The three classification systems discussed so far are used in conjunction to determine the difficulty of an extraction. For example, a mesioangular impaction with a class 1 ramus and a class A depth is easy to remove and is
essentially the extraction of an erupted tooth (Fig. 9-26): . However, as the ramus relationship changes to a class 2 and the depth of the impaction increases to a class B, the degree of difficulty becomes greater. A horizontal
impaction with a class 2 ramus relationship and a class B depth is a moderately difficult extraction and one that most general practitioners do not” want to attempt (Fig. 9-27). Finally, the most difficult of all impactions is a distoangular impaction with a class 3 ramus relationship at a class C depth. Even specialists view removing this tooth as a surgical challenge (Fig. 9-28).
FIG. 9-24 Pell and Gregory class B’ impaction. Occlusal plane of impacted tooth is between occlusal plane and cervical line of second molar.
FIG. 9-25 Pel! and Gregory class C impaction. Impacted tooth is below cervical line of second molar.
F!c,. 9· 27
Horizontal impaction with class’ 2 ramus relationship
and class B depth makes it moderately difficult to extract