Classification of Manddibular Third Molar Impactions

What is the need of Classification of Impacted Teeth? 

Classification of the impacted teeth using a variety of systems, the surgeon can approach the proposed surgery in a methodical fashion and predict whether any extraordinary surgical approaches will be necessary or if the patient will encounter certain postoperative problems.

Impacted-Tooth-ExtractionImage Source:

Which is the Radiograph of Choice for removal of Impacted Third Molars? 

The panoramic radiograph or OPG.

What are the Classification Systems for Impacted Teeth?

A: Angulation
B: Relationship to Anterior Border of Ramus
C: Relationship to the Occlusal Plane

What is the most commonly used classification system with respect to treatment planning of Impacted Teeth? 

Angulation is the most commonly used classification system.

How Angulation System Describes Impaction? 

It determines the angulation of the long axis of the impacted third molar with respect to the long axis of the adjacent second molar.

A: Classifications according to Angulation: (Archer and Kruger Classification) 

  1. Mesio Angular: (Most Common) 43% & Least Difficult to remove.
  2. Horizontal: (Less Common) only 3%. More difficult Than MesioAngular.
  3. Vertical Impactions: second greatest frequency, 38%. Considered Third in ease of removal.
  4. Distoangular impaction: only approximately 6%. Most Difficult to Remove.
  5. Buccoangular
  6. Linguoangular
  7. Inverted

Archer (1975) and Kruger (1984).
1Mesioangular, 2 distoangular, 3 vertical, 4 horizontal, 5 buccoangular, 6 linguoangular, 7 inverted

Why Distoangular impaction is Most Difficult to Remove? 

  • The tooth has a withdrawal pathway that runs into the mandibular ramus.
  • Its removal requires significant surgical intervention.
  • Third molar’s mesial root is very close to the root of the second molar.

The buccal or lingual position of the tooth does not greatly influence the approach to the surgery.

B: Relationship to Anterior Border of Ramus: Pell and
Gregory classification

  • Class 1 relationship: (Easiest to remove)
    If the mesiodistal diameter of the crown is completely
    anterior to the anterior border of the mandibular ramus.
  • Class 2 relationship:
    If the tooth is positioned posteriorly so that approximately one
    half is covered by the ramus.
  • Class 3 relationship: (Most Difficult to Remove)
    The tooth is located completely within the mandibular

C: Relationship to the Occlusal Plane: Pell and
Gregory classification

  • Class A impaction: (Esiest to Remove)
    Is one in which the occlusal surface of the impacted tooth is level or nearly level with the occlusal plane of the second molar.
  • Class B impaction:
    an impacted tooth with an occlusal surface between the occlusal plane and the cervical line of the second molar.
  • Class C impaction: Most Difficult to Remove)
    In which the occlusal surface of the impacted tooth is below the cervical line of the second molar.

Classification of impacted mandibular third molars according to Pell and Gregory : a) according to the depth of impaction and proximity to the second molar; b) their position according to the distance between the secondmolar and the anterior border of the ramus of the mandible.

∗ Mesioangular impaction with a class 1 ramus and a class A depth is usually straightforward to remove. 
∗ The most difficult of all impactions is a distoangular impaction with a class 3 ramus relationship at a class C depth. 


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