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Human Cementum

- Dr. Fatema1st Year MDS

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Contents

• Introduction• Tooth Development• Cementogenesis & Cells of the Cementum• Physical properties of Cementum• Chemical Properties of Cementum• Functions of Cementum• Cementodentinal junction• Cementoenamel junction• Age changes in cementum• Root caries.• Developmental and acquired anomalies.

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Contents…Contd

• Clinical Considerations.

• Conclusion.

• References.

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Introduction

• Cementum is the mineralized dental tissue covering the anatomic roots of human teeth.

• First demonstrated microscopically in year 1835.• Begins from CEJ and continues to the Apex.• Acts as a medium for anchorage for the tooth• It is a specialized connective tissue similar to

compact bone but avascular in nature.

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Tooth Development

• Stages of Development– Bud Stage– Cap Stage– Bell Stage– Advanced Bell Stage

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Tooth Development• At the 6th week of embryonic life.

Localized proliferation of ectoderm

Horse shoe shaped structure

(Primary Dental Lamina)

Maxilla Mandible

Vestibular Dental Vestibular Dental

Lamina Lamina Lamina Lamina

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Stages of Development – Bud Stage

• Initial stage wherein the epithelial cells of the dental lamina proliferates and produces a bud like projection into the adjacent ectomesenchyme.

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Stages of Development - Cap Stage

• Cap like structure outer enamel epithelium • Inner enamel epithelium • Network of cells called stellate reticulum

(Branched reticular arrangement of cellular elements.)

• The rim of Enamel organ is called the cervical root.

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Stages of Development - Bell stage

• Cells forming the loop continue to proliferate, further invagination of the enamel organ into the mesenchyme.

• The ectomesenchyme of the dental papilla is partially enclosed by invaginating epithelium.

• In this stage blood vessels become established in the dental papilla.

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Stages of Development - Advanced Bell Stage

• Condensed ectomesenchyme (surrounding the enamel organ) + dental papilla complex = dental sac.

Develops into periodontal ligament

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Cementogenesis & Cells of the Cementum

• Deposition of dentin along the inner aspect of Hertwig’s epithelial root sheet (HERS).

• HERS derives from the coronoapical extension of inner and outer dental epithelium.

• It sends an inducted message by secreting enamel proteins to ectomesenchymal pulp cells.

Differentiate into odontoblasts and predentin

• HERS becomes interrupted, ectomesenchymal (inner portion)cells come in contact with the predentin.

• Cells from connected tissue are responsible for cementum formation. • Sheet cells that migrate towards the dental sac rests of malassez

(periodontal ligaments)

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Cementogenesis

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Cementogenesis - Cementoblasts

• Undifferentiated mesenchyme cells (connected tissue) differentiates into cementoblasts.

• These synthesize :

Collagen + Protein polysaccharides.

Organic matrix

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Cementoblast

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Cementogenesis – Cementoid

• After cementum matrix is laid down mineralization begins

• Uncalcified matrix is called cementoid

• Calcium and phosphate ions in the tissue fluid are deposited into the matrix

Unit cells of hydroxyapetite

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Cementogenesis – Cementoid ….contd

Cells of the cementum- Cementocytes

• Found only in cellular cementum

• They are located within lacunae and have numerous cytoplasmic processes.

• These cells remain vital. Their metabolic activity is low.

Cells of the cementum Periodontal fibroblasts

• These cells belong to the periodontal ligament and are responsible for synthesis of principal fibres.

• They indirectly participate in cementum formation.

Cells of the cementum cementoclast

• These are multi nucleated giant cells similar to osteoclasts.

• They are responsible for extensive root resorption in primary tooth exfoliation and for localized cemental resoption e:g adult dentitions (also during orthodontic therapy)

Morphogenes and Growth FactorsMorphogenes and growth factorsMorphogenes and growth factors Suggested functions related to Suggested functions related to

cemenogenesis.cemenogenesis.

Growth Factors:Growth Factors:

Bone morphogenic proteinsBone morphogenic proteins

Platelet-derived growth factor, Platelet-derived growth factor, insulin- like growth factor.insulin- like growth factor.

Fibroblast growth factorsFibroblast growth factors

Promotes cell differentiation and Promotes cell differentiation and cementogenesis (Development and cementogenesis (Development and regeneration)regeneration)

Promotes cementum formation by Promotes cementum formation by altering cell cycle activities.altering cell cycle activities.

Promotes cell proliferation, migration Promotes cell proliferation, migration also vasculogenesis – formation and also vasculogenesis – formation and regeneration of periodontal issues.regeneration of periodontal issues.

Adhesion moleculesAdhesion molecules

Bone sialo protein.Bone sialo protein.

OsteopontinOsteopontin

Promotes adhesion of selected cells Promotes adhesion of selected cells to newly forming root also involved in to newly forming root also involved in mineralization, osteopontin regulates mineralization, osteopontin regulates extent of crystal growth. extent of crystal growth.

Epithelial / Enamel like factors.Epithelial / Enamel like factors. Promotes follicle cells along Promotes follicle cells along cementoclasts. Some promote cementoclasts. Some promote periodontal repair.periodontal repair.

CollagenCollagen Type I and III regulates periodontal Type I and III regulates periodontal tissues in development and tissues in development and regeneration. Type IX assists in regeneration. Type IX assists in maintaining PDL space.maintaining PDL space.

Gla ProteinsGla Proteins

Matrix Gla proteinMatrix Gla protein

Bone Gla Protein (Osteocalcin)Bone Gla Protein (Osteocalcin)

Gamma carboxyglutamic acid and Gamma carboxyglutamic acid and hence the name Gla Protein.hence the name Gla Protein.

Osteocalcin associated with Osteocalcin associated with mineralization and regulator of mineralization and regulator of crystal growth. crystal growth.

Matrix Gla protein helps in Matrix Gla protein helps in preventing abnormal ectopic preventing abnormal ectopic calcification.calcification.

Morphogenes and Growth Factors

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Physical characteristics

• Light yellow in colour.

• Lack of luster.

• Has darker hue.

• Permeable to a variety of materials

• Thickness of Cementum at CEJ is 20 to 50 µ.m and towards the apex 150 to 200 µ.m

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Chemical composition

• 40% to 50% inorganic Substances– Calcium and phosphate in the form of

hydroxyapatite– Highest fluoride content

• 50% to 55% organic material– Type 1 collagen and protein polysaccharides

Functions of Cementum

• Primary function of cementum – attachment of collagen fibers that bond the tooth to alveolar bond.

• Continuous deposition of cementum is of functional importance.

• Cementum serves as a major reparative tissue for root surfaces.

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CLASSIFICATION OF CEMENTUM

• Based on location – Radicular cementum– Coronal cementum

• Based on it’s cellularity – Acellular cementum– Cellular cementum.

• Based on the presence or absence of collagenous fibrils– Afibrillar– Fibrillar cementum 

• Based on the origin of collagenous fibrils– Intrinsic fibers– Extrinsic fibers

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CLASSIFICATION OF CEMENTUM

• Schroder in 1986 gave the classification of cementum as:– Acellular extrinsic fiber cementum (Primary

Cementum)– Acellular afibrillar cementum.– Cellular intrinsic fiber cementum (Secondary

Cementum)– Cellular mixed fiber cementum.– Intermediate cementum.

Type Type Origin of Origin of fibers fibers

LocationLocation FunctionFunction

AcellularAcellular ExtrinsicExtrinsic From Cervical From Cervical to apical 3to apical 3rdrd

AnchorageAnchorage

CellularCellular IntrinsicIntrinsic Middle to Middle to apical 3apical 3rdrd , , furcations.furcations.

Adaptation Adaptation and repairand repair

MixedMixed Extrinsic and Extrinsic and IntrinsicIntrinsic

Apical portion Apical portion and furcationsand furcations

AdaptationAdaptation

Acellular Acellular afibrillarafibrillar

-- Spurs and Spurs and patches over patches over enamel and enamel and dentin along dentin along

CEJCEJ

No known No known function.function.

Intermediate Cementum

• Non Cellular amorphous layer of hard tissue, 10 microns thick.

• Deposited by inner epithelial cells of root sheet and occurs before the HERS disintegrates.

• First layer of hard tissue deposited, seals the tubules of dentin.

• Contains enamel proteins.

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Cementoenamel junction

• There are 3 types– Cementum overlaps enamel – 60% to 65%– Edge to edge – 30%– Cementum does not meet enamel 5% to 10%

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Cementodentinal junction

• CDJ in deciduous teeth may be scalloped.

• Attachment between cementum and dentin is quite firm.

Age changes in cementum

• With ageing the smooth surface of cementum becomes more irregular.

• This is caused by the calcification of some ligament fiber bundles attached to the cementum.

• In ageing a continous increase in cementum in apical zone may obstruct the apical canal.

• Cementum resorption is one characteristic of ageing.

• Resorption becomes active for a period and then stops. Deposition of cementum occurs in that period creating reversal lines.

Root caries• Gingival recession increases risk of root

caries.• Dark areas associated with

remineralization.• Broad spectrum of

microorganisms.MS,lactobacilli,a.viscusus..• Shallow initially.• Light brown to yellow.• Rapid development.• Restorations are done

with GIC or composites.

Cementricles

• These are globular masses of acellular cementum less than 0.5 mm in diameter which form within PDL.

• They are of 3 types– Free cementricles– Embedded cementricles– Attached cementricles

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Cementricles

Developmental and acquired anomalies

• Hypercementosis : it is a non neoplastic deposition of excessive cementum that is continuous with the normal radicular cementum.– Occurs predominantly in adults,

frequency increases with age.– May show hereditary influence.– If overgrowth improves functional

qualities – cementum hypertrophy – If overgrowth occurs in non functional

teeth – hyperplasia

Developmental and acquired anomalies

• Local factors associated with Hypercementosis– Abnormal occlusal trauma– Adjacent inflammation– Tooth repair– Un opposed teeth (Embedded, impacted)

• Systemic factors associated with Hypercementosis: – Acromegaly and pitutiary gigantism.– Paget’s disease– Thyroid goiter

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Hyperplastic cementum

Excementosis

• In Localized Hypertrophy a spur or prong like extension of cementum is seen.

• Found in teeth exposed to great stress.

• These provide large surface area for firm anchorage.

Ankylosis

• The cessation of eruption after emergence is called Ankylosis.

• Occurs from anatomic fusion of tooth cementum with alveolar bone.

• Pathogenesis is unknown.• Disturbances from local

metabolism, trauma, injury, chemical or thermal irritation, failure of bone growth and abnormal pressure from tongue.

Hypophosphatasia

• Hereditary disease first recognized by Rathbun in 1948.

• Deficiency of enzyme alkaline phosphatates and excretion of phosphothanolamine in the urine.

• In children characterized by premature exfoliation of deciduous teeth.

Concrescence

• Is usually a form of fusion which occurs after root formation is completed.

• These are united by cementum only maybe result of traumatic injury or crowding of teeth.

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Clinical Considerations

• Cementum more resistant to resorption than bone hence orthodontic tooth movement is possible.

• By means of orthodontic appliance

Side of Pressure Side of Tension

Bone resorbed New bone formed

Cementum resorption is minimum

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Clinical Considerations

• Cemetum resorption occurs after trauma or excessive occlusal forces. The damage is repaired by formation of acellular or cellular or both types of cementum - Anatomic repair.

• In a deep resorption root outline is not reconstructed and a bay like recess remains.

• In such areas periodontal space is restored by bony projections for functional relationship - functional repair.

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Repair by cementum

Conclusion

• Cementum being a mineralized dental tissue covering the anatomic roots of the human teeth

• Its main function being anchorage for the tooth and its reparative properties are of clinical significance.

• Cementum forms the tissue that makes functional adaptation of teeth possible.

• Alterations in the exposed cementum are of particular interest as it ay interfere with healing during periodontal therapy.

References

• Orban’s – Oral Histology and Embryology – 11th Edition

• Ten Cate’s - Oral Histology, Development, structure and functions – 6th Edition

• Sturdedant’s – Art and science of operatve dentistry – 5th Edition.

• Cohen – Pathways of Pulp – 9th Edtion

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