Cementum is a thin layer of hard dental tissue covering the anatomic roots of teeth. It is formed by cells known as cementoblasts. It is a part of periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament. The different categories of cementum are based on the presence or absence of cementocytes, as well as whether the collagen fibres are extrinsic or intrinsic. It is thought that fibroblasts, and some cementoblasts, secrete extrinsic fibres, but only cementoblasts secrete intrinsic fibres. The extrinsic fibres within acellular extrinsic fibre cementum, travel perpendicular to the surface of the root and allow the tooth to attach to the alveolar bone by the periodontal ligament (PDL), continuous with the cementodentinal junction (CDJ). Acellular cementum only contains extrinsic collagen fibres. Whereas, cellular cementum is quite thick and contains both extrinsic and intrinsic collagen fibres. The first cementum to be formed during tooth development is acellular extrinsic fibre cementum. The acellular layer of cementum is living tissue that does not incorporate cells into its structure and usually predominates on the coronal half of the root; cellular cementum occurs more frequently on the apical half.In summary, the main types of cementum are as follows: Acellular Afibrillar Cementum (AAC), Acellular Extrinsic Fibres Cementum (AEFC), Cellular Intrinsic Fibres Cementum (CIFC) and Mixed Stratified Cementum (MSC) which displays both cellular and acellular cementum. Cellular cementum contains cells and is the medium of attachment of collagen fibres to the alveolar bone. It is also responsible for minor repair of any resorption by continued deposition to keep the attachment apparatus intact. Acellular cementum does not contain cells and has a main purpose of adaptive function.

1. CEMENTUM
By: Danish Hamid
Roll No. 02
3rd Prof

2. Contents
 Introduction
 Physical Characteristics
 Chemical Composition
 Development
 Functions
 Types of Cementum
 Schroeder Classification
 Cementoenamel Junction
 Cementum Resorption and Repair
 Clinical Considerations

3. Introduction
o Cementum is calcified, avascular mesenchymal
tissue that forms the outer covering of the
anatomical root.
o It is part of the PERIODONTIUM.
o It begins at cervical portion of the tooth and
continues to apex.

4. Physical Characteristics
o Pale yellow in color.
o Lighter color, softer and more permeable than
dentin.
o Shows irregular surface.
o Thickness ;
– At coronal half:- 16 to 60 µm
– At apical third & furcation area:- 150 to 200 µm

5. Chemical Composition
Organic
50 – 55%
Type I (90%)and
Type III (5%) collagen
fibers are embedded
in ground substance.
Proteins and
Polysaccharides
Inorganic
45 -50 %
Hydroxyapatite
Calcium
Phosphorous
Fluoride
Water

6.  Source of collagen fibers
Extrinsic Fibers
o Formed by fibroblasts.
o Embedded portion of
principal fibers of PDL.
o Run in same direction
of principal fiber
o Also called Sharpey’s
fibers.
Intrinsic Fibers
o Produced by
cementoblasts.
o Belong to
cementum matrix.
o Run parallel to root
surface.

7. Development of Cementum
o Rupture of Hertwig Root Sheath allows the
mesenchymal cells of dental follicle to contact
dentin where they start forming a continuous
layer of cementoblasts.
o Begins with deposition of irregular meshwork of
collagen fibrils sparsely distributes in ground
substance called pre-cementum or cementoid.

8. .
o Followed by phase of matrix maturation, which
subsequently mineralizes to form cementum.
o Sometimes cementoblasts may get enclosed
and trapped in the matrix, they are referred as
cementocytes , and remain viable.
o The formation of cementum is incremental , so
we obtain Incremental lines of Salter.

9. .
Development of Cementum

10. Functions of cementum
Primary function of cementum is
anchorage that is by furnishing a
medium for attachment of collagen
fibres that bind the tooth to alveolar
bone.
Apical cementogenesis compensated
for attrition of enamel, thereby
maintaining functional occlusal
relationship.

11. It serves as reparative tissue in case root
fracture or resorption.
It provides for fiber reattachment or
relocation consequent to mesial drifting
of teeth.

12. Types of cementum
Cementum is of 2 two main types; Acellular and Cellular.
1. Acellular Cementum:-
o It is the first cementum formed also known
as Primary cementum.
o It doesn’t contain cells.
o It covers cervical third or half of the root.

13. .
o It is formed before the root
reaches the occlusal plane.
o Sharpey’s fibers makeup
most of structure and are
inserted at rt. angles into
root surface.
o Thickness:- 30-230 µm.

14. 2. Cellular cementum:-
o It is formed after the formation of Acellular
cementum so called Secondary cementum.
o It contains cells (Cementocytes) present in
lacunae.
o It covers apical third and inter-radicular region.

15. o It is formed after the
tooth reaches the
occlusal plane.
o Sharpey’s fibers occupy
smaller portions and are
separated by other fibers
arranges parallel to root
surface.

16. Fig.;- Cellular and Acellular Cementum
(with Cementocytes in lacunae)

17. Schroeder’s Classification
This classification is based on location, morphology
and histological appearance.
1. Acellular afibrillar cementum(AAC)
2. Acellular extrinsic fiber cementum(AEFC)
3. Cellular mixed stratified cementum(CMSC)
4. Cellular intrinsic fiber cementum(CIFC)
5. Intermediate cementum (The hyaline layer of Hope
Well Smith)

18. Acellular Afibrillar Cementum (AAC)
o It neither contains cells nor extrinsic or intrinsic
collagen fibres.
o It only contains mineralizes ground substance.
o It is a product of cementoblasts and is found as
coronal cementum.
o Thickness: 1-15 µm

19. Acellular extrinsic fiber cementum
(AEFC)
o It is composed entirely of densely packed bundles
of Sharpey fibres and lacks cells.
o It is a product of fibroblasts and cementoblasts.
o It is found in cervical third of root.
o Thickness: 30-230 µm

20. Cellular Mixed Stratified Cementum
(CMSC)
o It is composed of extrinsic and intrinsic fibers and
may contain cells.
o It is a co product of fibroblasts and
cementoblasts.
o It appears in apical third of roots, apices and
furcation areas.
o Thickness: 100-1000 µm

21. Cellular Intrinsic Fiber Cementum
(CIFC)
o It is composed of intrinsic fibres and cells
but no extrinsic fibers.
o It is a product of cementoblasts.
o It fills the resorption lacunae.

22. Intermediate cementum
o It is an ill-defined zone near cemento-dentinal
junction.
o It contains cellular remnant of the Hertwig’s
sheath embedded in calcified ground substance.
o It contains enamel like proteins which help in
attachment of cementum to dentin.

23. .

24. Cementoenamel junction
Three types of relationships can occur at cemento-
enamel junction.
a. Overlapping:- In 60-65% of cases, cementum
overlaps the enamel. It occurs when the
enamel epithelium degenerates at cervical
termination permitting connective tissue to
come in contact with the enamel surface.

25. b. Touching:- In about 30% of cases, an edge to
edge butt joint exists between enamel and
cementum.
c. Gapping :- In 5-10% of cases, the cementum
and enamel fail to meet. It occurs when
enamel epithelium at cervical portion is
delays its separation from dentin.

26. Fig:- Cementoenamel junction

27. Cementum Resorption and Repair
o Cementum is less susceptible to resorption
than bone under same pressure because of
being avascular.
o Average number of resorption areas per tooth
is 3.5 and are located in apical third (76.8%),
middle third (19.2%) and gingival third (40%).

28. o Caused by local or systemic factors.
o Local conditions include trauma from
occlusion, orthodontic movement pressure,
cysts, periapical & periodontal diseases.
o Systemic conditions include calcium
deficiency, hyperthyroidism, hereditary fibrous
osteodystrophy and Paget disease.

29. o Resorption areas appear as bay-like
concavities.
o Cementum resorption is not continuous and
may alternate with periods of repair and
deposition of new cementum.
o The reparative and resorbed cementum are
demarcated by an irregular reversal line.

30. .
o The repair of cementum requires the presence of
cementoblasts and viable connective tissue.
o The reparative cementum is less mineralized and
exhibits small calcifies globules.
 Anatomic repair:- outline is re-established.
 Functional repair:- little cementum is formed and
rest is filled by alveolar bone.

31. Fig:- Cementum Resorption and Repair

32. Clinical considerations
1. Hypercementosis
 It is an age-related phenomenon and refers to
prominent thickening of cementum.
 It may be localized to one tooth or affects entire
dentition.
 Occurs as generalized thickening of cementum
with nodular enlargement of apical third of root.

33.  It appears as spike like excrescences, created
either by coalescence of cementicles or
calcification of PDL fibres at site of insertion into
cementum.
 Roots appear thick with rounded apices.
 The causes can of hypercementosis can be:
accelerated elongation of tooth, inflammation,
tooth repair or Paget’s disease.

34. Hypercementosis
Hypercementosis

35. 2. Ankylosis
oIt is the fusion of the cementum and the
alveolar bone with obliteration of PDL.
oIt results in resorption of the root and its
gradual replacement by bony tissue.
oIt occurs in case of cemental resorption, occlusal
trauma, chronic periapical inflammation,
reimplanted or embedded teeth.

36. .
o Ankylosed teeth lack physiologic mobility of
normal teeth and give dull, muffled metallic
sound on percussion.
o Physiological drifting and tooth eruption
doesn’t occur.
o Radiographically, blending of the bone with
the root is apparent.

37. Fig:- Molars showing ankylosis
Normal Ankylosis

38. 3. Cementicles
o These are small areas of dystrophic calcified
tissue, which lie free in the periodontal
ligament of lateral and apical root areas.
o They may be formed by calcification of
epithelial rests, CT between Sharpey’s fibers, or
thrombosed capillaries.

39. o They may be free in PDL or attached or
embedded in cementum.

40. 4. Concrescence
o It is the union of two or more fully
formed teeth through cementum only.
o It is a result of traumatic injury or
crowding of teeth with resorption of
interdental bone by which two roots
come in contact and become fused by
cementum deposition.

41. 5. Cemental Spurs
o These are symmetrical spheres of cementum
attached to root surface.
o Found near cementoenamel junction.
o These result from irregular deposition of
cementum on the root.
o Can’t be easily removed since they are hard
dental tissue.

42. Bibliography
o Newmann and Carranza’s Clinical Periodontology
o Orban’s Oral Histology and Embryology
o Shafer’s Textbook of Oral Pathology
o Researchgate.net
o Wikipedia.org
o Slideshare.net