Apical actinomycosis: case report.

Actinomycosis has increasingly been recognized as a cause of persistent or recurrent periapical disease associated with endodontic therapy. After conventional root canal therapy of the lower left first and second molars, a 24-year-old woman presented with a persistent periapical lesion associated with one of the sinus tracts. The lesion was surgically removed, and actinomycosis was diagnosed on the basis of biopsy results. The clinical and histologic features of this rare condition are discussed.