The oral anti-volatile sulphur compound effects of zinc salts and their stability constants

Volatile sulphur compounds (VSC) produced in the oral cavity, are a major cause of oral malodour. Zinc (Zn) ions inhibit VSC formation. The objective of this study was to examine whether Zn salts with low stability constants were more suitable as sources of Zn in lozenges than salts with high stability constants, The former provide free Zn ions upon dissolution in water, whereas the latter provide almost no free Zn. Identical lozenges containing Zn-acetate and -gluconate, which have low stability constants, and Zn citrate and amino acid-chelated Zn, which have extremely high stability constants, were tested. All the lozenges contained 0.9% w/w Zn. Ten volunteers sucked the lozenges until dissolved, and oral VSC were measured by gas chromatography. Zn-acetate, -gluconate and -chelate had an impressive anti-VSC effect even 3 h after the lozenges were taken. Zn citrate had significantly less effect than the other lozenges except Zn acetate after 2 and 3 h. It was concluded that the anti-VSC effect was not related to the stability constants of the Zn compounds tested. Alternative ligands, with stronger affinity for Zn than the ligands in the lozenges, must be present in the oral cavity to explain these results. It is suggested that the sulphide ion may serve this function.