Understanding Impacted Third Molars

An impacted third molar is one that fails to erupt fully into a normal functional position due to lack of space, abnormal angulation, or obstruction by adjacent structures. Mandibular third molars are the most commonly impacted teeth encountered in oral surgery practice.

Classification Systems

Winter's Classification (Based on Angulation)

  • Mesioangular impaction
  • Distoangular impaction
  • Horizontal impaction
  • Vertical impaction

Pell and Gregory Classification

  • Based on ramus relationship (Class I, II, III): Amount of space available between the anterior border of the ramus and the distal surface of the second molar.
  • Based on depth (Position A, B, C): Depth of the impacted tooth relative to the occlusal plane of the second molar.

Common Complications of Impacted Third Molars

  • Pericoronitis - inflammation of the soft tissue surrounding a partially erupted tooth.
  • Caries in the third molar or the adjacent second molar due to poor access for cleaning.
  • Root resorption of the adjacent second molar.
  • Cystic changes, such as dentigerous cyst formation around the impacted crown.
  • Recurrent infection and abscess formation.
  • Occasional association with adjacent periodontal bone loss.

Surgical Management: Step-by-Step

  1. Pre-operative Assessment: Clinical examination and radiographic evaluation (OPG or CBCT) to assess proximity to the inferior alveolar nerve canal.
  2. Anaesthesia: Administration of appropriate local anaesthesia (typically inferior alveolar and lingual nerve block for mandibular third molars).
  3. Flap Reflection: Raising a mucoperiosteal flap to expose the impacted tooth and surrounding bone.
  4. Bone Removal: Careful removal of overlying bone using a surgical bur under copious saline irrigation.
  5. Tooth Sectioning: Sectioning the tooth into segments when necessary to facilitate atraumatic removal, especially in horizontal or distoangular impactions.
  6. Debridement and Closure: Thorough irrigation of the socket followed by suturing the flap back into position.
  7. Post-operative Care: Instructions on pain management, swelling control, and oral hygiene to promote uneventful healing.

Conclusion

Accurate pre-operative classification and imaging assessment are essential for anticipating surgical difficulty and minimising complications during impacted third molar removal. A systematic surgical approach reduces operative time and improves patient outcomes.