Both are fixed caps that cover a damaged tooth. A zirconia crown is made entirely of a strong, tooth-coloured ceramic with no metal. A porcelain-fused-to-metal (PFM) crown has a metal core covered with porcelain. Zirconia usually looks more natural at the gum line and avoids metal, while PFM has the longer track record.
Two kinds of crown, one purpose
A crown is a custom-made cap that covers the whole visible part of a tooth after a large cavity, a crack or root canal treatment. The difference lies in what they are made of, and that affects appearance, strength, how much of the tooth is reshaped and how the crown behaves over the years. If you are new to crowns, our guide to the different types of dental crowns and when you need one gives the full background.
Zirconia crowns
Zirconia (zirconium dioxide) is a white, metal-free ceramic known for its very high strength. A crown can be milled from a single solid block, called monolithic zirconia, or zirconia can serve as a core with a thin layer of porcelain on top for a more lifelike surface.
Porcelain-fused-to-metal (PFM) crowns
A PFM crown has a thin metal shell, called a substructure, that fits over the prepared tooth. Layers of porcelain are then baked onto it to create a tooth-coloured surface. The metal provides the strength and the porcelain provides the appearance. PFM crowns have been used for many decades and remain a well-documented option.
The main differences at a glance
The table summarises the general differences; results always depend on the tooth, the bite and the laboratory work.
| Feature | Zirconia | Porcelain-fused-to-metal |
|---|---|---|
| Material | Ceramic only, no metal | Metal core covered with porcelain |
| Gum line | Tooth-coloured throughout | A grey edge may show if the gum recedes |
| Strength | Very high, especially monolithic zirconia | High, but the porcelain layer can chip |
| Tooth reshaping | Often less, with monolithic zirconia | Usually a little more |
| Metal sensitivity | Not relevant | Rarely, a reaction to certain alloys |
| Track record | More recent, now widely used | Used for many decades |
Appearance: what you see when you smile
In a PFM crown, the metal has to be hidden under an opaque layer, so the crown can look slightly flatter than a natural tooth, which lets some light pass through it. The edge of the metal also sits close to the gum. If the gum recedes over the years, a thin grey line can become visible at the margin, which matters most on front teeth.
Zirconia has no metal to hide, so there is no grey edge. Early zirconia was quite opaque, but newer, more translucent types and layered zirconia look considerably more natural. For the most visible front teeth, some dentists prefer a glass-ceramic such as E.max; our article on choosing zirconia or E.max crowns for front and back teeth explains that choice.
Strength, chipping and your other teeth
Both materials are strong enough for chewing on back teeth. The weak point of a PFM crown is its porcelain layer: it can chip, and sometimes a chip exposes the metal underneath. The Cleveland Clinic overview of dental crowns mentions this risk and describes zirconia crowns as very durable and able to withstand heavier forces than other ceramic crowns.
Monolithic zirconia is particularly resistant to chipping, which is why it is often chosen for molars and for people who clench or grind their teeth (bruxism). When it is well polished, it is also gentle on the opposing teeth. Layered zirconia, like PFM, has a porcelain surface that can chip, so the design is matched to your bite.
- Heavy grinding or a strong bite: monolithic zirconia is often preferred.
- Little space between the upper and lower teeth: zirconia can usually be made thinner.
- Neighbouring PFM crowns or an existing PFM bridge: matching the material can sometimes make sense.
How much of the tooth is reshaped?
To make room for any crown, the dentist removes a thin layer from the outside of the tooth. A PFM crown needs space for both the metal and the porcelain, so it usually requires a little more reduction. Monolithic zirconia can often be made thinner while staying strong, which helps preserve healthy tooth structure.
The metal in a PFM crown is an alloy, based on precious or non-precious metals. A true allergy is uncommon, but if you know you react to a metal such as nickel, tell your dentist so that a metal-free option can be considered.
The procedure, comfort and aftercare
The treatment is the same for both materials and usually takes two visits, although timings vary:
- Examination and X-ray to check the root, the nerve and the surrounding bone.
- Preparation under local anaesthesia, which numbs the area so you feel pressure rather than pain. This visit often takes about an hour.
- An impression, meaning a precise mould of the tooth, followed by a temporary crown while the laboratory makes the final one, usually over one to two weeks.
- Fitting: the dentist checks the fit, the bite and the colour before cementing the crown in place.
Mild sensitivity to hot and cold, or a slightly tender gum, is common for a few days. Look after a crown as you would a natural tooth: brush twice a day, clean between the teeth with floss or interdental brushes, and keep your regular check-ups, because the tooth underneath can still decay at the edge of the crown.
How long they last and what affects the cost
With good care, both zirconia and PFM crowns commonly last many years, and many last well beyond ten. Oral hygiene, grinding habits, the position of the tooth and the precision of the fit matter as much as the material itself. Our article on how long crowns and bridges last looks at these factors in more detail.
There is no single price, because the cost depends on the material, the type of zirconia or alloy, the position of the tooth, whether a build-up or root canal treatment is needed first, and how many teeth are involved. A consultation is the clearest way to receive a personalised plan.
Choosing your crown at Ajam Dental Clinic in Tripoli
At Ajam Dental Clinic in Tripoli, crowns are part of our prosthodontic and aesthetic work. Dr. Abdel Rahman Ajam holds a DDS and an MSc in Aesthetic and Prosthetic Dentistry, and his focus includes crowns, bridges and smile design. We offer zirconia crowns and ceramic crowns, including E.max, and we explain the advantages and limits of each option for your particular tooth before any treatment begins. Patients come to our clinic on Fouad Chehab Boulevard from across Tripoli — Al-Qobbeh, Bab al-Tabbaneh, Jabal Mohsen and Dam wa Farez — as well as from Beddawi, Minieh and the rest of North Lebanon.
You can learn more about our crowns, bridges and other prosthodontic treatments. To have a tooth assessed, contact us by WhatsApp or phone to book a consultation.
Frequently asked questions
Can I replace my old PFM crown with a zirconia crown?
Yes, in many cases. People often ask for this when a grey line has appeared at the gum or the porcelain has chipped. The old crown is carefully cut off, the tooth underneath is checked for decay and for the condition of its nerve or root filling, and a new crown is then made. Removing a crown carries a small risk for the tooth, so replacement is usually advised when there is a real reason, such as decay, a poor fit, a fracture or a visible cosmetic problem, rather than as a routine step.
Why is there a dark line around my crown near the gum?
With a PFM crown, a dark or grey line usually comes from the metal edge of the crown becoming visible, often because the gum has receded slightly over time. It is not necessarily a sign of a problem, but it should be examined, because a dark margin can also be caused by decay at the edge of the crown or by a darkened tooth underneath. Your dentist will check the area, sometimes with an X-ray, and explain whether monitoring, gum care or replacing the crown makes the most sense for you.
Can a zirconia or PFM crown be whitened?
No. Whitening products lighten natural enamel but do not change the colour of zirconia or porcelain. If you are thinking about whitening, it is usually best to whiten your natural teeth first, wait about two weeks for the shade to settle, and then have the crown made to match the new colour. If you already have a crown and whiten your other teeth later, the crown may look darker than its neighbours and might eventually need to be replaced to restore a good match.
Which crown is better for a molar after root canal treatment?
Both can work well on a back tooth that has had root canal treatment. Monolithic zirconia is frequently chosen for molars because it is very strong, resists chipping and often needs less reshaping, which helps preserve the remaining tooth. A PFM crown remains a reasonable option, especially when it needs to match an existing PFM bridge next to it. The decision depends on how much tooth is left, the space available, your bite and whether you grind your teeth, so the dentist discusses the options after examining the tooth.
Can a chipped crown be repaired?
Sometimes. A very small chip in the porcelain of a PFM crown or a layered zirconia crown can often be smoothed and polished, and in some cases repaired with tooth-coloured composite resin. Such repairs are practical but usually not permanent. If the chip is large, exposes metal, leaves a sharp edge or affects your bite, replacing the crown is usually more reliable. Until it has been examined, avoid chewing hard food on that side and keep the area clean to protect the tooth underneath.
Is zirconia the same as porcelain?
Not exactly. Porcelain is a traditional dental ceramic that is built up in layers and fired in an oven; it looks lifelike but is relatively brittle on its own. Zirconia is a different and much stronger ceramic that is usually milled from a solid block. In everyday language, many people call any tooth-coloured crown a porcelain crown, which can cause confusion. When you discuss your options, it helps to ask which material the crown is actually made of and whether it is fully ceramic or has a metal core.
Have a question about your teeth?
Send a WhatsApp message to Dr. Abdel Rahman Ajam or Dr. Soumaya Ajam, or call the clinic to book a consultation.
This article provides general information for patients. It does not replace an examination by a dentist, who can advise you on your own situation.