What is the name of the lesion associated with an unerupted tooth and painless bone expansion?

The lesion associated with an unerupted tooth and painless bone expansion is known as a dentigerous cyst. A dentigerous cyst commonly forms around the crown of an unerupted tooth, typically the mandibular third molars or maxillary canines, and is characterized by its fluid-filled cavity that results in the expansion of the surrounding bone. This expansion is usually painless, which aligns with the presentation of this type of lesion.

While adenomatoid odontogenic tumors do occur around unerupted teeth and can also lead to bone expansion, they are typically more complex in their presentation and are not solely defined by the presence of an unerupted tooth as the primary characteristic. Therefore, dentigerous cyst is the more precise answer regarding the features of painless bone expansion associated specifically with an unerupted tooth.