Dental-crown alloys: High noble (precious), Noble (semiprecious), Base (nonprecious).
When making plans to have a crown placed, your dentist may ask you to make a decision about what type of metal alloy is used when it is fabricated. (This is a decision that needs to be made for all-metal and porcelain-fused to metal dental crowns.)
In general, there are 3 basic types of dental alloys that can be used. They are: high noble, semiprecious, and nonprecious (this classification system based upon the metal's composition). Each type has its own advantages and disadvantages, including: cost, insurance plan coverage, color (gold or "white"), as well as general physical properties.
What types of metals are used to make crowns?
Crowns (all-metal and porcelain-fused-to-metal) are made using specific types of dental alloys. No pure metals are used for crowns, not even gold. This is because the physical properties of dental alloys are superior.
The classification of dental alloys.
Here's the formal classification system that is used to categorize dental alloys.
1) High noble alloys (Precious metals)
This group of alloys has a composition that is over 60% noble metal (gold, palladium and/or platinum), of which more than 40% must be gold.
These metals constitute the "gold standard" of dental alloys; all others are compared to them. High noble alloys are the easiest type of metal to work with (for both the dentist and dental laboratory) and create the most predictable bond with porcelain.
2) Noble alloys (Semiprecious metals)
These alloys have a noble metal content that is, at minimum, over 25%.
3) Non-noble (Nonprecious metals)
These alloys are also referred to as base metals. Their noble metal content is less than 25%. They often contain large percentages of nickel, chromium or beryllium.
Why should I care what metal is used to create my dental crown?
There are several reasons why the type of dental alloy that is used to fabricate your dental crown should be important to you. Some of these reasons will affect you directly. Others will be more of a concern to your dentist, or the dental laboratory that makes it.
A) Color - Dental alloys can be white or yellow.
In those cases where an all-metal dental crown is being placed, you might have a preference as to whether it should have a yellow (like gold) or silver ("white") coloration. The alloy's composition determines its color.
B) Costs - High noble metal alloys cost more.
The "noble" dental metals are gold, platinum and palladium. These metals are pricey. And the greater the percentage of them found in the composition of an alloy, the greater its cost will be. With some applications, the overall cost between using a high noble or base metal alloy might be small. But in the case of an all-metal crown for a large molar, it might be a consideration.
C) Dental plan and insurance policy limitations.
If some type of dental plan is paying a part of your bill, you might check to see if there are any limitations as to the type of metal that can be used for crowns. The policy might state that they do not cover the cost of high noble alloys. Or the level of coverage might change based on the type of alloy that is used.
D) Some people have metal allergies.
Studies report that about 10% of the female population and 5% of the male have an allergic response to nickel, chrome and/or beryllium alloys. These metals are often found in the composition of nonprecious dental alloys.
E) The physical properties of the alloy are an important consideration.
Dentists and dental laboratories often have a set opinion about which types of dental alloys they will consider working with. This is because their goal is getting the job done right, the first time. They know that any difficulties or problems experienced will just end up costing them money. So, if choosing a certain type of alloy makes getting a positive result more likely, then that's the one they are probably going to want to work with.
Advantages of precious dental alloys.
In general, dentists and dental labs prefer to work with high noble alloys. These metals are easiest to cast, provide the most accurate fit on the tooth, offer some degree of malleability (so the fit of the metal can be adjusted, if needed), and offer the most predictable bond with porcelain.
Which type of alloy should you choose for your dental crown?
As mentioned above, assuming that cost is not a factor, high noble dental alloys makes the best choice.