Probiotics and Oral Health Anna Haukiojaa,b ABSTRACT The number of products containing probiotics, viable bacteria with proven health benefits, enter- ing the market is increasing. Traditionally, probiotics have been associated with gut health, and most clinical interest has been focused on their use for prevention or treatment of gastrointestinal infec- tions and diseases; however, during the last decade several investigators have also suggested the use of probiotics for oral health purposes. The aim of this review is to examine potential mechanisms of probiotic bacteria in the oral cavity and summarize observed effects of probiotics with respect to oral health. The review focuses on probiotic lactobacilli and bifidobacteria, genera that are most used in various probiotic products. (Eur J Dent 2010;4:348-355) Key words: Probiotics; Oral health; Lactobacillus; Bifidobacterium. INTRODUCTION Probiotics can be defined as living microbes, or as food ingredients containing living microbes, that beneficially influence the health of the host when used in adequate numbers.1 Both definitions have in common the idea that probiotic microor- ganisms are living. Furthermore, the efficacy and safety of probiotics should be scientifically proven. Probiotic effects are strain specific; thus each in- dividual bacterial strain must be tested separately for the health benefit in question, and the effects described for one strain cannot be directly applied to others.2 Traditionally, probiotics have been associated with gut health, and most clinical interest has fo- a Institute of Dentistry, University of Turku, Turku, Finland. b National Institute for Health and Welfare (THL), FI-00300 Helsinki, Finland. Corresponding author: Anna Haukioja (PhD) Institute of Dentistry, Lemminkäisenkatu2, Turku, 20520, Finland Tel: + 358 44 011 0234 Fax: + 358 2 333 8356 E-mail: anna.haukioja@utu.fi cused on the prevention or treatment of gastroin- testinal infections and diseases; however, during the last decade, an increasing number of estab- lished and proposed health effects of probiotic bacteria have been reported, including enhance- ment of the adaptive immune response, treatment or prevention of urogenital and respiratory tract infections, and prevention or alleviation of aller- gies and atopic diseases in infants.2,3 Several in- vestigators have also suggested probiotics for oral health purposes. Interestingly, probiotics are also suggested to increase the lifetime of voice pros- thesis by inhibiting the adhesion of unwanted mi- crobes.4-6 The most commonly used probiotic bacterial strains belong to the genera Lactobacillus and Bifi - dobacterium.3 These bacterial genera are regarded as a part of the normal human microbiota. In the oral cavity, lactobacilli usually comprise fewer than 1% of the total cultivable microbiota, but no species specific to the oral cavity has been found. In contrast, some species are found in both oral and fecal samples.7,8 Species commonly isolated 348 European Journal of Dentistry