Crown materials

Metal-free crowns and metal allergy: what is in a metal-ceramic crown and when it matters

Plenty of people react to cheap earrings or a jeans stud and wonder whether a crown with metal in it will do the same. The honest answer is that it is possible but uncommon, and that metal-free crowns remove the question entirely.

Medically reviewed by Dt. Hüseyin Yavuz Özbek, implant surgeon · Updated October 2026

Short answer

Porcelain-fused-to-metal crowns use an alloy core, which may be gold-based, palladium-based or a base metal such as nickel-chromium or cobalt-chromium. Nickel allergy is common on the skin, affecting roughly 8 to 19% of European adults, but clinically relevant reactions in the mouth are much rarer: in one study of 206 people patch-tested for suspected dental metal allergy, only 7% had a relevant oral reaction. Zirconia and E-max crowns contain no alloy, so they avoid metal exposure altogether. If you know you react to nickel, say so before treatment.

A lot of people who ask us about crowns mention, almost in passing, that they cannot wear cheap jewellery. It is a fair thing to raise. For decades the standard crown in the UK was porcelain bonded to a metal base, and some of those metals are the same ones that cause itchy earlobes. This article explains what is actually inside a metal-ceramic crown, how often the mouth reacts to it, and what changes if you choose a metal-free crown instead.

What is inside a porcelain-fused-to-metal crown

A porcelain-fused-to-metal crown has a thin cast metal cap fitted to the tooth, with tooth-coloured porcelain fired over it. The Oral Health Foundation describes it as one of the most common crown types: a strong metal base covered with porcelain so it looks natural.

"Metal" covers a wide range of alloys. Broadly, dental casting alloys fall into a few families:

High-gold alloys, mostly gold with platinum or palladium.
Palladium-based alloys, with silver or other metals.
Base-metal alloys, usually nickel-chromium or cobalt-chromium. These are cheaper and very rigid, and they are common in lower-cost metal-ceramic work.

A 2004 review of casting alloys by Wataha and Messer pointed out that selection has become complicated because there are so many alloys, and urged dentists to focus on properties such as corrosion and biocompatibility rather than colour and short-term cost. Unless your dentist or lab tells you, you usually will not know which alloy is under an existing crown.

All alloys release something

Metal in the mouth is not inert. A 2002 review in Dental Materials by Schmalz and Garhammer stated plainly that all dental cast alloys release metal ions into the mouth, and that the amount and type released are not directly related to what the alloy is made of. Those ions can interact with the gum and cheek through several routes, of which allergy is one.

The same review made two points worth keeping in mind together. First, the number of cases where a local reaction can be safely pinned on the alloy is small. Second, the comparatively high rate of nickel allergy should push dentists to replace nickel-containing alloys whenever there is a suitable alternative.

How common is nickel allergy?

On the skin, very common. The NHS lists metals such as nickel and cobalt in jewellery among the common triggers of allergic contact dermatitis. A 2019 meta-analysis of more than 20,000 patch-tested people from the general population found nickel was the most common contact allergen, with a pooled prevalence of 11.4%. A clinical review from the same year put nickel allergy at roughly 8 to 19% of European adults, with a strong female predominance. A 2010 review estimated up to 17% of women and 3% of men are allergic to nickel, and 1 to 3% of people to cobalt and chromium.

That review also flagged two other dental metals. Palladium allergy is mainly the result of cross-reaction in people already sensitive to nickel. Gold allergy shows up often on patch tests but is rarely clinically relevant.

Why your age may matter

Nickel allergy is mostly caused by skin contact, and Europe changed the rules on that. The 2019 clinical review reported that European regulation limiting nickel release from consumer items led to a fall in nickel allergy, and the 2010 review described a decrease in nickel allergy among young Danish women with pierced ears after the rules came in. Jewellery and metal in clothing are still the main sources. In other words, the nickel figures above are averages across all ages, and the picture keeps shifting. None of this tells you about your own sensitivity, which only a patch test can.

How often does the mouth actually react?

Much less often than the skin figures suggest. The lining of the mouth is a different environment from skin, and the contact is different too.

A 2009 German study looked back at 206 people who had been patch-tested specifically because a dental metal allergy was suspected. This was a group already worried about their dental work, not the general population. Twenty-eight had a positive patch test to at least one dental metal, most often gold, palladium or nickel. But only 14 people, 7% of the group, had a clinically relevant allergy with oral symptoms (lichen planus-type changes or inflammation of the mouth) next to dental metal containing the allergen. The authors concluded that clinically relevant allergies to dental metals are infrequent.

So a positive skin test does not mean your crown is causing trouble, and a sore patch near a crown is not automatically an allergy. Schmalz and Garhammer recommended a thorough dental and medical examination for anyone linking oral symptoms to metal, partly because general illnesses and medicines can produce similar signs.

What going metal-free changes

Metal-free crowns, mainly zirconia and lithium disilicate (E-max), contain no alloy. Zirconia is zirconium dioxide, a ceramic oxide. Lithium disilicate is a glass-ceramic. That changes a few things:

No alloy exposure

There are no nickel, cobalt, chromium or palladium ions from the crown. For someone with a confirmed nickel allergy, this simply removes the question. Zirconia's colour comes from small amounts of metal-oxide pigment. A 2025 systematic review found these pigments did not affect the growth of gum cells in laboratory tests, though they do change some physical properties of the material.

Looks

There is no metal core to mask, so the crown can let light through more like a natural tooth.

Strength and bite

Zirconia is strong enough for back teeth and bridges. For heavy grinders or long bridges, we may recommend zirconia rather than E-max. Our crown types page compares the options.

What it does not change

Metal-free does not mean problem-free. Gum health around any crown still depends on how well the edge fits and how well you clean it, and a crown can still fail through decay at the margin or fracture. Metal-ceramic crowns also have a long track record; a 2026 systematic review found five-year survival for metal-ceramic single crowns of 97.1%, similar to zirconia. The case for metal-free is mainly about allergy, appearance and avoiding metal altogether, not about metal crowns being dangerous.

What your dentist will want to know

If you raise a possible allergy, a good dentist will ask a few practical questions before deciding anything. Have you been patch-tested, and to what? Do you react to jewellery, watch straps or jeans buttons? Do you already have metal in your mouth, such as old crowns, a post, a brace wire or a partial denture frame, and have you ever had soreness next to it? Are there other explanations for any mouth symptoms, such as a skin condition, a new medicine or a sharp edge rubbing the cheek? Answers to those questions often settle the matter faster than any test.

If you think you have a metal allergy

Tell your dentist before any planning, and say what you react to.
If you have never been tested and symptoms are a real concern, ask your GP about referral to a dermatologist. The NHS describes patch testing as the best way to test for a reaction to allergens.
Do not have sound crowns replaced on suspicion alone. Re-preparing a tooth removes more of it.
If a confirmed allergy lines up with symptoms next to a metal restoration, replacing that restoration with a metal-free one is a reasonable step to discuss.

At our clinic we prefer to protect a healthy tooth rather than crown it, and that applies to replacing old crowns too. If you want to talk through metal-free options, or whether an existing crown needs changing at all, send us your details through our contact page for a free written plan.

Common questions

I react to nickel jewellery. Will a metal crown cause a reaction?

Not necessarily. Many people with nickel allergy on the skin never react to dental alloys, and studies find clinically relevant oral reactions are uncommon. But reviewers have recommended replacing nickel-containing alloys where a suitable alternative exists, and metal-free crowns are that alternative. Tell your dentist about the allergy before planning.

What does an allergy to a dental metal look like?

Reported signs include redness, soreness or white lacy patches of the gum or cheek right next to the restoration. These signs have many other causes too, so diagnosis needs a dental examination and usually patch testing by a dermatologist.

Are zirconia and E-max crowns completely metal-free?

They contain no metal alloy. Zirconia is zirconium dioxide, a ceramic oxide, and lithium disilicate is a glass-ceramic. Colouring pigments in zirconia are metal oxides in small amounts, which a 2025 review found did not harm gum cells in laboratory tests.

Should I replace my old metal crowns to be safe?

Not just because they contain metal. Replacing a crown means re-preparing the tooth, which carries its own risks. Replacement is usually worth considering when a crown has failed, has decay underneath, or when a confirmed allergy is linked to symptoms next to it.

Do you still offer porcelain-fused-to-metal crowns?

We can discuss them. A porcelain-fused-to-metal price is not published; your written plan gives it. Zirconia and E-max prices are on our crown prices page.

Sources

Checked October 2026. Where we give our own view as a clinic, we say so.

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