KYT Dental Services
SDF · Applied Scenario

Why old crowns fail after 15 yearsMargins don’t “expire.” Systems drift.

Many crowns don’t fail because the crown material suddenly becomes bad. They fail because the tooth, margin, and force environment changes over time. Within the Structural Decision Framework (SDF), the long game is stability: how margins behave under repeated load, aging, and maintenance reality.

Back to aging patterns

Quick answer

Old crowns often fail because margins become stress zones over years: microleakage, cement fatigue, bite drift, and repeated overload. The crown may be fine — the interface and the system around it changes.

Aging crown that stays stable vs crown that becomes a failure site

The difference is usually force + margin biology + time — not whether the original work was ‘good.’

Stable
When crowns stay quiet for decades
Margins are clean, force is controlled, and maintenance stays consistent.
  • Margins stay clean and accessible
    Hygiene and recall keep inflammation low.
  • Contacts stay stable
    No new high spots or force migration patterns.
  • Supporting tooth remains sound
    No new cracks undermining the foundation.
  • Bite forces are managed
    Grinding is buffered instead of testing the interface nightly.
Failure site
When crowns start failing in patterns
The interface becomes the stress riser as aging and load drift.
  • Margins leak over time
    Microleakage invites recurrent decay and sensitivity.
  • Cement/interface fatigue
    Repeated load can loosen, flex, or open microscopic gaps.
  • Bite drift creates overload
    Contacts migrate and concentrate force on the crown.
  • Cracks form under the crown
    The tooth structure can fatigue even if the crown looks intact.
5–10 year outlook

Old crowns usually fail as a pattern: small signs first, then a bigger step.

Think in forces + foundation + follow-through.
Quiet ownership
Lower risk
Crown stays stable and uneventful with consistent maintenance.
  • Healthy gums at margins
  • Stable contacts
  • No repeat sensitivity
Interface warning
Moderate risk
Signs start: food packing, sensitivity, recurrent decay at the edge, or chips.
  • Early margin leakage
  • Localized inflammation
  • Small contact changes
Re-do event
Higher risk
A structural or decay event forces replacement — and sometimes escalates beyond a crown.
  • Deep decay under the crown
  • Crack progression
  • Possible root canal or extraction decision
What to do with an aging crown

The goal is not to replace crowns on a timer. The goal is to catch instability early.

Monitor intelligently and protect force
Often the goal
Track margins and contacts and control overload so the interface stays stable.
Best for
  • Crowns with stable margins
  • No symptoms
  • People committed to maintenance
Tradeoffs
  • Requires consistent recalls
  • Needs bite monitoring over time
Watch for
  • Ignoring new bite changes or gum inflammation at the edge
Replace when early instability appears
Situational
Re-do becomes safer when problems are early, not after deep decay or fracture.
Best for
  • Early margin leakage
  • Recurrent decay risk
  • Food packing or bite changes
Tradeoffs
  • Irreversible step
  • The tooth may have less reserve than the first time
Watch for
  • Waiting until it becomes a root canal or fracture event
Wait until it breaks
Not always right
Sometimes it works out. Often it narrows options and increases escalation risk.
Best for
  • Short-term constraints with risk accepted
Tradeoffs
  • Deep decay can happen quietly
  • Cracks can progress under the crown
Watch for
  • Sensitivity, gum swelling, food packing, or a ‘different’ bite feel
How SDF evaluates an old crown

A crown is a system: tooth + margin + force + time.

Structure
What is the remaining tooth foundation under the crown?
Force
Is load stable, or drifting into overload at the crown?
Timing
Is this early leakage you can correct — or late-stage damage control?
Long-term stability
If this repeats for 5–10 years, what fails first — margin, tooth, or force environment?
Related scenarios

Stay inside the same decision space. Compare one nearby scenario and one adjacent hub.

Back to Aging patterns
Why teeth crack with age
Aging patterns
Structural collapse patterns
Restoration thresholds
Crown vs root canal
Restoration thresholds
How redo dentistry compounds over decades
Failure patterns