The oral flora is a complex, finely balanced ecosystem. It comprises millions of microorganisms that colonize the entire oral cavity – on the teeth, gums, tongue, palate, and in saliva. Just as in the gut, this microbial community also fulfills essential functions in the mouth: It protects against pathogens, supports digestion, regulates inflammation, and contributes to tooth remineralization. But what happens when the balance is disturbed? Which bacteria are "good" and which are problematic? And how can the oral microbiome be specifically supported with probiotics?
What is oral flora and why is it important?
The oral flora, also known as the oral microbiome, consists of over 700 known bacterial species—of which approximately 200–300 are active in every person. These bacteria live in a delicate balance. When healthy, they prevent pathogens from spreading. They regulate the pH level, prevent excessive plaque growth, and support the immune system of the oral mucosa. An intact oral flora therefore provides a natural protective shield against tooth decay, periodontitis, gingivitis, and bad breath.
Composition of a healthy oral flora
A healthy oral flora is characterized by a wide variety of commensal—beneficial—bacteria. These include, in particular:
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Streptococcus salivarius : One of the first germs to colonize the mouth after birth. It produces antibacterial substances (bacteriocins) and has anti-inflammatory effects.
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Streptococcus mitis & S. oralis : Support the oral mucosa and prevent the colonization of pathogenic germs.
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Actinomyces naeslundii : Helps with plaque formation, but in a controlled way that promotes health.
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Veillonella spp. : Breaks down lactic acids produced when sugar is consumed, thereby protecting tooth enamel.
These bacteria work synergistically, promoting a neutral pH and modulating local immune responses. Their presence is a marker of a stable, healthy oral environment.
What disturbs the balance of the oral flora?
Several factors can negatively influence the composition of the oral flora. These include poor oral hygiene, an unbalanced diet (especially high-sugar diets), tobacco use, certain medications (e.g., antibiotics or antidepressants), systemic diseases, and hormonal changes. Stress also plays a significant role, as it weakens the immune system and alters the bacterial composition.
When the number of "good" bacteria decreases, pathogenic germs gain the upper hand. Dysbiosis occurs—an imbalance in the microbiome that promotes the development of various oral diseases.
Typical bacteria in a disturbed oral flora
In a dysbiotic oral flora, the following pathogenic bacteria usually predominate:
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Porphyromonas gingivalis : Main cause of periodontitis, has the ability to manipulate the immune system.
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Fusobacterium nucleatum : Mediates inflammatory processes, promotes biofilm formation and can have systemic effects.
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Prevotella intermedia : Frequently detected in acute gingivitis and periodontitis.
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Tannerella forsythia : Associated with deep periodontal pockets and tissue breakdown.
These germs are strictly anaerobic, meaning they thrive in oxygen-poor environments—such as those found in deep gum pockets or on uncleaned tongue coating. Their metabolic products often contain sulfur, which leads to unpleasant bad breath.
Which bacteria cause bad breath?
Bad breath (halitosis) occurs when bacteria decompose proteins, releasing volatile sulfur compounds (VSCs)—particularly hydrogen sulfide, methyl mercaptan, and dimethyl sulfide. The main causes are:
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Solobacterium moorei : Mainly located on the tongue, produces strong-smelling gases.
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Fusobacterium nucleatum : In addition to inflammation, it is also responsible for bad breath.
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Treponema denticola : Component of the so-called "red complex" in periodontitis.
These bacteria are particularly found in people with inadequate tongue hygiene and chronic periodontal disease. They are closely linked to inflammation and biofilm formation and are difficult to control through normal dental care.
How can probiotics improve oral flora?
Probiotics are live microorganisms that, when administered in sufficient quantities, exert health benefits. In the oral cavity, they compete with harmful germs for space and nutrients, produce antimicrobial substances, and modulate the immune system. The following probiotic strains have been particularly studied:
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Streptococcus salivarius K12 : Produces bacteriocins against S. pyogenes and other pathogenic bacteria. It has been proven to reduce bad breath and improve bacterial balance.
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Streptococcus salivarius M18 : Effective against caries-causing germs, promotes healthy tooth surfaces and helps against bad breath.
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Lactobacillus reuteri : Reduces plaque formation and inflammatory markers in gingivitis.
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Lactobacillus paracasei : Supports the reduction of S. mutans and other cariogenic bacteria.
Such probiotics can be taken via lozenges, mouth sprays, or toothpaste. Daily use over several weeks is important, as the bacteria need time to establish a permanent home. Studies show that initial effects are often noticeable after just 14 days.
Scientific studies on probiotics in oral health
Several controlled studies confirm the effectiveness of probiotic therapeutic approaches. For example, administration of S. salivarius K12 and S. salivarius M18 significantly reduced the concentration of volatile sulfur compounds in the breath. Other studies showed that patients with chronic gingivitis treated with S. salivarius M18 exhibited a significantly reduced bleeding tendency. Positive effects have also been described in the prevention of caries and the remineralization of tooth enamel.
However, probiotics do not replace thorough oral hygiene, but should be understood as a complementary measure – ideally embedded in a holistic oral health concept.
How to support your oral flora in everyday life
A balanced diet with high-fiber foods, a low-sugar lifestyle, regular dental cleaning, including cleaning the tongue and interdental spaces, and sufficient fluids form the basis for a stable oral flora. The sparing use of antibacterial mouthwashes is also recommended, as these can otherwise also eliminate beneficial bacteria.
Probiotics can be used specifically, for example, after antibiotic therapy, for recurring bad breath, or as an adjunct to periodontal therapy. It's important to choose high-quality products with documented bacterial counts and scientifically tested strains.
Conclusion: Oral flora – underestimated, but essential
The oral flora is far more than a collection of bacteria. It is a finely tuned ecosystem that forms the basis for a healthy mouth, fresh breath, and a strong immune system. Understanding and caring for your oral flora lays the foundation for long-term health. In this context, probiotics open up new possibilities for maintaining or specifically restoring bacterial balance – scientifically sound, gentle, and effective. A conscious approach to diet, hygiene, and lifestyle is the best partner for a healthy mouth – every day.
