Dental Ceramics: Types, Properties and How They Are Classified

Dental ceramics are inorganic, non-metallic materials used to make crowns, veneers, inlays, onlays, bridges and implant abutments. Published reviews sort them by structure into three groups: glass-matrix ceramics, polycrystalline ceramics (such as zirconia and alumina) and resin-matrix ceramics. The group decides how strong a material is, how translucent it is and whether it can be etched with hydrofluoric acid.

This page is general reference for researchers, laboratory staff and clinic staff. It describes materials and published classifications; it is not medical advice and does not describe clinical procedures.

Short answer

A dental ceramic is a restorative or prosthetic material built from a glass phase, a crystalline phase, or both, sometimes combined with a polymer. A widely cited open-access review of contemporary products groups contemporary products into glass-matrix, polycrystalline and resin-matrix families, and a 2025 narrative review of 58 articles confirms that several competing classification schemes describe the same materials in different words. Strength is not the whole story: the 2025 review states that flexural strength and clinical performance are not directly correlated.

Definition and scope

In this context “ceramic” covers materials from feldspar-based porcelains to yttria-stabilised zirconia. The older word “porcelain” describes only part of the field. In United States federal regulation, 21 CFR 872.6660 defines “porcelain powder for clinical use” as a mixture of kaolin, feldspar, quartz or other substances, intended for artificial teeth, jacket crowns, facings and veneers, that is heated in an oven to a glass-like finish. FDA classifies that device as Class II.

Modern products reach well beyond that definition. Machinable blocks for chairside and laboratory milling, pressable ingots, zirconia discs and polymer-infiltrated hybrids are all discussed under the same heading in the clinical and materials literature, which is why this page follows the structural grouping used by the review articles cited at the end.

How dental ceramics are classified

There is no single universal scheme. The 2025 review by Cuzic and colleagues (Materials, 2025;18(10):2235) summarises three that are in common use:

• Kelly and Benetti: predominantly glassy materials, particle-filled glasses, and glass-free polycrystalline materials.
• Gracis (2015): polycrystalline ceramics, glass-matrix ceramics and resin-matrix ceramics.
• McLaren and Giordano: glass-based systems, glass-based systems with a crystalline second phase, interpenetrating-phase systems and polycrystalline systems.

The review of contemporary dental ceramic materials uses the three-family version: glass-matrix ceramics contain a glass phase, polycrystalline ceramics contain no glass and are purely crystalline, and resin-matrix ceramics have a polymer matrix filled mostly with inorganic refractory particles. The rest of this page uses those three families because they map directly onto how a material behaves in the laboratory.

How the families differ in practice

Glass-matrix ceramics

These include feldspathic porcelain, leucite-reinforced glass-ceramic, lithium disilicate, zirconia-reinforced lithium silicate and fluorapatite glass-ceramic. Because they contain a glass phase, hydrofluoric (HF) acid dissolves part of the surface. In feldspathic and leucite materials this leaves micro-porosities; in lithium disilicate and zirconia-reinforced lithium silicate it exposes the crystals. The 2025 review lists glass ceramics as treated with HF etching followed by silane in its surface-treatment table.

The reviews place these materials in different roles. Feldspathic and leucite ceramics are described for veneers, inlays, onlays and anterior crowns, with leucite noted as not suited to posterior bridges. Lithium disilicate is described for anterior and posterior single crowns and for three-unit anterior or premolar bridges. Fluorapatite glass-ceramic is a veneering material rather than a substructure.

Polycrystalline ceramics

Alumina and zirconia contain no glass, so HF etching does not roughen them. The 2025 review therefore lists airborne-particle abrasion with an MDP-containing primer for zirconia and alumina, and cautions that excessive roughening can initiate cracks. Alumina is described as above 500 MPa in flexural strength but prone to bulk fractures. Zirconia, mainly yttria-stabilised tetragonal zirconia polycrystal (Y-TZP), is above 900 MPa, with Vickers hardness of about 1200-1350 and fracture toughness of 6-15 MPa·m^0.5 in that review, which calls it “ceramic steel” because of transformation toughening. The same review notes that zirconia can undergo low-temperature degradation in the presence of water, with the tetragonal phase converting toward monoclinic.

Zirconia is indicated in the reviews for multi-unit and long-span restorations, posterior teeth and implant abutments. Glass-infiltrated alumina and zirconia systems (In-Ceram) are described as abandoned because of manufacturing complexity.

Resin-matrix ceramics

These hybrids pair a polymer with a ceramic phase. VITA Enamic is a polymer-infiltrated ceramic network of about 86 wt% feldspar network and 14 wt% polymer; Lava Ultimate and Cerasmart are resin-matrix blocks. That review reports Lava Ultimate near 200 MPa and does not recommend it for crowns; the 2025 review notes that hybrids are less abrasive to opposing teeth.

Zirconia generations: translucency against strength

Zirconia is the clearest example of a design trade-off. According to Cuzic and colleagues, adding cubic phase makes the material more translucent and less strong. The table below restates their account; it does not rank the products.

Type	Description in the review	Reported use
3Y-TZP	Strongest, opaque	Non-aesthetic areas
Highly translucent 3Y-TZP	Reduced alumina content (below 0.05%)	Reported as a translucent variant of 3Y-TZP
4Y-PSZ	Introduced in 2017; a balance of strength and aesthetics	Between the two extremes
5Y-PSZ	About 50% cubic phase; better aesthetics, lower strength	Mainly anterior crowns

Surface treatment categories by material family

The 2025 review’s surface-treatment table is the most useful single bench-level cross-reference between composition and handling. At category level:

Family	Glass phase	HF etching	Category named in the review
Feldspathic, leucite	Yes	Dissolves glass, leaves micro-pores	HF etching plus silane
Lithium disilicate, zirconia-reinforced lithium silicate	Yes	Exposes crystals	HF etching plus silane
Zirconia, alumina	No	Resistant	Airborne-particle abrasion plus MDP primer

The review also states that no dental cement meets all biomechanical requirements, and that total-etch, self-etch and self-adhesive approaches each involve trade-offs. Product-specific protocols belong to the manufacturer’s instructions for use.

Strength figures and why they conflict

The data table below collects flexural-strength ranges reported in the two reviews. Where the sources give different values for the same material, the range spans them. For lithium disilicate, for example, one review’s text and table differ, and the 2025 review gives about 407 MPa in text and 360 MPa in its table. That spread is a reminder that published figures depend on the specific product, the test method and the processing route, and are not a specification to design against.

Where it matters for labs, clinics and supply decisions

• Dental materials research. Flexural strength, hardness, fracture toughness and low-temperature degradation are standard outcome measures. The reviews underline that bench strength alone does not predict clinical performance, so study designs that report only flexural strength answer a narrow question. See what dental research covers for the wider field.
• Laboratory handling. Whether a block is etchable or needs particle abrasion follows from its phase composition, so correct material identification at receipt matters. Mixed glass and polycrystalline stock should be labelled by family.
• Regulatory status. Porcelain powder for clinical use is Class II under 21 CFR 872.6660. Optical impression systems for CAD/CAM are Class II with special controls and, under 21 CFR 872.3661, exempt from premarket notification subject to the limitations in 21 CFR 872.9. Related prosthetic materials are discussed in denture teeth types.
• Related materials work. Digital workflows overlap with biocompatible 3D printing materials, and internal structure of restorations is sometimes examined with micro-CT.

That review lists situations where ceramic restorations are not recommended: insufficient remaining tooth structure, subgingival preparations, poor oral hygiene and heavy bruxism. These are material-level cautions from the literature, not advice for any individual patient.

Common misunderstandings

• “Ceramic” and “porcelain” mean the same thing. Porcelain is one glass-matrix type. Zirconia and alumina are ceramics with no glass phase.
• Higher flexural strength means a better restoration. The 2025 review explicitly states the two are not directly correlated. Indication, thickness, bonding and occlusion also matter.
• All ceramics can be etched with hydrofluoric acid. Only glass-containing materials respond; zirconia and alumina do not.
• Zirconia is one material. Cubic-phase content changes translucency and strength, so generations are not interchangeable.
• A single published strength number is a specification. The reviews’ own figures differ between text and tables; treat them as ranges.

FAQ

What are dental ceramics made of?

Glass-matrix types contain a glass phase, often with crystals such as leucite or lithium disilicate. Polycrystalline types such as zirconia and alumina are purely crystalline. Resin-matrix types combine a polymer with inorganic filler or a ceramic network.

What are the main types of dental ceramics?

Three families: glass-matrix, polycrystalline and resin-matrix, following the review of contemporary materials and the Gracis scheme described by Cuzic and colleagues. Other schemes use four categories or emphasise glass content.

Is zirconia a ceramic?

Yes. Zirconia is a polycrystalline ceramic with no glass phase, which is why it resists hydrofluoric-acid etching.

Are dental ceramics regulated as medical devices?

Some are. Porcelain powder for clinical use is Class II under 21 CFR 872.6660, as read in the Code of Federal Regulations on 12 November 2026.

Sources

• Contemporary Dental Ceramic Materials, A Review: Chemical Composition, Physical and Mechanical Properties, Indications for Use. PubMed Central, PMC6182519. pmc.ncbi.nlm.nih.gov/articles/PMC6182519. Read 12 November 2026.
• Cuzic C, et al. Clinician’s Guide to Material Selection for All-Ceramics in Modern Digital Dentistry. Materials (Basel) 2025;18(10):2235, PMC12113582. pmc.ncbi.nlm.nih.gov/articles/PMC12113582. Read 12 November 2026.
• 21 CFR 872.6660, Porcelain powder for clinical use. law.cornell.edu. Read 12 November 2026.
• 21 CFR 872.3661, Optical impression systems for computer assisted design and manufacturing (CAD/CAM) of dental restorations. law.cornell.edu. Read 12 November 2026.