Bad breath (oral malodor, lat. halitosis) is amongst most common patients' complaints in the dental office. Ironically, available literature and research done on this topic thus far are relatively scarce. Oral malodor is most commonly caused by oral bacteria (87%), yet it can also be sourced from ear, nose and throat region and in a small percentage from distant parts of the body or is of unknown origin. Periodontal pathogens and other Gram(-) anaerobic microorganisms such as Porphyromonas gingivalis, Treponema denticola, Prevotella intermedia, Fusobacterium nucleatum, Enterobacter cloacae, Prevotella loescheii and Porphyromonas endodontalis are regarded as producers of malodorous gases. Namely, these bacterial species and periodontal pathogens particularly produce so called volatile sulfur compounds (VSC) which give mouth air its malodorness. Methylmercaptan, hydrogen sulfide and dimethyl sulfide are waste products of bacterial metabolism, specifically degradation of sulfur-, methionine- and cysteine-containing aminoacids. Offensive smells also stem from other compounds which do not contain sulfur, diamines and polyamines such as cadaverine, putrescine and skatole.

Probiotics are defined as living microorganisms which are considered to have beneficial health effect on their host when consumed in adequate amount. Regarding their advantageous role in periodontal disease, inhibition of specific periodontal pathogens and alteration of host immune response through multifactorial causes are thought to be their main working mechanisms. Reuterin and reutericyclin are two bacteriocins produced by Lactobacillus reuteri that inhibit growth of pathogenic bacteria, while bacterium also exhibits strong capacity of host tissue adherence and subsequent competition with pathogens.

Based on this data, research on efficacy of probiotic lozenges on halitosis in patients with chronic periodontitis.