The biology in one minute
The human mouth carries an oral microbiome that includes several hundred bacterial species (the most-cited figure from the Human Oral Microbiome Project is around 700 distinct taxa).2 Most are harmless commensals — they live on the tongue, in saliva, and in the spaces around the teeth without doing harm. Under the right conditions (warmth, moisture, food residue, lack of mechanical disturbance), some species organise themselves into a structured community called a biofilm. The plaque you can scrape from teeth is one such biofilm.
Plaque begins to form on a clean tooth surface within hours. Brushed away daily, it never matures. Left undisturbed, it changes character: anaerobic species — bacteria that thrive in oxygen-poor environments — become dominant. Plaque can begin to mineralise into calculus (tartar) within a few days. Once calculus has formed, brushing cannot remove it; instrumentation by a dental professional is required.
Calculus that has formed below the gum line is the problem. The body recognises the bacteria as a chronic threat and mounts an immune response. The response itself — the release of inflammatory cytokines, the recruitment of white blood cells — begins to destroy the body's own tissue around the tooth. Over years to decades, the destruction of bone, ligament, and gum produces what we call periodontitis.
This sequence — plaque forms, biofilm matures, calculus accumulates below the gum, immune response damages supporting tissue — is the chain of events behind every case of gum disease.
What causes it
Plaque bacteria are the necessary cause. But you can find patients with poor oral hygiene who never develop periodontitis, and patients with excellent oral hygiene who do. The difference is host susceptibility — how strongly your immune system responds to the bacterial challenge.
Susceptibility is influenced by:
- Genetics. Family history of tooth loss to gum disease is one of the strongest predictors.
- Smoking. Smoking is one of the strongest established risk factors: in Tomar and Asma's analysis of US national data, current smokers were approximately four times more likely than non-smokers to have periodontitis, and roughly half of cases were attributable to current or former smoking.3 Smokers also respond less well to periodontal treatment.
- Diabetes. Uncontrolled diabetes worsens periodontitis, and periodontitis worsens glycaemic control. The relationship runs both ways.
- Stress and immune suppression. Chronic stress, immunosuppressive medication, HIV, or any condition that impairs immune function increases risk.
- Hormonal changes. Pregnancy, menopause, and oral contraceptives can amplify gingival inflammation.
- Local factors. Crooked teeth, overhanging restorations, ill-fitting crowns, and mouth-breathing all increase the difficulty of cleaning specific sites and concentrate disease there.
The take-away: gum disease is not just "you didn't brush well enough." It is a disease of bacterial challenge meeting individual susceptibility. The treatment plan has to address both.
How it differs from cavities (caries)
Cavities and gum disease are caused by different bacterial communities and damage different structures:
| Cavities | Gum disease | |
|---|---|---|
| What it attacks | The crown of the tooth (enamel and dentine) | The supporting tissues around the tooth (gum, ligament, bone) |
| Main culprit bacteria | Streptococcus mutans, Lactobacillus | Periodontal pathogens (P. gingivalis, T. forsythia, T. denticola) |
| Symptoms | Visible holes, pain on hot/cold/sweet | Bleeding, recession, loose teeth |
| Treatment | Filling, root canal, crown | Specialist deep cleaning, sometimes surgery |
| Reversibility | Damage requires restoration | Early stage reversible; advanced is manageable not reversible |
A patient can have both. They are usually addressed by different practitioners working in coordination.
What untreated gum disease leads to
Untreated periodontitis tends to follow a slow, broadly predictable course. The rate of progression and exact pattern vary significantly between patients, but the sequence below is typical of moderate to severe untreated cases:
- Gums bleed when brushed, sometimes progressing to spontaneous bleeding.
- Bad breath develops as anaerobic bacteria thrive in deeper pockets.
- Recession begins — the gum margin moves down the root, making teeth look longer.
- Gaps open between teeth as the supporting fibres dissolve and teeth drift.
- Mobility — teeth begin to feel loose during chewing.
- Pain on biting, particularly on harder foods.
- Tooth loss.
The disease typically progresses over years to decades rather than months — but the rate is highly individual, and a small proportion of patients have an aggressive form that progresses much faster. Earlier intervention generally results in simpler treatment and better long-term outcomes; the earliest stage (gingivitis) is fully reversible.
The endpoint matters at a population level: worldwide, periodontitis and dental caries are the two leading causes of tooth loss in adults (Frencken et al., 2017).4 South African population data is fragmented, so we do not publish a SA-specific figure here; the international picture is well established.
What to do if you suspect you have it
If your gums bleed when you brush, the gum line has receded, or your dentist has used the word "periodontitis" in a check-up, ask for a referral to a periodontist or book a consultation directly. A specialist consultation (current fee R 1,400 at our practice — see How much does a consultation cost?) provides a diagnosis with stage and grade, and a treatment plan you can act on.
This article is general educational content. It cannot diagnose your specific condition. If you are concerned about your gums, please arrange an examination with a registered dentist or specialist periodontist.