A dental crown is a tooth-shaped cap placed over a damaged or weakened tooth. This restoration protects the remaining structure, restores the tooth’s original size and shape, and improves its appearance. Crowns are often recommended after a root canal, to restore a broken tooth, or to cover a dental implant. Material selection directly impacts the crown’s longevity, strength, and aesthetic outcome.
The Four Primary Types of Dental Crown Materials
All-Metal Crowns, often called gold crowns, are composed of metal alloys that may contain gold, platinum, and copper. This composition results in an exceptionally strong and durable restoration that resists wear, chipping, and fracture. Metal crowns are highly biocompatible and require the least amount of natural tooth reduction during preparation compared to other options.
Porcelain Fused to Metal (PFM) crowns combine the strength of a metal substructure with a tooth-colored porcelain overlay. The underlying metal core provides structural integrity and resistance to chewing forces. PFM crowns offer a balance of durability and a pleasing appearance, making them a versatile option.
All-Ceramic crowns represent a metal-free alternative, with Lithium Disilicate (E-max) being a prominent example. This material is a high-strength glass-ceramic known for its superior light-refracting properties, which closely mimic the translucency of natural tooth enamel. Lithium disilicate is composed of quartz, lithium dioxide, and other oxides, forming a crystalline structure. All-Ceramic options are favored for highly visible teeth where aesthetics are paramount.
Zirconia crowns are made from zirconium dioxide, a highly durable ceramic material often stabilized with yttrium oxide. Although derived from the metal zirconium, the final product is a ceramic with exceptional fracture resistance and strength. Zirconia is available in two main types: monolithic, which is extremely strong but more opaque, and high-translucency, which is more aesthetic but slightly less strong. This material is widely regarded for its biocompatibility and its ability to withstand significant biting pressure.
Essential Factors Guiding Material Selection
The determination of the “best” crown material depends entirely on the specific clinical situation. Dentists assess several variables to recommend a material that provides the optimal balance of function and aesthetics. The location of the tooth is a primary consideration; posterior teeth, such as molars, must endure heavy masticatory forces, making strength and durability the priority. Anterior teeth, visible when smiling, prioritize aesthetic qualities like translucency and color matching.
A patient’s history, such as the presence of bruxism (chronic teeth grinding), dictates the need for materials that resist high-impact wear. This typically leads to a recommendation for an extremely durable material like metal or high-strength zirconia. The chosen material must be able to withstand these constant, abnormal forces without fracturing.
The health of the surrounding gum tissue is another important factor, particularly the material’s interaction with the gingival margin. Materials like gold and zirconia are generally highly biocompatible and well-tolerated by soft tissues, minimizing the risk of irritation. Conversely, some base metal alloys used in PFM crowns can occasionally lead to tissue sensitivity or recession, potentially revealing the dark metal underneath.
Consideration must also be given to the crown material’s effect on the opposing tooth during chewing. A material significantly harder than natural enamel can cause excessive wear on the tooth it bites against. Gold alloys exhibit a wear rate similar to natural enamel, making them gentle on opposing teeth. While the hardness of some older zirconia types posed a risk, newer, polished formulations have improved this characteristic.
Side-by-Side Comparison of Performance and Cost
All-ceramic crowns, particularly lithium disilicate, rank highest for aesthetics due to their ability to mimic the light-handling properties of natural enamel. These crowns are the preferred standard for single-tooth restorations in the highly visible anterior zone. High-translucency zirconia has rapidly improved its aesthetic rating, offering an attractive, metal-free option suitable for posterior teeth as well.
In terms of pure strength and durability, the all-metal alloys, especially high-noble gold, historically offered the longest service life, often lasting decades without chipping. Modern monolithic zirconia now rivals or exceeds metal in fracture resistance, making it an excellent choice for posterior use where function is paramount. PFM crowns provide a mid-range solution, balancing the good strength from the metal core with sufficient aesthetics for many areas of the mouth.
The relative cost of crowns generally reflects the complexity of the material and its properties. All-metal crowns, particularly base metal alloys, are often the most economical choice, followed by PFM crowns. All-ceramic (E-max) and zirconia crowns typically represent a higher upfront investment due to the advanced technology and materials involved in their fabrication.