H2S generation and Eh reduction in cysteine challenge testing as a means of determining the potential of test products and treatments for inhibiting oral malodor

Bacterial degradation of the sulfur-containing amino acid, cysteine, involves two biochemical processes that contribute significantly to oral malodor generation. The first is production of hydrogen sulfide, a major component and common indicator of oral malodor formation. The second is generation of the sulfhydryl anion, HS-, an anion that is central to the lowering of the oxidation-reduction potential (E-h). A reduced E-h is fundamental to the growth and metabolism of the oral Gram negative anaerobic bacteria. These microorganisms are responsible for oral putrefaction, a process primary to both oral malodor generation and gingivitis-periodontitis development. One purpose of this paper is to report on the testing of a number of anti-malodor treatments and products for their effects on H2S formation and Eh reduction, two processes that occur rapidly and do so simultaneously after the oral bacteria are challenged with cysteine. A second is to report on aspects of cysteine challenge testing in the development of an anti-malodor product composed of ZnCl2 and sodium chlorite that simultaneously inhibits both H2S formation and E-h reduction and effectively inhibits oral malodor.