Do crowns wear down the teeth they bite against?

Here is a reasonable worry. Zirconia is one of the hardest materials used in dentistry, much harder than tooth enamel. If you put a zirconia crown on a lower molar, will it slowly sand down the upper tooth it chews against? A 2013 review in the Journal of Prosthodontic Research noted exactly this concern, pointing out that zirconia is more than twice as hard as porcelain. The same review then reported that highly polished zirconia actually caused less wear on opposing teeth than porcelain. Below is how that came to be understood, and what it means if you are choosing crowns.

Why hardness is not the whole story

Wear between two surfaces depends a lot on roughness. A very hard surface polished like glass can slide over enamel with little damage. A softer surface that is rough, or that breaks up into hard particles as it wears, can act like sandpaper. Veneering porcelain shows the point well: it is softer than zirconia, yet in the laboratory studies below it caused the most enamel wear of any crown surface tested.

So "how hard is the crown?" is the wrong first question. A better one is "how smooth is it, and will it stay smooth?"

What laboratory studies found

Most wear research uses chewing simulators: extracted human tooth cusps rubbed against flat samples of crown material under a set load for hundreds of thousands of cycles, standing in for months or years of chewing.

Polished zirconia against glazed zirconia

A 2013 study in the Journal of Prosthetic Dentistry compared polished zirconia, glazed zirconia, zirconia that had been polished and then reglazed, veneering porcelain, and natural enamel. Polished zirconia was the smoothest surface and caused the least wear on the opposing enamel. It also showed no measurable wear itself. Glazed and reglazed zirconia caused significant enamel wear, and the glaze itself wore away. Veneering porcelain caused the most enamel wear of all. The authors concluded that polished zirconia is "wear-friendly" to the opposing tooth and that surface roughness helped predict how much wear would happen.

Zirconia against lithium disilicate after adjustment

Crowns are often adjusted in the mouth to perfect the bite, and adjustment roughens the surface. A 2014 study in the Journal of Dentistry tested zirconia and lithium disilicate (the material in E-max crowns) in three states: adjusted only, adjusted and polished, and adjusted and glazed.

Veneering porcelain produced several times the enamel wear of the polished ceramics. Polished zirconia and lithium disilicate were not significantly different from enamel rubbing against enamel. Adjusted-only and glazed zirconia caused more enamel wear than polished zirconia. For lithium disilicate, glazing worked about as well as polishing, while adjusted-only surfaces did worse. The authors advised polishing both materials after any adjustment, and avoiding veneering porcelain on surfaces that take bite contact.

Newer translucent zirconia

The more translucent 5Y zirconia used for front teeth was tested in a 2018 study. Polished 5Y and 3Y zirconia both showed no measurable wear of their own, and opposing enamel wear was not significantly different between 5Y zirconia, 3Y zirconia, lithium disilicate and enamel. We explain the different grades in 3Y, 4Y and 5Y zirconia.

A caution about lab studies

A 2014 systematic review of laboratory zirconia wear studies found the methods varied so much (loads, movements, cycles, sample preparation) that wear rates could not be compared between studies. What every study agreed on was that enamel wear was lower against polished zirconia. The review recommended polishing full-contour zirconia for that reason.

What about wear on the crown itself?

Wear runs both ways. The 2014 study found that zirconia showed less wear than lithium disilicate, and that lithium disilicate wore at a rate roughly equivalent to natural enamel. In the 2018 study, polished 3Y and 5Y zirconia showed no measurable wear at all after 300,000 cycles, while lithium disilicate lost a small, measurable amount (0.28 mm³), close to what enamel lost against enamel in the same test.

For most people this is a good thing either way. A crown that wears at about the rate of enamel keeps pace with the natural teeth around it. A crown that barely wears at all stays the same shape for years, which suits a heavy bite but means the bite on that tooth will not "settle in" by itself. That is one reason the fit of the bite at the try-in matters: a zirconia crown left slightly high will stay high. Our article on a bite that feels high after new crowns explains what to do if that happens.

What happens in real mouths

Clinical studies are smaller but closer to what you will experience.

A German group placed monolithic zirconia molar crowns in 20 patients and measured wear against the opposing teeth, comparing it with the matching natural teeth on the other side of the mouth. After six months, opposing enamel had lost on average 33 micrometres, against about 10 micrometres between natural teeth on the other side. Night-time grinding and sex were identified as factors that affected wear. In a later study by the same group, with 20 different patients and heavy grinders excluded, mean enamel loss opposite zirconia after two years was 46 micrometres, against 19 to 26 micrometres on control teeth. The authors judged zirconia crowns justified anyway, because other dental ceramics had caused more wear in earlier studies.

A 2015 study in India gave each of 10 young adults one polished monolithic zirconia crown and one glazed metal-ceramic crown on opposite sides. After a year, enamel opposite the metal-ceramic crowns had worn significantly more than enamel opposite zirconia (for molars, about 180 against 127 micrometres), and both caused more wear than natural enamel did.

For scale, a micrometre is a thousandth of a millimetre. These amounts are small and not something you would notice in a year. They matter more over decades, in heavy grinders, or when a whole arch of crowns bites against natural teeth.

What this means when choosing crowns

• Back teeth biting against natural teeth: a polished monolithic surface makes sense, whether zirconia or lithium disilicate. A porcelain layer on the biting surface is the least friendly choice for the opposing tooth, as well as the most likely to chip. Our article on monolithic or layered zirconia covers the chipping side.
• After any bite adjustment: the adjusted area should be polished again, not left rough. It is fine to ask.
• If you grind: the clinical data show grinding increases wear. A night guard may be advised to protect both crowns and natural teeth, and for heavy grinders we may recommend zirconia over E-max. Not wearing an advised night guard can also void our crown guarantee, which is explained on the guarantee page.
• Old crowns: an ageing porcelain crown with a rough, worn surface may be wearing its opposing tooth faster than a new polished one would. That alone is not usually a reason to replace a sound crown, but it is worth your dentist checking.

At our clinic the bite on new crowns is checked at a try-in before they are fixed. If you would like a free written plan for your own teeth, including which material suits each position, get in touch through our contact page.

Common questions

Is zirconia too hard for the opposite teeth?

Hardness alone does not predict wear. Very smooth, polished zirconia has caused little enamel wear in laboratory tests, while softer but rougher porcelain caused much more. Problems come mostly from rough, unpolished or worn-through glazed surfaces.

Which crown material is kindest to the opposing teeth?

In a 2014 laboratory study, polished zirconia and polished lithium disilicate caused the least enamel wear, comparable to enamel against enamel. Veneering porcelain caused the most. Finish matters as much as material.

My dentist adjusted my crown. Should it be polished afterwards?

Yes. Grinding leaves zirconia and glass-ceramic rough, and studies found adjusted but unpolished surfaces caused more enamel wear than adjusted and polished ones. It is a reasonable thing to ask about at the end of any bite adjustment.

I grind my teeth. Does that change things?

Yes. In one clinical study, night-time grinding was among the factors that significantly affected wear around zirconia crowns. If you grind, a night guard may be advised to protect both crowns and natural teeth. See our aftercare page.

Will my crowns wear down themselves?

Polished zirconia showed no measurable wear in laboratory tests. Glazed surfaces wear through over time, which is one reason a glaze on the biting surface is less useful than polish there.

Sources

1. Lawson NC, Janyavula S, Syklawer S, McLaren EA, Burgess JO (2014). Wear of enamel opposing zirconia and lithium disilicate after adjustment, polishing and glazing. J Dent
2. Janyavula S, Lawson N, Cakir D et al. (2013). The wear of polished and glazed zirconia against enamel. J Prosthet Dent
3. Passos SP, Torrealba Y, Major P et al. (2014). In vitro wear behavior of zirconia opposing enamel: a systematic review. J Prosthodont
4. Stober T, Bermejo JL, Rammelsberg P, Schmitter M (2014). Enamel wear caused by monolithic zirconia crowns after 6 months of clinical use. J Oral Rehabil
5. Stober T, Bermejo JL, Schwindling FS, Schmitter M (2016). Clinical assessment of enamel wear caused by monolithic zirconia crowns. J Oral Rehabil
6. Mundhe K, Jain V, Pruthi G, Shah N (2015). Clinical study to evaluate the wear of natural enamel antagonist to zirconia and metal ceramic crowns. J Prosthet Dent
7. Kwon SJ, Lawson NC, McLaren EE, Nejat AH, Burgess JO (2018). Comparison of the mechanical properties of translucent zirconia and lithium disilicate. J Prosthet Dent
8. Miyazaki T, Nakamura T, Matsumura H, Ban S, Kobayashi T (2013). Current status of zirconia restoration. J Prosthodont Res

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