Tooth Decay: Stages, Risks, Prevention, and Treatment

Tooth Decay: Stages, Risks, Prevention, and Treatment
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Tooth Decay: Stages, Risks, Prevention, and TreatmentClinical Content Reviewed by Dr. Jay Khorsandi, DDS
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Table of Contents

  1. What is Tooth Decay?
  2. Stages
  3. Causes
  4. Risk Factors
  5. Symptoms
  6. Diagnosis
  7. Treatments
  8. Complications If Untreated
  9. Prevention
  10. Children & Tooth Decay
  11. Frequently Asked Questions
  12. References

Tooth decay (also known as dental caries, or cavities) is one of the most common health problems in the world. Bacteria in your mouth break down carbohydrates in the residue of the food you eat. The breakdown produces acid that weakens and eventually destroys your teeth.

The risk of not paying attention to tooth decay is not just the pain that envelopes teeth and gums but also the eventual loss of one or more teeth as well as a decline in overall health. Oral health is linked directly to overall health.

You can prevent tooth decay with a healthy diet and effective dental care at home as well as with regular visits to the dentist.

Caught in its early stages, decay can sometimes be reversed using the same methods. If decay progresses into the tooth’s dentin layer, an oral care professional will need to treat it with a filling or crown or by performing an extraction.

Untreated tooth decay will continue to worsen over time, eventually developing into a severe infection which can put your overall health at risk.

What Is Tooth Decay?

Tooth decay is damage caused by the presence of a common oral bacteria called streptococcus mutans (S. mutans for short). These bacteria bond together to produce a sticky substance called dental plaque.

When you eat or drink anything that contains carbohydrates, the saliva in your mouth breaks those carbohydrates down into sugars. The S. mutans bacteria in the plaque on your teeth consume these sugars. As the bacteria eat, they produce acid that gradually breaks down the enamel on your teeth. This produces a hole known as a cavity.

Tooth decay can appear on any surface of a tooth, including the sides, biting surfaces, pits and fissures, and even the contact points between two teeth. It is sometimes visible with the naked eye, but often needs special tools to detect. It also develops over time, often taking months or even years to develop.

Stages of Tooth Decay

Tooth decay goes through four main stages as it develops.

Stage 1: Plaque gathers on the tooth.
At this stage, no permanent damage has been done. Thorough brushing can remove the plaque and restore the tooth to normal.
Stage 2: Decay forms in the tooth’s enamel.
It begins on the surface of the tooth and slowly moves inward, forming a cavity. This stage is called incipient decay and can be reversed if the affected tooth is kept clean and not exposed to too many sugars. Some dentists will recommend observing the tooth to see if you can stop the decay. Others will recommend immediate treatment.
Stage 3: Decay progresses into the tooth’s dentin.
At this point, the decay will start to progress much more quickly. This is because the dentin layer is much softer than the enamel that covers it. All dentists will recommend treating a cavity that has reached this stage.
Stage 4: Decay reaches the tooth’s pulp.
It may spread to the tooth’s nerve, causing severe pain. The pulp may also become infected, causing a systemic reaction that requires emergency treatment.


Changes in acidity in your mouth cause tooth decay:

  • When your mouth is too acidic, your tooth enamel becomes weak and loses some of the minerals in its structure. This is called demineralization.
  • When your teeth are not exposed to acid, they can slowly rebuild themselves using the minerals in your saliva. This is called remineralization.

If your teeth spend more time demineralizing than re-mineralizing, they will begin to decay.

Most demineralization occurs when you eat or drink anything other than water. Items that are high in carbohydrates cause a stronger reaction.

Timing matters, too. The total amount of sugars you consume matters less than the amount of time you spend consuming them.

Eating a chocolate bar is less harmful to your teeth than eating single squares of chocolate throughout the day. This is because eating slowly gives the bacteria in your mouth more time to feed on the sugars, causing them to continually produce acid.

Risk Factors

Certain factors put you at greater risk of developing tooth decay. Among them:

  • Poor oral hygiene. If you do not clean the plaque and food residue off your teeth, your teeth will constantly be exposed to acid.
  • A diet high in carbohydrates. Carbohydrates quickly break down into sugars that feed the bacteria in your mouth.
  • A snacking or sipping habit. Snacking and sipping causes your mouth to spend more time exposed to acid, increasing your risk of developing tooth decay.
  • Living in communities with no water fluoridation. People who do not receive regular doses of fluoride through their tap water do not get as many opportunities to expose their teeth to beneficial fluoride.
  • Certain dental conditions, such as amelogenesis imperfect. These conditions affect the structure of your enamel and make your teeth more vulnerable to decay.
  • Health conditions or medications that reduce your saliva flow. Without enough saliva, your teeth cannot get the minerals they need to rebuild themselves.
  • Very young or very old age. Young children often struggle with dental hygiene tasks. Older people suffer from higher rates of dry mouth and may also develop arthritis and motor difficulties that make brushing and flossing challenging.


Early-stage tooth decay produces few symptoms. You may notice white or brown discoloration visible where the decay is forming.

As the decay becomes more advanced, you may experience:

  • Sensitivity to hot, cold and sweet foods and drinks
  • A toothache (constant or intermittent)
  • Bad breath
  • A bad taste in your mouth
  • Dark shadowing beneath the affected tooth’s enamel

Not all tooth decay produces noticeable symptoms. A lack of tooth pain does not necessarily mean you do not have any cavities.

Visit your dentist regularly to have your teeth examined for decay regardless of whether you have been experiencing any symptoms.


Diagnosing tooth decay is not an exact science, but your dentist will look for any indications of decay during your regular dental checkups through a series of X-rays of the inside your mouth. Healthy teeth are solid objects that should appear entirely white on an X-ray.

If any shadowy areas show up inside the x-ray images of your teeth, there may be decay present.

Some dentists use additional diagnostic methods, including:

  • Visual inspection
  • Inspection with a small handheld laser
  • Examination with a dental probe (a long, sharp metal device). If the probe sticks in a particular spot, there is decay in that area

Some dentists do not consider tooth decay to be clinically significant until it has broken through your tooth’s enamel and begun to destroy the dentin underneath. Others recommend treating all decay immediately to prevent it from getting worse. This is why two different dentists might diagnose different numbers of cavities from the same set of x-rays.


Tooth decay can be treated with:

  • A filling or crown
  • A root canal (often followed by a crown)
  • Tooth extraction

Some dentists treat cavities in children with silver diamine fluoride, a compound that arrests the development of the cavity so it never progresses to its later, more dangerous stages. They can apply it the same day they identify a cavity. The application causes no pain.

The compound does have some unpleasant side effects. Applying it permanently stains the decaying area of the tooth black. It also cannot repair structural damage caused by the cavity, so it can be difficult for patients to keep the arrested area clean and prevent new decay from forming there.

For these reasons, it is typically reserved for treating primary teeth that will eventually fall out anyway.

Complications of Untreated Tooth Decay

Untreated tooth decay will only grow worse, creating more pain and an increasingly likelihood of an eventual extraction. The speed of progression depends on:

  • Your oral hygiene. Poor hygiene leads to faster decay.
  • Your diet. The more carbohydrates your oral bacteria have access to, the more damage they can do.
  • Your saliva levels. People experiencing dry mouth and other conditions that reduce saliva flow have more acidic mouth environments that promote faster decay.
  • How advanced the existing decay is. Tooth decay that is only present in a tooth’s enamel progresses very slowly and can even stop growing altogether. Once the decay breaks through to the dentin or pulp layers of the tooth, it progresses much more quickly.

The closer that decay gets to the center of the tooth, the more serious the problem becomes.

You may develop an infection in the root of your tooth. When this happens, a root canal must be performed to control the infection and save the tooth.

If you still do not get your tooth decay treated when it reaches this stage, the decay will continue to get worse. Eventually, it will become so severe that you will have no choice but to have the tooth extracted.

Longstanding tooth decay also threatens your overall health. The infection may cause an abscess to form on the outside of your gums. From there, it may spread to other parts of your body. If this happens, you could develop sepsis and even die.


Nearly all tooth decay is preventable. You can protect your teeth by:

  • Brushing and flossing regularly. Maintaining good oral hygiene is the most important thing you can do to keep your teeth healthy and strong.
  • Cutting down on snacking. The less time you spend with food and drink in your mouth, the more time your teeth have to rebuild their enamel and stave off decay.
  • Drinking more water. Water lowers the acidity of your mouth and is often fluoridated, giving your teeth some extra minerals to use when rebuilding their enamel.
  • Quitting smoking. Smoking dries out your mouth and promotes bacterial growth that can harm your teeth.
  • Getting dental sealants. These thin coats of plastic are applied to parts of the teeth that are particularly vulnerable to decay, such as the fissures of the back molars. The sealants shield these areas from plaque and acids.
  • Getting regular fluoride treatments. Fluoride helps your teeth resist acid attacks and rebuild after they occur. Your dentist can apply fluoride to your teeth during your regular dental checkups using fluoride gels, varnish, foam, and other treatments.

Tooth Decay in Children

Children as young as 12 months old can develop cavities. As soon as a tooth erupts, or pushes up from the gums, it becomes vulnerable to decay.

Even though most children do not have all their permanent teeth, they still require treatment for tooth decay. Depending on your child’s age and abilities, their dentist might recommend:

To protect your child from tooth decay:

  • Brush your child’s teeth twice a day with a tiny smear of fluoride toothpaste as soon as their first tooth erupts. Use a pea-sized amount of paste when they turn 3.
  • Floss your child’s teeth each day after they turn 2.
  • Limit your child’s consumption of carbohydrates. If you want to offer them a treat like cookies or candy, do so as part of a meal.
  • Do not offer your child a bottle filled with anything but water. Juice, milk or even baby formula will all leave residue on the teeth that can cause tooth decay.
  • Adopt a rigid nursing habit. If you must nurse your child at night, wipe down their teeth and gums with a clean, soft cloth before returning them to bed.
  • Take your child to the dentist every 6 months for regular cleanings and checkups.

Frequently Asked Questions

How do you get rid of tooth decay?
All tooth decay that has progressed into the tooth’s dentin layer must be drilled away. Decay that has not reached this point can sometimes be reversed with good oral hygiene and a healthy diet.
What happens if tooth decay is left untreated?
If tooth decay is not treated, it will advance and destroy more of your tooth’s structure. Eventually, it will kill the tooth and may spread the infection to the rest of your body. If this happens, you could become extremely sick or even die.
Can tooth decay go away on its own?

Early tooth decay can sometimes be reversed with excellent oral hygiene and dietary habits. However, this is not always possible, even if the decay is not very advanced.

If you spot signs of early decay in your teeth, visit your dentist for guidance. They can tell you whether it is realistic to try to reverse your decay and recommend additional measures (such as in-office fluoride treatments or high-fluoride toothpaste) to help you manage the problem.


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Disclaimer: This article is intended to promote understanding of and knowledge about general oral health topics. It is not intended to serve as dental or other professional health advice and is not intended to be used for diagnosis or treatment of any condition or symptom. You should consult a dentist or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment.