Dental Cyst: What It Is, What It Looks Like, and Whether It Needs Treatment

Many patients, especially those who haven’t visited a dentist in a long time and have severely damaged teeth, may hear the diagnosis «dental cyst», more specifically referred to as a cystic lesion or periapical cyst. But is this diagnosis something to be afraid of? Can a cyst resolve on its own? What are the potential consequences, and what should you do if a cyst is found on your tooth?

What Is a Dental Cyst?

A tooth cyst is a pathological formation at the tip of the tooth root within the bone. It typically has a round shape, though variations exist, and it is filled with fluid. A cyst develops as the body’s response to infection or trauma.

Here’s how it happens: bacteria escape from the tooth root and penetrate the bone tissue. In response, the immune system attempts to contain the infection by forming a dense membrane around the affected area, preventing inflammation from spreading to healthy tissues. Essentially, the cyst acts as a protective barrier, stopping the infection from spreading further.

What Does a Dental Root Cyst Look Like?

A dental cyst can be detected using an X-ray. On the scan, it appears as a dark spot with well-defined borders near the tooth root. However, if the cyst is significantly large, a histological examination may be necessary to confirm the diagnosis and rule out malignant causes, as the underlying issue may not always be bacterial.

Symptoms of a Dental Cyst

A cyst cannot be detected without an X-ray, especially in its early stages. One of the defining characteristics of this condition is that symptoms are often absent until the cyst reaches an acute stage, requiring urgent surgical treatment. The most common symptoms include:

• Persistent aching pain
• Gum swelling
• Fever
• Discomfort while eating
• General weakness and fatigue

Unfortunately, a tooth cyst will not disappear on its own. Even if it doesn’t cause pain, it won’t go away. Additionally, rinses and medications cannot dissolve a cyst.

Stages of Cyst Development

Initially, cyst formation progresses slowly. Bacteria multiply gradually, while the body attempts to contain them. Over time, the cyst enlarges as bacterial growth continues within the tooth root.

As the cyst grows, it can lead to bone loss around the affected and neighboring teeth. This process often occurs over an extended period in a chronic, asymptomatic phase, meaning the patient may feel no discomfort and remain unaware of the condition. The cyst keeps growing, but there are no symptoms.

At this stage, only a dentist can detect the cyst during a routine check-up, especially if an X-ray is taken. This is why regular dental visits and examinations are crucial.

If a radicular cyst is in its chronic phase, it continues to grow. When the immune system weakens, bacteria multiply much faster, accelerating cyst growth. It’s important to remember that immune suppression can be triggered by various factors, including viral infections, colds, prolonged exposure to cold, alcohol consumption, and more.

When immune function drops significantly, the cyst may start growing faster than the bone can break down. At this stage, the patient begins to feel pressure and pain. In cases of severe immune suppression, the condition can escalate to extensive swelling and an abscess (dental phlegmon).

This is the point at which the cyst is easiest to detect, but by then, bacteria have already invaded the bone, leading to pus formation. Pus is essentially a mixture of destroyed bone tissue, bacteria, and proteins that the body cannot process quickly enough. As a result, the body expels it through the soft tissues, forming a fistula (drainage channel). For the patient, this may appear as a pimple on the gum or a red, inflamed area with discharge.

Causes of a Dental Cyst

There are several possible causes of cyst formation, but we will focus on the two most common ones.

1. Tooth Decay (Cavities)

Advanced or improperly treated tooth decay can reach the dental nerve, allowing bacteria to enter. The immune system tries to protect the bone from the decaying nerve tissue, bacteria, and infections that spread through the damaged tooth. Since this bacterial source is continuous, the cyst grows rapidly.

However, such a tooth can still be saved. If there is a remaining part of the tooth above the gum line that can be restored, the treatment process typically involves:

• Cleaning and treating the root canals
• Reducing inflammation with medication
• Filling the canals
• Placing a post and a crown to restore the tooth

2. Recurrent Inflammation

A previously treated tooth (where the nerve was removed) can become reinfected because, even after the most thorough treatment, a tiny percentage of bacteria may remain at the tip of the root canal.

If the immune system is strong, it can keep the infection under control. However, if immunity weakens over time, a new inflammation can develop 5–10 years later, first entering a chronic phase and eventually becoming active, requiring repeat root canal treatment.

Common Causes of Recurrent Inflammation:

• Weakened immune system
• Poor-quality root canal treatment or filling
• Outdated canal filling materials – If the treatment was done 15–20 years ago, the medication inside the canals has likely worn off, allowing bacteria to multiply uncontrollably.

Why Secondary Root Canal Treatment Is More Expensive

In cases of recurrent infection, the canals need to be reopened, cleaned, and refilled, which is more complex and costly than the initial treatment. The old materials must be removed first before the new treatment can begin.

3. Missed Root Canal

A large tooth can have up to six root canals, although this is quite rare. For example, in an upper first molar (the "sixth" tooth), there are typically four canals. However, the problem is that only three canals are reliably and easily found, while the additional canals can only be detected with a special dental microscope.

If these extra canals are not located and properly sealed, inflammation can develop over time, eventually leading to the formation of a radicular cyst. The only solution in this case is to find the missed canals and complete the treatment.

4. Undiagnosed Root Fracture

Another possible cause of cyst formation is an undiagnosed root fracture. When a root is fractured, inflammation occurs due to bone destruction, which can result in a cyst. However, in cases of a transverse root crack, bone destruction can happen even without forming a cystic sac. Instead, the gum tissue starts growing into the tooth, attempting to replace the lost bone structure.

Should a Dental Cyst Be Treated, or Will It Go Away on Its Own?

Many people live with a dental cyst for years without undergoing surgical treatment. However, as mentioned earlier, a cyst will not disappear on its own, and sooner or later, it will require treatment.

When addressing a cyst, it’s essential to take a comprehensive approach to dental health, rather than simply focusing on removing the cyst itself.

Success Rates of Treatment

• Primary root canal treatment has a 95% long-term success rate (5+ years).
• Secondary treatment (retreatment of a previously treated tooth) drops the success rate to 50–60%.
• With each subsequent retreatment, the chances of saving the tooth decline significantly.

Surgical Treatment of a Cyst

If a cyst reappears or if the root cannot be accessed using standard methods, a surgical cyst removal procedure may be required. The most common method is apicoectomy (root tip resection).

• Using modern guided surgery, the procedure takes only 20–30 minutes.
• With traditional techniques, it can take about an hour, and the healing process is much longer due to deeper and larger incisions.

What Are the Risks of Untreated Root Canals and Cyst Formation?

Acute pain. When tooth decay reaches the nerve, a person experiences severe pain that forces them to drop everything and seek emergency treatment.

2) Transition from chronic to acute phase. Sooner or later, a chronic cyst enters an acute phase, causing pain and pus formation (abscess). In this case, urgent dental care is needed, but finding an experienced specialist on short notice may not always be possible due to their busy schedule. This often forces patients to see any available dentist, increasing the risk of extraction instead of saving the tooth. This leads to additional expenses in the future for a dental bridge or implant.

3) Bone loss. A large cyst may prevent immediate implant placement, meaning the tooth must first be removed, and the infected bone given time to heal. This delays treatment and often requires bone grafting, increasing both costs and recovery time.

4) If a tooth with a cyst is extracted but no implant is placed, adjacent teeth will gradually shift into the empty space. In this case, before getting an implant or a bridge, orthodontic treatment may be required to move the teeth back into their correct position, adding extra time and costs to the process.