ankylosis
• Fusion of alveolar bone and cementum with obliteration of PDL space
is termed as ankylosis2
• Occurs in cases of cemental resorption, may represent a form of
abnormal repair
• May develop after chronic apical inflammation, tooth re-plantation and
occlusal trauma
• Results in resorption of root and gradual replacement with bone tissue

60. Cemental tears
• The detachment of a fragment of cementum is described as a cemental
tear.
• Cemental tears have been reported in the periodontal literature
associated with localized, rapid periodontal breakdown.

61. CONCLUSION
 A thorough knowledge of the structure and function of cementum is
essential to understand its involvement in disease & also about its
treatment.
 Cementum by virtue of its structural and dynamic qualities, provides
tooth attachment & maintenance of occlusal relationship.
 Fibers in cementum helps in tooth anchorage. Certain pathologic
factors may cause irreversible damage to cementum else it is self
reparative to small disturbance .

62. REFERENCES
1. Carranza’s clinical periodontology (10th , 11th & 13th edition)
2. Orban’s –Text Book Of Oral Histology And Embryology 11th edition
3. Shafers textbook of oral pathology – 7th edition
4. Mallar KB, Girish HC, Murgod S, Yathindra Kumar BN. Age
estimation using annulations in root cementum of human teeth: A
comparison between longitudinal and cross sections. J Oral Maxillofac
Pathol 2015;19:396-404
5. Boscchardt D, Selvig K. Dental Cementum: The dynamic tissue
covering the root surface. Periodontology 2000. Vol. 13, 1997, 41-75

63. 6. Colard T et al. (2016) New Insights on the Composition and the
Structure of the Acellular Extrinsic Fiber Cementum by Raman
Analysis. PLoS ONE 11(12):e0167316.
7. Geetha HL, Baghisath VP, Vinay HB, Sudheer B, Kumar VJ,
Gayathri CH. Age estimation using tooth cementum annulations
method by different types of microscope: A comparative study. Int J
Oral Health Sci 2018;8:73-80.
8. Sundaram, et al.: Nanostructure of cervical third cementum in health
and chronic periodontitis JISP -2014 ;18( 5).
9. Raghavan V, Singh C. Hypercementosis: Review of literature and
report of a case of mammoth, dumbbell-shaped hypercementosis. J
Indian Acad Oral Med Radiol 2015;27:160-3.