A dental crown is a tooth-shaped cap placed over a damaged tooth to restore its original shape, size, strength, and appearance. This restoration is necessary when a tooth is cracked, heavily decayed, worn down, or after a root canal procedure. The material chosen determines the crown’s long-term success and aesthetic outcome. There is no single best material for all situations, as the ideal choice depends on the specific needs of the patient. The location of the tooth, the forces it must withstand, and the patient’s aesthetic goals all factor into the final selection.
Metal Alloys and Porcelain-Fused-to-Metal
Metal alloys are the traditional standard for dental durability, often used for teeth that bear the heaviest chewing forces. These alloys range from high noble alloys (containing gold, platinum, or palladium) to non-precious base metal alloys (like nickel-chromium or cobalt-chromium). Gold alloys are valued for their exceptional biocompatibility, resistance to corrosion, and low wear on opposing natural teeth. Metal crowns are incredibly strong, making them a suitable choice for molars and patients who exhibit bruxism, or teeth grinding.
Base metal alloys offer a cost-effective option, providing high strength and hardness for structural applications. Despite their strength, the metallic color of these restorations is their primary drawback, leading most patients to reserve them for non-visible back teeth. The strength of all-metal crowns allows for minimal tooth reduction during preparation, preserving more of the natural tooth structure underneath.
The Porcelain-Fused-to-Metal (PFM) crown was developed to combine the strength of a metal core with the appearance of porcelain. This design uses a metal substructure, or coping, for structural integrity, over which a tooth-colored ceramic layer is baked. PFM crowns provide a reliable balance between durability and aesthetics, making them a versatile option for both front and back teeth.
PFM crowns present aesthetic compromises despite their widespread use. The metal substructure can cause a dark line to become visible at the gumline, especially if the gums recede. PFM crowns also lack the natural translucency of enamel because the underlying metal blocks light transmission. There is also a risk of the porcelain layer chipping away, which can expose the underlying metal.
All-Ceramic and Zirconia Options
All-ceramic crowns represent the ultimate choice for patients prioritizing a natural, tooth-like appearance. These restorations are entirely metal-free, allowing light to pass through the material similar to natural enamel, which provides superior aesthetics and blending. Among the most popular all-ceramic options is Lithium Disilicate, often marketed under the brand name Emax.
Lithium Disilicate glass-ceramic is known for its high flexural strength, typically ranging from 360 to 500 megapascals (MPa), making it significantly stronger than older ceramic materials. This material’s combination of strength and high translucency makes it an excellent choice for restorations in the anterior (front) part of the mouth. It is also suitable for many posterior single-unit crowns, and its composition requires less aggressive tooth preparation than PFM crowns.
Zirconia, or zirconium dioxide, is a modern ceramic material that uniquely bridges the gap between the strength of metal and the aesthetics of porcelain. It is celebrated for its exceptional fracture resistance, with some forms exhibiting flexural strength comparable to metal alloys, often exceeding 900 MPa. This high performance makes zirconia a preferred material for use in the posterior region, where chewing forces are highest.
Zirconia crowns are available in different forms, allowing for customization based on the tooth’s location. Monolithic (solid) zirconia is milled from a single block and is prized for its maximum strength and resistance to chipping, making it ideal for molars or patients with severe clenching habits. Layered zirconia features a strong core covered with a more translucent porcelain layer to achieve better aesthetics, making it preferred for visible front teeth. High-translucency zirconia offers improved aesthetics but with a slightly reduced strength profile.
Defining the “Best” Crown: Key Selection Criteria
The choice of crown material is determined by a careful assessment of the tooth’s function and visibility within the mouth. Teeth in the anterior region, which are most noticeable when speaking or smiling, require materials with high aesthetic properties, such as lithium disilicate or layered zirconia. Posterior teeth, like molars, are subjected to much greater occlusal forces, making high-strength options like monolithic zirconia or metal alloys more appropriate to prevent premature failure.
Patient-specific factors also heavily influence the final selection. Individuals who suffer from bruxism need materials that can withstand intense, repetitive grinding forces, often leading to a recommendation for monolithic zirconia or a high-strength metal alloy. Conversely, patients with known sensitivities or allergies to nickel or other base metals should select a metal-free alternative, such as all-ceramic or zirconia.
The economic aspect remains a practical consideration, as different materials carry varying costs. Generally, base metal alloys are the most cost-effective option, while the newest, high-aesthetic ceramic materials tend to represent a higher investment. The longevity and performance of the final restoration are directly tied to how accurately the chosen material matches the unique demands of the patient’s oral environment.