Cross-reactivity between gutta-percha and natural rubber latex: assumptions vs. reality

BACKGROUND: Immunological cross-reactivity between gutta-percha and natural rubber latex, or NRL, has not been demonstrated clearly despite recent concerns and several suspected cases reported in the literature. METHODS: The authors analyzed aqueous extracts of commercial gutta-percha points and raw gutta-percha samples for cross-reactivity to NRL by radioallergosorbent test, or RAST, inhibition; immunoblot inhibition; direct enzyme-linked immunosorbent assay, or ELISA; and ELISA inhibition using sera from NRL-allergic people as the source of anti-NRL immunoglobulin E, or IgE, antibodies. To confirm in vitro results, the authors conducted skin prick testing, or SPT, on a patient with type I NRL allergy using aqueous extracts from raw gutta-percha, ammoniated gutta-percha and gutta-percha points. RESULTS: Aqueous extracts from commercial gutta-percha points did not cross-react to NRL in RAST inhibition or immunoblot inhibition, ELISA or ELISA inhibition assays. However, three of 13 sera from subjects with type I NRL allergy exhibited IgE binding to raw gutta-percha extracts in direct ELISA. Moreover, in ELISA inhibition, the binding of IgE to raw gutta-percha extracts was inhibited in a dose-dependent manner by raw NRL and vice versa. SPT results from a subject with type I NRL allergy were positive for NRL and raw gutta-percha extracts but negative for gutta-percha point extracts. CONCLUSIONS: The authors found no detectable cross-reactivity between NRL and commercial gutta-percha points. However, their ELISA and SPT results demonstrated that some allergenic cross-reactivity exists between raw gutta-percha and raw NRL. CLINICAL IMPLICATIONS: Gutta-percha alone is not likely to induce symptoms in patients with type I NRL allergy. However, other materials used in obturating root canals may be irritating and potentially allergenic in patients with pre-existing allergies.