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CEMENTUM

By Dr.Shashwati Paul 1st Year PG Dept. of Periodontology2

CONTENTS1. INTRODUCTION AND DEFINITION

2. HISTORY

3. CEMENTOGENESIS

4. PHYSICAL CHARACTERSTICS

5. BIOCHEMICAL COMPOSITION

6. CLASSIFICATION AND DETAILED ASPECTS OF TYPES

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7. FUNCTIONS OF CEMENTUM

8. INTERACTION WITH ADJOINING HARD TISSUES

9. CEMENTUM RESORPTION AND REPAIR

10.ALTERATIONS RESULTING FROM PERIODONTAL PATHOLOGY

11. CEMENTUM IN DISEASE

12. APPLIED ASPECTS

13. CONCLUSION

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INTRODUCTIONDerived from Latin caementum, quarry stone.

Component of tooth as well as periodontium.

Provides anchorage for collagen fibre bundles of periodontal ligament and supra-alveolar fibres of the gingiva.

Root surface area covered by it represents the ground available for connective tissue attachment.

Present irrespective of functional status

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DEFINITIONIt is the calcified, avascular, mesenchymal tissue that forms the outer covering of the anatomic root.

Cementum or simply cement is a component of the tooth as well as of the periodontium. It is a mineralized connective tissue, in part not unlike bone, that covers the entire surface of anatomical roots of teeth. Schroeder

Cementum is a hard, avascular connective tissue that covers the roots of teeth

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HISTORY EXAMINED FIRST BY- FRANKEL 1835 RASCHKOW AND BY HISTOLOGIST ANDERS ADOLF RETZIUS IN 1837

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CEMENTOGENESISPRE-FUNCTIONAL DEVELOPMENTAL STAGE

During root developmentTime range 3.75 to 7.75 years

FUNCTIONAL DEVELOPMENTAL STAGE

Commences when tooth reaches the occlusal planeContinues throughout life

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BASIC CONCEPTS IN CEMENTOGENESIS

INITIATION OF CEMENTUM FORMATION

Restricted 200-300 micrometer coronally from the advancing root end.

ORIGIN OF CEMENTOPROGENITOR CELLS

1.) From the dental follicle

2.) From Hertwigs epithelial root sheath: Epithelial mesenchymal transformation

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Hertwigs epithelial root sheath: inner and outer epithelium

Send an inductive message to the facing ectomesenchymal cells of pulp

Odontoblasts develop and predentin layer forms

Epithelial root sheath interrupted, cells of dental follicle in contact

CEMENTUM FORMS

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Cementoblasts differentiate along newly deposited unmineralized radicular dentin.

Extend numerous tiny cytoplasmic process into loosely arranged dentinal matrix.

Collagen fibrils of cemental matrix positioned along with fibrils in dentinal matrix- interdigitation

Mineralization of outermost dentinal matrix delayed till dentinal matrix completely covered by collagen of cementum

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PROPOSED ACTIVITY MOLECULAR FACTOR ASSOCIATED

1. ADHESION OR CHEMOATTRACTANT OSTEOPONTIN, BONE SIALOPROTEIN, LAMININ (EPITHELIAL FACTOR) FIBRONECTIN, COLLAGEN I, III, XIIPROTEOGLYCANS2. MITOGENESISGROWTH HORMONESTRANSFORMING GROWTH FACTOR- BETAINSULIN LIKE GROWTH FACTOR-I3.DIFFERENTIATION BONE MORPHOGENEIC PROTEIN-3PARATHYROID HORMONE RELATED PROTEINAMELOBLASTIN (EPITHELIAL FACTOR)

4. MINERALIZATIONOSTEOPONTIN (CRYSTAL GROWTH) , BONE SIALOPROTEIN (MINERALISATION), OSTEOCALCIN (CONTROLS MINERALIZATION, PREVENTS ANKYLOSIS), PROTEOGLYCANS, COLLGAEN TYPE I AND XII

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FATE OF HERS CELLS1.) Migrate away towards the dental sac- Epithelial rests of malassez

2.) Incorporated in the cementum

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PHYSICAL CHARACTERSTICSHARDNESS: Less than dentin

COLOUR: Light yellow (enamel: lighter with luster) (Dentin: Darker in colour)

PERMEABILITY: Permeable to dyes in young animals Canaliculi of cellular cementum continuous with dentinal tubules in some areas Decreases with age

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THICKNESS:

Varies form 16-60 micrometer on the coronal half to 150-200 micrometer in the apical third and furcation.

Thicker on distal than on mesial surfaces

Between 11 to 70 years of age thickness increases 3 times

Cemental deposition continues throughout life.

Deposition most rapid in apical areas.16

BIOCHEMICAL COMPOSITION INORGANIC PORTION (45-50%)

Mainly Calcium and Phosphate in the form of HydroxyapatiteHighest Fluoride content

ORGANIC PORTION (50-55%)Collagenous Non-Collagenous

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COLLAGENOUS PORTIONTYPE I (90%) : Predominant

TYPE III (5%) : less cross linked. high concentrations during development, repair.

TYPE XII : Binds with type I and non-collagenous proteins. Related to forces of occlusion.

OTHERS : Type V, VI, XIV (may be contaminants from PDL)

AMINO ACID ANALYSIS INDICATES SIMILARITY TO COLLAGEN OF DENTIN AND ALVEOLAR BONE.

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NON- COLLAGENOUS PROTEINSPROTEOGLYCANS :Heparan sulfate, Chondroitin sulfate etc, Dermatan sulfate.

Cell-cell, cell-matrix interactions

UNIQUE TO CEMENTUM:

Cementum derived attachment protein.Cementum derived growth factor

OSTEOPONTIN: Regulates mineralization

OTHERS: Bone sialoprotein, Alkaline phosphatase, Osteonectin, Dentin sialoprotein

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CEMENTOIDUnmineralized layer of cementum on cemental surface (precementum)

New layer forms as old calcifies

3 to 5 micrometer

Lined by cementoblasts

PDL fibres pass between the cementoblasts

Embedded portion- Sharpeys fibres

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SHARPEYS FIBERConnective tissue fibers from periodontal ligament pass between cementoblasts into the cementum

These fibers are embedded in the cementum & serve to attach the tooth to surrounding bone

Their embedded portions are known as Sharpeys fibers

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MINERALIZATIONBegins in depth of precementum

Fine hydroxyapatite crystals first between then within fibrils

Reach mature size within 1 to 4 micrometer from calcification font

Less mineralized than root dentin

Small amounts of amorphous calcium phosphate may be present

Crystals are parallel to long axis of collagen fibrils

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Crystals are smaller and so larger surface area available, thus more adsorption of fluoride and also readily decalcifies

Magnesium: 0.5- 0.9% , half than dentin, more in deeper layers

Fluoride : 0.9% weight more on surface layer and more in apical cementum

Sulfur: 0.1-0.3% as a constituent of organic matrix

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CELLS OF THE CEMENTUMCuboidal with large Nucleus, Mitochondria, ER, Golgi complex

Secrete organic matrix of cementum

Formed from undifferentiated mesenchymal cells after HERS breaks or may have an epithelial origin

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CEMENTOCYTES

Cementoblasts incorporated into the cemental matrix.

Sparse amount of cytoplasm , numerous cell processes or canaliculi, anastomose with similar processes of the adjacent cementocytes.

Lie in spaces known as lacunae

Directed towards PDL & derive nutrition from PDL

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CEMENTOCLASTS:

Multinucleated cells Involved with cemental resorption

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CLASSIFICATION OF CEMENTUMON THE BASIS OF:

Presence or absence of cells

Time of formation

Location

Presence or absence of Fibers

Origin of Fibers

Schroeders classification

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I.) BASED ON PRESENCE OR ABSENCE OF CELLSACELLULAR CEMENTUM

First formed

Sharpeys fiber make the most of it

Principal role in tooth support

CELLULAR CEMENTUM

Has cementocytes in lacunae communicate via canaliculi

Less calcified, lesser Sharpeys fiber

Role in cemental repair

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II.) BASED ON TIME OF CEMENTUM FORMATION

PRIMARY CEMENTUM

Formed before the tooth erupts

SECONDARY CEMENTUM

Formed after the tooth reaches the occlusal plane

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III.) BASED ON LOCATION

CORONAL CEMENTUM

RADICULAR CEMENTUM

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IV. BASED ON PRESENCE OR ABSENCE OF FIBRES

AFIBRILLAR

FIBRILLAR

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V.) BASED ON ORIGIN OF FIBRES

EXTRINSIC

INTRINSIC

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VI.) SCHROEDER IN 1986 CLASSIFIED CEMENTUM ACELLULAR AFIBRILLAR

ACELLULAR EXTRINSIC FIBRE CEMENTUM

CELLULAR MIXED STRATIFIED CEMENTUM

CELLULAR INTRINSIC FIBRE CEMENTUM

INTERMEDIATE CEMENTUM

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ACELLULAR AFIBRILLAR CEMENTUM

Has neither cells nor any fibres

Formed by cementoblasts, on the crown thickness 5-15 micrometer

Coronal cementocytes have similar origin as the root cementocytes

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ACELLULAR AFIBRILLAR CEMENTUM

In Amelogenesis imperfecta large areas devoid of REE and so AAC found over large areas Weinmann et al 1945; Listgarten 1967

CEMENTUM SPUR: When it is continuous with AEFC of the root surface.

CEMENTUM ISLAND: AAC completely isolated and remote from the root cementum.

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ACELLULAR-EXTRINSIC FIBRE CEMENTUM

Product of fibroblasts and cementoblasts

Densely packed Sharpeys fibres and no cells

In cervical third and middle third of root but may extend

30 to 230 micrometer in thickness

Short Fibres oriented perpendicular to the root surface

Eventually elongate, continuous with PDL

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ACELLULAR-EXTRINSIC FIBRE CEMENTUMApproximately 30,000 fibres/ mm2 insert in it Schroeder

Faster growth rate on distal (4.3 micrometer per year) than on mesial (1.4 micrometer per year) reflects an adaptation to functionally dictated alterations Shroeder

More mineralized than cellular cementum

Core of Sharpeys fibre calcified

Rate of deposition 3 micrometer per year

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CELLULAR MIXED STRATIFIED CEMENTUM

Extrinsic and intrinsic fibres and cells

Co- product of fibroblasts and cementoblasts

Apical third of roots, furcations

100-1000 micrometer

Cementoblasts incorporated in the cementum

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Identified easily with the help of light microscope

Inclusion of cementocytes within lacunae

Its laminated structure

The presence of cementoid on its surface

Fine intrinsic fibers running parallel to the root surface

Large extrinsic fibers running at right angles to the root surface.

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CELLULAR INTRINSIC FIBRE CEMENTUM

Contains cells, but no extrinsic collagen fibers.

Formed by cementoblasts, fills the resorption lacunae.

Cementoblasts become entrapped in the extracellular matrix they secrete

Adaptive function maintains tooth in proper position

Less mineralized

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INTERMEDIATE CEMENTUM

Term by Bencze (1927) to designate narrow layer with cells remains in apical third between dentin and cementum

Layer of Hopewell Smith or Hyaline layer

Origin either cementoblasts (Garant 89) or by HERS (Qwens 80)

Noncollagenous hyper calcified matrix- glycosylated tryptophan, proline and histidine, sparsely distributed collagen fibrils (Yamamoto et al 86)

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FUNCTIONS OF CEMENTUMIt provide anchorage of tooth to alveolus (sharpeys fibers).

It assists in maintaining occlusal relation by maintaining a balance between attrition and eruption.

It serves to maintain the width of PDL space at the apex.

Cementum repairs root fracture.

No resorption under masticatory or orthodontic forces so maintains tooth integrity and fulfils orthodontic requirement.

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THE CEMENTO-ENAMEL JUNCTIONIt is the point at which cementum and enamel meet.May be of three types.

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TYPES OF CEJ

CEMENTUM OVERLAPS60-65% BUTT JOINT 30%DO NOT MEET5-10%44

In some rare cases, a fourth type of cemento-enamel junction is seen.

In these rare cases, the enamel overlaps the cementum.45

CEMENTO-DENTINAL JUNCTION

At the terminal apical area the cementum joins the internal root canal dentin.

In root canal treatment the obturating material should terminate here

2 to 3 micrometers wide

Stable with age

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CEMENTAL RESORPTIONCan occur due to physiologic or pathologic causes

Local causes: Trauma from occlusion, orthodontic movement, cysts, tumors.

Systemic causes: Calcium deficiency, Hypothyroidism, Pagets disease.

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CEMENTAL RESORPTION

MICROSCOPICALLY: Bay like concavities in the root surface

Multinucleated Giant cells and large mononuclear macrophages found.

Not continuous alternated by periods of repair

Newly deposited cementum demarcated from old by deeply staining irregular line- Reversal line

Reversal line- Has few collagen fibrils and highly accumulated proteoglycans with mucopolysaccharides.

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CEMENTAL REPAIR Needs viable connective tissue if epithelium proliferates no repair

Origin of Cementoblasts and factors regulating their recruitment not understood.

Only odontogenic cells in PDL Epithelial rests of Malassez

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AGE CHANGES IN CEMENTUMCONTINOUS DEPOSITION Forms on roots throughout life

More apically than cervically

Reduces root surface concavities thicker layer in root surface grooves and in furcations.

Variation in tooth position influence pattern of deposition

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ALTERATIONS RESULTING FROM PERIODONTAL PATHOLOGY51

EFFECT OF GINGIVAL INFLAMMATION

Loss of collagen fibres of the gingiva

Dissolution of mineral crystals

Cervical root resorption

Undermining resorption

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EXPOSURE OF CEMENTUM TO ORAL ENVIRONMENT

Non-carious cementum is permeable to organic and inorganic ions

Bacterial invasion is common

Bacterial lipopolysaccharides detected . Hypermineralized surface zone depends on the inorganic ion concentration

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CHANGES ASSOCIATED WITH PERIODONTAL POCKETS :

Structural changes : Pathogenic granules- Areas of collagen degeneration.or areas where collagen fibrils have not been mineralised initially.

Increased mineralization due to ion exchange,on exposure to oral cavity.Mineral content increases.

Demineralization-exposure to oral fluids and bacterial plaqueProteolysis of embedded remnants of sharpeys fibres.May undergo cavitation.

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Chemical changes : Increased mineral contents

Cytotoxic changes :Bacterial penetration leads to fragmentation and breakdown of cementum surfaceResults in areas of necrotic cementum.Bacterial products-endotoxins detected in cementum wall of periodontal pocket

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CEMENTUM IN DISEASE

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PATHOLOGICAL CONDITIONS ASSOCIATED WITH CEMENTUMFusion of cementum and alveolar bone with obliterated PDL

Occurs in teeth with cemental resorption

After periodontal inflammation, tooth replantation, occlusal trauma.

Resorption of root and its gradual replacement by bone

Lack physiological mobility, metallic percussion

No proprioception

ANKYLOSIS57

CEMENTICLES

Abnormal, calcified bodies in the periodontal ligament

Form from remnants of HERS

Usually ovoid or round

Size ranges from 0.1- 0.4 mm.

Classified as Free, Attached or Embedded

Local trauma

Appear in increasing numbers in the aging person

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HYPERCEMENTOSISHypercementosis is a nonneoplastic deposition of excessive Cementum that is continuous with the normal radicular cementum.Factors Associated with HypercementosisLOCAL FACTORSAbnormal occlusal traumaAdjacent inflammationUnopposed teeth [e.g., impacted, embedded, without antagonist)SYSTEMIC FACTORSNeoplastic and non neoplastic conditions including benign cementoblastoma, cementifying fibroma, cemental dysplasia Acromegaly and pituitary gigantismPaget's disease of boneRheumatic feverThyroid goiter

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Acceleration in the elongation of a tooth owing to loss of an antagonist is accompanied by hyperplasia of the cementum. This hypercementosis is most prominent in the apex of the root.

Inflammation in the root apex, as a result of pulpal infection sometimes stimulate excess deposition of cementum. Cementum is laid down on the root surface at some distance above the apex.

Occlusal trauma results in mild root resorption. Such resorption is repaired by secondary cementum.

Cemental tears, detachment of strips of cementum from the root due to trauma, are repaired by cementum growing into and filling the defects and eventually uniting with the torn cementum60

CLINICAL FEATURES:Hypercementosis occurs predominantly in adulthood, and the frequency increases with age. Its occurrence has been reported in younger patients, and many of these cases demonstrate a familial clustering, suggesting hereditary influence.RADIOGRAPHIC FEATURE:Radiographically, affected teeth demonstrate a thickening or blunting of the root. but the exact amount of increased cementum often is difficult to ascertain .Radiolucent shadow of PDL and radiopaque lamina dura always seen

NO TREATMENT REQUIRED.

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CONCRESCENCE

Fusion of teeth by fusion of cementum

After root formation has been completed

Traumatic injury or crowding of teeth with resorption of the interdental bone

Difficulty in extraction

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REGRESSIVE ALTERATION OF TEETHAbrasionAbrasion is the pathologic wearing of tooth substance through some abnormal mechanical process.Abrasion usually occurs on the exposed root surfaces of teeth, but under some circumstances, it may be seen elsewhere on toothAbrasion caused by dentrifrice manifests as a v-shaped or wedge shaped ditch on the root side of cej in teeth with recession.

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NEOPLASMS ASSOCIATED WITH CEMENTUM64

CEMENTOBLASTOMAThe benign cementoblastoma is probably a true neoplasm of functional cementoblasts which form a large mass of cementum or cementum-like tissue on the tooth root.Clinical featuresUnder age of 25 years,mostly in mandible.Mostly in mandibular 1st permanent molar.Slow growing,may cause expansion of cortical platesRadiographically, well circumscribed dense radioopaque mass often surrounded by a thin ,uniform radioluscent line.Treatment :Extraction of tooth though pulp is vital-it might cause expansion of jaws

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CEMENTIFYING FIBROMAResemble focal cemento-osseous dysplasiaThe neoplasm is composed of fibrous tissue that contains a variable mixture of bony trabeculae, cementum like spherules or both.origin of these tumors is odontogenic or from periodontal ligament.CLINICAL FEATURE:3RD AND 4TH decades, female predilection.The mandibular premolar and molar area is the most common site.seldom cause any symptoms and are detected only on radiographic examination.66

Radiographically, the lesion most often is well defined and unilocular.Depending on the amount of calcified material produced in the tumor, it may appear completely radiolucent, or more often varying degrees of radiopacity.True ossifying fibromas that become largely radiopaque with only a thin radiolucent periphery are uncommon.TREATMENT: Enucleation of the tumor.

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FAMILIAL GIGANTIFORM CEMENTOMAFamilial gigantiform cementoma is a disorder of gnathic bone that ultimately leads to the formation of massive sclerotic masses of disorganized mineralized material.CLINICAL FEATURES:autosomal dominant disorder that demonstrates variable expressivity.the gnathic enlargement in most patients results in significant facial deformity, as well as impaction, malposition, and malocclusion of the involved dentition.

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RADIOGRAPHIC FEATURES:Initially- multiple radiolucency in the periapical region.With progression, the affected sites expand to replace much of the normal bone within the involved quadrant and develop a mixed radiolucent and radiopaque pattern.the lesions become predominantly radiopaque but often maintain a thin radiolucent rim.TREATMENT: SURGICAL TREATMENT

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INFLUENCE OF SYSTEMIC DISEASES ON CEMENTUM70

PAGETS DISEASEPagets disease is characterized by enhanced resorption of bone.Etiology: unknown, viral infection, inflammatory cause, autoimmune, connective tissue and vascular disorder.CLINICAL FEATURES:Middle age and both males and females are effected.Involvement of facial bone- LEONTIASIS OSSEA.MAXILLA- progressive enlargement, alveolar ridge widened, palate flattened, tooth become loosened.MANDIBLE: findings are similar but not as severe as maxilla.GENERALISED HYPERCEMENTOSIS of the tooth seen.RADIOGRAPHIC FINDING:COTTON-WOOL appearance of pagets bone. CHARACTERISTIC HISTOLOGIC FEATURE: JIGSAW OR MOSAIC PATTERN.TREATMENT:No specific treatment.

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HYPOPHOSPHATASIAHypophosphatasia is a rare metabolic bone disease that is characterized by a deficiency of tissue-nonspecific alkaline phosphatase.One of the first presenting signs of hypophosphatasia may be the premature loss of the primary teeth presumably caused by a lack of cementum on the root surfaces.The histopathologic examination of either a primary or permanent tooth that has been exfoliated from an affected patient often shows an absence or a marked reduction of cementum that covers the root's surface.TREATMENT:The treatment of hypophosphatasia is essentially symptomatic because the lack of alkaline phosphatase cannot be corrected.

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HYPERPITUITARISMGigantism is the childhood version of growth hormone excess and is characterized by the general symmetrical overgrowth of the body parts. Prognathic mandible, frontal bossing, dental malocclusion, and interdental spacing are the other features. Intraoral radiograph may show hypercementosis of the roots.Acromegaly is characterized by an acquired progressive somatic disfigurement, mainly involving the face and extremities, but also many other organs, that are associated with systemic manifestations. Dental radiograph may demonstrate large pulp chambers and excessive deposition of cementum on the roots

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APPLIED ASPECTS

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REMOVAL OF DISEASED CEMENTUM

Nyman et al.(1986) -Beagle dog study-Removal of diseased cementum not necessary for successful periodontal therapy.

In a later study in humans, Nyman et al(1988) showed that the same degree of improvement of periodontal status was achieved regardless of whether cementum was removed or not.

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BIOMODIFICATION OF THE ROOT SURFACE

RATIONALE: Changes in the tooth surface wall of periodontal pocket interfere with new attachment and treated root surface has higher chances of accepting new attachment.

BIOMODIFICATION AGENTS: Citric acid Tetracycline EDTA Fibronectin

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CEMENTAL REGENERATIONGuided tissue regeneration: Nyman et al(82) , using Millipore membranes, introduced the concept of a membrane barrier

Molecular Approach: Platelet-derived growth factor(PDGF) , insulin-like growth factor(IGF), transforming growth factor-b1 (TGF-B1), basic fibroblast growth factor(BFGF) and BMPs.

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CEMENTUM IN FORENSIC ODONTOLOGYAge estimation in adults by gustafsons method:In 1950,gosta gustafson proposed a method for age estimation based on morphological and histological changes of the teeth.

The method assessed regressive changes such as attrition(A), secondary dentin deposition(s), loss of periodontal attachment(p), cementum apposition at the root apex(c), root resorption at the apex(r) and dentin translucency(t).

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Assigned grades ranging from 0-3.

Adding the allotted grade for each variable, a total score(x) was obtained.

Increase in total score corresponded with increase in age.

Age was estimated using the formula age=11.43 + (4.56 * x)79

CONCLUSION80

REFERENCESClinical Periodontology and Implant dentistry- Lindhe 4th Edition

Carranzas Clinical Periodontology- 10th Edition

Orbans oral histology and embryology- 12th Edition

Ten Cates Oral histology- 6th edition

Dental cementum:the dynamic tissue covering of the root. Periodontology 2000. 1997;13 :41-75

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REFERENCESThe Periodontium- Schroeder

Shafers textbook of oral pathology seventh edition

Oraland MaxillofacialPathology,4thEdition.ByNeville

Development and general structure of the periodontium Periodontology 2000, Vol. 24, 2000, 927

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Thank you !!!83