cementum

IntroductionDefinitionPhysical charactersticsChemical compositionCementogenesisStages of cementum formationCementogenesisClassificationCEJCDJ Aging of the cementumFunctions RepairAnamoliesMesodermal tumoursClinical cosiderationsConclusionReferences

CONTENTS

Introduction It was first demonstrated microscopically in 1853 by Frankel and

Raschkow. One of the components of the periodontium other than the gingiva,

periodontal ligament and alveolar bone is cementum. The word cementum comes from the latin word “cement” which

means quarried stone.Cementum is the calcified mesenchymal tissue that forms the outer

covering of the anatomic root.

Definition

It is a mineralized dental tissue covering the anatomic roots of human teeth (Orbans).

PHYSICAL CHARACTERISTICS

Calcified structure whose calcification and hardness is less than

dentin

More permeable than dentin

Light yellow in color

Softer and lighter than dentin

Lacks luster and is dark, and is therefore differentiated from

enamel

Less readily resorbed than bone

EXTENSION:Begins at the cervical portion of the tooth at the CEJ and

continues to the apex

THICKNESS:

At CEJ : 10 micrgons ( thinnest )

At Apical Region : 200-300 microns ( thickest )

CHEMICAL COMPOSITION

Organic content and water - 50 – 55% Inorganic content - 45 – 50 %

ORGANIC CONTENTCollagen fibers embedded in an interfibrillar ground

substance consisting of glycoproteins.Types of collagen :-

Type IType IIIType VType IXType XIV

Interspersed between the collagen fibrils are the glycosaminoglycans(GAGs).

Chondroitin 4-sulphate. Dermatan sulphate

NON COLLAGENOUS PROTEINSAlkaline phosphataseBone sialoproteinFibronectinOsteocalcinOsteonectinOsteopontinVitronectin

Cementum derived attachment protein Insulin like growth factor-I

INORGANIC CONTENT

Calcium and phosphate in the form of hydroxyapatite

Trace elements like

Copper,Fluorine,Iron,Lead,Potassium,Silica,Sodium and

Zinc in varying amounts.

Cementum has the highest fluoride content

CEMENTOGENESIS

Stages of cementum formation Phase I : Laying down of cementoid tissue (matrix formation)Phase II : MineralizationApatite crystals are deposited along the fibrils.Cementum formation takes place rhythmically.A thin layer of cementoid is seen on the surface of

cementum lined by cementoblasts.These fibers are embedded in the cementum and

attaches tooth to the surrounding bone. Sharpey’s Fibers.

Cementum is laid down much slowly while the tooth is erupting. This cementum is acellular or primary.The mineral content in this cementum is first seen as thin plates or lamellae away from cementoblasts.

When the tooth comes in occlusion , more cementum forms around the apical two-thirds of the root, which has greater proportion of collagen.The cementoblasts become trapped in lacunae within this matrix. This cementum is called cellular ( secondary) cementum.In this cementum,the minerals are seen as globules scattered throughout the matrix and also between the cementoblasts themselves.These spherules increase in size and engulf the cementoblasts.

The rate of formation of cellular cementum is much more rapid than that of acellular cementum.

Classification of cementumBased upon – A. Location .B. Presence or absence of cells.C. Origin of collagenous fibers of the matrix.D. Acc to Schoreder

A) Location

Radicular cementum Coronal cementum

Cementum that forms on the enamel covering the

crown.

Cementum that is found on the root surface.

B) Presence or absence of cellsI. AcellularII. Cellular Acellular cementum/ Primary

cementum- 1st formed cementum and

form the cervical third or half of the root.

Does not contain cells. Is formed before the tooth

reaches the occlusal plane. Thickness ranges from 30

to 230 um. Sharpey’s fibersmake up

most of the structure of Acellular cementum(ACC)

Cellular cementum – Is formed after the tooth reaches the occlusal plane.Covers apical 2/3 rdMore irregular and contains cells (cementocytes).Cellular cementum is less calcified than acellular

cementum.Sharpey’s fibers occupy a smaller portion of Cellular

cementum.Less mineralized and more permeable.

Acellular cementum Cellular cementum

1) First formed Secondary cementum

2)Present on the cervical third or half of root.

Mainly on apical third of root.

3)It does not contain cells. Contains cells called cementocytes in individual spaces lacunae.

4)It is formed before the tooth reaches the occlusal plane.

Formed after the tooth reaches the occlusal plane.

5)More calcified Less calcified.

6) Sharpey’s fibers are main compenent which inserted at approximately right angles onto the root surface.

Sharpey’s fibers occupy smaller portion & occpy other fibers that are arranged parallel to the root surface.

7) Rate of development is faster . Slow .

8) Incremental lines are wide apart. Closer.

CementocytesA typical cementocyte has

numerous cell processes or canaliculi radiating from its cell body.

Most of the processes are directed towards the periodontal surface of the cementum .

Cytoplasm of cementocytes in deeper layers of cementum contains (a) few organelles ,(b)the endoplasmic reticulum appears dilated and (c) mitochondria are sparse .

(C) Origin of collagenous fibers of the matrix-

Organic matrix derived from 2 sources: (1)Periodontal ligament ( Sharpey’s fibers). (2) Cementoblasts.

Extrinsic fibers if derived from PDL. These are in the same direction of the PDL principal fibers i.e. perpendicular or oblique to the root surface.

Intrinsic fibers if derived from cementoblasts. Run parallel to the root surface and at right angles to the extrinsic fibers.

The area where both extrinsic and intrinsic fibers is called mixed fiber cementum

Schoreder Classification :

(1) Acellular afibrillar cementum (AAC)(2) Acellular extrinsic fiber cementum (AEC)(3) Acellular intrinsic fiber cementum (AIFC)(4) Cellular mixed stratified cementum (CMSC)(5) Cellular intrinsic fiber cementum (CIFC

Acellular afibrillar cementumConsists of mineralized matrix.Contains neither cells nor extrinsic

or intrinsic collagen fibers.This cementum does not have any

function in tooth attachment.Less homogenous.Acc to Schoreder 1986 – Connective tissue cells are

responsible for AAC formation when they come in contact with enamel surface.

Is a product of cementoblasts.Found in coronal cementum.

Acellular extrinsic fiber cementumConfined to coronal half

of the root.Its formation commences

therefore shortly after crown formation in completed.

Product of Fibroblasts and Cementoblasts.

Has the potential to adapt to functionally dictated alterations such as mesial tooth drift.

Cellular Intrinsic Fiber CementumContains cells but no

collagen fibers.Formed by

cementoblasts.Fills resorption lacunae.

Cellular Mixed Stratified Cementum

Contains cells. Composed of Extrinsic

(Sharpey’s) and intrinsic fibers. Co product of Fibroblasts and

cementoblasts. Appears primarily in the apical

3rd of the root and the apices and in the furcation areas.

With light microscope this tissue is easily identified b/coz –

(a) It includes cementocytes within lacunae with processes in canaliculi directed towards the PDL.

(b) Its laminated structure.(c) The presence of cementoid on

its surface.

Cemento-Enamel Junction Cementum overlaps

enamel – 60%Cementum just meets

enamel – 30% Small gap between

cementum and enamel – 10%

CEMENTODENTINAL JUNCTION

•The cementum is attached to the dentin firmly

•CDJ is scalloped in deciduous teeth and is smooth in permanent teeth.

•Near apical end, sometimes an intermediate layer intervenes between cementum and dentin which does not look either like cementum or dentin

Kuttler study • Narrowest diameter of the canal identified not at

the site of the exiting of canal.• He refferred to the position as minor diameter

(apical - constriction)• Major diameter is at the site of the exit of the canal• Distance between the major and minor diameter • Age- 18 to 25 0.524mm 55 or more 0.659mm• Using kutler’s method is the most scientific

method for calculation of working length.

Aging of Cementum Smooth surface becomes

irregular.

Continues deposition of cementum occurs with age in the apical area.

Cementum resorption active for a period of time and then stops for cementum deposition creating - reversal lines.

Resorption of root dentin occurs with aging which in covered by Cemental repair.

FUNCTIONS OF CEMENTUM

1. Medium for the attachment of periodontal ligament fibers to the tooth

2. Tooth wear compensation.3. Repair :fracture or resorption of root surface4. Does not show resorption under masticatory or

orthodontic forces as it is harder than bone.During heavy orthodontic forces, tooth integrity is maintained and alveolar bone being elastic in nature changes its shape, fulfilling the orthodontic requirement

REPAIR

ANATOMIC REPAIR

Generally occurs when the degree of destruction is low

The root outline is re-established as it was before cemental resorption

FUNCTIONAL REPAIR

Occurs in cases of large cemental resorption or destruction

To maintain the width of periodontal ligament, the adjacent alveolar bone grows and takes the shape of defect following the root surface. This is done to improve the function of tooth

anamolies in Cementum

Concresence

This is a form of fusion which occurs after the root formation has been completed.

Here the teeth are united by cementum only, as a result of traumatic injury or crowding of teeth with resumption of the interdental bone so that the two roots are in approximate contact and become fused by deposition of cementum between them.

Concresence can occur before or after teeth have erupted and usually involves two teeth.

Cementicles

These are globular masses of cellular cementum less than 0.05mm in diameter which form within the periodontal ligament.

They may lie free within the periodontal ligament(free cementicles) or become fused to the radicular cemental surface(sessile or attached cementicles).

It has been postulated that cementicles originate from degenerating cells or epithelial cell rests in the periodontal ligament.

Enamel Projections If the amelogenesis is not turned off

after the enamel of the crown has been laid down. The enamel organ may continue to produce enamel over the root dentin.

This additional enamel often takes the shape of enamel spurs that project into the furcation of the multirooted tooth.

Successful treatment of periodontal pockets caused by this anomaly requires grinding away the enamel projection.By restoring the normal contour of the tooth and exposing the underlying dentin.

Enamel Pearls

Enamel pearls are localized masses of enamel that develop ectopically, typically over the root surface, in close proximity to cemento-enamel junction.

They may promote periodontal lesions by acting as plaque retentive structures.

HyperCementosisHypercementosis is an abnormal

thickening of cementum.It may affect all teeth of the

dentition, be confined to a single tooth or even effect only parts of one teeth.

Localized hypercementosis may sometimes be observed in areas in which enamel drops have developed on the dentin. Such knob like projections are designated as excemetosis.

The thickening of cementum is often observed on teeth that are not in function.

ANKYLOSIS

Fusion of cementum and alveolar bone with obliteration of periodontal ligament

It occurs due to:-1) Cemental resorption2) Chronic periapical inflammation 3) Tooth replantation4) Occlusal trauma

Osteitis DeformansPaget’s disease of bone.Generalized skeletal disease characterized by

deposition of excessive amounts of secondary cementum on the roots of the teeth and by the apparent disappearance of lamina dura of the teeth, as well as by other features related to the bone itself.

An excessive amount of cellular cementum is found deposited directly over the typically thin layer of primary acellular cementum.

Injuries to CementumVERTICAL FRACTUREPoor prognosis and usually it cannot be repaired by cementum easilyTreatment :extraction or stabilization by intracoronal splinting

HORIZONTAL FRACTUREVariable prognosis depending on the age and location of fracture.

Apical or middle third: it can be repaired by the cementum and prognosis for the vitality of the pulp of the tooth for survival is fair

The coronal third:prognosis for vitality of tooth is poor

Cemental tears:Detachment of a fragment of

cementum from the root surface is known as a cemental tear.

The separation of cementum, may be complete with displacement of a fragment into the periodontal ligament or it may be incomplete with cementum fragment partially attached to the roots.

The detached cementum, may be reunited to the root surface by new cementum. Or may be completely resorbed or may undergo partial resorption followed by addition of new layers.

Mesodermal Tumors of odontogenic Origin Related to Cementum in the Jaws

Cementoma

It is a lesion of rather common occurrence. Not considered a neoplasm.

Etiology unknown, may be due to mild chronic trauma.Occurs in and around PDL around the apex of tooth,

especially mandibular incisor, may occur as many lesions especially in connection, with the apices of mandibular anterior teeth or bicuspids.

Asymptomatic diagnosed accidentally, formation of a circumscribed area of periapical fibrosis accompanied by localized distraction of bone.

Cementoma

Central Cementifying Fibroma

The lesion is generally asymptomatic until the growth produces a noticeable swelling and mild deformity with displacement of teeth in the later stages.

The lesion grow by expansions equally in all directions and present as a round tumor mass.

Lesion is composed basically of many delicate interlacing collagen fibres, interspersed by large number of active proliferating fibroblasts or cementoblasts, this connective tissue characteristically presents many small foci of basophilic masses of cementum like tissue.

Benign Cementoblastoma

True neoplasm of functional cementoblasts.

Mandible more affected. Generally first permanent molar, tooth is vital, slowly progressing and may cause expansion of cortical plates of bone, asymptomatic, rarely causing pain.

Tumour mass attached to the tooth root appears as a well circumscribed dense radio opaque mass often surrounded by a thin uniform radiolucent line.

Benign Cementoblastoma

Gigantiform Cementoma

Familial multiple cementoma. It is rare and develops in all four quadrants.Occurred in families and appeared to be inherited as an

autosomal characteristic mostly in adult black females.Lesion is described as dense, highly calcified, almost

totally acellular cementum which is poorly vascularized and frequently becomes infected with ensuring suppuration and sequestration.

Gigantiform Cementoma

Clinical Consideration1. Cementum is essential for normal anchorage of the tooth .2. Cementum also provides a protective function to the tooth itself, as

it is less susceptible to resorption than bone. Hence helpful in orthodontic tooth movement.

3. Deposition in the apical portion of the root compensates to some degree for the slow tooth eruption that takes place throughout life to compensate for occlusal attrition.

4. Continuous cementum deposition around the apex of the tooth leads to constriction of apical foramen and alteration in number size and shape of the apical foramena.

5. Root surface caries progress round rather into the tooth. -Active leison – yellowish/ light brown soft and leathery consistency. -Inactive – darker with smooth surface ,harder in consistency.

Conclusion Cementum by virtue of its structural dynamic

qualities provide tooth attachment and maintains 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 .

References1.Tencate AR., Oral histology: Development Structure and function, 5th edition2. Orbans oral histology and embriology. 12th edition3.Shafers text book of oral pathology.6th edition4.ingle’endodontics 6th edition5.carranza’s clinical periodontology .10th edition.