Crown Loose or Fallen Out? Six Failure Warning Signs and How to Check

A crown that feels loose, comes off entirely, or develops a dark line at the edge — these are the common signals. The most dangerous one produces no sensation at all: decay developing underneath the crown, invisible from outside. A well-made, well-maintained crown commonly serves ten years or more, and bridges similarly, but the spread around that figure is enormous. What matters is not the number of years but marginal fit, remaining tooth structure, bite distribution and cleaning habits.

How long should crowns and bridges last — and what does the lifespan actually depend on?

Rather than memorising a number, understand the four factors that genuinely decide longevity:

• Marginal fit — the more intimately the crown edge seals against the tooth, the harder it is for bacteria and acids to creep in. This is the core marker of technical quality
• Remaining tooth structure — the more healthy tooth left beneath, the stronger the foundation; a root-treated tooth with little structure left is inherently more fragile
• Bite distribution — uneven loading, or a night-grinding habit, chronically overloads both the material and the cement layer
• Cleaning access — especially under bridge spans and along crown margins; the spot the brush cannot reach is where failure starts

The same crown can therefore last several times longer in one mouth than another. There is no standard replacement interval: replace when there is a problem, review regularly when there is not.

Why do crowns fail? The six main failure modes

• Marginal leakage and decay beneath the crown — the most common and the most insidious. Once the marginal seal is breached, decay develops under the crown, invisible from outside, often discovered only through pain or an X-ray
• Cement failure — the cement ages and dissolves, the crown gradually loosens or comes off entirely. A dislodged crown does not necessarily mean the tooth is ruined, but it must be dealt with promptly (see below)
• Material fracture — porcelain chipping or an all-ceramic crown cracking, related to bite forces and material choice
• Endodontic complication — the nerve beneath the crown becomes inflamed or dies; this can present as sudden severe pain, or as no symptoms at all until an abscess appears
• Periodontal breakdown of the supporting tooth — gum inflammation and bone loss loosen the tooth itself, and no crown survives a failing foundation
• Bridge abutment overload — a bridge transfers the missing tooth's biting load onto the neighbouring support teeth, which permanently carry more than their share

The specialist video below demonstrates each of these failure modes in real cases — the easiest way to compare them against your own situation.

Which warning signs can you notice yourself — and which are urgent?

See a dentist within days:

• The crown or bridge feels loose, or moves when you bite
• The crown comes off entirely — keep it safe and take it with you; do not re-glue it yourself with household adhesive (it contaminates the fitting surface, is very hard to remove completely, and can write the crown off). The exposed tooth is unprotected, and a long delay can leave it decayed or too sensitive to re-cement
• Spontaneous severe pain in the crowned tooth, or pain that wakes you at night — possible nerve involvement
• Gum swelling, pus, or a "gum boil" near the tooth

Book a check-up, without panic: floss that persistently frays or catches at the crown margin; a grey or dark line appearing at the edge; new cold sensitivity in that tooth; odour or taste localised to a bridge; gum recession exposing the margin. These are typically early signals of marginal or periodontal trouble — the earlier they are addressed, the better the odds of saving the existing restoration.

Why is a failing bridge more consequential than a failing single crown?

When a single crown fails, the damage is usually confined to that one tooth. Bridge failure is a chain reaction: the bridge stands on its two abutment teeth, and if one abutment decays or breaks down periodontally, the entire bridge is lost with it — and the failed abutment is often too damaged to keep, turning "one missing tooth" into two or three, and escalating the complexity of whatever comes next. Bridge wearers should therefore hold themselves to a higher standard of reviews and cleaning (especially threading floss under the span) than single-crown wearers. For the trade-offs between replacement options, see our implant vs bridge vs denture guide.

What separates a crown that lasts from one that doesn't?

Five factors — the first three are locked in the moment the crown is made:

• Margin placement and fit — the more precise the margin, the lower the long-term leakage risk
• Material selection — matched to position and bite force: back teeth prioritise strength, front teeth appearance; no single material is best in every situation
• Remaining structure and core build-up — where tooth structure is short, whether a proper core was built directly determines the foundation
• Occlusal adjustment — whether the biting contacts were balanced when fitted; for grinders, a night guard measurably extends restoration life — for the broader wear-and-bite-collapse picture, see our bite collapse and rebuilding guide
• The patient's cleaning and reviews — daily attention to the margins, plus periodic checks and X-rays, is the only way early leakage gets caught. The decision logic for when a restoration needs replacing follows the same principles as our guide on when fillings need replacing

If the same tooth keeps losing its crown, what should a second opinion examine?

A crown that fails repeatedly on the same tooth is rarely bad luck; there is usually an unaddressed underlying cause. A quality second opinion should work through, item by item: whether enough tooth structure remains to support another crown (or whether the honest conversation is now about other options); the state of the nerve (see our guide on root canal failure and retreatment); whether the bite is overloading the tooth or grinding has gone unmanaged; whether the margin design and material were appropriate; and the periodontal condition of the supporting tooth. If someone proposes "just make another one" without an X-ray or a bite examination, that second opinion itself deserves a third.

Frequently asked questions

My crown is ten years old and trouble-free — should it be replaced anyway?

No — age alone is not a reason. A crown with no leakage, no decay and a sound bite can stay; what matters is regular reviews and X-ray monitoring of the margins. It is the young-but-symptomatic crown that needs early attention, not the old-but-healthy one.

My crown came off — can it just be glued back?

Often yes, re-cemented promptly by a dentist — provided the tooth underneath is not decayed and the crown is undistorted. Never use household glue: it contaminates the fitting surface, many adhesives cannot be fully removed, and a salvageable crown can be ruined.

How can there be decay under my crown without me feeling anything?

Because it develops beneath the crown where it cannot be seen — and if the tooth is root-treated and has no nerve, it cannot hurt either. This is precisely what periodic X-ray checks exist to catch.

There's a dark line at my crown's edge — is that decay?

Not necessarily — it may be metal show-through or stained cement — but it can also be marginal decay. The eye cannot tell; an examination, usually with an X-ray, settles it.

Is sensitivity in a crowned tooth normal?

Mild sensitivity shortly after fitting can be an adaptation period. Sensitivity that appears anew after years of comfort, or steadily worsens, may signal leakage or nerve trouble and warrants a check.

I grind at night — will my crowns wear out faster?

Grinding chronically overloads both the crown and its cement layer, and chipping and debonding risks are clearly higher. A night guard is the most direct protection and is worth discussing with your dentist.

How do I clean under a bridge?

The underside of the span is unreachable with a brush: use a floss threader to pass floss beneath it, supplemented by interdental brushes or a water flosser. Neglected bridge undersides are the most common starting point for abutment decay.

How often should crowned teeth be checked?

Routine review intervals generally suffice, adjusted by your dentist to your risk profile (grinding, gum condition, number of crowns); people with bridges or multiple crowns typically need closer monitoring.