Glossary · Dysbiosis and disease
Periodontitis
In one sentence
Periodontitis is a chronic inflammatory disease of the tissues that support the teeth, associated with a dysbiotic bacterial biofilm. It causes loss of attachment and bone and, if uncontrolled, can lead to tooth loss.
Also known as: periodontal disease · gum disease · chronic periodontitis
What is periodontitis?
It is an inflammatory disease of the periodontium: the gums, periodontal ligament, cementum and alveolar bone. It starts with plaque building up along the gum line. In susceptible people, the host’s inflammatory response and a bacterial community in dysbiosis feed each other and break down the supporting tissues. Pockets form, teeth may loosen and, without control, be lost.
Smoking, poorly controlled diabetes, genetic susceptibility and oral hygiene all play a part.
How it is classified
The current classification comes from the 2017 World Workshop, published in 2018 (Papapanou and colleagues, Journal of Periodontology). It merged the former “chronic” and “aggressive” forms into a single category, periodontitis, described along two axes:
- Stage (I–IV): severity at presentation and the complexity of management.
- Grade (A–C): rate of progression and risk of a poor treatment response, taking into account factors such as smoking and diabetes.
Diagnosis is clinical and radiographic: periodontal probing (pocket depth, attachment loss, bleeding) plus X-rays. It is not made from a microbiological test.
The role of the microbiota
Socransky and colleagues (Journal of Clinical Periodontology, 1998) grouped subgingival plaque bacteria into “complexes”. The red complex, Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola, was strongly associated with pocket depth and bleeding on probing. Later work, notably the polymicrobial synergy and dysbiosis model of Hajishengallis and Lamont, frames the disease as driven by the community as a whole rather than one pathogen. In this model, low-abundance species such as P. gingivalis can act as “keystone pathogens” that tip the community out of balance. Much of that evidence comes from animal models.
Example
A periodontist is treating a patient with stage III, grade C periodontitis who has not responded as expected to root surface debridement. To inform follow-up, she requests an oral microbiota analysis. The report shows a high proportion of Porphyromonas and Fusobacterium. She weighs this against the probing chart and the patient’s risk factors. The result does not replace the clinical examination, but it adds information about the bacterial community.
Periodontitis at Xenogene
Xenogene’s oral microbiota test uses NGS to profile bacteria, archaea, fungi and viruses in the mouth from saliva or a buccal swab. According to the product sheet, it reports relative abundance, diversity indices, periodontal bacteria and resistance genes, and periodontal disease is among its listed indications. The sheet itself notes that the presence of pathogens does not always indicate active disease. The test is ordered by a professional, such as a dentist or periodontist, who interprets it together with the clinical examination.
Frequently asked questions
What is the difference between gingivitis and periodontitis?
Gingivitis is inflammation of the gums without loss of the supporting tissues, and it is reversible with good oral hygiene. Periodontitis involves loss of attachment and bone around the tooth. Not every case of gingivitis progresses to periodontitis.
Can periodontitis be reversed?
Lost bone and attachment do not usually grow back fully, but periodontal treatment and regular maintenance can control inflammation and halt progression in many cases. The plan is set by the dentist or periodontist.
Does gum disease affect the rest of the body?
It has been associated with diabetes, cardiovascular disease and pregnancy complications, among others. With diabetes the relationship appears to run both ways. For most of these links, association has been shown but causation has not.
Related terms
- Dysbiosis
Dysbiosis is a change in the composition or function of the microbiota away from what is considered compatible with health: loss of diversity, loss of beneficial microbes or overgrowth of others.
- Microbiota
The microbiota is the community of living microorganisms (bacteria, archaea, fungi, protozoa) that inhabits a specific site of the body, such as the gut, mouth, skin or vagina.
- Low-grade inflammation
Low-grade inflammation is a mild, persistent, systemic inflammatory activation with no acute infection or injury to explain it. It is detected through modest rises in markers such as high-sensitivity CRP.
- Candidiasis
Candidiasis is an infection caused by Candida yeasts, most often Candida albicans. It commonly affects the vulva and vagina or the mouth, and occurs when the yeast overgrows beyond normal colonisation.
Educational content for healthcare professionals and the general public. It does not replace assessment by a healthcare professional: ordering and interpreting any test is the responsibility of the requesting clinician.
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