Which of the following is not a treatment for an impacted third molar?

Performing orthodontic realignment is not a treatment for an impacted third molar because orthodontic treatments are primarily focused on aligning the teeth and correcting the bite rather than addressing the specific issue of an impacted tooth. When a third molar is impacted, it means that there is insufficient space for the tooth to fully erupt, causing it to become trapped within the jawbone or soft tissue.

The primary treatments for an impacted third molar typically include extraction of the third molar itself, as this directly addresses the problem by removing the source of potential pain, infection, or dental complications. Observation for natural eruption can also be a valid option, particularly if the tooth is not causing any immediate issues and there is still a chance for it to erupt successfully in the future.

On the other hand, the extraction of the second molar would not directly impact the third molar's situation, as the second molar is not the one causing the impaction. Therefore, while it could be a factor in some dental cases, it is generally not a standard treatment for an impacted third molar.