Systematic and meticulous classification of the position of
impacted molar teeth helps in assessing the best possible
path of removal of the impacted teeth and also in
determining the amount of difficulty which would be
encountered during removal.
Prediction of operative difficulty before the extraction of
impacted third molars allows a design of treatment that
minimises the risk of complications. Both radiological and
clinical information must be taken into account.
Factors such as sex, age, position of the molar tooth in
relation to the occlusal plane and operative difficulty as
judged by the surgeon, have all been reported to be
associated with a significantly increased duration of
postoperative recovery. It seems likely that patients
judged to be at higher risk for delayed recovery will benefit
from a more exhaustive postoperative follow-up and from
specific post-operative measures to aid recovery.
Prediction of operative difficulty is therefore important for
correct management. Various methods have been
proposed for the pre-operative evaluation of difficulty but
these have often been of limited validity. To overcoming
the limitations of these systems, the classification systems
can be used in conjunction with each other to determine
the difficulty of removal of the impacted tooth
Classification of Impacted Mandibular 3rd Molars
Based on the nature of the overlying tissues
Winter’s classification
Pell & Gregory’s classification
Based on the Nature of the Overlying Tissue
Based on the nature of the overlying tissue impaction,
impacted lower wisdom teeth can be classified into:
Soft Tissue Impaction. When the height of the tooth’s
contour is above the level of the surrounding alveolar
bone and the superficial portion of the tooth is
covered only by soft (though this can be dense and
fibrous) tissue. Soft tissue impaction is usually the
easiest of type of impacted tooth to remove.
Hard Tissue (‘Bony’) Impaction. This is where the
wisdom tooth fails to erupt due to being obstructed by
the overlying bone. This can be sub-divided into
Partial and Complete Bony Impactions.
Partial Bony. The superficial portion of the tooth is
covered only by soft tissue but the height of the
tooth’s contour is below the level of the surrounding
alveolar bone. Apart from cutting the gingiva (gum) &
possible bone removal from behind the tooth, the
tooth’s roots may need to be divided.
Complete Bony. The tooth is completely encased in
bone so that when the gingiva is cut and reflected
back, the tooth is not seen. Bone removal (large
amounts) together with root sectioning will be needed
to remove the tooth. These are often the most
difficult tooth to remove.
Winter’s Classification
The classification is based on the inclination of the
impacted wisdom tooth (3rd molar) to the long axis of the
2nd molar.
Mesio-Angular. The impacted tooth is tilted toward the
2nd molar in a mesial direction.
Disto-Angular. The long axis of the 3rd molar is angled distally / posteriorly away
from the 2nd molar.
Horizontal. The long axis of the 3rd molar is horizontal.
Vertical. The long axis of the 3rd molar is parallel to the long axis of the 2nd molar.
Buccal / Lingual Obliquity. In combination with the above, the tooth can be
buccally (tilted towards the cheek) or lingually (tilted towards the tongue)
impacted.
Transverse. This is where the tooth is in effect horizontally impacted but in a
cheek-tongue direction.
Inverse.
Significance. Each type of impaction has some definite path of withdrawl of the
teeth.
Mesially impacted teeth are (can be) easier to remove whereas distally impacted
teeth are (can be) the hardest to remove.
Bucally positioned maxillary (upper) teeth are easier to remove as the bone
covering the tooth is thinner whereas the palatally positioned tooth requires bone
removal and hence males the extraction difficult.
Pell & Gregory’s Classification
This is based on the relationship between the impacted lower wisdom tooth (3rd
molar) to the ramus of the mandible (lower jaw) and the 2nd molar (based on the
space available distal to the 2nd molar).
Class A. The occlusal plane of the impacted tooth is at the same level as the
occlusal plane of the 2nd molar. (The highest portion of impacted 3rd molar is on
a level with or above the occlusal plane).
Class B. The occlusal plane of the impacted tooth is between the occlusal plane
& the cervical margin of the 2nd molar. (The highest portion of impacted 3rd
molar is below the occlusal plane but above the cervical line of the of 2nd molar).
Class C. The impacted tooth is below the cervical margin of the 2nd molar. (The
highest portion of impacted 3rd molar is below the cervical line of the of 2nd
molar).
Class 1. There is sufficient space available between the anterior border of the
ascending ramus & the distal aspect of the 2nd molar for the eruption of the 3rd
molar.
Class 2. The space available between the anterior border of the ramus & the
distal aspect of the of the 2nd molar is less than the mesio-distal width of the
crown of the 3rd molar. It denotes that the distal portion of the 3rd molar crown is
covered by bone of the ascending ramus.
Class 3. The 3rd molar is totally embedded in the bone of the anterior border of
the ascending ramus because of the absolute lack of space. It is obvious that
Class 3 teeth present more difficulty in removal as a relatively large amount of
bone has to be removed and there is a risk of damaging the ID nerve or fracturing
the mandible (or both).
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