Pell and Gregory classification (Impacted 3rd molar)

  • Based on the amount of tooth covered by the anterior border of the ramus (1,2,or 3).
  • The depth of the impaction relative to the adjacent tooth (A,B,or C).
  • Helpful in predicting surgical difficulty.

3rd molar impaction can be:

Class I
Class I 3rd molar impaction: Situated anterior to the anterior border of the ramus.


Class II
Class II 3rd molar impaction: Crown ½ covered by the anterior border of the ramus.


Class III
Class III 3rd molar impaction: Crown fully covered by the anterior border of the ramus.


Class A
Class A maxilla 3rd molar impaction: The occlusal plane of the impacted tooth is at the same level as the adjacent tooth.


Class A
Class A mandible 3rd molar impaction: The occlusal plane of the impacted tooth is at the same level as the adjacent tooth.


Class B
Class B maxilla 3rd molar impaction: The occlusal plane of the impacted tooth is between the occlusal plane and the cervical line of the adjacent tooth.


Class B
Class B mandible 3rd molar impaction: The occlusal plane of the impacted tooth is between the occlusal plane and the cervical line of the adjacent tooth.


Class C
Class C maxilla 3rd molar impaction: The occlusal plane of the impacted tooth is apical to the cervical line of the adjacent tooth.


Class C
Class C mandible 3rd molar impaction: The occlusal plane of the impacted tooth is apical to the cervical line of the adjacent tooth.
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