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1. 1. Introduction
Cementum / simply cement is derived (from Latin CAEMETUM,
quarried stone) is a component of the tooth as well as the periodontium.
Definition: It is a mineralized dental tissue covering the anatomic roots of
human teeth (ORBANS).
Definition (Glickman) : It is the calcified mesenchymal tissue that forms
the outer covering of the anatomic roots.
It was first demonstrated microscopically in 1835 by Frankel and
Raschkow, 2 pupils of Purkinic.
- It begins at the cervical portion of the teeth at the CEJ and
continues to the apex.
- Cementum furnishes a medium for the attachment of collagen
fibres that binds the tooth to the surrounding structures.
- It is a specialized connective tissue that shares some physical,
chemical and structural characteristics with compact bone.
[Unlike bone however human cementum is AVASCULAR).
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2. DEVELOPMENT OF CEMENTUM / CEMENTOGENESIS
Cementum is mesodermal in origin with dentin, alveolar bone,
periodontal ligament.
- Cementum develops from dental follicle which surrounds the
teeth germ.
- Development of cementum starts after crown formation is
completed and before start of eruption.
- The outer and inner enamel epithelium after crown formation
form a double layered sheath which proliferates from the
cervical loop to form Hertwig’s epithelial roots sheath, which
separates the D papilla from D. follicle.
- Cells of peripheral dental papilla differentiate along HERS
into odontoblasts.
- These odontoblasts form a single layer of dentin, once the
dentin formation begins breaks occur in the ERS allowing the
newly formed dentin to come in direct contact with
connective tissue of the dental follicle.
- Cells derived from this connective tissue are responsible for
cementum formation.
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3. [Breakdown of HERS involves degeneration / loss of its basal lamina
on the cemental side which is soon followed by the appearance of collagen
fibres and cementoblasts] between the epithelial cells of the root sheath.
- Some sheath cells migrate away from the dentin towards the
dental sac, which become the epithelial rests of malassez
found in the periodontal ligament whereas others remain near
the developing tooth and are incorporated into the cementum.
Precementum/Cementoid – is the unmineralized tissue begins at the CDJ.
- The cementoid layer ranges from 3 to 5µm in the A3rd
(AC).
- It provides a compatible environment for CB and serves a
protective function – resists cementoclasia.
- Composition – is predominantly collagen.
PHYSICAL PROPERTIES
Cementum is LIGHT YELLOW in color and can be distinguished
from enamel by:
a) Its lack of luster and
b) Its darker hue.
- Cementum is somewhat lighter in color than dentin. But
clinically, it is not possible to distinguish cementum from
dentin based on color alone.
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4. - The density of completed mineralized cementum is found to
be less than that of dentin.
- Cementum is very permeable (C and A.C.C.) and permit the
diffusion of dyes from the pulp and from the external root
surface. [With age, the permeability of cementum
diminishes].
- The thickness of cementum on half of the root varies from 16
to 60µm and it is the thickness of hair.
- It attains greater thickness up to 150 to 200µm in the apical 3rd
and in the bifurcation and trifurcation area.
- It is thicker in distal surface than mesial surface probably
because of functional stimulation from mesial drift.
The average thickness of – 95µm at age 20.
– 215 µm at age 60.
(I) INORGANIC SUBSTANCE
- Consists mainly of Ca and phosphate ions in the form of
hydroxyapatite.
- Cementum has the highest fluoride content of all the
mineralized tissue.
- Trace elements – Cu, Lead, Iron, Na, Mg, K, Zn.
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5. (II) ORGANIC PORTION
- Primarily consists of Type I collagen fibres and protein
polysaccharides (proteoglycans).
- Collagen of cementum indicated close similarities to the
collagen of dentin and alveolar bone.
CHEMICAL COMPOSITION
Cementum from fully formed permanent teeth contains about
45% to 50% - INORGANIC SUBSTANCES.
50% TO 55% - ORGANIC MATERIAL AND H20
1) The ratio of O : InO and H2O in cementum is difficult
to determine because of
1. Age difference.
2. Difference in the prop of CC and A.C.C.
3. Contaminate of C samples by alien tissues.
2) C is less radiopaque than E and D.
MINERALIZATION
It is a highly odered and rhythmic process, that begins in the depth of
the pre-cementum.
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6. - Fine crystals are formed on, in and between the collagenase
elements. Needle and plate shaped crystal formation, occurs.
- These (needle) crystals are arranged parallel to the fibrils and
are smaller than those of E but similar to that of D and bone.
E. Pearls formation – is as a result from an atypical condition in which the
R.S. adhere to the dentin and the IEF of the R.S. Seen in bifurcation and
trifurcation areas when present more CERVICALLY – perio-procedures
should be carried out.
ACCESSORY CANALS – At times premature discontinuities may take
place in the R.S., here the OB are not formed because of the absence of IEF;
so the connective tissue of the [DF migrates into the break and continues
with RADICULAR PULP].
Undisturbed areas – Normal development and thus a channel is formed
A.C.
HISTOLOGY OF CEMENTUM
Histologic sections of cementum show:
a. Cells, fibres, ground substances, resting
lines.
b. Cemento-enamel junction.
c. Cemento-dentinal junction.
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7. CELLS: The cells associated with cementum are:
1. Cementoblasts.
2. Cementocytes.
3. Cementoclasts.
1. CEMENTOBLASTS – As soon as there is breakdown of HERS,
the UMC from adjacent CT differentiate into cementoblasts.
These cells have i. Numerous mitochondria
ii. Well-formed Golgi-apparatus.
iii. Large amounts of granular endoplasmic
reticulum.
- So. They actively synthesize COLLAGEN and PROTEIN
POLYSACCHARIDES which make up the organic matrix of
cementum.
- After, some cementum matrix is laid down, its mineralization
begins.
- These cells are found lining the root surface.
2. CEMENTOCLASTS – found in HOWSHIPS LACUNAE.
- These are unilocular / multilocular cells.
- Function : 1. Resorption of cementocytes trapped in lacunae
within their own matrix.
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8. 3. CEMENTOCYTES –
CELLULAR
CEMENTOBLASTS
1. These are active spider like
cells.
2. Size – 8 to 15µm
3. They are round / oval with
numerous radiating
processes. Body in lacunae
and processes – in canaliculi.
4. Acts as circulatory passages
and communicate with
process of neighbouring cells.
5. SPARSE CYTOPLASM
1. Are arranged in single
primary layers adjacent to
precementum using the RS.
2. Cuboidal in shape; when they
are active they are plump.
3. Exhibit same processes which
are long and few – they
represent the secretory ends.
4. The projections penetrate into
the PC.
5. Active CB – PULMP &
– BASOPHILIC
CYTOPLASM
– OPEN FACED NUCLI
– ROUGH ER
Resting CB – CLOSED NUCLEUS
– LESS CYTOPLASM
The Fibrous Matrix
- The collagen fibres of cementum are of 2 types:
i. Intrinsic fibres.
ii. Extrinsic fibres.
Intrinsic fibres – Are those formed as a result of cementoblasts activity.
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9. Extrinsic fibres – Are periodontal ligament fibre bundles which are
embedded into cementum. They are called Sharpey’s fibres (these fibres are
usually seen in recently formed cementum) contain numerous collagen
fibres.
INTRINSIC FIBRES EXTRINSIC FIBRES
1. Fibres are thin.
2. Diameter 1µm.
3. Completely mineralized.
4. Run parallel to the R.S.
1. Fibres are longer and thicker.
2. Diameter – 5 to 8µm.
3. Completely / partially
mineralized.
4. ⊥rt
angle to the extension
surface of tooth.
The Ground Substance
- The chemical mature of the PPS/GS of cementum is virtually
unknown.
Resting Lines
- Both acellular and cellular cementum are arranged in lamellae
separated by incremental lines parallel to the long axis of the
root.
- These lines represent rest periods in cementum formation and
are highly mineralized and have less collagen and more
ground substance.
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10. - These lines indicate Rhythmic and Regular deposition of
matrix.
- These are also known as INCREMENTAL LINES OF
SALTER.
CEMENTO ENAMEL JUNCTION
3 types of r/n involving the cementum may exist at the cemento-
enamel junction.
- r/n which cementum may bear to enamel at the neck of the
tooth.
1. 60% to 65% of cases – Cementum overlaps the enamel
- Overlap Type.
- Due to preparative degeneration of REE,
cementocyte in contact with enamel lay cementum.
2. 30% of cases – Edge to edge
- Butt Type
- Cementum and enamel meet at a sharp point.
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11. 3. 5% to 10% - Cementum and enamel fail to meet.
- GAP Type
- This is due to delayed degeneration of HERS.
- So here dentin may be covered by REE instead of
cementum.
Primary Teeth Deciduous Intermediate C layer
CEMENTO DENTINAL JUNCTION
- The dentin surface upon which cementum is deposited is
relatively smooth in permanent teeth in one of deciduous teeth
it is scalloped.
- Sometimes dentin is separated from cementum by a zone
known as the Intermediate cementum layer or Hopewell
Smith layer. This is predominantly seen in the apical 2/3rd
of
the roots of M’s and Pm’s and rarely in I’s and deciduous
teeth.
- It is believed that this layer represents area where cells of
HERS become trapped in a rapidly deposited dentin /
cementum matrix. It is continuous / isolated.
- Size – 10µm thickness, thin layer of cal tissue, amorphous
non cellular.
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12. CLASSIFICATION OF CEMENTUM
[I]
a. Acellular cementum
b. Cellular cementum
a) Acellular cementum – It is the Ist
formed cementum and covers
/ Primary cementum approximately the c 2
/3 / ½ of the root.
- It does not contain cells.
- This cementum is formed before the tooth
reaches the occlusal plane.
- Thickness ranges from 30 to 230µm.
- Sharpeys fibres make up most of the
structure of ACC.
- ACC also contains other collagen fibrils
they are calcified and irregularly
arranged / parallel to the surface.
b) Cellular cementum – It is formed after the tooth reaches the
/ Secondary cementum occlusal plane. Apical 2/3rd
.
- It is more irregular and contains cells
(cementocytes).
- Cellular cementum is less calcified than
the acellular cementum.
- SF occupy a smaller portion of CC.
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13. - Less mineralized and more permeable.
Cellular C Acellular C
1. Osteocytes in lacunae with
processes in canaliculi found.
2. Rate of development is Faster.
3. Incremental lines are Wide
Apart.
4. Precementum / cementoid
layer – Wide.
1. No cells in cementum.
2. Slow.
3. Closer.
4. Narrower.
[II] SCHOREDER CLASSIFICATION
1) Acellular afibrillar cementum.
2) Acellular extrinsic fibre cementum.
3) Cellular mixed stratified cementum.
4) Cellular intrinsic fibre cementum.
1) AAC – It is a product of cementoblasts.
- Found in coronal cementum.
- Contains neither cells/ extrinsic / intrinsic CF apart from
mineralized ground substances.
2) AEFC – Contains densely packed bundles of SF and lacks
cell.
- It is a product of FB and CB.
- Found in C3rd of roots.
3) CMSC – It is a product of FB and CB.
- Found in A 3rd
of roots and apices and furcation areas.
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14. - Contains extrinsic, intrinsic fibres and cells.
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15. 4) CIFC – It is a product of CB.
- It fills the resorption lacunae.
- Contains cells but no collagen fibres.
[III] Based on fibres – cementum is classified into:
1. Intrinsic fiber cementum.
2. Extrinsic fiber cementum.
3. Mixed fiber.
FUNCTIONS OF CEMENTUM
The principal function of cementum is assisting anchorage of the
tooth.
1. The primary function is to furnish a medium for attachment of
collagen fibers that bind the tooth to alveolar bone.
2. Cementum serves as the major reparative tissue for root surfaces.
Damage to roots such as #’s and resorption can be repaired by
deposition of new cementum.
- Continuous deposition of C is of functional importance
therefore SA for the attachment of fibres increases.
3. Less of occlusal surface substances is compensated by continuous
deposition of cement at apical portion.
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16. 4. Keeps the attachment apparatus intact because of increased mesial
drift a new layer gets deposited and helps in relocation and
readaptation.
CLINICAL CONSIDERATIONS
1. Cementum is more resistant to resorption than is bone and it is for
this reason ortho tooth movement is made possible.
2. Transverse # of the root may occur because of trauma and this may
heal by deposition of new cementum.
3. Cementum resorption can occur after trauma / excessive occlusal
wear.
4. Because of continuous cementum deposition around the apex, the
total length of tooth is maintained in spite of the loss of E from
occlusal wear. This deposition of cementum leads to a constriction of
apical foramen and alteration in number, size and shape of apical
foramena. The over all affect is that in older teeth the complexity of
apical foramina is increased. This should be kept in mind during
endodontic treatment.
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17. C. RESORPTION AND REPAIR : The cementum of erupted as well as
unerupted teeth is subjected to resorption. Very common and may occur
without any apparent etiology.
1. Idiopathic : TFO; or movement maligned teeth; cysts, tumors no
adjacent, pa disease.
2. Systemic : Ca deficiency; hypothyroidism, p disease hereditary
fibrous osteodystroy.
3. R may extend into D as well as P, but is usually painless.
4. C resp is not continuous and may alternate with periods of repair.
5. C repair can occur in devitalized as well as in vital teeth.
Anatomic repair and functional repair
Root surface changes:
1. Structural changes (pathological granules) – in heavily infected RC
they are at DCJ.
2. Areas of demineralization – RS caries progress round rather into the
tooth (proteolysis of S.F. brings about fragmental / cavitation).
Active Lesion : yellowish / light brown soft and leathery consistency.
Inactive : Darker with smooth surface (on probing) harder in consistency.
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18. HYPERCEMENTOSIS [Cementum hypoplasia] care while extraction
- Refers to as prominent, thickening of cementum.
- It may be 1) Localized
Circumscribed – surrounding root like a collar.
2) Diffused
- It might affect:
i. All teeth of the dentition.
ii. Single tooth.
iii. Part of a tooth surface.
Causes:
1. In the teeth with Pa inflammation caz of pulpal involvement –
extensive hyperplasia.
2. Accelerated growth of the teeth structure – in the absence of an
antagonist.
3. Mechanical stimulation / orthodontic forces / heavy occlusal forces
lead to excessive tension which results in spike like hypercementosis
(SPUR/ PRONG – LIKE EXTENSION).
4. Entire dentition – hypercementosis in patients with Pagets diseases
(Loss of lamina dura).
5. Cemental repair.
6. Ankylosis : is fusion of C and AB with obliteration of PDL occurs
due to:
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19. 1. Cemental resorption.
2. After chronic Pa inflammation.
3. It results in resorption of the root and its gradual replacement by
bony tissue.
4. When titanium implants are place in the jaw healing results in bone
tenned in direct apposition to the implant with any intervening CT.
- Ex cementosis (knob – like extensions of hypercementosis).
CEMENTOMA : Are masses of cementum; situated apically  may / may
not be attached. They are considered to be either odontogenic neoplasms /
developmental malformations. Seen in mandible > maxilla.
CEMENTICLES : Are globular masses of cementum arranged in connective
lamellae. They lie free on PDL attached to the cementum; developed from
calcified epithelial cells and SF’s.
Conclusion
Cementum is the part of tooth supporting apparatus and any
alteration in the normal form and function of this structure may result in
disruption of normal psychological function of the tooth.
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20. CONTENTS
1. Introduction
2. Development
3. Physical properties
4. Chemical composition
5. Histology of cementum
6. Classification of cementum
7. Functions
8. Clinical considerations
9. Conclusion
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