Tooth Decay: Symptoms & Treatment

Last Updated May 2023

Over time, the bacteria in our mouths can damage our teeth. This is known as tooth decay, and it’s very common. Almost one in three (31%) adults in the UK have tooth decay. It can cause black or brown spots on your teeth, tooth pain, tooth cavities and infections.

It’s important to identify the signs of tooth decay early, so you can take steps to stop it from progressing into more serious oral health issues. Read on to learn about the symptoms, stages, causes, and treatment options for tooth decay.

In this guide:

What is tooth decay?

Tooth decay is damage to the tooth caused by a build-up of bacteria in the mouth. Oral bacteria can form a sticky layer over the teeth known as plaque. Over time, this can lead to holes developing in the affected teeth. These holes are known as cavities. Depending on the severity of tooth decay, cavities can affect the outer and inner layers of the teeth.

What causes tooth decay?

Tooth decay is caused by a build-up of bacteria which forms a film over the teeth known as plaque. The bacteria feed off bits of food and drink that stick to your teeth, creating acid in the process. This acid gradually dissolves the outer enamel of the teeth, creating holes known as cavities. If left untreated, the cavities deepen and eventually damage the dentin inside the teeth.

Several things can lead to tooth decay, including:

Too much sugary food and drink in your diet

Plaque bacteria create acid from sugary and starchy food, which erodes tooth enamel. These foods are often clingy and can stick to your teeth even after you’ve eaten. A diet high in sugar means you’re more likely to have tiny amounts of sugar deposits in your mouth, which plaque feeds off. This can lead to cavities.

Poor dental hygiene

Not following an oral hygiene routine – including brushing, flossing, and rinsing – that adequately cleans your teeth and gums can lead to tooth decay. Plaque and decay can form if you don’t clean your mouth regularly after eating and drinking.

Stomach acid

Your stomach produces acid to break down food, but this can also damage your teeth. Acid reflux and being sick regularly (such as during pregnancy or when suffering from an eating disorder) can result in damage your tooth enamel.

Dry mouth

Saliva works to wash away food and plaque from your teeth, helping to prevent tooth decay. You may be more prone to tooth decay if you have a dry mouth which doesn't produce enough saliva.

Not enough fluoride

What is fluoride? Fluoride is a mineral that can reverse early tooth damage and helps to prevent dental cavities. It can be easily found in toothpaste and mouthwashes – including LISTERINE® Total Care 10 in 1.

Tooth decay symptoms

Tooth decay may not cause many noticeable symptoms at first. However, if left to worsen, it can lead to problems such as tooth pain and sensitivity, dental cavities, and potential infections.

Tooth decay symptoms can include:

  • Toothache
  • Sharp pain when eating or drinking hot, cold, or sweet things (sensitive teeth)
  • Pain when biting down or chewing
  • An unpleasant taste in your mouth
  • Bad breath (Halitosis)
  • White, brown, or black marks on the affected tooth
  • Infected teeth or gums, which can lead to a dental abscess.

There are different stages of tooth decay4, and symptoms can vary depending on how severe the decay has become. See your dentist if you experience any tooth decay symptoms, as they can take steps to prevent it from worsening.

Tooth decay stages

There are five stages of tooth decay. It’s best to see your dentist if you experience any of the tooth decay symptoms below:

  • Stage 1: Demineralisation

    The enamel that coats the outer layer of your teeth starts to weaken due to the acid produced by plaque. You may notice white marks on the teeth or find they become more sensitive to hot, cold, or sweet food and drinks. Fluoride mouthwash or fluoride treatment from your dentist can help to repair the damaged enamel at this stage.

  • Stage 2: Enamel decay

    This is when the enamel begins to break down, and small cavities start to form. Brown or black marks may be visible on the teeth.

  • Stage 3: Dentin decay

    If cavities are left untreated, the decay can spread further into the tooth, and your dentin can become damaged. Dentin is the softer part of the tooth beneath the enamel. It’s much more sensitive to plaque acid and will begin to decay much faster than the enamel. Your teeth will likely become much more sensitive while eating and drinking at this stage.

  • Stage 4: Damaged pulp

    The pulp is the innermost part of the tooth. It’s where the blood vessels and nerves that sustain and provide sensation to the tooth are located. Damage to the pulp can cause the tooth to swell, resulting in toothache. Pulp damage can also cause pulp death. Your tooth might change to grey or black and begin to smell or taste bad.

  • Stage 5: Abscess formation

    In the final stage of tooth decay, bacteria inside the pulp of the tooth can lead to infection. An abscess may form beneath the tooth, which causes severe pain in the gum, jaw, mouth, and face. At this stage, a visit to the dentist is needed for immediate assessment and action.

How to prevent tooth decay

There are ways you can protect your teeth from decay, including:

See your dentist

Don’t be a stranger at the dental surgery if you want to avoid cavities. Getting routine cleanings can help prevent decay early on, before it progresses to become cavities. If needed, your dentist can apply fluoride to any trouble spots to prevent tooth decay and cavities.

Brush with fluoride

Select a fluoride toothpaste, as this is known to protect teeth from tooth decay and cavities. Don’t rinse your mouth with water after brushing – as this will prevent the fluoride from binding to the teeth.

Rinse with fluoride

Using a mouthwash containing fluoride can also help prevent tooth decay. LISTERINE® Total Care mouthwash and LISTERINE® Smart Rinse mouthwash contain fluoride to help strengthen enamel.


Flossing or using an interdental brush at least once a day will help keep your teeth and gums healthy. Flossing reaches in between your teeth where regular brushing might not, helping to get rid of more food debris.

Change your snacks

Try to snack only a limited number of times a day, and when you do, aim to include foods that are good for the teeth. Whenever you eat food or drink liquid other than water, this allows bacteria to create acid that wears away tooth enamel. Try to avoid processed sugary foods such as sweets, dried fruit, and fizzy drinks. Limit the amount of acid that breaks down your teeth by limiting snack time to a few times a day.

If you’re concerned about the health of your gums, try to brush and rinse with LISTERINE® mouthwashes twice daily. When these tools are not available, try to at least rinse your mouth out with water after eating.

Stop smoking

Smoking can impede saliva production, which helps to keep your teeth clean. It can also contribute to gum disease, sensitive teeth, and other oral health issues.

Treat persistent dry mouth

Dry mouth can contribute to tooth decay, as saliva helps to keep the teeth clean and healthy. If you have dry mouth, it’s important to treat the cause to maintain healthy teeth and gums and minimise the risk of tooth decay.

Which dental treatments help stop tooth decay?

There are ways to prevent existing tooth decay from getting worse. Depending on what stage your tooth decay has reached, the treatment may require the help of a dentist or medical professional. Although stopping tooth decay from progressing can be effective, prevention is the best approach. It’s important to see your dentist regularly so they can identify any problems early on.

Here are some ways to stop tooth decay from getting worse:

Fluoride gel

In stage one of tooth decay, your dentist may notice increased sensitivity or white spots on your teeth from demineralisation. They may advise you to eat less sugary food and drink and reduce snacking. They might apply fluoride gel, varnish, or paste to the teeth at this stage to help strengthen the enamel.

Fillings and crowns

Stage two and three of tooth decay can usually be treated with fillings or crowns. This involves numbing the mouth with local anaesthetic. They will then remove the decayed area of the tooth and fill the hole or cap the tooth with amalgam, porcelain, silver alloy, or gold.

Root canal treatment

When tooth decay reaches stage four or five, your dentist may need to perform root canal treatment. This procedure removes the decayed pulp, nerves, and blood vessels from inside the tooth and fills it with a sealing material. Root canals are often topped with a crown.

Tooth removal

If tooth decay has badly damaged the tooth beyond repair, it may have to be removed. Your dentist might be able to insert an implant, bridge, or partial denture to replace the lost tooth.