ISSN 2398-2950      

Odontoclastic tooth resorption (resorptive lesions)

ffelis

Synonym(s): Feline odontoclastic resorptive lesion, FORL, RL, tooth resorption, neck lesion, cervical line lesion


Introduction

  • Non-carious destruction of hard dental tissue by odontoclastic cells.
  • >30% of cats affected.
  • Categorized into Type 1 and Type 2 tooth resorption (also combined; Type3).
  • Cause: odontoclastic resorption; resorption (destruction) - repair imbalance.
  • Etiology: uncertain - believed to be multifactorial. Type 1 inflammatory associated.
  • Signs: oral sensitivity/pain, periodontal disease or none.
  • Diagnosis: radiology, essential because most lesions subgingival.
  • Treatment: depends on type and stage of lesion - dental cleaning, extraction, root removal, coronal amputation.

Pathogenesis

Etiology

  • Loss of outer, protective blast-cell layer of root.
  • Persistence of stimulus causing root resorption - repair pattern.
  • Theories:
    • Inflammation - periodontal disease (gingivitis, periodontitis, gingivo-stomatitis Gingivitis and stomatitis).
    • Abfraction - mechanical loading of teeth (eg hard pet food)    →   micro-fractures   →   absorption of bacterial products   →   chronic inflammation.
    • Commercial pet foods   →   mechanical stimulus of periodontal tissues.
    • Vitamin D levels.
    • Others....

Predisposing factors

General

  • Periodontal disease -  inflammation.

Specific

  • Gingivitis, periodontitis, gingivo-stomatitis.

Pathophysiology

  • Abnormal remodeling of teeth by odontoclast cells.
  • Odontoclastic digestion of dental tissues initiates in cementum.
  • Type 1 lesions usually first affect the cervical ('neck') region.
  • Type 2 lesions generally affect more apical root regions initially.
  • Cementum and dentine resorbed, enamel resorption lacunae develop within crown.
  • Odontoclasts   →   resorption   →   repair:
    • Coronal lesion usually filled with healing tissue continuous with gingiva   →   tooth weakened   →   susceptible to fracture.
    • Subgingival lesion filled with fibrous tissue, reparative cementum or bony tissue.

Classification of lesions

Lesion type

  • Types 1 and 2 are thought by many to exist and parallel resorptive process types classified in humans.
  • Identified as Type 1 or 2 by radiographic appearance.
  • Teeth may show elements of Type 1 or 2 resorption simultaneously (Type 3).
  • Etiology of Types 1 and 2 in cats is not fully understood and may be specific or shared.
  • Type 1 = inflammatory resorption (peripheral inflammatory root resorption 'PIRR'):
    • Focal areas of resorption produce 'punched-out' and 'apple-core' type root lesions radiographically.
    • Periodontal ligament space remains visible.
    • Unaffected root areas are immediately adjacent to lesions.
  • Type 2 = replacement resorption:
    • Typified by loss of periodontal ligament space, indicating ankylosis of root to alveolar (socket) bone.
    • Gradual replacement of root dental tissues by bone leading to loss of clear outline, root density and pulp cavity.
    • Eventually total replacement produces 'ghost' roots radiographically; true anatomy cannot be discerned from adjacent bone.
  • Type 3 = tooth exhibiting Type 1 and 2 features simultaneously.

Lesions stages

  • Stages of tooth resorption are identified radiographically.
  • Nomenclature as recommended by the American Veterinary Dental College:
    • Stage 1 (TR1): mild dental hard tissue loss (cementum or cementum and enamel) Tooth resorption: stage 1 - diagram .
    • Stage 2 (TR2):  moderate dental hard tissue loss (cementum or cementum and enamel with loss of dentin that does not extend to the pulp cavity). NB Dentine erosion   →   pain if exposed to oral environment Tooth resorption: stage 2 - diagram .
    • Stage 3  (TR3): deep dental hard tissue loss (cementum or cementum and enamel with loss of dentin that extends to the pulp cavity); most of the tooth retains its integrity Tooth resorption: stage 3 - diagram .
      Erosion into pulp cavity   →    severe loss of tooth structure   →    very painful if exposed to oral environment, bleed after probing.
  • Stage 4 (TR4): extensive dental hard tissue loss (cementum or cementum and enamel with loss of dentin that extends to the pulp cavity); most of the tooth has lost its integrity:
    • TR4a - crown and root equally affected Tooth resorption: stage 4a - diagram .
    • TR4b - crown more severely affected than the root Tooth resorption: stage 4b - diagram .
    • TR4c - root more severely affected than the crown Tooth resorption: stage 4c - diagram .
  • Stage 5 (TR5): remants of hard dental tissue are visible only as irregular radiopacities and gingival covering is complete (ie a chronic lesion, complete resorption and replacement by bone) Tooth resorption: stage 5 - diagram . 

Timecourse

  • Variable on type and presence/severity of trigger and perpetuating factor, eg periodontal disease.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Gorrel C & Larsson A (2002) Feline odontoclastic resorptive lesions: unveiling the early lesion. JSAP 43 (11), 482-488 PubMed.
  • Reiter A M & Mendoza K A (2002) Feline odontoclastic resorptive lesions an unsolved enigma in veterinary dentistry. Vet Clin North Am Small Anim Pract 32 (4), 791-837 PubMed.
  • Ingham K E, Gorrel C, Blackburn J et al (2001) Prevalence of odontoclastic resorptive lesions in a population of healthy cats. JSAP 42 (9), 439-443 PubMed.
  • Merger M, Schwalder P, Stich H et al (1998) Differential diagnosis of resorptive dental lesions (FORL) and caries. EJCAP (2), 29-32 VetMedResource.

Other sources of information

  • Loprise H (2012) Tooth resorption: Feline. Five-Minute Veterinary Consult Clinical Companion Small Animal Dentistry. Wiley-Blackwell. pp 369-379.
  • Niemiec B (2010) Pathologies of the dental hard tissues. Small Animal Dental, Oral and Maxillofacial Disease. Manson, pp 136-139.
  • Gorrel C (2008) Root resorption - an introduction. Small Animal Dentistry. Saunders Elsevier. pp 105-107.

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