Cementum

CementumCementum

Aditya S.PatelAditya S.Patel

CEMENTUM IS STRUCTURALLY PART CEMENTUM IS STRUCTURALLY PART OF TOOTH & FUNCTIONALLY PART OF OF TOOTH & FUNCTIONALLY PART OF PERIODONTIUM.PERIODONTIUM.

INTRODUCTIONINTRODUCTION

A part of Periodontium that attaches A part of Periodontium that attaches Teeth to Alveolar bone. It begins at Teeth to Alveolar bone. It begins at the cervicle portion of the tooth that the cervicle portion of the tooth that is the Cemento-Enamel junction and is the Cemento-Enamel junction and continues upto apex.continues upto apex.

First described in 1853.First described in 1853.

DefinitionDefinition

Cementum is a non uniform, Cementum is a non uniform, mineralized connective tissue and is mineralized connective tissue and is avascular, and forms the outer avascular, and forms the outer covering of the root.covering of the root.

Bone like connective tissue that Bone like connective tissue that covers tooth from CEJ to and covers tooth from CEJ to and surrounding apical foramen. (James surrounding apical foramen. (James Avery)Avery)

INTRODUCTION…INTRODUCTION…

DEVELOPMENT OF DEVELOPMENT OF CEMENTUM CEMENTUM

(CEMENTOGENESIS)(CEMENTOGENESIS) Pre-fuctional: During tooth Pre-fuctional: During tooth

developmentdevelopment

Functional: When the tooth is about Functional: When the tooth is about to reach the occlusal level. Continous to reach the occlusal level. Continous thoughout life. thoughout life.

Cementum formation occurs along the entire tooth

Hertwig’s epithelial root sheath (HERS) Extension of the inner and outer dental epithelium

HERS sends inductive signal to ectomesenchymal pulp cells to secrete predentin by differentiating into odontoblasts

CEMENTOGENESIS…CEMENTOGENESIS…

HERS becomes interrupted

Ectomesenchymal cells from the inner portion of the dental follicle come in with predentin by differentiating into cementoblasts

Cementoblasts lay down cementum


The first formed cementum or The first formed cementum or cementoid is not only acellular but the cementoid is not only acellular but the fibrils take their origin from two fibrils take their origin from two sources, cells of the dental follicle and sources, cells of the dental follicle and later from the newly differentiated later from the newly differentiated cementoblast. cementoblast.

After fibrillogenic phase, the matrix After fibrillogenic phase, the matrix maturation that is second phase is maturation that is second phase is initiated and soon completed. Last initiated and soon completed. Last phase is the calcification phase that is phase is the calcification phase that is phase III. phase III.

How cementoblasts get activated to lay

down cementum is not known 3 theories:

1)Infiltrating dental follicle cells receive reciprocal signal from the dentin or the surrounding HERS cells and differentiate into cementoblasts

2)HERS cells directly differentiate into cementoblasts

3)What are the function of epithelial cell rests of Malassez?


Proteins associated with Proteins associated with CementogenesisCementogenesis

Growth factorsGrowth factors TGFTGF PDGFPDGF FGFFGF

Adhesion moleculesAdhesion molecules Bone sialoproteinBone sialoprotein OsteopontinOsteopontin


Epithelial/enamel-like factorsEpithelial/enamel-like factors CollagensCollagens Gla proteinsGla proteins

MatrixMatrix BoneBone

CollagensCollagens Transcription factorsTranscription factors

Cbfa 1 and osterixCbfa 1 and osterix OtherOther

Alkaline phosphataseAlkaline phosphatase

Proteins associated with Cementogenesis…Proteins associated with Cementogenesis…

PRECEMENTUM PRECEMENTUM (CEMENTOID)(CEMENTOID)

Its the unmineralised tissue which begins Its the unmineralised tissue which begins initially at the Cemento-dentinal junction initially at the Cemento-dentinal junction and persist for the life of the tooth as the and persist for the life of the tooth as the outermost layer of Cemental matrix. outermost layer of Cemental matrix.

located between calcified matrix and located between calcified matrix and Cementoblast. Cementoblast.

PRECEMENTUM (CEMENTOID)PRECEMENTUM (CEMENTOID)……

Width 3-5 micron metersWidth 3-5 micron meters

In H&E stain – EosinophplicIn H&E stain – Eosinophplic

Protective functionProtective function

Composition: mainly collagenousComposition: mainly collagenous

MINERALISATIONMINERALISATION

Begins in the depth of Precementum.Begins in the depth of Precementum. Hydroxyapatite crystals deposition.Hydroxyapatite crystals deposition. Cemental crystals are plate like structures that Cemental crystals are plate like structures that

appears as fine, electron dense threads when appears as fine, electron dense threads when

standing on edge. standing on edge. Oriented with their long axis parallel to the Oriented with their long axis parallel to the

direction of the collagen fibrils.direction of the collagen fibrils. The mineral content of this tissue does not change The mineral content of this tissue does not change

significantly which age.significantly which age.

COMPOSITION OF COMPOSITION OF CEMENTUMCEMENTUM

Dry weight basis:Dry weight basis:

Inorganic -- 45-50%Inorganic -- 45-50%

Organic and Water -- 50-55%Organic and Water -- 50-55% Matured CementumMatured Cementum

Inorganic -- 65%Inorganic -- 65%

Organic -- 23%Organic -- 23%

Water -- 12%Water -- 12%

ORGANIC MATERIAL (50-ORGANIC MATERIAL (50-55%)55%)

CollagensCollagens Ground SubstanceGround Substance

Glycoproteins Glycoproteins

Proteoglycans.Proteoglycans.

COMPOSITIONCOMPOSITION

CollagenCollagen

Two typical fibrial formed colagens Two typical fibrial formed colagens

present present

Type I collagen: 90%Type I collagen: 90%

Type III collagen: 5%Type III collagen: 5%

Two fiber System present Two fiber System present

Intrinsic fiber Intrinsic fiber

Extrinsic fiber (sharpye’s fibers)Extrinsic fiber (sharpye’s fibers)

COMPOSITION…COMPOSITION…

Ground substanceGround substance ((Noncollagenous proteinsNoncollagenous proteins ) )

Rich in glycoconjugates which Rich in glycoconjugates which represent either glycolipids, represent either glycolipids, glycoproteins or proteoglycans and glycoproteins or proteoglycans and other proteins.other proteins.


INORGANIC MATERIAL: (45-INORGANIC MATERIAL: (45-50%)50%)

Cementum is less mineralized than Cementum is less mineralized than the root dentin.the root dentin.

Hydroxyapatite crystals Hydroxyapatite crystals Magnesium 0.5 to 0.9% Magnesium 0.5 to 0.9% Fluoride 0.9% Fluoride 0.9% Sulfur 0.1 to 3% Sulfur 0.1 to 3%


STRUCTURAL COMPOSITION OF STRUCTURAL COMPOSITION OF CEMENTUM CEMENTUM

CEMENTOBLAST CEMENTOBLAST

Derive from dental Derive from dental folliclefollicle

Transformation of Transformation of epithelial cellsepithelial cells

cemento-progenitor cemento-progenitor cells synthesizes cells synthesizes collagen and protein collagen and protein polysaccharide polysaccharide

CEMENTOCYTECEMENTOCYTE

Cementocytes in lacunae and the channels that their processes extend are called the canaliculi

The central cells mass may appear The central cells mass may appear rounded, oval or sqamoid, diameter rounded, oval or sqamoid, diameter ranges from 8 to over 15 cm. ranges from 8 to over 15 cm.

The cytoplasm is palely basophilic The cytoplasm is palely basophilic and the nucleus is centrally located and the nucleus is centrally located

PHYSICAL CHARACTERISTIC OF PHYSICAL CHARACTERISTIC OF CEMENTUMCEMENTUM

Pale yellow with a dull surface More permeable than other dental tissues Hardness of the full mineralized cementum is less

than that of dentin Knoop’s Hardness number is 40. Relative softness and the thinness at the cervical

portion means that cementum is readily removed by the abrasion when gingival recession exposes the root surface to the oral environment

Permeability of cementum Permeability of cementum Permeability of cellular cementum is Permeability of cellular cementum is

greater than that of acellular greater than that of acellular

Thickness of cementum Thickness of cementum Varies in thickness:

thickest in the apex and

In the inter-radicular areas of multirooted teeth, and thinnest in the cervical area

10 to 15 m in the cervical areas to

50 to 200 m (can exceed > 600 m) apically

CEMENTO-DENTINAL JUNCTIONCEMENTO-DENTINAL JUNCTION

The dentin surface upon The dentin surface upon which cementum is which cementum is deposited in relatively deposited in relatively smooth in permanent teeth smooth in permanent teeth

In deciduous teeth C-D In deciduous teeth C-D junction is sometimes junction is sometimes scalloped or wavy. scalloped or wavy.

The attachment of The attachment of cementum to dentin is cementum to dentin is quite firm. quite firm.

Mucopoly sacchrides might Mucopoly sacchrides might have an important role in have an important role in cemento-dentinal junction cemento-dentinal junction formation. formation.

Hyaline layer of Hopewell-Smith (Intermediate

Cementum) Sometimes dentin is seperated from Sometimes dentin is seperated from

cementum by zone called intermediate cementum by zone called intermediate cementumcementum

Dosent exhibits charaters of either Dosent exhibits charaters of either cementum or dentincementum or dentin

Predminantly seen on apical two thirds of Predminantly seen on apical two thirds of roots of molars and premolarsroots of molars and premolars

Represents areas where cells of hertwigs Represents areas where cells of hertwigs epithelial root sheath get trapped in epithelial root sheath get trapped in rapidly depositing cemental matrixrapidly depositing cemental matrix

Intermediate cementum is situated between the granular dentin layer of Tomes and the secondary cementum

Approximately 10 m thick and mineralizes greater than the adjacent dentin or the secondary cementum

CEMENTO ENAMEL CEMENTO ENAMEL JUNCTION JUNCTION

CLASSIFICATIONCLASSIFICATION

According to location on teeth According to location on teeth (Kronfeld 1938)(Kronfeld 1938) Radicular cementumRadicular cementum Coronal cementumCoronal cementum

According to cellularity (Gottlieb According to cellularity (Gottlieb 1942)1942)

Acellular cementum (Primary cementum) Acellular cementum (Primary cementum) Cellular cementum (Secondary cementum)Cellular cementum (Secondary cementum)

CLASSIFICATIONCLASSIFICATION

According to presence of cells and According to presence of cells and organization of collagen fibrilsorganization of collagen fibrils

Acellular afibrilar cementum (AAC) Acellular afibrilar cementum (AAC) Acellular extrinsic fiber cementum Acellular extrinsic fiber cementum Cellular intrinsic fiber cementumCellular intrinsic fiber cementum Cellular mixed stratified cementumCellular mixed stratified cementum Acellular intrinsic fiber cementum Acellular intrinsic fiber cementum

Cellular and Acellular Cementum

1)Acellular cementum:

It is the first to be formed and covers approximately the cervical third or half of the root and it does not contains cells

formed before the tooth reaches the occlusal plane

thickness larges from 30 to 230m (Schroeder 1986)

1)CELLULAR CEMENTUM: formed after tooth reaches the occlusal plane is more irregular and contains cells (cenontocytes)

restricted to the apical segment of root

thickness of cellular cementum is greater than accelular

A: Acellular cementumB: Hyaline layer of Hopwell-SmithC: Granular layer of TomesD: Root dentin

Variations where acellular and cellular reverse in position and also alternate

Acellular afibrilar cementum Acellular afibrilar cementum (AAC):-(AAC):-

contains neither cells, nor extrinsic or contains neither cells, nor extrinsic or intrinsic fibers, apart from a intrinsic fibers, apart from a mineralised ground substancemineralised ground substance

It is a product of cementoblast and is It is a product of cementoblast and is found as deposited on the enamel found as deposited on the enamel

thickness is about 1 to 15thickness is about 1 to 15m. m. Lacks collagen so plays no role in Lacks collagen so plays no role in

attachmentattachment

Acellular extrinsic fiber Acellular extrinsic fiber cementum cementum

composed almost entirely of densely composed almost entirely of densely packed bundle of sharpey’s fibers and no packed bundle of sharpey’s fibers and no cellscells

product of fibroblast and cemetnoblastproduct of fibroblast and cemetnoblast found in the cervical third of roots found in the cervical third of roots thickness is between 30 to 230thickness is between 30 to 230m.m. high numerical density of fibers inserting high numerical density of fibers inserting

into acellular extrinsic fibes cementum into acellular extrinsic fibes cementum (approx 30,000/mm2)(approx 30,000/mm2)

primary function is tooth anchorageprimary function is tooth anchorage

Cellular intrinsic fiber Cellular intrinsic fiber cementumcementum

contains cells but no extrinsic contains cells but no extrinsic (sharpey’s) fibers (sharpey’s) fibers

formed by cementoblast formed by cementoblast form of resorptive cementumform of resorptive cementum repair a resoraptive defect repair a resoraptive defect occurs in the furcation and on the occurs in the furcation and on the

apical root portionsapical root portions

Cellular mixed stratified Cellular mixed stratified cementum cementum

contains both collagen fibers and calcified contains both collagen fibers and calcified matrixmatrix

co-product of cementoblast and fibroblast co-product of cementoblast and fibroblast consists of both extrinsic and intrinsic consists of both extrinsic and intrinsic

fibersfibers appears primarily in the apical third of the appears primarily in the apical third of the

roots and the apices and in furcation roots and the apices and in furcation areasareas

Acellular intrinsic fiber Acellular intrinsic fiber cementum cementum

acellular variant of cellular intrinsic acellular variant of cellular intrinsic fibers cementum fibers cementum

deposited during adaptive responses deposited during adaptive responses to external force to external force

forms without leaving cells behind forms without leaving cells behind (Bossharati and Schroeder 1990) (Bossharati and Schroeder 1990)

Distribution of Cementum on the RootDistribution of Cementum on the Root

Acellular afibrillar: cervical enamelAcellular afibrillar: cervical enamel Acellular extrinsic: Cervix to practically the Acellular extrinsic: Cervix to practically the

whole root (incisors, canines) increasing in whole root (incisors, canines) increasing in thickness towards the apical portion thickness towards the apical portion 5050200200μμmm

Cellular: Apical third, furcationsCellular: Apical third, furcations

FUNCTIONS OF CEMENTUMFUNCTIONS OF CEMENTUM

AnchorageAnchorage:- :- medium for the medium for the attachment of collagen fibers that attachment of collagen fibers that bind the tooth to alveolar bonebind the tooth to alveolar bone

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Cementum