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Tooth decay: causes, symptoms, prevention

by Josephine Andrews
Published: Last Updated on 464 views

Caries (tooth decay) is a process in which the tooth structure slowly breaks down and eventually a hole is formed in the tooth. Poor oral hygiene and a high-sugar diet promote the development of tooth decay. Symptoms range from discoloration of the teeth to severe pain. Without treatment, tooth decay will continue to grow. Read everything you need to know about tooth decay here.

quick overview

  • What is tooth decay? Widespread dental disease in which the tooth structure is gradually destroyed.
  • Causes : Interplay of microorganisms and harmful factors such as poor oral hygiene and a diet rich in sugar. Other risk factors include a lack of saliva and a weakened immune system.
  • Symptoms : initially often chalk-white spots or dark discolouration on the tooth, later the proverbial “hole in the tooth”. Pain occurs at the latest when the nerve of the tooth is affected.
  • Caries – what to do? Off to the dentist! He will first determine the extent of the tooth decay and then initiate appropriate treatment.
  • Prevent tooth decay : sugary foods and drinks only in moderation, regular brushing of teeth, use of fluoride toothpaste, dental floss and interdental brushes, regular check-ups at the dentist, professional tooth cleaning (PZR), use of fluoride varnish, fluoride gels or solutions

Tooth decay: description

Most people understand tooth decay to mean the proverbial “hole in the tooth”. In fact, this dental disease begins much earlier: In the case of dental caries, there is increasing decalcification (demineralization) of the hard tooth substance (enamel and dentine underneath). Acid-forming bacteria are responsible for this demineralization. Only if the decalcification process is not stopped does a hole in the tooth finally appear.

Instead of tooth decay, the term tooth decay is also often used. However, this is not entirely correct from a medical point of view – the tooth substance does not rot, but is broken down.

types of tooth decay

Doctors differentiate between different types of caries, depending on how much tooth substance the bacteria have already destroyed: In the case of initial caries , the surface is still intact and decalcification is beginning. With established caries , the surface is defective.

Depending on which layers of the tooth are affected, a distinction is made between sub-types:

  • Caries superficialis : defect in the enamel (most superficial layer of the tooth)
  • Caries media : defect down to the dentine (second layer of the tooth)
  • Caries profunda : Caries in all layers down to the pulp of the tooth, which also contains nerves
  • Caries sicca : Caries has come to a standstill.

Tooth decay: Affected tooth areas

Tooth decay is considered to be the most common dental disease worldwide. Almost everyone suffers from tooth decay at least once in their life. Milk teeth and permanent teeth can be equally affected.

Depending on the age at which tooth decay first forms, the question “What does tooth decay look like?” answered differently, since different areas of the teeth are particularly affected depending on age.

  • In young children, tooth decay affects the incisor and adjacent gums first and then slowly progresses to the edge of the tooth. This tooth decay in small children is also known as baby bottle tooth decay and is mainly caused by the wrong diet (e.g. tea sweetened with sugar) by the children.
  • In slightly older children and adolescents, tooth decay often first appears on the chewing surfaces. The cause here is usually an incorrect (sugar-rich) diet.
  • In adults, on the other hand, caries mainly occurs between the teeth. The reason for this lies on the one hand in the wrong or negligent dental care or also on heavily sweetened drinks such as coffee or tea.
  • In people over 60 years of age, tooth necks are particularly affected by tooth decay. With age, the gums often recede, which means that the individual tooth necks are exposed. In this area, however, the natural protective layer is thinner, which is why a “hole in the tooth” occurs more quickly. This form of caries is also known as root caries.

Tooth decay: symptoms

Caries describes a progressive course of tooth destruction. Sometimes “only” one tooth is affected, in other cases several teeth are carious. In addition, different symptoms occur depending on the stage of caries development.

Tooth decay: initial stage

In the beginning, caries is hardly visible. Doctors call this period of time the initial stage. Chalk-white spots (white spots) slowly develop on the teeth. There, minerals are already separating from the teeth and the enamel becomes porous. Dark discoloration of the teeth is also an indication of tooth decay.

Actually, the loss of minerals can still be compensated for at this stage: Regular and careful brushing of the teeth removes the harmful caries bacteria. And the fluoride contained in the toothpaste ensures that minerals from the saliva replace the loss in the tooth structure.

With poor oral hygiene, caries continues. Teeth that are rarely brushed become increasingly demineralized and eventually a cavity develops in the tooth. This is where pain can appear for the first time. However, pain sets in at the latest when the nerves of the teeth are also attacked by bacteria. At this stage, many teeth are also very sensitive to heat, cold or very sweet foods.

Caries: late stage

Without treatment, tooth decay progresses slowly. Caries can also spread from an affected tooth to other teeth. As the tooth structure wears down, so does the pain. An untreated tooth decay infection is very dangerous. The inflammation may spread to the jawbone and trigger inflammation there as well. Bacteria can also travel from the mouth to the entire body via the bloodstream and infect other organs.

Secondary caries (caries under filling / caries under crown)

If there has already been a hole in the tooth, the dentist drills it open and closes it with a filling. However, this treatment does not guarantee that you will be protected from tooth decay afterwards. Teeth often develop what is known as secondary caries:

Over the course of several years, small gaps form in the border area between the tooth and the tooth filling or crown. These are too small for the bristles of the toothbrush to reach. However, they are big enough for the microscopic bacteria to settle in. Dental caries also often occurs in places where a hole in the tooth has already been filled.

Tooth decay: causes and risk factors

Tooth decay is influenced by several factors: bacteria, dental hygiene and eating habits. The development of caries is based on an interaction of these factors. In addition, the saliva and the immune system also play a role.

To help children answer the question “How does tooth decay occur?” The history of the bacteria “Carius and Baktus” helps to explain this in more detail. It shows what happens in the teeth when there is caries. Today, the pair of bacteria can also be found on posters at the dentist, in the form of comics or in short stories that warn against caries in milk teeth.

caries bacteria

There are over 700 types of bacteria in our mouth. To a certain extent, these microorganisms are necessary for a healthy oral flora. However, some bacteria feed mainly on food residues, especially sugar. They use sugar from food and excrete acids as waste products. These attack the tooth enamel by leaching minerals. If this process is not stopped, eventually the hole will form in the tooth.

Diet high in sugar

The development of caries is promoted by sweet foods and drinks. Above all, table sugar (sucrose), grape sugar (glucose) and fruit sugar (fructose) can be easily utilized by caries bacteria and thus indirectly damage the teeth. On the other hand, long-chain sugar compounds, i.e. complex carbohydrates , such as those found in whole grain products, do not promote tooth decay.

dental hygiene

Brushing your teeth reduces the number of bacteria in your mouth. However, immediately after each brushing of the teeth, a coating of bacteria and saliva components slowly forms on the tooth surface – called plaque or biofilm. If someone brushes their teeth infrequently, irregularly, or carelessly, this plaque has enough time and opportunity to grow thicker and thicker. The problem with this is that it is mainly the bacteria that cause tooth decay that multiply in it.


If there is a lot of saliva, the minerals it contains can replace losses in the hard tooth structure. An increased amount of saliva also serves to liquefy ingested food. In this way, they can be transported away better and are less likely to get stuck on and between the teeth. Some components of the saliva also have a neutralizing effect on the acids produced by bacteria. Others have antibacterial properties.

In summary, this means that if there is little saliva, tooth decay is more likely to form. In the space between the teeth and on the crown of the tooth , food residues can then easily get caught and settle, which caries bacteria are happy about.

immune system

The condition of the immune system also determines how well the body can defend itself against harmful bacteria. People with a weakened immune system often suffer from tooth decay. A weakening of the immune system occurs, for example, with chronic diseases such as HIV or diabetes mellitus. Medications such as antibiotics or corticosteroids (e.g. cortisone) also reduce the resistance of the immune system.

Is tooth decay contagious?

Tooth decay is a bacterial infection and, like other bacterial infections, is contagious . In normal everyday life, however, the risk of infection with tooth decay does not play a major role. The bacteria that are responsible for the development of caries are carried in everyone’s mouth. Individual risk factors must therefore definitely be added before caries can break out. A transmission of caries-causing bacteria between two adult people (e.g. through kissing or shared cutlery) is therefore irrelevant for the development of caries.

The fact that caries is contagious plays a role in small children . They have fewer bacteria and microorganisms in their mouths than adults, and even none at all in small children without teeth. Theoretically, adults who, for example, briefly put their child’s pacifier in their mouth to clean it themselves, may transmit their caries bacteria to their offspring. Experts dispute whether the risk of infection is really that great.

family influence

Contrary to popular belief, tooth decay is not hereditary . Tooth decay can run in families. For example, hereditary factors such as deep tooth grooves (tooth fissures) represent a potential risk factor for caries. There are also eating and hygiene habits that children learn from their parents: in families where sweet foods and drinks are often served and/or little emphasis is placed on thorough and regular brushing of teeth, the risk of caries in children is far higher than in other families.

Tooth decay: investigations and diagnosis

If caries is suspected, the dentist is the right contact person. In a short conversation, he will first collect the medical history (anamnesis). You (or your child) have the opportunity to describe the symptoms in detail. The doctor can then ask further questions, for example:

  • When did the symptoms first become apparent?
  • Are there relatives who often suffer from dental problems?
  • Have you had problems with your teeth in the past?
  • How often do you brush your teeth a day?

thorough examination of the teeth is then carried out. The dentist can detect tooth decay by examining the teeth with a small mirror. The disease is initially noticeable through changes on the surface of the teeth. If such changes are present on the surface, the dentist uses a small probe (a kind of thin rod) to check how far the damage has progressed into the interior of the tooth. The treatment depends on it.

Since tooth decay is usually very difficult to detect in the initial stage, X-rays can be helpful. Carious areas can be identified very well on this. Incipient caries is often only discovered by chance on routine X-rays taken during a dental check-up.

There are also other modern methods that can be used to diagnose tooth decay. This includes, for example, the measurement of electrical resistance and various fluorescence methods:

  • Electrical resistance measurement : Healthy tooth enamel moistened with saliva conducts electricity. In the case of caries damage, this conductivity in the enamel increases, i.e. the electrical resistance – measured using a hand electrode – decreases.
  • Fluorescence methods: They are based on the fact that the tooth structure fluoresces under certain conditions. The fluorescence properties depend on the condition of the tooth substance: Carious areas fluoresce differently than healthy tooth substance.

Tooth decay: treatment

In the case of caries in the early stages, improved oral hygiene and avoiding a high-sugar diet is sometimes sufficient. However, tooth decay is often only discovered when it is more advanced. Then the dentist has to step in: He usually removes the decayed area on the tooth with a drill and closes the resulting hole with a filling.

You can read more about this and other options for caring for decayed teeth in the article Caries treatment .

Caries: course of the disease and prognosis

The loss of minerals can only be compensated for in the initial stage. At the latest when a hole has formed in the tooth, caries must be treated professionally (i.e. by the dentist).

After caries has been identified and treated, there are usually no more complaints. However, a one-off caries treatment does not guarantee that problems will not arise again. As soon as oral hygiene is neglected, tooth decay can develop again. Caries in milk teeth in particular tends to form again quickly.

If caries affects children, it can also be considered to prevent the affected teeth (milk teeth) from being extracted in order to prevent the caries from spreading.

prevent tooth decay

You can prevent tooth decay by consuming sugary drinks and foods in moderation and by practicing thorough and regular oral hygiene . If possible , you should brush your teeth after every meal – regardless of whether you have eaten something containing sugar or not. In this way, leftover food residues are removed immediately and the bacterial coating on the teeth is reduced. If brushing your teeth after eating is not possible, chewing gum containing xylitol also helps . Xylitol is a sugar substitute. It stimulates salivation and can partially neutralize the acids formed by the bacteria.

After consuming acidic foods (such as citrus fruits or cola) you should wait a little before brushing your teeth. Because the acid softens the tooth enamel so that it is more easily removed when brushing. Therefore, wait about 30 minutes before brushing your teeth.

Use fluoridated toothpaste . It hardens the tooth enamel and thus helps to prevent tooth decay. Use dental floss and/or interdental brushes to clean between your teeth .

Proper oral hygiene is important for children : as soon as the first tooth comes through, the mouth should be cleaned regularly with a soft children’s toothbrush. Once the child has all the milk teeth and the swallowing reflex is established, brushing should begin twice a day.

Regular check-ups at the dentist in children and adults help to identify tooth decay at an early stage. A professional tooth cleaning ( PZR ) also supports the health of the teeth. It should be carried out at least twice a year in adolescents and adults.

If there is an increased risk of tooth decay, the dentist may apply fluoride varnish to the tooth surface or recommend fluoride gels or solutions for use at home.

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