Probiotics – A new approach to oral health

What are probiotics?

Probiotics are usually defined as microbial food supplements with beneficial effects on the consumers. The gut flora can be broadly divided into three main groups: Bifidobacteria (probiotic beneficial ‘good’ bacteria), bacteroides species (pathogenic micro organisms) and prebiotics (non digestible food ingredients that encourage the growth of bifidobacteria). Most probiotics fall into the group of organisms known as lactic acid producing bacteria and are normally consumed in the form of yoghurt and other fermented foods.

The most commonly used species of lactic acid bacteria in probiotic preparations include Lactobacillus, Bifidobacterium, Enterococcus and Streptococcus species.

How do they work?

The Lactobacillus genus has over 125 species and is a major part of the lactic acid bacteria group, named as such because most of the strains convert lactose into lactic acid. Their primary mode of action involves lowering gut pH thereby limiting the proliferation of pathogenic bacteria, competing for pathogen binding and receptor sites, and modulation of the local and systemic inflammatory immune response.

The GI tract serves as an interface between the gut and immune system, with the intestinal lining functioning as a barrier, decreasing the passage of bacteria from the gut into the bloodstream. The background thinking is that harmless microorganisms, such as species of lactobacilli, can preferentially occupy a space or a biofilm that would otherwise be colonised by a pathogen.

What are the oral health benefits?

Due to their mechanisms of bacterial adhesion, competitive colonization of bioflim, and possible effects on immunomodulation, probiotic treatment of oral diseases such as dental caries and periodontal disease is under investigation.

Lacobacillus reuteri

L. reuteri is now well established as one of the most ubiquitous members of the lactic acid producing bacteria. In the late 1980s Dobrogosz and Casas et al, discovered that L. reuteri produced a novel broad-spectrum antibiotic substance via the organism’s fermentation of glycerol. They named this substance ‘reuterin’.

Reuterin, it was found, inhibits the growth of some harmful Gram-negative and Gram-positive bacteria, along with yeasts, fungi, and protozoa. Researchers found that L. reuteri can indeed secrete sufficient amounts of reuterin to cause the desired anti-microbial effects while keeping normal gut flora intact.

L. reuteri and caries

A number of recent studies have demonstrated the ability of L. reuteri to inhibit the growth of Streptococcus mutans through a variety of delivery systems.

Nikawa et al found that the consumption of yogurt containing L. reuteri resulted in a significant growth inhibition of Streptococcus mutans. Caglare et al investigated the effect of the probiotic bacterium L. reuteri on the levels of salivary mutans streptococci when ingested via straws and tablets. A significant reduction of the mutans streptococci levels was recorded via both systems. Recently, new research has evaluated the effect of probiotic chewing gums containing two strains of L. reuteri on the levels of salivary mutans streptococci. Daily chewing of the gum containing probiotic bacteria also reduced the levels of salivary mutans streptococci significantly.

Lozenges, powder, gelatine, straw, or tablets can also deliver Probiotics. It has been suggested that slowly melting tablets would allow a more thorough contact between the probiotic and oral environment.

L. reuteri and periodontal disease

More recently studies have shown the ability of L. reuteri to inhibit the proliferation of the main periodontal pathogens including AA and PG. Krasse et al have also been able to demonstrate the ability of L. reuteri to colonise the oral cavity within two weeks of exposure. In addition a reduction in both gingivitis and plaque levels was observed. In this study two strains of L reuteri were trialed, (L. reuteri ATCC 55730/ L. reuteri ATCC PTA 5289) both strains were shown to have successfully colonised the oral cavity. A 59% reduction in gingivitis levels was recorded and a 42% reduction in plaque levels after 4 weeks of treatment.

L. reuteri and immune function

New emerging evidence suggests that L. reuteri may also be able to modulate the immune system. Significant increases in B-lymphocytes, T cells and sIgA levels after exposure to L.reuteri have been demonstrated in a number of studies. Probiotics can enhance both specific and nonspecific immune responses. These effects are believed to be mediated through activating macrophages, increasing levels of cytokines, increasing natural killer cell activity and/or increasing levels of immunoglobulins. Moreover, probiotics might prevent infection because they compete with pathogenic bacteria for binding sites on epithelial cells. L.reuteri may also inhibit the growth of pathogenic bacteria by producing bacteriocins such as reuterin.

Oral colonisation

For a probiotic to be effective they should adhere to dental tissues as a part of the biofilm (or plaque) and compete with the growth of cariogenic bacteria or periodontal pathogens. The most effective colonization appears to be from L. reuteri with 95% colonization after 14 days. Close interaction with host tissues through adhesion is crucial when establishing residence in the gastrointestinal tract or cells of the mucosa. Not all probiotics have the same adhesion factors, L. reuteri, however, has been shown to have superior adhesion and ability to colonise the entire digestive tract (including the oral cavity) when compared to other lactobacilli.

L. reuteri prodentis

The multistrain probiotic L.reuteri prodentis (PerioBalance) has been developed as a combination of two complementary stains of L.reuteri, (L.reuteri ATCC 55730 and L. reuteri ATCC PTA 5289). In a number of studies both strains of L reuteri were trialed, with both strains successfully colonising the oral cavity. While a monostrain has to overcome barriers presented by the host and its endogenous microflora, multistrain probiotics have a greater divergency and the enhanced chance of survival than one strain alone.

The safety of consuming L reuteri on a daily basis has been well established through a number of studies on diverse populations, including adults, children, newborn infants, premature infants and immuno-compromised adults.


The oral administration of probiotic therapies therefore, may be beneficial in the treatment of oral disease. The primary effect appears to be both local (colonisation of plaque biofilm) and systemic (modulation of the immune system).

Unfortunately, the concentration of probiotics in food products varies tremendously and there are currently no national standards of identity for levels of bacteria required in yogurt or other fermented products.

Presented as L.reuteri prodentis, PerioBalance is able to provide a multistrain L.reuteri probiotic dose with a consistent potency of 200 million active microorganisms. Taken as a slowly melting lozenge once a day after brushing and flossing ensures consistent exposure to L.reuteri on a daily basis with little or no negative side effects.

Extra info

Properties of L. reuteri prodentis:

• Colonises whole digestive tract including the


• Competitive colonisation of plaque biofilm

• Superior adhesion factor to mucus membrane

• Produces anti bacterial agent reuterin

• Prevents pathogen binding

• Inhibits Streptococcus mutans

• Inhibits periodontal pathogens including AA

and PG

• Modulates inflammatory immune response

• Safe for all population groups

Author information

Juliette Reeves EDH, DipNMed, CMA is an expanded duties hygienist with over 20 years’ experience. She writes regularly for the dental press and is a founder member of the British Dental Society for Clinical Nutrition

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