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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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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[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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- 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 3 rd

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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(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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- 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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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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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.

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Intrinsic fibres – Are those formed as a result of cementoblasts activity.

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 FIBRES1. 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.

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- These lines represent rest periods in cementum formation and

are highly mineralized and have less collagen and more

ground substance.

- 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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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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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.- Less mineralized and more permeable.

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Cellular C Acellular C1. 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.

- Contains extrinsic, intrinsic fibres and cells.

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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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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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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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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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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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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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