The oral anti-volatile sulphur compound effects of zinc salts and their stability constants Young AR, Jonski G and RoÈlla G. The oral anti-volatile sulphur compound effects of zinc salts and their stability constants. Eur J Oral Sci 2002; 110: 31±34. # Eur J Oral Sci 2002 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 signi®cantly 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 af®nity 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. Alix Young, Grazyna Jonski, Gunnar RoÈ lla Faculty of Dentistry, University of Oslo, Oslo, Norway Alix Young, Department of Cariology, Faculty of Dentistry, University of Oslo, PO Box 1109 Blindern, N-0317 Oslo, Norway Telefax: +47±22±852386 E-mail: alixr@odont.uio.no Key words: foetor ex ore; halitosis; zinc; sulphide ion Accepted for publication October 2001 Metal ions with high af®nity for sulphur are known to inhibit formation of volatile sulphur compounds VSC), which are the major cause of oral malodour 1). The relative effects of these metal ions are correlated with their af®nity for sulphur 2). Zinc Zn) is the metal ion of choice for this purpose due to its low toxicity and to its other favorable properties, such as not causing dental staining. It is thought that Zn operates by forming sulphides of low solubility with precursors of VSC i.e. HS x ,S 2x and CH 3 S x ), thus inhibiting further production of VSC, as long as Zn ions are available in the oral cavity. Zinc salts with low stability constants provide an abundance of free Zn ions when dissolved in water or saliva. As the anti-VSC effect of Zn appears to be dependent on the presence of Zn ions 2±5), it seems likely that Zn salts with low stability constants would be the preferable source of Zn in formulations designed to inhibit oral VSC formation. The hypothesis to be tested in the present study was that there is a negative correlation between the stability constant of a Zn salt and its effect as a VSC inhibitor. Another possibility which was considered is that the solu- bility product of a Zn salt could be of signi®cance in this respect, i.e. that Zn salts of high solubility are preferable as VSC inhibitors to those of low solubility. Zinc lozenges containing either Zn acetate, Zn gluc- onate, Zn citrate and an amino acid chelate of Zn Fig. 1) were obtained. This investigation is thus limited to the choice of Zn salts that are used in a dry state in lozenges. All the lozenges contained 0.9% by weight of Zn. Of the different Zn sources, Zn acetate and Zn gluconate provide free Zn ions log K 1 =1.0 and 1.5, respectively), whereas Zn citrate and the chelated Zn have log K 1 of 4.5 and 8.0, respectively information from Albion Laboratories, Clear®eld, UT) and provide scarcely any free Zn Fig. 2 6)). Material and methods Lozenges The lozenges, which were a gift from EFI, Oslo, Norway, had a weight of 0.6 g and each contained 6.8 mg of Zn 0.9% by weight) in the form of Zn acetate, Zn gluconate, Zn citrate or amino acid chelated Zn Albion, Clear®eld, UT). Amino acid-chelated Zn is bound to two amino acids Fig. 1), is known to be very stable, and is mainly used as a dietary supplement 7). The Zn chelate is absorbed from the gut as a chelate, a mechanism that facilitates uptake of Zn. The lozenges looked identical and had a peppermint Eur J Oral Sci 2002; 110: 31±34 Printed in UK. All rights reserved Copyright # Eur J Oral Sci 2002 European Journal of Oral Sciences ISSN 0909-8836