12/10/2025
PFM (porcelain fused to metal) crowns are bilayered restorations made by layering ceramic over a metal substructure. Traditionally, feldspathic porcelain was used for most PFMs, though today there are PFM options made with advanced ceramics â including Glidewellâs ObsidianÂŽ Fused to Metal restorations, which are made with lithium silicate. PFMs have been used in dentistry since the late 1950s. At that time, dentists had limited material options available for full-contour crowns, with crowns being either cast metal or fully porcelain.2 Because of their two-material composition, PFMs offer a happy medium between full-metal restorations and all-porcelain crowns. A PFMâs metal substructure adds strength and longevity, and its ceramic covering creates a tooth-colored appearance more widely accepted by patients. PFMs have evolved over the decades, with newer generations of metals and ceramics featuring both enhanced strength and appearance. What Are the Key Differences Between Zirconia and PFM Crowns? PFM vs Zirconia image PFM and zirconia crowns are differentiated by the number of material layers and the composition of those layers. To summarize the above, the key differences between zirconia and PFM crowns are the number of layers and the composition of said layers. Zirconia crowns are made from a single high-strength material, while PFMs are made from two materials: metal and a layering ceramic. Ultimately, the material makeup significantly impacts the definitive performance of a restoration. Take PFMs, for example. Historically, they have displayed high rates of chipping, fracturing and shearing off of the layering ceramic. There are two primary reasons behind these breakages. First, because the ceramic layer is so thin, the material is less durable. Second, there are a difference between the thermal expansion characteristics of the substructure metal and those of the layering ceramic, which means that the layers expand and contract at differing rates during manufacturing. This imparts imperfections and weaknesses into the finalized restorations, especially at the location where the ceramic and metal meet. Zirconia crowns, on the other hand, are milled from a solid block of zirconia and sintered as fully shaped restorations. The monolithic nature of the material means that all areas of the restoration share the same material characteristics, eliminating the issues observed in PFMs. Moreover, zirconia imparts significant performance characteristics, having nearly 10 times the flexural strength of an average feldspathic layering ceramic.3,4 However, while zirconia is substantially stronger than the ceramics used for PFM crowns, the monolithic material does have a weakness: Zirconia bridges with long spans in an area with limited vertical space may fracture over time, an issue arising due to the bridge connectors having a small volume. At Glidewell, for these bridges, we typically recommend that dentists use PFM restorations because their metal substructure ensures a longer-lasting solution in those compact areas. When to Use Zirconia? Hammer Test image Zirconia offers extremely high strength and lasting durability. Zirconia is an extremely versatile material that can be used in virtually any indication, including crowns, bridges up to 16 units, veneers, inlays and onlays, screw-retained crowns and bridges, and full-arch implant prostheses. Zirconia best serves patients who require durable, affordable, high-performing restorations, as well as those with metal allergies. And due to continuous improvements in zirconia materials, todayâs zirconia restorations offer patient-pleasing esthetics and can address most of dentistryâs everyday restorative and cosmetic challenges. When to Use PFMs? PFMs are a great solution when there isnât enough occlusal clearance for zirconia. PFMs are a great solution when there isnât enough occlusal clearance for zirconia. With zirconia restorations taking over many of the common indications for which PFMs would traditionally be used, there are fewer indications today for which PFMs are ideal. Compared with zirconia crowns, PFMs exhibit inferior performance in most restorative scenarios in dentistry. However, there are specific indications in which they still represent the better material option, including bridge cases that lack the vertical height necessary for adequate zirconia connectors, cases where the restoration must match nearby PFMs, and the restoration of endodontically treated teeth with crown or root staining that would bleed dark shadows through all-ceramic restorations.
Dentistryâs half-century workhorse, the PFM crown, still has an important role to play for the practitioner. But modern materials like zirconia crowns offer substantially enhanced performance and appearance characteristics for most indications, thanks to advances in materials science. For more information please call Dental Arts of Freehold at (732) 462-4445
