Dr. James Belcher, December 19, 2025

Good bacteria, bad bacteria – why every mouth needs microbes

Millions of bacteria live in your mouth – and that's not necessarily a bad thing. Some of them are true "bodyguards" for your oral health, while others can promote inflammation and even disease. Here you'll learn why you absolutely need these beneficial inhabitants and how they protect you – plus tips on how you can support them.

Gute Bakterien, schlechte Bakterien – warum jeder Mund Mitbewohner braucht

What's behind it?

Hundreds to thousands of microorganisms —bacteria, fungi, and viruses—live in every mouth, forming the oral microbiome . Some of these microbes are beneficial and protect your oral cavity, while others can become harmful if the balance is disrupted. A healthy balance keeps harmful bacteria in check and supports oral health (Rajasekaran et al., 2018) .

Why is it relevant?

An imbalance in the oral microbiome ( dysbiosis ) can trigger inflammation —and such inflammation is the starting point for caries, gingivitis, or periodontitis . At the same time, a healthy oral microbiome also influences your overall health . Studies show that a stable oral flora can help reduce inflammation and health risks throughout the body (Baker et al., 2025).


Infobox
Your mouth houses a multiple of Bacteria, as long as there have been humans on Earth – and that in over 700 different n species (Krishnan et al., 2017)!

Scientific background

The mouth and body are closely connected—the oral microbiome acts like a protective community : beneficial bacteria displace harmful ones, regulate the immune system, and build protective barriers (Rajasekaran et al., 2024) . However, if this balance is disrupted—for example, by sugar, smoking, poor oral hygiene, or harsh mouthwashes—pathogenic bacteria can proliferate (Hallang et al., 2021). This dysbiosis promotes inflammation, mucosal irritation, and gum disease . Modern approaches aim to block only the pathogenic mechanisms of certain bacteria, rather than killing all bacteria (as with classic antiseptics and harsh mouthwashes), thus preserving and stabilizing the "good" microbiome (Taudte et al., 2025).

Practical tips for everyday life

  • ✓ Brush your teeth twice a day and don't forget the spaces between your teeth (Worthington et al., 2019).  
  • ✓ Avoid aggressive mouthwashes or disinfectants that kill all bacteria — they threaten the balance of your microbiome and opt for microbiome -friendly toothpastes and care products (Koromantzos et al., 2025). 
  • ✓ Pay attention to a balanced diet , reduce sugar and acidic foods — this helps the microbiome to remain stable (Sabine Elisabeth et al., 2025).
  • ✓ Have your teeth and gums checked regularly to detect and treat inflammation or dysbiosis early (Salvi et al., 2023). 

At a glance

ⓘ Your mouth is home to a complex microbiome made up of many microorganisms. 

ⓘ Good microbes protect – bad ones can cause disease.  

ⓘ Microbiome-friendly care and conscious habits maintain oral health and support overall health. 

Sources

  • Azzolino D, Felicetti A, Santacroce L, et al. The Emerging Role of Oral Microbiota: A Key Driver of Oral and Systemic Health. American Journal of Dentistry . 2025.

  • Baker JL, Mark Welch JL, Kauffman KM, McLean JS, He X. The Oral Microbiome: Diversity, Biogeography and Human Health. Nature Reviews Microbiology . 2024.

  • Hallang S, Esberg A, Haworth S, Johansson I. Healthy oral lifestyle behaviors are associated with favorable composition and function of the oral microbiota. Microorganisms . 2021.

  • Koromantzos PA, Bobetsis YA, Giota C, et al. Effect of Adjunctive Use of Commercial Daily Mouthwashes on Periodontal Health: An Umbrella Review. Journal of Clinical Periodontology . 2025. doi:10.1111/jcpe.70061.

  • Marsh PD. In Sickness and in Health – What Does the Oral Microbiome Mean to Us? An Ecological Perspective. Advances in Dental Research . 2018.

  • Rajasekaran JJ, Krishnamurthy HK, Bosco J, et al. Oral Microbiome: A Review of Its Impact on Oral and Systemic Health. Microorganisms . 2024.

  • Salvi GE, Roccuzzo A, Imber JC, et al. Clinical Periodontal Diagnosis. Periodontology 2000 . 2023. doi:10.1111/prd.12487.

  • Sabine Elisabeth G, Yuxi Z, Jiawen Y, et al. Systemic, lifestyle and environmental modifying factors in the pathogenesis of periodontitis. Journal of Periodontal Research . 2025.

  • Tartaglia GM, Kumar S, Fornari CD, Corti E, Connelly ST. Mouthwashes in the 21 Century: A Narrative Review About Active Molecules and Effectiveness on the Periodontal Outcomes. Expert Opinion on Drug Delivery . 2017;14(8):973–982.

  • Taudte N, et al. Effect of a Bacterial Glutaminyl Cyclase Inhibitor on Multi-Species Biofilms. Frontiers in Oral Health . 2025;6:1716625. doi:10.3389/froh.2025.1716625.

  • Worthington HV, MacDonald L, Poklepovic Pericic T, et al. Home Use of Interdental Cleaning Devices, in Addition to Toothbrushing, for Preventing and Controlling Periodontal Diseases and Dental Caries. The Cochrane Database of Systematic Reviews . 2019;4:CD012018. doi:10.1002/14651858.CD012018.pub2.

  • Krishnan K, Chen T, Paster BJ. A Practical Guide to the Oral Microbiome and Its Relation to Health and Disease. Oral Diseases . 2017. 

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