Tooth decay stages

Tooth decay: What is it?

Tooth decay results from an imbalance in the biofilm which is the bacterial plaque covering the surface of our teeth. Due to various factors, certain bacteria develop and transform food residues into acids that destroy the tissues of the tooth.
Tooth decay, therefore, goes through different stages. It first attacks the enamel (the tissue which covers the crown), then the dentin (the tissue under the enamel), finally the pulp which represents the heart of the tooth. Once the pulp is reached, dental sensitivities may appear as well as infections.

How did tooth decay appear?

Tooth decay is one of the most widespread infectious diseases in the world, characterized by irreversible destruction of hard tissues (enamel and dentin), and tends to evolve towards the pulp (center of the tooth).
It is a multifactorial disease, which is well demonstrated by 'Keyes' diagram:

keyes diagram

Cavities appeared with the introduction of sugary foods and cereals in our diet. This phenomenon happens through the production of acids as the bacteria metabolize the ingested nutrients.
When the mouth undergoes dramatic or long-lasting periods of high acidity, it can cause cavity-causing bacteria to grow, however, friendly bacteria that help us in digestion and protect us from other harmful bacteria do not tolerate acidity and will therefore die.

Experts say this is not a new problem. In fact, it would have grown in importance about 10,000 years ago, when human nutrition became based on sugars.

Tooth decay stages

Tooth decay evolves in 4 stages:

superficial stage

superficial stage

At this stage, the cavity is not sensitive. Good hygiene and good eating habits can help stop the progression of cavities if they are very superficial. Otherwise, it will continue to progress deeper into the tooth. It is necessary to treat cavities at their earliest stage, your dentist is in the best position to judge whether the tooth can be left under control or whether it is better to treat it.

Dentin stage

Caries progresses to the middle layer: the dentin. At this stage the cavity begins to be painful, and the more so as it approaches the heart of the tooth: the pulp. At this stage, the progression of caries is faster, the cavity is too deep to be cleaned by brushing. As the dentin is less hard than the enamel, caries widen creating an often larger cavity than before.

Deep stage

deep stage

If we waited too long to treat the cavity, it reaches the heart of the tooth: the pulp where the blood vessels and the nerve are located. The tooth is painful, sometimes spontaneously. The nerve is irritated: it is the stage of pulpitis.

Final stage

When caries reaches the pulp, the tooth goes into irreversible pulpitis which can be necrosed if it is not treated. It is, therefore, necessary to do a root canal treatment and then crown the tooth if the tooth still has enough healthy structure to be reconstructed. The infection can form an abscess at the root level and extraction is sometimes necessary.

final stage

Treatments available depending on the tooth decay stage

The treatment of tooth decay depends on its severity and location, the aim is to keep the affected tooth as much as possible.

Initial stage:

At the initial stage, there is no cavity. There are superficial lesions on the tooth enamel that are reversible and can be treated easily by adopting good hygiene and following the advice of your dentist. The objective is to promote the remineralization of the affected tooth with calcium, phosphorus, and fluoride. After the treatment, you must take care of your teeth so as not to wake up the lesions.

Advanced stage:

When the cavity is visible, we are no longer in the reversible stage. Tooth decay has irreversibly destroyed the hard tissues of the tooth.
At this stage, surgical treatment is required to remove the infected tissue.
Your dentist will remove the damaged tissue then he will fill the cavity with dental material. The most common are Amalgam and Resin-based composites.

Inlay and Onlay

Another solution is to perform an Inlay-Onlay. Indicated if the tooth has been very damaged. It helps to restore the shape of the tooth and provides sufficient resistance to it for better durability.

For extensive decay or weakened teeth, you may need a crown.

If decay has attacked the pulp, the dentist must remove the nerve from the tooth and disinfect the dental canal before closing it. The tooth is devitalized.

Whatever the technique proposed, the goal of the treatment is to stop the spread of cavities and ensure a seal, to prevent any recurrence.

The last option is extraction. Unfortunately, it can happen that the tooth becomes fragile and impossible for the dentist to save it. Here are the main causes that justify tooth extraction: Severe caries that has reached a very advanced stage, a broken tooth that has not been treated, infection. After extraction, the missing tooth will leave a gap. If possible, consider getting a bridge or a dental implant to replace the missing tooth.


Dental abscess

Dental abscess is an emergency that must be quickly managed. Untreated, the infection can be generalized leading to more serious complications. Characterized by swelling of the gum, intense pain with difficulty during chewing.


At an advanced stage, the swelling will be seen in external tissues (skin, muscles, cheek).
The pus makes its way through the tissues and pierces an exit orifice, which will end on the gum, sometimes on the face (cheek, chin). Septicemia (general infection): Bacteria that come from cavities can reach the bloodstream through the pulp or by ingestion.
Once the bloodstream is reached, the bacteria can affect the heart, lungs, kidneys, or any other organ.

People with disorders related to these organs are therefore the most fragile.


The roots of the upper molars are located near the sinuses. If the tooth abscess generates pus, the sinuses can then be filled with this pus. These can cause pain in the cheekbones and when the head is thrown forward. In some cases, a purulent discharge may occur and a feeling of bad smell.

Bacterial endocarditis

Bacteria from the dental abscess can reach the heart through the bloodstream. These pathogenic bacteria can infect the valves and lead to fatal consequences.

Abscess of the brain

The infection could spread from the teeth to the brain through the veins. Brain infection can lead to a coma.

To stop the infection and avoid serious complications, consult the doctor at the first symptoms. Go to the emergency if the fever exceeds 38 °C or if it becomes difficult to swallow and eat.


To prevent tooth decay, especially if you are at risk
  • Brush with fluoride toothpaste after eating or drinking.
  • Rinse your mouth with natural mouthwashes.
  • Visit your dentist regularly.
  • Drink a lot of water.
  • Balance your diet.
  • Avoid snacking and sipping frequently.
  • Eat healthy foods for your teeth that are rich in minerals and water like green vegetables, cheese, apples, tea, fish...
  • Consider fluoride treatments.
  • Learn about antibacterial treatments. If you're especially vulnerable to tooth decay — for example, because of a medical condition — your dentist may recommend special antibacterial mouth rinses or other treatments to help cut down on harmful bacteria in your mouth.