As a dentist, I often discuss options for dental crowns with my patients. A crown is a common restoration used to replace missing tooth structure and protect a tooth from wear and fracture. We have a variety of materials available today, each with its own advantages. Let’s explore some of the most common ones.
Historically, gold was one of the earliest materials used for dental crowns. The gold used isn’t pure but rather an alloy containing metals like silver, platinum, palladium, copper, and zinc, with gold making up to 60%. Gold crowns are incredibly strong and resistant to fracture and chipping. This strength allows them to be made quite thin, meaning less of your natural tooth structure needs to be removed during preparation. Gold is also malleable and has a similar hardness to enamel, so it wears much like a natural tooth.
However, the most obvious drawback to gold is its appearance; it doesn’t match the color of natural teeth. For this reason, we typically recommend gold crowns for teeth further back in the mouth where they are less visible. Gold doesn’t bond directly to tooth structure and relies on mechanical retention. Gold crowns must also be fabricated in a dental laboratory, which is a labor-intensive process requiring a temporary crown while your permanent one is being made. The cost of gold crowns tends to be higher due to the materials and lab work involved.
A significant advancement in dentistry came with the development of porcelain materials that could mimic the look of natural teeth. Early ceramics were somewhat weak and needed support, leading to the creation of the Porcelain Fused to Metal (PFM) crown. For many years, PFM crowns were a standard, providing an esthetically pleasing option that resembled natural teeth.
The main disadvantage of PFM crowns is that they require even more tooth structure to be removed compared to gold, to accommodate both the metal base and enough porcelain to mask the metal color. Like gold crowns, PFM crowns are also labor-intensive to create in a lab and require a temporary crown. While the metal is strong, the ceramic layer can be brittle and prone to fracturing off the metal. The cost is comparable to or sometimes more than a gold crown.
As dental material science has progressed, we’ve seen the development of stronger ceramic restorations. One notable advancement was the introduction of Lithium Disilicate in 1998, which was stronger than previous ceramics and offered excellent esthetics. This material was refined and became known as EMax.
EMax crowns have become very popular due to their ease of fabrication, strength, and beauty. They can be made in a lab by pressing molten ceramic into a mold or using CAD/CAM technology. The CAD/CAM process even allows us to fabricate EMax crowns in the office on the same day, eliminating the need for a temporary crown. Additionally, improvements in bonding techniques work very well with EMax, allowing us to preserve more natural tooth structure. While the reduction needed for EMax is less than for PFMs, it is still slightly more than for gold crowns.
Another material that has gained prominence is Zirconia. Zirconia is a metal oxide found in nature as the mineral Zircon. It’s a very strong and biocompatible material with a ceramic-like appearance but the strength of metal. Zirconia crowns are typically fabricated using CAD/CAM milling in a partly sintered state and then heated to increase their strength.
The strongest Zirconia crowns, while white, can sometimes appear very opaque and don’t transmit light like natural teeth. However, their strength is similar to metal, allowing for thin crowns. More recently, translucent Zirconia has become available, offering better transparency and a more natural look, though with a slight trade-off in strength. The strength of translucent Zirconia is comparable to that of an EMax crown. Zirconia bonding is different from ceramic bonding and traditionally used more like a metal crown, but recent advancements are making Zirconia bonding more predictable. Zirconia is also often less expensive due to its abundance.
While other materials are used, these are some of the most common options we utilize today. If you have any questions about dental materials or which option might be best for you, please feel free to contact our office.
