Common PFM Crown Problems — And How to Avoid Them
PFM crowns are reliable, but they have known weak points. Here's what can go wrong and how the right lab work prevents it.
PFM is proven — but not perfect
Porcelain-fused-to-metal crowns have decades of clinical success behind them and remain a dependable, economical choice. But the very thing that gives them strength — a metal substructure under porcelain — is also the source of their characteristic problems. Knowing them helps you prescribe and place PFM well.
The common problems
- Grey gumline margin
The metal can show as a dark line at the margin, especially if the gingiva recedes — most visible on anterior teeth.
- Porcelain chipping
The porcelain layered over metal can chip under heavy load or in bruxers.
- Gum recession & shadowing
Thin biotype gums can show a greyish shadow from the underlying metal.
- Opacity
PFM can look slightly more opaque than all-ceramic in highly visible positions.
Why these happen
Most PFM problems trace back to the metal substructure and how the porcelain is built over it. A poorly finished metal margin, an uneven porcelain thickness, or the wrong case selection (a PFM on a highly visible anterior with a thin gum biotype) make these issues more likely.
How good lab work prevents them
- Porcelain-shoulder margins
A porcelain margin instead of exposed metal minimises any grey line.
- Controlled metal thickness
Even copings allow consistent porcelain support and reduce chipping.
- Right case selection
Choosing zirconia for high-aesthetic anterior cases avoids the problem entirely.
- Careful firing & QC
Proper firing and margin checks under magnification catch issues before delivery.
When to choose zirconia instead
If the tooth is highly visible, the gum biotype is thin, or the patient is a heavy grinder, metal-free zirconia sidesteps the grey-margin and chipping issues altogether. For long-span bridges and budget posterior work, a well-made PFM remains an excellent choice. We'll honestly recommend the better option per case.
Frequently asked questions
Why does my PFM crown have a dark line at the gum?+
That's the metal substructure showing at the margin, often as the gum recedes. A porcelain-shoulder margin reduces it, and for highly visible teeth a metal-free zirconia crown avoids it completely.
Can a chipped PFM crown be repaired?+
Minor chips can sometimes be polished or repaired chairside, but significant porcelain fracture usually means a remake. Good metal design and case selection reduce the risk.
Should I choose PFM or zirconia to avoid these problems?+
For highly visible anterior teeth or heavy grinders, zirconia avoids grey margins and chipping. For long-span bridges or budget posterior cases, a well-made PFM is still a strong, economical choice.