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Health condition · Clinically reviewed

Cavities, what actually causes decay, and what actually prevents it.

Tooth decay is common, largely preventable and, caught early, often reversible. The right routine and the right dentist are worth more than any mouthwash on the shelf.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE, Delivering Better Oral Health (DBOH) and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK guidance including fluoride varnish, resin infiltration, silver diamine fluoride and the amalgam phase-out.

Key facts

Cavities at a glance.

The essentials in plain English - what a cavity actually is, where they form and what makes the biggest difference to keeping them at bay.

  • What it is

    Progressive destruction of tooth structure by acid from a cariogenic bacterial biofilm fermenting dietary sugars.

  • The bacteria

    Streptococcus mutans and S. sobrinus drive early lesions; Lactobacillus species dominate deeper cavities.

  • Where it happens

    Pits and fissures on chewing surfaces, between teeth, at the gumline, on exposed roots and around old fillings.

  • How common

    One of the most common preventable diseases worldwide, affecting most adults and around a quarter of UK five-year-olds.

  • Reversibility

    Early enamel demineralisation (white spot) is reversible with fluoride, diet change and better plaque control.

  • Foundation therapy

    Twice-daily brushing with fluoride toothpaste plus reduced sugar frequency remains the strongest evidence-based measure.

Why this guide matters

A prevention plan, not a lifetime of fillings.

Cavities are one of the most preventable diseases we treat. The three ideas below shape everything else on this page.

  • Fluoride is the foundation

    Twice-daily brushing with fluoride toothpaste plus professional varnish is the single best-evidenced protection for teeth of every age.

  • Sugar frequency drives risk

    How often you have sugar and acidic drinks matters more than the total amount - water between meals is a genuine dental intervention.

  • Early lesions are reversible

    White-spot enamel lesions can be arrested or reversed. That’s why regular dental checks catch problems worth catching.

How the diagnosis is made

From first check to a clear plan.

What a UK dentist will normally do in order, so you know what to expect and why the recall interval matters as much as the exam itself.

  1. 01

    Assessing

    Dental history and risk

    Diet frequency, medications, dry mouth, previous fillings and past caries experience shape the exam plan.

  2. 02

    Assessing

    Visual and tactile exam

    A dentist inspects each surface with a mirror, probe and drying, looking for white spots, brown stain and cavitation.

  3. 03

    Assessing

    ICDAS caries scoring

    The International Caries Detection and Assessment System grades lesions from early enamel change to deep dentine involvement.

  4. 04

    Confirming

    Bitewing radiographs

    Bitewings pick up interproximal (between-teeth) caries that the eye cannot see; frequency is set by risk.

  5. 05

    Confirming

    Adjuncts when needed

    Transillumination, DIAGNOdent laser fluorescence, panoramic or CBCT imaging in selected cases.

  6. 06

    Planning

    Saliva and systemic review

    For dry mouth or high risk, saliva flow, buffering and screening for diabetes or immunosuppression may follow.

  7. 07

    Planning

    Personalised prevention plan

    Findings feed a Cariogram or DBOH-based plan: fluoride strength, recall interval, sealants and diet coaching.

Typical timeline: from an examination to a personalised prevention plan in a single visit.

Symptoms

What tooth decay actually feels like.

Early cavities are usually silent. Sensitivity, food packing or visible cavitation come later, and severe pain or swelling is a signal to act quickly.

  • White spot lesions

    The earliest visible sign - chalky patches on enamel that can remineralise with fluoride and better hygiene.

  • Brown discolouration

    Slow-progressing lesions often stain brown; colour alone does not decide whether a filling is needed.

  • Sensitivity

    Sharp, short-lived pain to cold, hot or sweet suggests dentine involvement rather than deep pulp disease.

  • Visible cavitation

    A hole in the tooth, catching floss or trapping food, means the surface has broken down and needs restoring.

  • Halitosis and food packing

    Persistent bad breath or food repeatedly getting stuck around one tooth is a classic clue to a hidden cavity.

  • Spontaneous, throbbing pain

    Unprovoked pain, worse lying down or waking you at night, points to irreversible pulpitis and often root canal territory.

  • Facial swelling and fever

    A swollen cheek, gum boil (fistula), fever or lymphadenopathy suggests a periapical abscess needing urgent care.

  • Red flag - airway or spreading infection

    Trismus, difficulty swallowing, tongue elevation or neck swelling can signal Ludwig’s angina - a 999 emergency.

Treatment

How cavities are treated in the UK.

Prevention and remineralisation first, minimally invasive restorations next, and root canal or extraction only when the tooth needs it.

  • Fluoride varnish

    22,600 ppm varnish applied twice a year from age three (four times a year for high-risk) to slow and reverse early lesions.

  • High-fluoride toothpaste

    Prescription 2,800 or 5,000 ppm pastes for adults and older teenagers at high caries risk, alongside standard brushing advice.

  • Fissure sealants

    Resin sealants over the deep grooves of permanent molars in children - a proven way to prevent occlusal caries.

  • Resin infiltration (ICON)

    A microinvasive resin that seals early interproximal or white-spot lesions without drilling, for suitable early caries.

  • Composite filling

    Tooth-coloured resin bonded into a prepared cavity - the everyday restoration for most small and medium lesions.

  • Inlay, onlay or crown

    Indirect lab-made restorations for larger cavities where a direct filling would be too weak, especially on molars.

  • Root canal treatment

    For irreversible pulpitis or a periapical abscess in a restorable tooth - removes infected pulp and seals the root system.

  • Silver diamine fluoride (SDF)

    Arrests active caries in young children, frail adults or where drilling is not feasible; the lesion turns dark but stops progressing.

What this guide is based on

The sources behind every claim on this page.

UK national guidance, WHO advice and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not dental advice.

Your dentist knows your teeth and history and can tell you which parts apply to you. If in doubt, get seen.

  • NICE. Dental checks: intervals between oral health reviews (CG19).

  • Office for Health Improvement and Disparities. Delivering Better Oral Health: an evidence-based toolkit for prevention (DBOH, 4th edition).

  • World Health Organization. Guideline: sugars intake for adults and children.

  • Faculty of General Dental Practice / College of General Dentistry. Selection Criteria for Dental Radiography.

  • Minamata Convention on Mercury and MHRA guidance on the UK dental amalgam phase-out (2025).

Red flags

When tooth decay needs urgent attention.

Most cavities can wait for a routine appointment. These situations cannot - and one of them is a genuine airway emergency.

  • Facial swelling with fever

    A hot, tense swelling of the face or jaw with fever suggests a spreading dental infection - seek urgent dental or A&E care the same day.

  • Ludwig’s angina features

    Bilateral floor-of-mouth swelling, raised tongue, drooling or trouble breathing is a 999 airway emergency.

  • Severe unprovoked toothache

    Constant throbbing pain, worse when lying down or biting, usually means irreversible pulpitis and needs prompt dental review.

  • Gum boil or draining sinus

    A pimple-like swelling on the gum that discharges pus points to a chronic abscess and should not be ignored.

  • Trauma with tooth mobility

    A loose, displaced or knocked-out tooth after injury needs emergency dental care within hours to preserve the tooth.

  • Early childhood caries

    Brown or broken front teeth in toddlers (‘baby bottle’ caries) needs paediatric dental referral and family support.

  • Rapid new decay in an adult

    A sudden burst of new cavities in someone previously stable can signal dry mouth, diabetes, eating disorder or recreational drug use.

  • Radiotherapy to head and neck

    Post-radiotherapy xerostomia causes aggressive rampant caries - needs specialist restorative and preventive care.

  • Immunocompromised patients

    Dental infection in someone on chemotherapy, biologics or with poorly controlled diabetes deserves earlier and lower-threshold review.

Living with it

A preventable condition, with a clear routine.

Four small habits do most of the heavy lifting - fluoride brushing, sensible sugar timing, daily cleaning between teeth and keeping your dental recall.

A quiet reminder

Consistency beats intensity, every time.

Small, steady habits kept up for months do more for your teeth than any heroic week that doesn’t last.

  1. 01 Brush

    Twice-daily fluoride brushing

    Two minutes, last thing at night and one other time, with 1,350 to 1,500 ppm fluoride paste. Spit, don’t rinse.

  2. 02 Sugar

    Cut the frequency, not just the amount

    Free sugars kept to mealtimes only, with water between meals, do more for your teeth than any mouthwash.

  3. 03 Between

    Clean between your teeth daily

    Floss or interdental brushes reach the surfaces a toothbrush can’t - where a lot of adult decay starts.

  4. 04 Reviews

    Keep your recall interval

    Your dentist sets three to twenty-four monthly checks based on risk - the point is to catch lesions while they’re still reversible.

Frequently asked

Everything we get asked about cavities.

Quick answers on fluoride, sugar, root canals, amalgam and how often you should really see the dentist.

  • What actually causes a cavity?

    A sticky biofilm of bacteria - mainly Streptococcus mutans and Lactobacillus - ferments sugars from food and drink into acid. Repeated acid attacks dissolve minerals from enamel, and if this outpaces the natural repair from saliva and fluoride, the surface breaks down into a cavity.

  • Can early tooth decay be reversed?

    Yes. Early enamel demineralisation, seen as a white spot lesion, can remineralise with regular fluoride toothpaste, professional fluoride varnish, better plaque control and fewer sugar attacks. Once the surface has cavitated, though, a filling or other restoration is usually needed.

  • How often should I have a dental check?

    NICE recommends an interval set individually - as short as three months for high-risk patients and up to twenty-four months for low-risk adults. Children are usually seen at least yearly. The interval reflects your caries risk, gum health and medical history.

  • Is fluoride toothpaste really safe?

    Yes, at the strengths advised by UK guidance. Adults and children over seven use 1,350 to 1,500 ppm; younger children use smaller amounts of lower-strength paste supervised by an adult. High-fluoride prescription pastes (2,800 or 5,000 ppm) are reserved for adults and older teenagers at high risk.

  • What about amalgam fillings in 2026?

    The UK is phasing out dental amalgam in line with the Minamata Convention, and most new fillings are tooth-coloured composite. Existing sound amalgams do not routinely need replacing; your dentist will discuss options if one fails.

  • When do I need a root canal instead of a filling?

    If decay reaches the pulp and causes irreversible pulpitis - spontaneous throbbing pain, lingering pain to hot, or a periapical abscess - a filling is no longer enough. Root canal treatment removes the infected pulp and seals the root system so the tooth can be saved with a crown.

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