What are the three materials in brief?
Porcelain-fused-to-metal (PFM) consists of porcelain fired onto a cast metal framework. It is the oldest and most studied type of crown. The colour of the metal is hidden by an opaque layer, which limits light transmission and can create a grey line at the gum margin.
Lithium disilicate (often referred to by the brand name E.max) transmits light very much like a natural tooth thanks to its glassy structure. Its flexural strength is about 260–360 MPa, sufficient for single crowns and veneers but limited for long bridges.
Zirconia (zirconium dioxide) is the strongest ceramic in dentistry, with a flexural strength of about 900–1,500 MPa. The classic type (3Y) is very strong but more opaque; the newer translucent types (4Y, 5Y) look more natural but give up some strength. The crown is either made in one piece (monolithic) or layered with aesthetic porcelain.
Comparison table: strength, aesthetics, reduction and typical use
The table below summarises findings from textbooks and systematic reviews. The values are laboratory and population-level data; the choice that applies to your tooth is made at the examination.
| Property | Monolithic zirconia | Lithium disilicate (E.max) | Porcelain-fused-to-metal |
|---|---|---|---|
| Flexural strength (approx.) | 900–1,500 MPa | 260–360 MPa | Porcelain 60–80 MPa, carried by the metal framework |
| Aesthetics | Good; very good in translucent types | Very good, most natural light transmission | Opaque layer; possible grey margin |
| Typical use | Molar crowns, bridges, patients who clench, implant crowns | Front single crowns, veneers, short front bridges | Long bridges, tight spaces, high load |
| Reduction needed | Can be thinner (about 0.8–1.5 mm) | 1–1.5 mm; 1.5–2 mm at the incisal edge | 1.2–1.5 mm on the front surface; 2 mm at the incisal edge |
| Most common problem | Rare fracture; wear if not polished | Fracture, especially in back bridges | Porcelain chipping, margin decay, grey gum line |
| Wear of opposing teeth | Low if polished | Moderate | Veneering porcelain wears enamel |
| Research history | Growing 5-year data | Good data for single crowns | Longest follow-up |
Durability: what does research show?
For single crowns, all three materials report high survival. In systematic reviews, about 91–93% of zirconia-based crowns and about 95% of PFM crowns are in the mouth and functioning at 5 years. For lithium disilicate single crowns, a 2014 review reported survival well above 95% at 2–5 years.
The real distinction appears in bridges. In multi-unit bridges, PFM has shown higher 5-year survival than zirconia-based bridges, with more porcelain chipping seen in veneered zirconia bridges. Lithium disilicate performs markedly worse in back-tooth bridges, so it is generally limited to single crowns, veneers and short front bridges.
The failure modes also differ: PFM crowns mostly fail through decay and loosening, veneered zirconia through porcelain chipping and glass-ceramic through fracture. All the factors that affect lifespan are set out on how long do zirconia crowns last.
Aesthetics: light transmission and the gum margin
A natural tooth partly transmits and partly reflects light. The material that comes closest to this is lithium disilicate, which is why it is often chosen for front teeth, especially when the neighbouring teeth remain natural. With translucent glass-ceramics the colour of the cement also affects the result, so shaded resin cements are used.
The classic type of zirconia is more opaque; a porcelain layer used to be added for a natural look. The newer translucent types (5Y) transmit enough light to be used in one piece on front teeth, but this translucency comes at the cost of some strength. Translucent types are therefore reserved for front single crowns, and strong types for molars and bridges.
The aesthetic limit of PFM is the opaque layer that hides the metal. As the gum recedes slightly over the years, the metal at the margin can show as a grey line. Ceramics without metal do not have this problem, which also removes the need to bury the margin deep under the gum and benefits gum health.
Amount of tooth reduction and preserving the tooth
Every crown requires a certain amount of tooth to be removed to give the material a safe thickness. In PFM, the metal, opaque layer and porcelain are stacked, so at least 1.2–1.5 mm must be removed from the front surface and about 2 mm from the incisal edge. This is one of the major disadvantages of the PFM crown.
For all-ceramic crowns the classic target is a rounded shoulder of about 1 mm around the tooth, 1–1.5 mm on the front surface and 1.5–2 mm of clearance on the incisal or chewing surface. Thanks to its high strength, monolithic zirconia can be designed thinner in some areas, which means less tooth structure removed.
The amount of reduction is not only a material question. In younger patients the pulp is large and extensive reduction raises the risk; more conservative options such as veneers or composite may then come to the fore. The relationship between reduction and sensitivity is covered on sensitivity and tooth preparation for zirconia crowns.
In which situation does which material come to the fore?
The decision logic in textbooks runs as follows: if aesthetics is the priority and the tooth can provide proper support, all-ceramic; if chewing force is high, the bridge is long or space is tight, high-strength zirconia or PFM.
- Front single crown or veneer: lithium disilicate or translucent zirconia. Shade matching with the neighbouring teeth is decisive here.
- Molar crown: monolithic zirconia; load is high and the aesthetic demand lower.
- Clenching (bruxism): monolithic zirconia or PFM together with a night guard. Weak glass-ceramic is not recommended.
- Long bridge, especially in the molar region: PFM has the longest evidence base; strong zirconia is also an option if an adequate connector cross-section can be achieved.
- Metal allergy or a wish to avoid metal: zirconia contains no metal and can be used in every region.
- Very short tooth or limited bite clearance: PFM may be safer; crown lengthening is considered as an alternative.
An edge-to-edge bite, heavy clenching and lack of room for a 1 mm shoulder on the tooth are the textbook cautions against a weak all-ceramic crown. In these cases a stronger material is chosen.
Wear of the opposing teeth and the bite
Older textbooks warn that porcelain, particularly on PFM crowns, wears the lower incisors that bite against it. This warning remains valid for veneering porcelain, which has a rough, hard surface.
For monolithic zirconia the picture is different. Clinical studies have shown that well-polished zirconia causes wear on the opposing enamel similar to natural tooth-to-tooth contact and less than veneering porcelain. The critical point is leaving the surface smooth; surfaces not re-polished after adjustments in the mouth cause more wear.
Lithium disilicate causes moderate wear. Whichever material is chosen, a bite check after fitting, removal of high spots and polishing are necessary for the life of both the crown and the opposing teeth.
How is the material chosen at our clinic?
The material decision is not made in isolation; the position of the tooth, remaining tooth structure, pulp condition, gum health, bite and habits are assessed together. In our clinic in Bahçelievler, Istanbul, planning is supported by 3D CBCT imaging and digital impressions; digital smile design lets you preview shade and shape in the front region.
The decision usually proceeds in this order:
- The pulp, root and gum condition of the tooth are established by examination, X-ray and, where needed, CBCT.
- The bite, clenching habits and the opposing teeth are assessed.
- The aesthetic expectation and the strength required are weighed according to the position of the tooth.
- Shade and shape are previewed with a digital design; the material and the margin position are finalised.
- The result is checked at the try-in stage and corrected if necessary.
A common approach is mixed use in the same mouth: lithium disilicate or translucent zirconia on the front teeth, monolithic zirconia on the molars. Each region then receives the material suited to its needs. If you are undecided between zirconia and porcelain veneers, our porcelain veneers vs zirconia crowns page may help; for bridges and implant crowns see zirconia bridge and implant zirconia.
To find out which material suits your teeth, you can request a pre-assessment on WhatsApp at +90 544 289 66 33. The definitive plan is set at the examination and X-ray assessment in our clinic in Bahçelievler; if you are travelling, send your recent X-rays in advance where possible.
Frequently asked questions
Which is more aesthetic, E.max or zirconia?
For front teeth, lithium disilicate (E.max) generally gives a more natural result in terms of light transmission. The newer translucent zirconia types have closed much of this gap, but the translucency is achieved by giving up some strength. E.max may be preferred where the neighbouring teeth remain natural and the load is low, translucent zirconia where chewing load is higher. Shade matching and the final decision are assessed together at the examination.
Is porcelain-fused-to-metal an outdated method?
No. PFM is the crown type with the longest research history and still shows the highest reported survival in long bridges. Its disadvantages are that it requires more tooth reduction to hide the metal, has low light transmission and can create a grey line at the gum margin. For single crowns and short bridges, zirconia has closed this gap.
Is zirconia suitable for bridges?
Yes, particularly its strong monolithic types perform well in short and medium-length bridges. Textbooks require the connectors of all-ceramic bridges to be of adequate thickness; if this cannot be achieved on very short teeth or with limited bite clearance, PFM may be safer. For long molar bridges, the metal-ceramic design has more follow-up data.
Can E.max be used on a molar?
As a single crown, yes; lithium disilicate single crowns also report good survival in the back of the mouth. When used as a bridge in the molar region, however, the fracture risk rises markedly, so it is generally limited to single crowns, veneers and short front bridges. For patients who clench, zirconia is more commonly preferred on molars.
Which material requires the least tooth reduction?
Monolithic zirconia can be designed thinner in some areas thanks to its high strength and is the crown material requiring the least reduction. Lithium disilicate needs about 1–1.5 mm, and PFM, because of the metal and opaque layer, at least 1.2–1.5 mm on the front surface and 2 mm at the incisal edge. Every crown still requires some tooth structure to be removed.
Does zirconia wear down the opposing teeth?
In clinical studies, well-polished monolithic zirconia has shown wear on the opposing enamel close to that between natural teeth and less than veneering porcelain. The problem is surfaces left rough or not re-polished after bite adjustment. A bite check and polishing after fitting reduce this risk; for patients who clench, a night guard also protects the opposing teeth.
Can different materials be used in the same mouth?
Yes, this is a common approach. Lithium disilicate or translucent zirconia on the front teeth and monolithic zirconia on the molars give each region the material suited to its needs. What matters is choosing harmonious shades and planning the bite as a whole; digital design makes it easier to preview this harmony.
I have a metal allergy. Which material is suitable?
Zirconia and lithium disilicate contain no metal and can be used in every region for patients with metal sensitivity. The alloys used in PFM vary, and gum reactions have been reported, though rarely. If you have a known allergy or suspect one, mentioning it at the examination directly affects material planning and avoids unnecessary risk.
Related guides
Contact: Yayla Dental Akademi, Ferit Selimpaşa Cad. No:44A, Bahçelievler, Istanbul (Basın Sitesi, opposite Migros; about 600 m from İlkyuva metro station, line M3). Monday–Saturday 10:00–21:00, Sunday closed. WhatsApp and phone: +90 544 289 66 33 · Online booking: DoktorTakvimi.
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Search the databases: PubMed · Google Scholar · NIH PMC · Cochrane (institutional access may be required).
This page is for information only; diagnosis and treatment plans are determined by a dentist after an examination. Figures are population averages from the cited sources and do not describe an individual outcome.
