What is an infection under a crown?
An infection under a crown is an infection or inflammation in a crowned tooth: in the pulp, around the root tip or in the surrounding gums. The pain of an infection under a crown is different from the normal sensitivity after a new crown: it is typically a deep ache, with swelling and sometimes fever.
This kind of infection can develop years after the crown was placed and is not necessarily related to the quality of the original work. Even well-made dental crowns can develop problems over time. Diagnosis is based on a clinical examination and X-rays, and when indicated, 3D imaging (CBCT), taken at the clinic, to find the source and extent of the infection and tailor the treatment.
Symptoms of an infection under a crown
- Pain when chewing or when the tooth is tapped
- Sensitivity that does not go away
- Swelling of the gum around the tooth
- Pus or a bad taste in the mouth
- Throbbing pain
Pain, swelling or sensitivity call for a dental examination; fever or spreading swelling need urgent care.
Infection under a crown: the causes
Inflammation under a crown can have several causes, the most common being bacteria entering through a small gap between the crown and the tooth. Even when a crown was well fitted, the cement can wash out over time, or gum recession can expose the crown margins and let bacteria in.
01
Incomplete root canal treatment
Another cause is incomplete root canal treatment. When a root canal was done before the crown but not every canal was treated properly, or bacteria remained inside a canal, the infection can flare up again, even years later. This usually shows up as sudden, sharp pain, sometimes with a fistula (a small draining bump) on the gum.
02
Trauma or overload
Trauma or excessive forces can crack the tooth under the crown. Root-canal-treated teeth in particular are more brittle and can crack under heavy chewing forces or teeth grinding (bruxism). These cracks give bacteria an easy way in.
03
Poor crown fit
The fit of the crown matters just as much. A poorly fitting crown leaves gaps where food and plaque collect, which eventually leads to recurrent decay and infection. This is why a precise fit is important, whether the crown is made digitally (CAD/CAM) or by hand in a dental lab.
What to do about an infection under a crown
If a tooth with a crown hurts, swells or is sensitive, contact an emergency dentist or your own dentist soon. Delaying treatment can make things worse and let the infection spread to nearby tissues, including the bone around the tooth. For pain relief until the appointment, ask your dentist or pharmacist which medication and dose are right for you; this is only a temporary measure. Fever, swelling that spreads toward the eye or neck, or difficulty swallowing or breathing require going to the emergency room immediately. In rare cases, an untreated dental infection can spread and cause sepsis, an extreme response of the body to an infection and a medical emergency.
At the clinic, the visit starts with a full assessment, including a clinical examination and X-rays, to identify the source of the problem. In some cases, the crown has to be removed to treat the infection underneath. Often the existing crown can be reused after treatment; in other cases a new crown is made that fits better and helps prevent similar problems.
Many patients worry about the treatment, especially for a front tooth that affects their smile. Tooth-colored temporary crowns can be used during treatment to keep a natural appearance.
Treating infection under a crown
Treatment depends on the source and severity of the problem. In many cases, when bacteria have entered through a crack or gap, treatment involves removing the crown, cleaning the tooth and removing the inflamed tissue. Root canal treatment or root canal retreatment is sometimes needed when the infection comes from the root canals; prescription antibiotics are considered only when there are general signs, such as fever or feeling unwell, or when the infection is spreading.
After the infection is treated, the tooth is restored with the existing crown or a new one, for example a metal-free zirconia or E.max crown.
Examination, treatment plan and price quote
detailed and personalized
During the consultation, Dr Haim Aseriel examines your teeth, explains all the options and gives you a transparent price quote, with no obligation. The clinic is at 12 HaTnufa Street, Jerusalem.
Do you need antibiotics for a tooth infection under a crown?
According to American Dental Association (ADA) guidelines, healthy adults do not need antibiotics in most cases of pulp inflammation or a localized abscess: the main treatment is dental treatment, such as a root canal, drainage or extraction. Antibiotics are considered when there are general signs such as fever or feeling unwell, or when the risk of the infection spreading is high, and they are given by prescription only, at the dentist's or doctor's discretion (Lockhart et al., Journal of the American Dental Association, 2019). Patients with a weakened immune system need an individual medical assessment.
Antibiotics are not a complete solution for a tooth infection; at most, they are one part of a treatment that must address the underlying cause.
When mouth pain comes from an infection in a crowned tooth, a dentist needs to assess it carefully before any antibiotic is prescribed, because not every dental infection requires medication.
Can an infection under a crown affect the gums?
Yes. An infection in a crowned tooth can significantly affect the surrounding gum tissue. Bacteria from an infected tooth can spread to the gums through the root canal or through the space between the crown and the tooth, especially if the crown does not fit well.
In many cases, the first signs of infection in a crowned tooth appear in the gums: redness, swelling, bleeding when brushing, and sometimes a deep periodontal pocket.
These symptoms are the immune system's response to bacteria coming from the infected tooth or from a poor seal between the crown and the tooth. Gum infection next to an inflamed crowned tooth can speed up the loss of supporting bone, which threatens the long-term stability of the tooth. This is why treatment should address both the source of infection in the tooth and the associated gum inflammation.
Gum inflammation around a crown: what to know
Gum inflammation around a crown (gingivitis) is inflammation of the gum tissue around the crown margins, which needs an accurate diagnosis and early care to prevent long-term damage. The term "peri-implant mucositis" describes inflammation around a dental implant, not around a crown on a natural tooth.
Gum inflammation around a crown is caused mainly by bacterial biofilm building up between the crown margin and the gumline.
The main contributing factors are a poor marginal fit, an unpolished crown surface, irritating materials in the crown and insufficient oral hygiene. A particularly common problem is crown margin impingement, when the edge of the crown sits too deep in the gum's biological space and disrupts the balance of the tissues.
It is essential to tell apart inflammation caused by a faulty crown from infection coming from the tooth's root canal system. Sometimes both are present and feed each other in a cycle of chronic inflammation. A thorough clinical examination, including a check for marginal leakage and pulp vitality tests, may be needed to understand the source of the problem.
How to prevent a recurring infection under a crown
Preventing a recurring infection in a crowned tooth starts with thorough treatment of the original cause. After that, prevention means a personalized oral hygiene routine, regular check-ups and ongoing monitoring of gum health. When a crown is faulty, replacing it with a better-fitting crown may be necessary to prevent recurrences.
Cleaning techniques designed for crowned areas are especially important, including special floss, correctly sized interdental brushes and antiseptic mouth rinses. A water flosser may also help remove plaque around crown margins. For patients who grind their teeth, a night guard reduces the load on the crowns.
Early detection of problems with existing crowns is key. Signs such as increased sensitivity near the gums, changes in gum color or discomfort when chewing may point to a developing problem. Regular check-ups, with X-rays when needed to spot changes in the bone, are an essential preventive measure.
After root canal retreatment, is the infection gone for good?
For many infections under a crown, root canal retreatment is an effective long-term solution. It deals with the source of the infection: bacteria that have entered the root canals. During retreatment, the existing crown is usually removed or accessed through, the canals are cleaned again, thoroughly disinfected and sealed. It is a demanding procedure that requires a high level of skill.
Treatment success
No one can guarantee a permanent solution in every case. Many factors affect success, including the structure of the tooth, the extent of the damage, the presence of cracks and the quality of the previous treatment. According to a systematic review, the pooled success rate of root canal retreatment is about 77%, and a large lesion around the root tip or a poor restoration over the tooth lowers the chances (Ng et al., International Endodontic Journal, 2008). Careful cleaning and disinfection of the canals and a good seal over the tooth improve the chances of success.
Regular follow-up
After root canal retreatment, regular follow-up is important. Check-ups, as often as your dentist advises based on your oral health and individual risk, make it possible to detect and treat problems early. Poor oral hygiene, an unbalanced bite or trauma can affect the treated tooth even years later, so patients receive detailed guidance on keeping the results.
Alternative solutions
When root canal retreatment does not succeed or is not possible, alternatives such as root-end surgery (apicoectomy) or extracting the tooth and replacing it with a dental implant are considered. The decision depends on the condition of the tooth, the bone and surrounding tissues, and the patient's general health. The aim is always to keep the natural tooth when possible, but sometimes removing and replacing it is the right way to restore quality of life and oral health.
An infection under a crown needs prompt professional attention. At Dr Haim Aseriel's clinic in Jerusalem, infections in crowned teeth are diagnosed and treated, from root canal retreatment to full mouth rehabilitation. If a crowned tooth hurts, swells or feels uncomfortable, contact the clinic soon.
The approach is based on keeping natural teeth whenever possible. After the diagnosis, you receive a clear explanation in English of the proposed treatment, its pros, cons and alternatives, and a detailed written estimate with no obligation (see also root canal cost). The clinic is at 12 HaTnufa Street in Talpiot, south Jerusalem.
Infection under a crown: frequently asked questions
If a tooth with a crown hurts, swells or is sensitive, see a dentist soon so the source of the infection can be found and treated. For pain relief until the appointment, ask your dentist or pharmacist which medication and dose are right for you. Fever, swelling that spreads toward the eye or neck, or difficulty swallowing or breathing require going to the emergency room immediately.
Sometimes, yes. According to the American Association of Endodontists (AAE), root canal treatment is sometimes performed through an opening in the existing crown when the crown is in good condition, and the opening is then sealed. Before sealing, the dentist checks that there is no decay; if there is decay under the crown, the preferred option is to remove the crown and the decay, and the tooth is then restored with a new crown.
An infection under a crown is most often caused by bacteria entering through a small gap between the crown and the tooth. Other causes are a root canal treatment that did not clean every canal, and cracks in the tooth under the crown caused by trauma or overload, for example from teeth grinding.
In most cases of infection under a crown, the main treatment is dental treatment, such as root canal treatment, root canal retreatment, drainage or extraction, not antibiotics. According to American Dental Association (ADA) guidelines, antibiotics are considered when there are general signs such as fever or feeling unwell, and they are given by prescription only, at the dentist's or doctor's discretion.
Root canal retreatment is often an effective long-term solution for an infection under a crown, but success is not guaranteed. According to a systematic review, the pooled success rate of root canal retreatment is about 77%, and it depends in part on the size of the lesion around the root tip and on the quality of the restoration over the tooth. When retreatment does not succeed, root-end surgery (apicoectomy) or extraction is considered.
Sources
- Lockhart PB et al., Journal of the American Dental Association, 2019 – Link to study
- American Dental Association, Antibiotics for Dental Pain and Swelling Guideline, 2019 – Link to source
- Carrasco-Labra A et al., Journal of the American Dental Association, 2024 – Link to study
- Ng YL et al., International Endodontic Journal, 2008 – Link to study
- National Institute of General Medical Sciences (NIH), Sepsis – Link to source
- Fee PA et al., Cochrane Database of Systematic Reviews, 2020 – Link to study
- American Association of Endodontists, Endodontics: Colleagues for Excellence, Restoration of Endodontically Treated Teeth, 2004 – Link to source
