Relationship to Anterior Border of Ramus
Another method for classifying. impacted mandibular third molars is based on the amount of impacted tooth that is covered with the bone of the mandibular ramus .• This classification is known as the Pell and GregQIJ’classification and is sometimes referred to as the Pell and Gregory
classes 1, 2, and 3. For this classification it is important that till surgeon carefully examine the: relationship bctw.-c n the tooth and the anterior part of the ramus. If the mesiodistal diameter of the crown is completely anterior to the anterior border of the mandibular ramus, it is in a class- 1 relationship. If the tooth is angled in a vertical direction, the chances for the tooth to erupt into a normal position are good (Fig. 9-20). If the tooth is ‘Positioned posteriorly so that approximately one half is covered by the ramus, the tooth’s relationship with the ramus is class 2. In the class 2 situation the tooth cannot become completely free from bone, because a small shelf of bone overlies the distal portion of . the tooth (Fig. 9-21). A class 3 relationship between the tooth and ramus occurs when the tooth is located completely within the mandibular ramus (Fig. 9-22). It should be obvious that the lass 1 relationship will provide the greatest accessibility to the impacted tooth and therefore will be easiest to remove. The class 3 relationship provides the least accessibility and therefore presents the greatest difficulty.
molar has sufficient anteroposterior room (i.e., anterior-to-anterior
border ~f ramus) to erupt.
FiG. 9-21 Pel! and Gregory class 2 impaction. Approximately .half
is covered by anterior portion of ramus of mandible.