Cementum Vb

8/3/2019 Cementum Vb

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DEPARTMENT OF PERIODONTICS

Under the Guidance of- Submitted By-

Dr. Suraj Pandey Saurabh Verma

BDS 3rd Yr.


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CEMENTUM


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CONTENT:- Introduction Physical characteristic Chemical composition Classification

Cementogenesis Cemento-dentinal junction Cemento-enamel junction Function Exposure of cementum Cemental anomalies


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INTRODUCTION

o Also called as Substantia Osseao Cementum is the mineralized dental tissue covering the

anatomical root of teeth.

o First demonstrated microscopically in Yr.1835 by two pupil ofPurkinje.

o It begins at the cervical portion of the tooth at theCEJ(cementoeamel junction) & continues to the apex.

o Cementum is avascular & non-innervated.o It furnishes a medium for the attachment of collagen fibers, that

binds the tooth to the surrounding tissue.


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PHYSICAL CHARACTERISTICS

o Light yellow in colour.o Can be distinguish from enamel by its lack of luster and its

darker hue.

o Thickness:-At CEJ = 20-50 um.

At Apex = 150-200 um.

o Hardness :- less than Dentin.o Least calcifiedo More permeable than Dentin.


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CHEMICAL COMPOSITION

INORGANIC SUBSTANCE :-

o 4550 %o Mainly calcium & phosphate in form of hydroxyapatite.o Cementum has highest fluoride content of all mineralized tissue.

ORGANIC SUBSTANCE :-

o 5055 %o Mainly type I collagen & protein

polysaccharides(proteoglycan).

o Type III, V,VI,XII collagen are also seen.

Non collagenous protein play important role in matrixdeposition, initiation & controle of mineralization matrix

remodelling.

Cementum derived attachment proteinis an adhesion moleculeunique to cementum, helps in the attachment of mesenchymalcells to the extracellular matrix.


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CLASSIFICATIONSCHROEDER has classified cementum, as follows-

ACELLULAR AFIBRILLAR

CEMENTUM(AAC) :-

o Contains neither cells nor extrinsic/intrinsic collagen fibers,apart from a mineralized ground substance.

o Product of cementoblast.o Found as coronal cementum in human.o Thickness = 1-15 Am

ACELLULAR EXTRINSICFIBER

CEMENTUM(AEFC):-o Composed of densely packed bundles of Sharpeys fibers & lack

cells.

o Product of fibroblast & cementoblast.o Found in Cervical Third portion of root.o Thickness = 30-230 Am


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CELLULAR MIXED STRATIFIED

CEMENTUM(CMSC):-

o Composed of Sharpeys fibers and intrinsic fibers & maycontain cells.

o Co-product of fibroblast & cementoblast.o Found primarily in the Apical Third portion of root & in

furcation areas.

o Thickness = 100-1000 gym

CELLULAR INTRINSIC FIBER

CEMENTUM(CIFC):-o Contains cells but no extrinsic fibers.o Product of cementoblast.o In humans, it fills resorption lacunae.

INTERMEDIATE CEMENTUM :-

o An ill-defined zone, near the CEJ.o Found in certain teeth that appears to contain cellular remnants of

HERS(Hertwig Epithelial Root Sheath), embedded in calcified

ground substance.


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ACELLULAR&CELLULAR

CEMENTUM

ACELLULARCEMENTUM:-o First to be formed, so also called Primary Cementum.o Cover cervical third of root.o Formed before the tooth reaches the occlusal plane.o Sharpeys fiber comprises most of part of it.o

These fiber are completely calcified.o Also contains intrinsic collagen fibers.o Thickness = 30-230 Am


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CELLULAR CEMENTUM:-o Forms after acellular cementum. o Secondary cementum o Formed after tooth reaches the occlusal plane.o More irregular & contains cells.o Less calcified than acellular cementum.o Sharpeys fiber occupies a smaller portion.o Sharpeys fiber of cellular cementum, have a central, uncalcified

core surrounded by a calcified border.


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CEMENTOGENESIS

Define as the process of cementum formation.

CEMENTUM FORMATION:-o Cementum formation in the developing tooth is proceded by the

deposition of dentin along the inner aspect of Hertwigs

epithelial root sheath.

o For cementogenesis to begin, HERS must fragments.o Once HERS fragments, the dentin comes in contact with

connective tissue of dental follicle.

o Cells derived from this connective tissue are responsible forcementum formation, i.e. Cementoblast.


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CEMENTOBLAST :-o Cementoblast synthesize collagen & protein polysaccharides,

which makeup the organic matrix of cementum.

o Have numerous mitochondria, a well-formed golgi apparatus, &large amounts of granular endoplasmic reticulum.


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MINERALIZATION OF CEMENTUM :-

o Highly organised event.o Gla proteins osteocalcin, osteonectin act as nucleator for

mineralization.

o Alkaline phosphate promote mineralization.o Osteopotin regulate growth of apatite crystals.o Uncalcified matrix is called Cementoid .


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CEMENTO-DENTINAL JUNCTIONo Narrow interface zone between Cementum & dentin, can be

detected with Electron Microscope.

o Presence of proteoglycan is the major factor in this attachment.o Smooth in permanent teeth.o Scalloped in deciduous teeth.o Sometime, dentin is separated from Cementum by a zone,

known as Intermediate Cementum Layer. Also known as

HYALINE LAYER.

o Hyaline layer is seen in Apical 2/3rd portion of root of Molar &Premolar.


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CEMENTO-ENAMEL JUNCTION

o It is the junction of cementum & enamel at the cervical region ofteeth.

o In 60% of the teeth, cementum overlaps the cervical end ofenamel for a short distance.

o In 30% of all teeth, cementum meets the cervical end of enamelin a relatively sharp line.

o In 10% of the teeth, enamel & cementum do not meet.o Recent observation showed a 4th type of CEJ, in which the

enamel overlapping the cementum.


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FUNCTION

o Cementum function is a single unit, but can be described under- Anchorage Adaptation Repair

ANCHORAGE :-

o Primary function of cementum is to furnish a medium for theattachment of collagen fibers, that binds the tooth to the alveolar

bone.

ADAPTATION :-

o Cementum is the tissue, helps in the functional adaptation ofteeth possible.

o As- Deposition of cementum in an apical area to compensate forloss of tooth surface from occlusal wear.

REPAIR :-

o Cementum is major tissue for repairing root surface.o Any damage to root surface, such as fracture can be repaired by

deposition of new cementum.


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EXPOSURE OF CEMENTUM TO

ORAL ENVIRONMENTo Cementum exposed to oral environment in case of

Gingival recession Loss of attachment in pocket formation

o Bacterial invasion of cementum occurs in periodontal disease.o Cementum become permeable to organic substance, inorganic

ions & bacteria in above condition.

AGING OF CEMENTUM :-

o Surfaces become rough.o Cemental resorption.o Permeability decreases.o More cemental deposition lead to closure of apical foramen.


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CEMENTAL ANOMALIES

HYPERCEMENTOSIS :-

o Abnormally prominent thickening of the cementum on theroot surface.

o Two type :- Localized

Cemental spikes

Excementosis Generalized

Pagets diseaseChronic periapical infection


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CEMENTAL HYPERPLASIA &

HYPERTROPHY :-

o Cementum overgrowth, where growth dose not help inincreasing function of tooth. i.e. Cemental hyperplasia.

o If cemental overgrowth helps in increase functioning of tooth,i.e. Cemental hypertrophy.

CEMENTICLES :-

o Round lamellated cemental bodies, that lies free in PDL orattached to the root surface.

o Mostly found in aging person or at site of trauma.

CEMENTAL RESORPTION &

REPAIR :-

o Cementum undergoes resorption & repair alternativelyaccording to change in environment faced by it.

oCauses :-

LOCALTraumaCyst & tumourPeriapical pathologyExcessive orthodontic force


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SYSTEMICDeficiency of calciumDeficiency of Vit. A & DHypothyroidism

Resorption of cementum and dentin. A multinuclear osteoclast

is seen at X. The direction of resorption is indicated by the

arrow. Note the scalloped resorption front in the dentin (D). The

cementum is the darkly stained band at the upper and lower right.

P Periodontal ligament.


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CLINICAL

CONSIDERATIONSo Cethan is bone, & it is for this reason that orthodontic tooth

movement is made possible.

o It is because bone is richly vascularized, whereas cementum isavascular.

o Cementum resorption can occur after trauma or excessiveocclusal forces.

o Cementum is more resistant to resorptiono In most cases of repair, there is a tendency to re-establish the

former outline of the root surface by cementum. This is called

anatomic repair.

o However, if only a thin layer of cementum is deposited on thesurface of a deep resorption, the root outline is notreconstructed, & a bay like recess remains.

o In such areas the periodontal space is restored to its normalwidth by formation of a bony projection, so that a proper

functional relationship will result. the outline of the alveolar

bone in these cases follows that of the root surface. This is

called functional repair.

Cementum Vb

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