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RESORPTION OF TEETH

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Dental hard tissues are resorbed bymultinucleate cells called ODONTOCLASTSor DENTINOCLASTS.

They are considered to be same type asosteoclasts because they possess the same ultrastructure and histochemical characteristics.

However, dentinoclasts or odontoclasts maycontain fewer nuclei than osteoclasts.

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Classification:

1. Physiological2. Pathologicala) External root resorption

a.1) Resorption due to trauma-surface ,inflammatory and replacement resorption

a.2) Resorption due to pulp or apical pathologya.3) Resorption due to pressure

b) Internal root resorptionc) Idiopathic root resorptionRecently, a clinical oriented classification has been

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This new classification is based on tworequirements, namely-

*injury to protective tissues: chemically ormechanically

*stimulation: by infection or pressure

Injury is related to non mineralized tissuecovering the external surface of the root-ie.,pre cementum or internal surface of theroot canal-ie., pre dentine.

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Injury:Mechanical- dental trauma, surgical procedures,

excessive pressure from tumours or impacted teeth

Chemical-bleaching with 30% H2O2

Following injury denuded mineralized tissue becomecolonized by multinucleated cells which initiate theresorption process.

However, without stimulation, resorption process endspontaneously and reparative changes occur.

Therefore, continuation of the resorption process dependon continuous stimulation by either pressure orinfection

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Present classification is based on differentstimulation factors.

It is clinically oriented as the resorptionprocess can be reversed by removing thestimulation factor.

Classification1. Pulpal infection root resorption2. Periodontal infection root resorption3. Orthodontic pressure ,,4. Impacted tooth/tumour ,, ,,5. Ankylotic root resorption

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Pulpal infection root resorption

*most common stimulation factor

*following injury to pre cementum or predentine inflammatory process within periradicular or pulpal tissue initiate externalor internal resorption

*radiolucency is observed in the external rootsurface of dentine & bone, or in the internalroot canal dentinal wall

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Treatment:

Internal resorption- pulptectomy: to removegranulation tissue/ blood supply of resorbingcells

External resorption- pulptectomy: critical toremove bacterial stimulation from dentinaltubules using calcium hydroxide.

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Periodontal infection root resorption*external root resorption may occur apical

to the epithelial attachment, followed bybacterial stimulation originating fromperiodontal sulcus.

*injury may be caused by dental trauma,bleaching agents, orthodontic treatmentor periodontal procedures

*bacteria penetrate the patent dentinaltubules coronal to epithelial attachmentand exist apical to

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*radiologically, seen as a single resorptionlacuna (radiolucency) at the crestal bonelevel.

*treatment: As long term bacterial removalfrom the periodontal sulcus is not practical,effective therapy is to expose the resorptivelacunae orthodontically or surgically toremove granulation tissue followed byrestoration with composite.

Endodontic therapy is only necessary if theresorption process extend in to pulp.

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Orthodontic pressure resorption

*pressure applied to roots during toothmovement can cause apical root resorption.Continuous pressure stimulate resorbingcells of the apical third of the root, leadingto shortening of the root.

*teeth are usually vital if undue pressure isnot applied

*located at apical one third of the root, but nosigns of radiolucency can be observed.

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*treatment: removal of the pressure source isusually sufficient. Operative procedures arenot necessary.

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Impacted tooth/ tumour pressure resorption

*impacted tooth pressure resorption can beobserved during eruption of the permanentdentition Max 3….Max2, Man 3….Man 2.

*tumours impinging on the tooth roots cancause pressure resorption. Tumours thatproduce resorption are slow growinglesions as ameloblastoma, giant celltumours ect.,

* usually, asymptomatic with vital pulps

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*radiologically, resorption area is locatedadjacent to the stimulation factor.Radiolucencies are not observed asinfection is not involved. The site is filledwith stimulation factor.

*treatment:surgery to remove the stimulationfactor

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Ankylotic root resorption*in severe traumatic injuries eg intrusive

luxation or avulsion injury to the toothsurface may be large so that healing withcementum is not possible and the bonecomes in contact with root surface withoutperiodontal ligament. This is known asdento-alveolar ankylosis.

*Although, there is no stimulation factor andthe process proceeds as a result of directbone attachment to dentine, the termankylotic resorption is used.

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*radiologically, the resorption lacunae arefilled with bone and the periodontalligament space is missing. No radiolucentarea is observed.

*treatment: as there is no stimulation toremove, no predictable treatment isavailable.

Best approach is to minimize periodontalligament damage.

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Invasive cervical resorption

Relatively uncommon form of external rootresorption.

Characterized by cervical location and invasivenature, resorptive process can lead to loss oftooth structure

Etiology is poorly understood, however,intracoronal bleaching, orthodontic toothmovement, trauma ect., are considered aspredisposing factors.

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• ClassificationClass 1: small invasive resorptive lesion near the

cervical area with shallow penetration in todentine

Class 2: well defined invasive resorptive areathat has penetrated close to coronal pulp butshows no extension in to radicular pulp.

Class 3: deeper invasion of both coronal andcoronal third of radicular dentine byresorptive process

Class 4: large resorptive focus that has extendedbeyond coronal third of root

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Osteoclast*derived from monocyte macrophage

haemopoietic lineage.*cell responsible for bone resorption*multinucleated cell containing 4-20 nuclei*usually found in Howship’s lacunae*ultrastructure: contain numerous golgi

complexes around each nucleus andmitochondria and transport vesicles loadedwith lysosomal enzymes

*most characteristic feature is the presence of theruffled border and the sealing attachment

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*osteoclasts synthesize and secrete tartarateresistant acid phosphatase and cathepsinKinto the extracellular bone resorbingcompartment. In addition, cells also secreteMMP 9 & 13 which stimulate pre-osteoclastmigration and bone matrix digestion.

*attachment of osteoclast to bone surface isessential for bone resorption and involvesintegrins.

*thereafter, avb3 binding activatescytoskeletal reorganization within the cellincluding cell spreading and polorization.

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stem cell

PU1

OPG/RANKL

Osteoclast progenitor

Differentiation

macrophage

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RANK

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Fusion

Polarization

Activation

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