Tooth Decay in Children: Causes, Signs, Treatment and Prevention

Tooth decay in children is common, but it is also largely preventable. It can affect baby teeth as well as adult teeth, and it can cause pain, infection, sleepless nights, difficulty eating, missed school and stressful emergency dental visits.

Many parents are surprised to learn that decay can start very early, sometimes soon after the first teeth appear. It may begin as faint white patches near the gumline before turning brown, black or cavitated. By the time a child complains of toothache, the decay may already be deep.

This guide explains what causes tooth decay in children, how to spot early signs, why baby teeth matter, what dentists can do, how NHS treatment works, and the daily habits that help prevent decay.

You may also find these related guides useful: Children’s Teeth: Complete UK Parent Guide, Tooth Decay Explained, Dental Emergencies: What Counts as Urgent?, Toothache: Causes, Relief and When to See a Dentist, Dental Abscess: Symptoms and Treatment and How to Choose a Dentist in the UK.

What is tooth decay?

Tooth decay, also called dental caries, is damage to the tooth caused by acid. The acid is produced when bacteria in plaque feed on sugars from food and drinks. Over time, this acid can weaken the enamel, create holes and allow infection to reach deeper parts of the tooth.

In children, decay can affect both baby teeth and adult teeth. It often develops in areas that are difficult to clean, such as the grooves of back teeth, between teeth, around the gumline, or on teeth that are frequently exposed to sugary drinks or snacks.

NHS guidance explains that sugar causes tooth decay and that the risk is not just about how much sugar a child has, but how often and how long teeth are in contact with sugar. The NHS baby teeth guidance explains this here.

Why baby teeth matter

Baby teeth are temporary, but they are very important. They help children bite, chew, speak, smile and develop normally. They also hold space for adult teeth.

Untreated decay in baby teeth can cause:

• Toothache.
• Difficulty eating.
• Sleep disruption.
• Bad breath or bad taste.
• Dental abscesses.
• Facial swelling.
• Early tooth loss.
• Dental anxiety after painful treatment.
• Problems with adult teeth if infection or early tooth loss affects development.

A baby tooth with decay is not “fine because it will fall out anyway”. Some baby molars are needed until around age 10 to 12, and losing them early can affect chewing and spacing.

What causes tooth decay in children?

Tooth decay usually develops when several factors come together: plaque bacteria, sugar exposure, time and vulnerable tooth surfaces.

Frequent sugary foods and drinks

The more often teeth are exposed to sugar, the more acid attacks happen. A child who sips sweet drinks or grazes on sweet snacks through the day may be at higher risk than a child who has something sweet occasionally with a meal.

Common sources include:

• Squash and fruit juice.
• Fizzy drinks.
• Flavoured milk drinks.
• Sweets and chocolate.
• Biscuits, cakes and pastries.
• Sweet cereals.
• Dried fruit bars and fruit snacks.
• Sweet yoghurts and puddings.
• Sports drinks and energy drinks in older children and teenagers.

Bottles at bedtime

Putting a child to bed with a bottle of milk, formula, juice or sweet drink can increase decay risk once teeth have come through. During sleep, saliva flow is lower, so sugars sit around the teeth for longer.

Water is the safest drink for teeth after brushing.

Not brushing effectively

Children need help brushing for longer than many parents expect. The NHS advises that parents and carers should brush children’s teeth when they are young, and that children aged 7 and over may still need watching to make sure they brush properly for about 2 minutes. NHS children’s teeth guidance explains brushing by age.

Common missed areas include:

• Back molars.
• The gumline.
• Inside surfaces of lower teeth.
• Teeth that are crowded or overlapping.
• New adult molars coming through at the back.
• Around braces or fixed retainers.

Not enough fluoride exposure

Fluoride helps strengthen enamel and reduce decay risk. NHS guidance recommends fluoride toothpaste for children, with a smear for children under 3 and a pea-sized amount for children aged 3 to 6. Government oral health guidance notes that fluoride toothpaste of 1,000ppm fluoride or above helps prevent dental caries in both baby and adult teeth. You can read the Delivering Better Oral Health fluoride guidance here.

Deep grooves in back teeth

Adult molars often have deep grooves and pits where food and plaque collect. These are common places for decay to start, especially around age 6 when the first adult molars come through behind the baby teeth.

Dry mouth or medical factors

Saliva helps protect teeth. A dry mouth can increase decay risk. Some medicines, mouth breathing, dehydration, snoring, certain medical conditions and some disabilities can make oral care harder or increase risk.

Braces and orthodontic appliances

Braces can trap plaque around brackets and wires. Clear aligners can also increase risk if children or teenagers drink sugary drinks while wearing them or do not clean their teeth before putting aligners back in.

Read more: Invisalign and Clear Aligners in the UK.

Early signs of tooth decay in children

Early tooth decay may not hurt. This is why regular dental check-ups are important.

Possible signs include:

• White chalky patches near the gumline.
• Yellow, brown or black marks.
• Rough or dull-looking enamel.
• Small holes or pits.
• Food getting stuck in one tooth.
• Sensitivity to cold or sweet foods.
• Pain when biting.
• Bad breath or bad taste.
• A child avoiding chewing on one side.
• Complaints of toothache, especially at night.

White chalky patches are important because they may be an early warning sign before a hole forms. At this stage, decay may sometimes be slowed or stopped with better brushing, fluoride and diet changes.

Signs tooth decay may be more serious

Decay can become urgent if it reaches the nerve or causes infection.

Seek dental advice promptly if your child has:

• Toothache that lasts more than a day or two.
• Pain that wakes them at night.
• Pain when eating or drinking.
• A hole in a tooth.
• A gum boil or pimple on the gum.
• Pus or bad taste.
• Swollen gum, cheek, jaw or face.
• Fever with dental pain or swelling.
• A child who cannot eat, sleep or concentrate because of pain.

Call 999 or go to emergency care if facial swelling affects breathing or swallowing, if the child is very unwell, or if there is serious facial trauma.

How dentists diagnose tooth decay in children

A dentist will examine your child’s teeth, gums and bite. They may use a small mirror, gentle air, light and sometimes X-rays if needed.

The dentist may check:

• Which teeth are affected.
• Whether decay is early or has formed a cavity.
• Whether decay is close to the nerve.
• Whether there are signs of infection.
• Whether adult teeth are developing normally.
• Whether diet, brushing or medical factors are increasing risk.
• Whether fluoride varnish or fissure sealants would help.

X-rays are not always needed, but they can help find decay between teeth or assess how deep a cavity is.

Can early tooth decay be reversed?

Very early decay, before a hole forms, may sometimes be stopped or partly repaired by minerals returning to the enamel. This is called remineralisation.

To support this, the dentist may recommend:

• Better brushing with fluoride toothpaste.
• Spitting, not rinsing, after brushing.
• Reducing how often the child has sugar.
• Fluoride varnish.
• Regular dental reviews.
• Fissure sealants for vulnerable adult molars.

Once a cavity has formed, the tooth usually needs dental treatment because brushing cannot rebuild the lost tooth structure.

Treatment for tooth decay in children

Treatment depends on the child’s age, the tooth involved, symptoms, cooperation, decay depth and whether the tooth is a baby tooth or adult tooth.

Fluoride varnish

Fluoride varnish is painted onto the teeth by a dental professional. It helps strengthen enamel and reduce decay risk. NHS Inform explains that fluoride varnish applied directly to teeth twice a year has been proven to reduce decay. NHS Inform explains fluoride varnish and fissure sealants here.

Fissure sealants

Fissure sealants are protective coatings placed in the grooves of back teeth, usually adult molars. They help prevent food and plaque from settling in deep grooves.

Sealants are preventive. They are not usually used to treat a deep cavity, but they can protect teeth at risk.

Fillings

If a cavity has formed, a filling may be needed. The dentist removes decayed tooth tissue and fills the space with a suitable material.

In children, the type of filling depends on the tooth, size of cavity, cooperation, moisture control and how long the tooth needs to last.

Stainless steel crowns for baby molars

Badly decayed baby molars may sometimes be treated with preformed metal crowns, often called stainless steel crowns. These protect the tooth and can be useful when a normal filling is less likely to last.

Some children may have these placed using the Hall Technique, where a crown is fitted over the tooth without drilling in selected cases. Your dentist can explain whether this is suitable.

Baby tooth nerve treatment

If decay has reached the nerve of a baby tooth but the tooth can still be saved, a dentist may consider a pulpotomy or other baby-tooth nerve treatment. This is not the same as adult root canal treatment, but it aims to keep the baby tooth comfortable and functional until it naturally falls out.

Extraction

If a tooth is too badly decayed, infected or painful to restore, extraction may be needed. Removing a baby tooth early is not ideal, but sometimes it is the safest option.

If a baby molar is removed early, the dentist may consider whether space maintenance is needed to help prevent neighbouring teeth drifting.

Referral for sedation or hospital care

Some children need referral if they are very young, very anxious, have complex medical needs, need several teeth treated, or require extractions that cannot be managed comfortably in a normal dental appointment.

Options may include local anaesthetic, inhalation sedation, community dental services or hospital care depending on the child and local services.

NHS treatment for tooth decay in children

NHS dental treatment is free for children under 18, and for young people under 19 if they are in full-time education. The NHS explains who can get free dental treatment here.

NHS children’s dental care may include:

• Check-ups.
• Prevention advice.
• Fluoride varnish if appropriate.
• Fissure sealants if appropriate.
• Fillings.
• Baby tooth crowns where suitable.
• Extractions.
• Urgent dental care.
• Referral to community or hospital services when needed.

Private treatment may be chosen by some families for appointment availability, specific materials, sedation options or specialist children’s dentistry, but clinically necessary NHS care should be available where NHS dental access exists.

Private costs for children’s tooth decay treatment

Private costs vary widely by clinic, region, tooth, treatment type and whether sedation or specialist paediatric dentistry is needed.

These are broad guide prices only. Ask for a written treatment plan and whether prevention, X-rays, reviews or sedation are included.

How to prevent tooth decay in children

Prevention is usually simpler, kinder and cheaper than treating tooth decay. The key is reducing sugar frequency, using fluoride correctly, brushing well and seeing a dentist regularly.

Brush twice daily with fluoride toothpaste

Brush in the morning and last thing at night. Night-time brushing is especially important because saliva flow reduces during sleep.

The NHS recommends brushing children’s teeth twice daily for about 2 minutes with fluoride toothpaste, including last thing at night and one other time. It also recommends spitting out after brushing and not rinsing, because rinsing washes away fluoride. See NHS children’s brushing advice.

Use the right amount of toothpaste

• Under 3 years: use a smear of fluoride toothpaste.
• Ages 3 to 6: use a pea-sized amount.
• Age 7 and over: use fluoride toothpaste, usually 1,350ppm to 1,500ppm fluoride unless advised otherwise.

Keep toothpaste out of reach so children do not eat or lick it from the tube.

Help children brush until at least age 7

Children may be able to hold a toothbrush before they can clean effectively. The NHS says children aged 7 and over should be able to brush their own teeth, but it is still a good idea to watch them to make sure they brush properly and for about 2 minutes.

For younger children, let them have a turn first if they want independence, then an adult should finish the brushing properly.

Keep sugar to mealtimes

It is not realistic for every child to avoid all sugar forever. A more practical rule is to reduce frequency. Keep sweet foods and drinks to mealtimes rather than grazing throughout the day.

Between meals, choose tooth-friendly options such as:

• Water.
• Plain milk.
• Cheese.
• Plain yoghurt.
• Vegetable sticks.
• Toast or breadsticks with low-sugar toppings.

Avoid sugary drinks as everyday drinks

Water and plain milk are the best everyday drinks for teeth. Juice, squash, fizzy drinks and sports drinks should not be regular sipping drinks.

Even “no added sugar” drinks may be acidic. Frequent acidic drinks can contribute to enamel erosion even when sugar is lower.

Be careful with dried fruit and fruit snacks

Whole fruit is a healthy food, but dried fruit and fruit snack bars can be sticky and high in sugar. The NHS notes that dried fruits such as raisins can bathe teeth with sugar if eaten frequently between meals.

If your child eats dried fruit, it is usually better with meals rather than as frequent snacks.

Do not put babies to bed with bottles

Avoid bottles of milk, formula, juice or sweet drinks in bed once teeth are present. If a drink is needed after brushing, water is safest for teeth.

Visit the dentist early

The NHS advises taking children to the dentist when their first milk teeth appear, or before they are 12 months old. Early visits help children get used to the dentist and allow problems to be identified early.

Fluoride varnish: what parents should know

Fluoride varnish is a sticky protective coating painted onto the teeth by a dental professional. It sets quickly and gradually releases fluoride to help protect enamel.

It is often recommended for children, especially if they are at increased risk of decay. Your dentist will advise how often it is needed.

After fluoride varnish, the dental team may advise your child to avoid eating or drinking for a short time and to avoid brushing until later, depending on the product and local advice.

Fissure sealants: what parents should know

Fissure sealants are thin protective coatings placed on the chewing surfaces of back teeth. They are usually used on adult molars, especially if the grooves are deep or the child is at higher risk of decay.

Sealants do not replace brushing. Children still need fluoride toothpaste and good diet habits.

Tooth decay in toddlers

Toddler tooth decay often affects the upper front teeth and back molars. It may be linked to frequent bottles, sweet drinks, snacks, difficulty brushing or delayed dental visits.

Warning signs include:

• White or brown marks near the gumline.
• Front teeth chipping or crumbling.
• Bad breath.
• Difficulty brushing because the child says it hurts.
• Swelling or gum boils.
• Poor sleep or unexplained irritability.

Toddlers need adult brushing. It is normal for some toddlers to resist, but brushing still needs to happen every day.

Tooth decay in school-age children

Around age 6, the first adult molars come through at the back of the mouth. These teeth are permanent and need protection from the start.

School-age decay often affects:

• Grooves of adult molars.
• Between back teeth.
• Teeth around old fillings.
• Teeth affected by frequent snacks or drinks.
• Areas missed during rushed brushing.

This is a good age to ask about fissure sealants, fluoride varnish and whether your child is brushing effectively.

Tooth decay in teenagers

Teenagers may be more independent, but they can still be high risk. Braces, irregular routines, energy drinks, vaping, sports drinks, snacking, late nights and less parental supervision can all contribute.

Common risks include:

• Energy drinks and fizzy drinks.
• Sugary coffees or bubble tea.
• Frequent snacks while studying or gaming.
• Poor cleaning around braces.
• Skipping night-time brushing.
• Not wearing retainers cleanly.
• Wisdom tooth food trapping in older teenagers.

Teenagers should be encouraged to take ownership of their dental health, but reminders and regular dental visits still matter.

Tooth decay with braces

Braces do not cause decay by themselves, but they make plaque harder to remove. If plaque sits around brackets, children can develop white marks, gum inflammation and cavities.

Children with braces should:

• Brush carefully around every bracket.
• Use interdental brushes if advised.
• Use fluoride mouthwash if recommended, usually at a different time from brushing.
• Avoid frequent sugary and fizzy drinks.
• Keep orthodontic appointments.
• Continue routine dental check-ups during orthodontic treatment.

What if your child is scared of dental treatment?

Dental anxiety is common, especially if a child has already had pain. Tell the dental team before the appointment. A good dentist will usually try to explain things in child-friendly language and build trust.

Helpful steps include:

• Book early in the day if your child gets tired or anxious later.
• Bring a comfort item.
• Avoid using frightening words at home.
• Do not promise “nothing will happen” if treatment may be needed.
• Ask about tell-show-do techniques.
• Ask whether staged visits, fluoride first or referral is appropriate.

If treatment is difficult, referral to a dentist with more experience in children, community dental services or sedation services may be considered.

Children with additional needs and tooth decay risk

Some children need extra dental support because brushing, diet or dental visits are more difficult. This may include children with autism, ADHD, learning disabilities, sensory differences, physical disabilities, medical conditions, reflux, dry mouth or medicines that contain sugar.

Practical support may include:

• Adapted toothbrush handles.
• Electric toothbrushes with small heads.
• Visual brushing charts.
• Short, familiarisation dental visits.
• Fluoride varnish at regular intervals.
• High-fluoride toothpaste if prescribed for older children at high risk.
• Community dental referral if routine care is not suitable.

What not to do if you suspect tooth decay

• Do not wait for pain before seeing a dentist.
• Do not assume baby tooth decay does not matter.
• Do not use adult whitening products on children’s teeth.
• Do not put aspirin directly on a painful tooth or gum.
• Do not give leftover antibiotics.
• Do not rely on mouthwash instead of brushing.
• Do not let temporary pain relief delay dental care if there is swelling or infection.

When is children’s tooth decay urgent?

Tooth decay becomes urgent when there are signs of pain, infection, swelling or trauma.

Contact a dentist urgently or use NHS 111 if your child has:

• Severe toothache.
• Toothache with fever.
• A swollen gum, cheek, jaw or face.
• Pus or a gum boil.
• Pain that stops eating or sleeping.
• A broken tooth with pain.
• A child who is very distressed or cannot open their mouth properly.

Call 999 or go to emergency care if swelling affects breathing or swallowing, if there is serious facial injury, or if your child seems seriously unwell.

Questions to ask your child’s dentist

• Does my child have any early decay or white spot lesions?
• Which teeth are at highest risk?
• Are we using the right fluoride toothpaste?
• Should my child have fluoride varnish?
• Would fissure sealants help?
• Does my child need X-rays?
• Can this tooth be treated without a filling?
• If a filling is needed, what material will be used?
• Is the tooth close to infection?
• Can the baby tooth be saved?
• Would extraction affect adult tooth spacing?
• How often should we come back?
• What should we change at home first?

Red flags parents should not ignore

Book dental care promptly if you notice:

• White chalky patches on teeth.
• Brown or black marks.
• Visible holes.
• Toothache.
• A child chewing only on one side.
• Pain with cold or sweet foods.
• Bad breath or bad taste.
• Bleeding or swollen gums.
• A gum boil.
• Facial swelling.
• A broken or crumbling tooth.
• Adult molars coming through with deep grooves or early staining.

How to choose a dentist for a child with tooth decay

Children with decay need a dentist who is calm, preventive and practical. The aim is not only to repair teeth, but to stop the cycle of decay.

Look for:

• Experience with children.
• Clear explanation of prevention.
• Fluoride varnish and fissure sealant advice.
• Kind handling of nervous children.
• Clear NHS and private options.
• Referral options for complex treatment, sedation or community care.
• Focus on home habits, not blame.
• Written treatment plan if several teeth are affected.

You can browse local dental providers through All Health and Care, including our Top 10 Dentists in the UK and local pages such as Top 10 Dentists in London.

Final thoughts

Tooth decay in children can be painful and stressful, but it is often preventable. The most important habits are simple: brush twice daily with fluoride toothpaste, supervise brushing, keep sugary foods and drinks to mealtimes, avoid bottles at bedtime, and take children to the dentist early.

Baby teeth matter. Early marks matter. Toothache and swelling should never be ignored. If you spot signs of decay, book a dental appointment rather than waiting for pain.

With the right support, many children can avoid repeated fillings, extractions and dental fear — and grow up with healthier adult teeth.

For more patient-friendly dental guides, visit our Dental Health & Dentistry section.

Frequently asked questions about tooth decay in children

What causes tooth decay in children?

Tooth decay is caused when bacteria in plaque use sugar to produce acid that damages tooth enamel. Frequent sugary foods and drinks, poor brushing and low fluoride exposure increase risk.

Can baby teeth get cavities?

Yes. Baby teeth can decay, hurt and become infected, just like adult teeth.

Does decay in baby teeth matter?

Yes. Baby teeth help children eat, speak and hold space for adult teeth. Decay can cause pain, infection and early tooth loss.

What does early tooth decay look like in children?

Early decay may look like white chalky patches, yellow or brown marks, rough areas or small pits, especially near the gumline or in back tooth grooves.

Can early tooth decay be reversed?

Very early decay before a hole forms may sometimes be stopped with fluoride, better brushing and diet changes. Once a cavity forms, dental treatment is usually needed.

When should I start brushing my child’s teeth?

Start brushing as soon as the first tooth comes through.

How often should children brush their teeth?

Children should brush twice daily, including last thing at night before bed.

What toothpaste should children use?

Use fluoride toothpaste. Children under 3 need a smear, children aged 3 to 6 need a pea-sized amount, and older children usually use family fluoride toothpaste unless a dentist advises otherwise.

Should children rinse after brushing?

It is better to spit out after brushing and not rinse with lots of water, so fluoride stays on the teeth.

Until what age should I help my child brush?

Help or supervise until at least age 7. Some children need help for longer, especially around back teeth.

Are fruit juices bad for children’s teeth?

Fruit juice contains sugar and acid. It is better kept to mealtimes and should not be sipped through the day.

Are raisins bad for children’s teeth?

Raisins and dried fruit can be sticky and high in sugar. They are better with meals than as frequent snacks.

Can milk at bedtime cause tooth decay?

Milk contains natural sugars. Frequent night-time exposure after teeth come through can increase decay risk, especially if teeth are not brushed before sleep.

What are the best drinks for children’s teeth?

Water and plain milk are the best everyday drinks.

Can children get fluoride varnish on the NHS?

Yes, fluoride varnish is commonly offered in NHS dental care when appropriate.

What are fissure sealants?

Fissure sealants are protective coatings placed in the grooves of back teeth to reduce the risk of decay.

Are fissure sealants worth it?

They can be very useful for children with deep grooves in adult molars or higher decay risk. Your dentist can advise if they are suitable.

How is tooth decay treated in children?

Treatment may include fluoride varnish, fissure sealants, fillings, baby tooth crowns, baby tooth nerve treatment or extraction, depending on severity.

Will my child need a filling?

If a cavity has formed, a filling may be needed. Very early decay may sometimes be managed without a filling if there is no hole.

Will a decayed baby tooth need removing?

Not always. Some baby teeth can be restored. Extraction may be needed if the tooth is badly decayed, infected or painful.

Is children’s dental treatment free on the NHS?

Yes. NHS dental treatment is free for children under 18, or under 19 if in full-time education.

What if I cannot find an NHS dentist for my child?

Keep checking local practices and use NHS dental search tools where available. If your child has urgent pain, swelling or infection, contact NHS 111 for urgent dental advice.

When is tooth decay urgent?

It is urgent if your child has severe toothache, swelling, fever, pus, a gum boil, facial swelling or pain that stops eating or sleeping.

Can tooth decay cause a dental abscess?

Yes. Deep decay can infect the nerve and cause an abscess, which may lead to pain, swelling, pus and fever.

Can tooth decay affect adult teeth?

It can. Infection, early baby tooth loss and poor oral habits can affect oral health and adult tooth development.

How can I stop my child getting more cavities?

Brush twice daily with fluoride toothpaste, supervise brushing, reduce sugary snacks and drinks, keep sugar to mealtimes, attend dental check-ups and ask about fluoride varnish or sealants.

Can mouthwash prevent decay in children?

Mouthwash is not a substitute for brushing. Some children may be advised to use fluoride mouthwash, but it should usually be used at a different time from brushing and only if age-appropriate.

Are electric toothbrushes better for children?

They can help some children, especially if they have a timer and small brush head. Technique and adult supervision matter more than the type of brush.

Can braces increase decay risk?

Braces can make cleaning harder and increase plaque traps. Good brushing, interdental cleaning and limiting sugary drinks are especially important.

How often should a child with tooth decay see a dentist?

It depends on risk and treatment needs. Some children with decay may need reviews every 3 to 4 months, while others may need different intervals.