Figure 15. Talc-contaminated gutta percha as a potential cause of endodontic failure. Note the apical periodontitis (AP) characterized by foreign-body giant cell reaction to gutta-percha cones contaminated with talc (a). The same field when viewed in polarized light (b). Note the birefringent bodies distributed throughout the lesion (b). The apical foramen is magnified in (c), and the dark-arrowheaded cells in (c) are further enlarged in (d). Note the birefringence (BB) emerging from slit-like inclusion bodies in multinucleated (N) giant cells. B, bone; D, dentin. Magnifications: (a,b) 25x; (c) 66x; and (d) 300x. (From Nair, 1998b.)