10 Most Common Problems with Dental Crowns (And How to Fix Them)

1. Tooth Decay Under the Crown

• Why decay can still happen under a crown: You may have thought that decay couldn’t happen under a crown. Unfortunately, while the crown itself cannot get tooth decay, the area between the crown and the tooth is still vulnerable. Some patients believe they no longer need to watch their diet or brush properly after getting crowns, but that is not the case. Any area of tooth enamel or dentine is always susceptible to decay. We recommend excellent oral hygiene and the application of fluoride varnish every six months by a hygienist to the joint between the tooth and the crown for the best results.
• Spotting the signs: Unless you have a dental light and mirror, you are unlikely to see signs yourself. Decay often starts in the least visible places, such as between the teeth, and is usually only visible on X-rays or during a careful dental examination. Sometimes, early signs of demineralisation can be spotted before actual decay occurs. At this stage, the process can be stopped by fluoride treatment and good oral hygiene, which is why regular check-ups are essential.
• How dentists treat and prevent it: If caught early, remineralisation is possible. When decay has progressed to a cavity, the outcome depends on how deep it has gone. Often, the underlying dentine has been hollowed out, and the long-term prognosis of the crown is very poor. If a small cavity is present, it may be possible to place a small filling, though this is not an optimal solution.

2. Sensitivity to Hot, Cold, or Pressure

• What Causes Post-Crown Sensitivity?: The process of crown preparation involves drilling away the outer layer of enamel. This usually means the protective enamel is completely removed, and dentine is exposed. Dentine is porous, and these tiny tubules allow air, cold, or pressure to reach the nerve in the tooth.
• Typical Recovery Timeline: In most cases, the tooth settles within a week or two after crown preparation and fitting. A good seal from the new crown typically prevents nerve irritation. Approximately 10% of crowned teeth may require root canal treatment within 10 years. This may result from pain or infection. Be cautious of unethical overseas clinics that carry out root canal treatment on all teeth requiring crowns – this is absolutely unnecessary. The longest lifespan for crowns occurs when the underlying tooth remains healthy.
• Remedies: Short-term remedies include using desensitising toothpaste, such as Sensodyne. Long-term, dental sealants can be applied to exposed dentine. Sometimes bite adjustments are required, as an uneven bite can also irritate the nerve.

3. Ill-Fitting or Misaligned Crowns

• How poor fit affects bite and comfort: The fit of a crown needs to be exceptionally precise for long-term success. Oral bacteria are much smaller than even the best-fitting crown margin. A margin of 20 microns is considered excellent, but bacteria are as small as 0.2 microns. Fortunately, good adhesives can block bacteria if the margin is well sealed. If the gap is larger, bacteria can lead to decay and loosening of the crown. If the biting surface is not properly adjusted, the bite may be heavy and uncomfortable – even a few microns can make a difference. A review appointment a few weeks after fitting is essential.
• Risks of food traps: A poorly fitted crown can cause food traps, which can irritate gums and increase the risk of decay.
• When to seek a crown adjustment: If you experience sensitivity after the first couple of weeks, an uncomfortable bite, or food traps, you should see your dentist.

4. Loose or Dislodged Crowns

• Causes: Crowns are more likely to loosen if there is little natural tooth structure left. If the dentine core is intact, a crown will rarely come loose. Teeth broken near the gum line with posts have a worse prognosis. Poorly fitting crowns, faulty cement, or decay are also common causes.
• Do-it-yourself care before visiting the dentist: If you cannot see a dentist quickly, you can use temporary crown cement from a pharmacy, or a product such as Fixodent, to hold the crown in place. However, you should see a dentist urgently.
• Professional re-cementing or replacement: If a crown comes off early, it may be due to the cement, and stronger adhesives can often fix the problem. If the crown comes off repeatedly, a replacement may be necessary. A loose crown leaves the tooth unprotected and carries the risk of being swallowed or inhaled.

5. Chipping, Cracks & Fractures

• Why do porcelain crowns chip: Porcelain crowns are attractive but can be fragile. Just like fine bone china, they look beautiful but lack the strength of metal. Modern materials such as E-max and zirconia combine aesthetics with strength, while older porcelains are more prone to fracture. A lifespan of 10+ years is considered good.
• Recognising minor vs major damage: If the chip is small and limited to the outer surface without cosmetic impact, it may be polished or left alone. If the fracture extends deeper towards the tooth, replacement is usually advised.
• Repair options: For a small chip, composite bonding with silane treatment is recommended, although it is not as strong as the original porcelain.
• Major damage: full crown replacement for the most secure, long-lasting result.

6. Nerve Irritation or Pulp Issues

• Causes of lingering pain: In rare cases, the nerve can be damaged during crown preparation or fitting. Around 10% of crowned teeth may require root canal treatment within 10 years.
• When to suspect nerve involvement: If pain is lingering, especially sensitivity to heat lasting more than a few seconds, consult your dentist.
• Treatments: Root canal treatment may be required. This involves removing the nerve and sealing the tooth. In some cases, the crown may need replacement afterwards.

7. Gum Irritation, Recession & Grey Lines

• How crowns affect gums: Thin gum tissue, which is common in Irish patients, can be more prone to irritation and recession. Even the smoothest crown margin can irritate gums microscopically. Modern zirconia crowns are much kinder to gum tissue, giving better long-term results.
• Aesthetic vs health implications: Slight gum recession may cause sensitivity and cosmetic concerns, especially at the front of the mouth.

Fixes

• Gentle brushing if over-brushing is the cause.
• Bite adjustment if excessive pressure is contributing.
• Use of pink porcelain or composite to mask recession.
• Gum grafting or growth procedures are used in severe cases.

8. Allergic Reactions to Crown Materials

• Metal reactions: Reactions are rare today but were more common with older crowns containing metals such as nickel or silver.
• Symptoms: Redness, rash, or gum irritation.
• Solution: Switch to metal-free crowns such as zirconia or porcelain.

9. Implant or Abutment Failures

• Crowns on implants: unique risks: Unlike natural teeth, implants lack a shock absorber (periodontal ligament). This means forces on implants can be much higher, increasing the risk of fractures, loosening, or overload.
• Recognising loosening: A strange taste, click, or altered bite can all indicate a loose implant crown.
• Treatment: The screw inside the implant can sometimes be tightened. Bite forces should also be reviewed, especially if teeth have been lost elsewhere in the mouth.

10. Problems with Temporary Crowns

• Temporary stage: Temporary crowns are bonded with soft cement designed to last only a few weeks. Avoid sticky or hard foods.
• When to call your dentist: If it comes off or causes pain, see your dentist. If this is not possible, use temporary cement from a pharmacy – do not leave it out.
• Tips to protect your temporary crown: Temporary crowns can feel secure, but they are vulnerable to decay at the margins. Always return for your permanent crown as directed.

Final Thoughts

Fortunately, these problems are not common, especially when crowns are made with high-quality materials and fitted by a skilled dentist. When deciding where to have dental crowns placed, always choose a trusted dentist to ensure the best long-term outcome for your smile.

If you’re experiencing problems with a dental crown or if you’d like advice on your options, our team at Seapoint Clinic is here to help. Call us today on (01) 284 2570 or book an appointment.