When to Replace a Crown: Fixed Lifespan, Dark Lines at the Gum and Whether It Must Be Removed to Check

My crown is 20 to 30 years old and painless. Do I still need to replace it?

Crowns have no fixed, uniform replacement lifespan [1]. They are commonly used for a long time when there are no symptoms, the edge (margin) between crown and tooth still fits well and there is no secondary decay inside. On the other hand, replacement is considered if pain, decay underneath, margin leakage or a fracture is found [1]. Whether to replace a crown is judged from the condition seen at regular checkups, not from its age alone [1].

When DentStat analyzed 800 patient comments on replacement timing, two themes appeared repeatedly: suspicion from people told to replace crowns they had used without trouble for 20 to 40 years, and regret from people who replaced symptom-free restorations and then struggled for a long time [4]. At the same time, there were opposite accounts of putting off replacement until the problem underneath progressed to extraction and an implant, showing that neither keeping nor replacing is the right answer in every case [4].

My gums have receded and the metal looks dark. Is it decayed?

Looking dark does not necessarily mean decay [1]. When gums recede, the metal edge of a crown can be exposed and look like a dark line, so this exposure must be told apart from active decay [1]. Staining and exposed metal are mostly a cosmetic issue, while active decay that has reached the dentin needs treatment, so they are distinguished by probing and X-rays [2]. Gum recession itself is a separate issue related to aging, brushing habits and gum health, so when a dark line appears, checking the cause in the gums is sometimes considered before replacing the crown [1]. If no symptoms or decay are found, looking dark alone is not a reason to replace it urgently [1].

I was told the inside cannot be seen on X-rays and it has to be removed to check. Should a sound crown be removed?

It is true that a restoration can hide part of the inside on X-rays, but if there are no symptoms and checkup findings are good, immediate removal is not the rule [1]. Because the tooth under a crown cannot be seen directly, regular checkups and follow-up X-rays are used to look for signs of a margin gap or decay underneath, and removal is considered when a suspicion is confirmed [1][2]. The comment analysis included accounts of crowns removed for checking that turned out fine, leaving only the cost of a remake [4]. Crown remakes are mostly non-covered (not paid by Korea’s National Health Insurance), so costs vary by clinic, and the extra tooth removal involved is also part of the decision [3].

After replacement it feels worse. Why?

Adjusting to a new restoration, the bite and additional tooth removal can cause temporary discomfort [1]. Replacement is an irreversible process of removing the old crown and reshaping the tooth, which can leave the remaining tooth thinner, and the comments included many cases of regret where a sound restoration was replaced and discomfort lasted a long time [4]. Conversely, there were also cases where secondary decay progressing through a margin gap while replacement was delayed led to extraction, so both keeping and replacing need a basis [4]. For this reason, one approach is to confirm the reasons (symptoms and test findings) before replacement and compare another dentist’s opinion if views differ [1].

Common misconceptions and the facts

• Some believe “crowns must be replaced after 10 years,” but there is no fixed lifespan, and crowns are commonly kept when there are no symptoms and the fit is good [1].
• Some think “a dark line means it is all decayed,” but it may be metal exposed by gum recession, so it needs to be told apart from decay [1].
• Some also think “since you can’t know if it’s decaying inside, replace it in advance,” but decay underneath is judged after checking with regular X-rays [2].

Crown materials, links to root canal treatment and other topics are covered in the crown and inlay guide, and regional clinic data in Find a dentist.