Dental crown alloys -

High noble (precious), Noble (semiprecious), Base (nonprecious). | Advantages, disadvantages and applications for each type.

When making plans to have an all-metal (gold, white gold) or porcelain-fused-to-metal (PFM, PFG) crown made, your dentist may ask you to make a decision about what type of dental alloy is used.

There are 3 kinds.

In general, there are 3 basic categories of dental alloys that can be used. They are: high noble, semiprecious, and nonprecious. This classification system is based upon the metal's composition.

Each is different.

Each type has its own specific advantages and disadvantages, including: cost, insurance coverage, color (yellow or "white"), as well as general physical properties.

This page discusses each of the above considerations. However, if cost is not a factor, the alloy having the highest precious metal content typically makes the best choice.

Dental alloys.

Types of crowns that have a metal component (all-metal, porcelain-fused-to-metal) are made using specific types of alloys.

No pure metals are used, not even gold. This is because for dental applications, the physical properties of alloys are superior.

(In the case of gold, it is too soft to provide good wear characteristics. And forces directed onto a pure gold object will tend to deform it.) (Knosp 2003) [page references]

Alloy classifications.

Here's the formal classification system that is used to categorize dental alloys.

1) High noble alloys (Precious metal)

This group has a composition that is over 60% noble metal (gold, palladium and/or platinum), of which more than 40% must be gold.

Examples of high noble dental alloys.
  • Product: JRVT  /  Alloy Color: Yellow  /  Composition: 77% Gold, 13% Silver, 8.5% Copper, 1.0% Palladium, Less than 1% Indium, Iridium, Zinc
  • Product: Noble-Cast 67  /  Alloy Color: Yellow  /  Composition: 64.0% Gold, 23.4% Silver, 3.0% Palladium, 0.1% Platinum
  • Product: Encore (White High Noble)  /  Alloy Color: Silver (white)  /  Composition: 48% Gold, 40% Palladium, 4.3% Zinc, 3.9% Tin, 3.75% Indium, 0.05% Rhenium

2) Noble alloys (Semiprecious metal)

These alloys have at least 25% noble metal content.

Examples of noble dental alloys.
  • Product: Argenco 20  /  Alloy Color: Yellow  /  Composition: 20% Gold, 20% Palladium, 40% Silver, 18% Indium, 2% Zinc, Less than 1% Iridium.
  • Product: Argelite SR+  /  Alloy Color: Silver (white)  /  Composition: 79% Palladium, 8.4% Tin, 5.0% Cobalt, 5.0% Gallium, 2.0% Gold, 0.6% Ruthenium

3) Non-noble (Nonprecious metal)

These alloys are also referred to as base metals. Their noble metal content is less than 25% (they may have none). They often contain large percentages of nickel, cobalt, chromium or beryllium.

Examples of non-precious (base) dental alloys.
  • Product: Argeloy N.P. Supreme  /  Alloy Color: Silver (white)  /  Composition: 61% Cobalt, 27% Chromium, 6% Molybdenum, 5% Tungsten, 1% Silicon, Less than 1% Manganese, Iron, Carbon
  • Product: Argeloy N.P.  /  Alloy Color: Silver (white)  /  Composition: 54.0% Nickel, 22.0% Chromium, 9.0% Molybdenum, 4.0% Iron, 4.0% Niobium, 4.0% Tantalum, 3.0 % Trace elements.

Why should you care what alloy is used to make your crown?

There are several reasons why you should care what metal is used. Some of them will affect you directly. Others will be more of a concern to your dentist, or the dental laboratory that makes your crown.

a) Costs - High noble metal alloys cost more.

The "noble" dental metals are gold, platinum and palladium.

Nowadays 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 restorations where the overall amount of metal they contain is relatively small, the price difference between using a high-noble or base-metal alloy might be small.
  • But in the case where an all-metal restoration is made for a large molar, the cost difference might be significant enough to affect your decision.
b) 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 which type is used.

Picture of a deep-yellow gold dental crown.

This gold crown has a yellow color.

c) Color - Dental alloys can be white or yellow.

In those cases where an all-metal crown is being placed, you might have a preference as to whether it should have a yellow (like gold) or silver ("white," white gold) coloration. The alloy's composition determines its color.

d) Some people have metal allergies.

Studies report that about 10% of the female population and 5% of males have an allergic response to nickel, chrome and/or beryllium. These metals are often found in the composition of nonprecious (base) alloys.

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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.

Picture of a porcelain-fused-to-metal dental crown.

A porcelain-fused-to-metal dental crown.

The advantages of precious dental alloys.

High noble alloys constitute the "gold standard" of dental metals. All others are compared to them.

Dentists and dental lab technicians generally prefer working with these alloys, especially those that have a high gold content. That's because:

  • They are the easiest to cast and polish.
  • Restorations made using them are known for their accurate fit on their tooth. But also, this type of alloy is relatively malleable so the fit of the restoration can be adjusted if needed.
  • These metals generally offer the most predictable bond with porcelain (an important consideration with porcelain-fused-to-metal restorations). (Uusalo 1987)
  • They offer superior corrosion resistance.

Which type of alloy should you choose for your dental crown?

As mentioned above, assuming that cost is not a factor, opting for a high noble dental alloy makes the best choice.


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