Tooth cyst: how it differs from a granuloma, when root canal treatment is enough and when surgery is needed

What is a tooth cyst and how does it differ from a granuloma?

A tooth cyst, or radicular cyst, and a dental granuloma are two forms of chronic inflammation at the tip of the root, which dentists call a periapical lesion. Both start the same way: bacteria from a dead or unsuccessfully treated pulp escape through the root tip, and the bone around it is destroyed. The American Association of Endodontists (AAE) describes this condition as inflammation of the periapical tissues of pulpal origin, visible on an X-ray as a darker area next to the root.

A granuloma is a cluster of inflammatory tissue, while a cyst is a cavity lined with epithelium and filled with fluid. In a histopathological study of 256 lesions removed together with extracted teeth, granulomas made up 50%, abscesses 35% and cysts 15%, although it had previously been thought that almost half of such lesions were cysts (Nair et al., 1996).

The authors of this study divided cysts according to whether their cavity connects with the root canal. In their view, pocket cysts, which are open to the canal, can heal after root canal treatment, while true cysts, which are closed, heal after it less often.

What symptoms does a cyst on a tooth root cause?

A cyst on a tooth root most often causes no symptoms at all and is found by chance, on an X-ray taken for another reason. The AAE calls this asymptomatic apical periodontitis: the lesion shows on the X-ray but does not hurt. A review of 114 studies from many countries reports that 52% of the people examined have at least one tooth with a periapical lesion, and that a lesion is visible on 5% of all teeth and on 39% of root-treated teeth (Tibúrcio-Machado et al., 2021).

When symptoms do appear, they depend on whether the inflammation is chronic or acute. Each of the signs on the list is a reason for a visit with an X-ray, and what to do in general with toothache and an abscess is covered in a separate article.

• Pain on biting, on tapping the tooth or on pressing the gum over the root.
• A fistula, a small blister on the gum from which pus drains from time to time, usually with little or no pain.
• Rapidly increasing spontaneous pain and swelling of the gum or face, typical of an acute abscess.
• Swelling spreading towards the eye or neck, a fever with facial swelling, difficulty breathing or swallowing: the hospital emergency department (SOR) or 112, the emergency number.

How is a tooth cyst detected: an X-ray or a CBCT scan?

A tooth cyst is detected on an X-ray, most often an intraoral one, and in more difficult cases on cone beam computed tomography (CBCT). In a 2016 meta-analysis based on artificially created bone defects, the accuracy of CBCT was 0.96 and that of an intraoral X-ray 0.73 on a scale from 0 to 1; no data were found for panoramic X-rays. Indications for CBCT and radiation doses are discussed in the article on CBCT and panoramic X-rays.

No X-ray, however, can say for certain whether it is a cyst or a granuloma. In a study of 45 patients before apicoectomy, two radiologists assessing CBCT images were right in 51% and 63% of cases, and the authors concluded that only a biopsy with histopathological examination settles the question (Rosenberg et al., 2010).

Examining the tooth itself matters just as much: a cold test, tapping, an assessment of the gum. A healthy, vital pulp does not cause inflammation at the root tip, and in an analysis of 236 histopathological results more than a quarter of the teeth associated with odontogenic cysts had a vital pulp, so root canal treatment was not indicated for them.

Does a tooth cyst need to be removed? The steps of treatment

Not every tooth cyst needs to be removed surgically. The cause of the lesion is infection in the canals, so the first step is usually endodontic (root canal) treatment, and when the tooth has already been treated, root canal retreatment. The 2023 guideline of the European Society of Endodontology (ESE) found no difference in effectiveness between surgery at the root tip and root canal treatment or retreatment, and provides for surgery when treatment through the crown is not feasible.

A large lesion does not automatically mean surgery. In a study of 42 front teeth with cyst-like lesions 7 to 18 mm in diameter, root canal treatment alone led to complete healing in 73.8% of cases and partial healing in a further 9.5%, with follow-up of 2 to 10 years (Çalışkan, 2004). How retreatment works is described in a separate article; a review of studies reports healing in about 77% of cases for it.

What do apicoectomy and cyst enucleation involve?

Apicoectomy (root-end resection) is a surgical procedure in which the dentist exposes the bone over the root, removes the inflammatory tissue and the end of the root, and seals the canal with a filling placed from the root tip. This is how the 2023 ESE guideline describes it: curettage of the lesion, resection of the root tip, and preparation and filling of the end of the canal.

A review of 21 studies reports success in 94% of cases for endodontic microsurgery, performed under magnification, and in 59% with the traditional technique (Setzer et al., 2010). These are averages from studies, not a forecast for a particular tooth, because the result also depends on how tight the restoration is and on the condition of the root.

Cyst enucleation is the surgical removal of the whole cyst through the bone. The removed tissue is sent for histopathological examination, described below, and the dentist follows bone healing after the procedure on follow-up X-rays, just as after root canal treatment.

Why is a removed cyst examined under a microscope?

Histopathological examination is the only way to establish what a lesion in the bone really is. The vast majority of lesions at the roots are inflammatory lesions of dental origin: in the archive of a laboratory that assessed 2,238 such lesions, they made up 92.6%, and malignant tumours 0.2% of the total (Barbosa et al., 2026).

The remaining lesions are mainly cysts of other origins, more rarely benign tumours, which cannot be told apart on an X-ray but need different treatment or longer follow-up. That is why tissue removed during the procedure is usually sent for examination, and the result establishes the final diagnosis and the follow-up plan.

A radicular cyst is not the only cyst of the jaws. In a British archive of more than 7,000 odontogenic cysts, radicular cysts made up 52.3%, and the second most common were dentigerous cysts (18.1%), which surround the crown of an unerupted or partially erupted tooth. A cyst around an impacted wisdom tooth is one of the indications for its removal under the UK NICE guideline, and in children such cysts are increasingly treated in a way that allows the tooth to erupt.

How long is the lesion monitored after treatment?

Bone healing at the root tip takes months, so the result of treatment is assessed on follow-up X-rays, not by the pain going away. The ESE recommends an assessment after at least a year, and then, if needed, for up to 4 years; it regards a good result as no pain, swelling or fistula, a functioning tooth and a normal periodontal ligament space around the root on the X-ray.

A lesion that clearly shrinks on successive X-rays is also a sign of healing. When the picture remains unclear, the 2023 ESE guideline recommends extending the follow-up period.

How it works at DentalBlue

At DentalBlue in Białystok, intraoral X-rays, panoramic X-rays and CBCT scans are taken in the clinic’s own radiology unit, so a lesion at the root can be assessed on site. Root canal treatment and retreatment are carried out under a microscope. Surgical procedures such as apicoectomy or cyst enucleation are performed under local anaesthesia or, for qualified patients, under general anaesthesia. In the clinic’s price list, “Wyłuszczenie torbieli” (cyst enucleation) costs 1 000 zł, “Badanie histopatologiczne” (histopathological examination) 100 zł and “Tomografia komputerowa, szczęka lub żuchwa” (CBCT scan, upper or lower jaw) 300 zł. The dentist sets the final scope and cost after the examination, and prices may change.