Inhibitory Effects of Zinc Chloride and Citric Acid on Release of Volatile Sulfur Compounds

Abstract

Research into halitosis (commonly referred to as “bad breath”) has been increased recent years. Public awareness of halitosis has also increased, as a result of improved attention to hygiene, and the number of dental patients being treated for halitosis is increasing globally. Halitosis is known to be caused by volatile sulfur compounds (VSCs), formed by decomposition of sulfur-containing amino acids, and these can lead to infection of periodontal tissue. Previous studies have shown that zinc chloride and citric acid effectively suppress VSC release. In this study, we compared the VSC-inhibiting effects of zinc chloride alone, and of a zinc chloride/citric acid combination, in artificial saliva and in distilled water, each containing hydrogen sulfide. Our results showed that the inhibition of VSC release from distilled water achieved using citric acid/zinc chloride (18%) was less than that obtained using zinc chloride alone (27%). However, 100% inhibition was achieved in artificial saliva using the combined solutions, compared with 18% using zinc chloride alone. We believe that at the pH of the artificial saliva, some hydrogen sulfide is present as bisulfide ions, which readily react with zinc ions. Also, zinc ions form a chelate with citric acid, preventing formation of insoluble, unreactive zinc hydroxide. Our results suggest that a zinc chloride/citric acid combination would be an effective treatment for halitosis.