Bone Exostosis

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Mandibular tori
Palatal torus
  • Nodular swellings of normal bone in the oral cavity
  • Also known as tori (torus = singular)
  • Common sites:
    • Hard palate (torus palatinus)
    • Lingual premolar region of the mandible (torus mandibularis)
    • Buccal alveolar bone of maxilla or mandible

Epidemiology[edit]

  • Incidence varies between different races[1]
    • More common in Inuit, Native American and Asian populations
  • Torus palatinus
    • More common than mandibular tori
    • Incidence - 9-66%
    • ♀ > ♂
  • Torus mandibularis
    • Incidence - 0.5-63.4%
    • ♂ > ♀

Clinical Features[edit]

  • Firm swellings with normal overlying mucosa
    • Whilst mucosa is normal it is usually thin and can have a blanched appearance (sometimes can ulcerate)
  • Small-sized lesions → <3mm elevation and <10mm diameter
  • Medium-sized lesions → 3-5mm elevation and 10-15mm diameter
  • Large-sized lesions → >5mm elevation and >15mm diameter
  • Usually only affects one site in an individual
  • Torus palatinus
    • Occurs in the midline of the palate (usually in the mid-third)
    • Usually symmetrical but if large can also become an irregular rounded mass
  • Torus mandibularis
    • Found on the lingual surface of the mandible
    • Usually adjacent to premolars and above the mylohyoid attachment
    • If very large can interfere with tongue movement
    • Common presentations:
      • Bilateral solitary > bilateral multiple > unilateral solitary > unilateral multiple
  • Other sites
    • Multiple bone exposes can also affect the buccal aspect of maxilla or mandible

Aetiology and Pathogenesis[edit]

Aetiology[edit]

  • Largely unknown
  • Some suggestions:
    • Hereditary (autosomal dominant inheritance has been described in some)
    • Masticatory hyperfunction

Pathogenesis[edit]

  • Also largely unknown
  • In palatal tori, there is suggestion of continued activity of the embryonic osteoblasts which pile up at the palatal suture after the median palatal suture junction is completed

Investigations[edit]

Imaging[edit]

  • Radiographically tori appear as radiopaque masses
  • Dense bone ∴ they can obliterate details of the teeth and maxillary sinus in plain film radiographs
  • In large tori - the spongy layer in the middle appears less dense than the cortical bone

Histology[edit]

  • Torus palatinus
    • Cross-sectional analysis of tori palatine demonstrate three layers:
      1. Nasal compact layer - same thickness irrespective of size of tori ∴ confirming that development occurs by downward growth (nasal floor always remains flat)
      2. Middle spongy layer - may not be seen in smaller tori
      3. Oral compact layer
  • Torus mandibularis
    • Seen as lamellar periosteal outgrowth of the mandible

Management[edit]

  • No active treatment needed
  • Patient reassurance
  • Removal is sometimes needed if they interfere with function or to facilitate dental prosthesis
  • Tori have been described as a source of autogenous bone graft in implant placement[2][3][4]

Prognosis and Complications[edit]

  • Benign
  • Recurrent ulceration can occur due to thin overlying mucosa
  • Large lesions can interfere with function and dental prosthesis

Follow-up[edit]

  • None needed

References[edit]