Role of saliva and salivary components as modulators of bleaching agent toxicity to human gingival fibroblasts in vitro.

Mild oxygenating agents generating H2O2 are used for effective at-home tooth bleaching, but can cause gingival ulcers in some patients. There are concerns about the possible pathological effects of relatively long-term exposure of oral tissues to bleaching agents. Previous work in our laboratory showed that a bleaching agent, which generates approximately 3% H2O2 from carbamide peroxide, was toxic to human gingival fibroblasts in vitro, but that the toxicity was abolished by treatment with the H2O2-destroying enzyme catalase. The purpose of the present study was to determine if whole saliva, the salivary enzyme lactoperoxidase (LP) (which, like catalase, removes H2O2), or salivary mucin protected fibroblasts from bleaching agent toxicity. The cells were exposed to 0.05% agent with or without saliva, LP, mucin or catalase (as a positive control based on our previous study) and assessed for effect on viability/morphology (by microscopic observation), proliferation (by [3H]-thymidine incorporation), and the production of fibronectin (FN) and type I collagen (by ELISA). While the bleaching agent at 0.05% caused cell death, the cells appeared viable and morphologically normal when treated with the bleaching agent and LP (> or = 0.1 microM), saliva LP, and catalase from agent inhibition of proliferation (P < or = 0.04) and FN production (P < or = 0.01). Mucin had statistically insignificant or no protective effect as assessed by the above parameters. Treatment with saliva, LP, mucin, and catalase gave complete or partial protection from agent-inhibition of collagen production (P < or = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)