Which of the following is NOT associated with gingival enlargement?

The choice that is NOT associated with gingival enlargement is antihistamines. Gingival enlargement, also known as gingival hyperplasia, is typically linked to certain medications that affect gum health by causing an increase in gum tissue.

Calcium channel blockers, anticonvulsants, and immunosuppressants are well-documented to cause gingival enlargement as a side effect. For instance, medications like phenytoin (an anticonvulsant) and certain calcium channel blockers such as nifedipine can lead to increased fibroblast activity and extracellular matrix production, which contribute to the proliferation of gingival tissues. Immunosuppressants, particularly cyclosporine, are also known to cause gingival overgrowth.

On the other hand, antihistamines, which are primarily used to relieve allergy symptoms, do not have a typical association with gingival enlargement. They can cause xerostomia (dry mouth), which may indirectly affect oral health but not through enlargement of the gums. Therefore, the lack of a connection between antihistamines and gingival enlargement makes it the correct answer to the question.