All-metal dental crowns / Gold crowns -

Advantages / Disadvantages / Applications where they make a best choice. / Selecting the right dental alloy: high-noble, noble vs. non-precious. / Yellow vs. white gold.

What are all-metal crowns?

Just as their name implies, this type of crown has a construction that's 100% metal.

A gold dental crown.

The classic all-metal is the "gold" crown, however, they can also be made using silver-colored metals too ("white gold").

What type of metal is used?

Crowns aren't made out of pure metals because none has the ideal physical properties required for dental applications (good strength, resistance to tarnish and corrosion, wear resistance and characteristics that make it easy for the lab technician to fabricate the restoration and the dentist to adjust it).

Dental alloys.

What is used is some type of dental alloy (a blend of metals). One that's been engineered so its physical properties approach the ideal.

That means your "gold" dental crown isn't 24 karat (pure gold). In fact, the "precious" yellow-gold alloys used to make all-metal dental crowns usually only run about 15 to 20 karat. (See below for more details.)

Advantages of all-metal / gold crowns.

Opting for an all-metal crown can make an excellent choice, if you don't mind the fact that it's not tooth-colored. Here's why:

a) Superior strength.

Due to their 100% metal construction, there's no type of crown that's stronger than an all-metal one. (That can be said no matter what type of dental alloy has been used to make it.)

Failure due to breaking is an extremely rare event. In comparison, that's a real possibility with an all-ceramic crown. Or in the case of a porcelain-fused-to-metal one (PFM), a significant portion of its porcelain covering may fracture off thus resulting in restoration failure.

b) Superior longevity.

Due to their single-component construction and the great strength and durability characteristics they possess, no other type of dental crown can be expected to provide more lasting service than an all-metal one.

Considerations.

That doesn't mean that other types of crowns can't provide lasting service too. But in terms of predictability (what type of things might go wrong and how often these events occur), an all-metal crown is the safest bet possible.

c) Good biocompatibility.

In terms of how your crown might affect you or your mouth, all-metal crowns generally offer good biocompatibility.

Minimal wear to opposing teeth.

The wear coefficient of dental alloys is typically similar to tooth enamel. That's good because it means that restorations made using them won't cause excessive wear on the teeth they bite against.

The specific metal used may matter. - As rules of thumb, "gold" (high-noble, see below) alloys typically are "kind" to teeth in this manner. Possibly base-metal alloys are comparatively more abrasive to opposing teeth. (Yin 2004) [page references]

Considerations.
  • Keeping in mind how many decades a person's teeth might be in perpetual contact with the crown opposing them, this might be a significant point to consider. Especially in the case where they have a habit of clenching or grinding their teeth.
  • In comparison to all-metals, porcelain-surface crowns that have not been polished or glazed appropriately (a failure on your dentist's part) are likely to cause tooth wear, possibly significantly so.

    Beyond that, due to the wide range of ceramics that can be used to make tooth-colored crowns, no other hard and fast rules can be stated. Studies do suggest however that some types of ceramics are kinder or gentler to opposing dentition than others, possibly on the same order as high-noble dental alloys. (Yin 2004)

Hypoallergenic

While possible, it's relatively rare for a person to have an allergic sensitivity to a crown that's been made using a "gold" (high-noble) dental alloy. This same statement cannot be made for base-metal ones (see below).

Considerations.

In cases where potential complications with a metal allergy are a concern, placing an all-ceramic dental crown can sidestep this issue entirely.

Gold dental crowns have a very accurate fit.

d) Superior fit.

When a "gold" (high-noble) dental alloy is chosen for an all-metal crown, no other type of restoration exceeds the crown-to-tooth fit that's possible.

  • Precious alloys have characteristics that make them easy and predictable to work with during crown fabrication.
  • And even if the dentist identifies a slight aspect of the crown's original fit that needs improvement, the malleable (pliant, workable) nature of a high-noble metal allows that an adjustment can be made.

    (In comparison, base-metals are considered fairly unworkable. Dental ceramics have no potential for this same type of adjustment.)

e) Less tooth reduction is required.

When preparing (trimming) a tooth for dental crown placement, comparatively less tooth reduction is needed for an all-metal as opposed to a porcelain-fused-to metal or (almost all types of) all-ceramic crowns.

That's because crown strength is the only consideration involved. And since dental alloys are so strong, only about 1.5 mm of thickness is required (about the same thickness as a penny). In comparison, most porcelain-surface crowns require 2 mm or more.

Disadvantages of all metal crowns.

a) Their shiny metallic appearance.

The single disadvantage of an all-metal is the obvious. It simply doesn't look white like a tooth.

If that were not the case, in the vast majority of cases choosing a "gold" (high-noble alloy) crown would make the very best choice.

Gold crowns on a 1st and 2nd molar.

A gold crown on a molar that shows prominently.

The look of one or both might be too much for some people.

Minimal-visibility applications.

Metal crowns do make a great choice for those teeth that are hard for others to see.

Each individual person's situation will be different but possible candidates might include: 1) lower 2nd and 3rd molars, 2) upper third molars, 3) possibly some upper second molars, 4) possibly some lower first molars.

Upper first molars are typically too prominent in a person's smile to have a shiny metal crown placed on them.

Ask your significant other's opinion.

Crowns are expensive items and there are no free do-overs. Make sure to ask your significant other (the person who spends the greatest amount of time looking at you) for their opinion when making this decision.

b) Metal allergies.

About 10% of women and 5% of men experience an allergic response to nickel, chrome and/or beryllium. Base-metal dental alloys (see below) frequently contain these metals and for that reason may prove problematic for some patients.

The use of a high-noble ("gold") alloy instead of a base one may offer a solution. The more predictable alternative would be to place an all-ceramic (non-metallic) crown.


Which dental alloy should be used to make your crown?

There are a number of types of alloys that can be used to make all-metal dental crowns. And each one has its own specific composition, and therefore its own unique physical properties, that makes it best suited for certain types of applications.

You may be asked to make a decision.

Dentist frequently require input from their patient as to which type should be used (this usually has to do with dental insurance or cost factors).

The following information is aimed at helping you understand the issues associated with making this decision.

1) Types of dental alloys.

a) High noble (precious).

This category represents the "gold standard" of dental alloys, and the one by which all other types are compared.

The composition of a high-noble must include over 60% precious metal (gold, platinum, and/or palladium), of which over 40% is gold.

b) Noble (semiprecious).

Alloys in this group must have a composition that's over 25% precious metal (gold, platinum, and/or palladium).

c) Non-noble (base).

These alloys contain less than 25% precious metal. A large portion of their content may be nickel, chromium or beryllium. (Some people are allergic to these metals, see above.)


Issues to consider when choosing the type of alloy for an all-metal crown.

a) Dental alloys can be white or yellow.

The color of the metal used to make your crown may be the only one of its characteristics that's much of a concern to you. Dental alloys can be gold (ranging from a very pale to very deep yellow) or silver ("white," "white gold") colored.

Composition.

It's an alloy's blend of metals that dictates its color. But color alone doesn't necessarily give a hint to its exact composition. Some high noble alloys are white ("white gold"), even though by definition they contain over 40% of the metal gold, which is of course yellow.

In regard to this topic, your dentist doesn't care what color your crown is. They only care about the physical characteristics of the metal used to make it. And many white and gold alloys have similar properties.

b) Noble metals are more expensive.

Cost considerations.

Noble and high-noble dental alloys cost more than their non-noble (base-metal) counterparts due to the fact that they contain a greater percentage of precious metals (gold, platinum, and/or palladium). High-noble alloy contains the highest percentage and is therefore the most expensive.

How much more expensive?

Only the dentist performing your work can tell you exactly, but as a ballpark figure you might expect a crown made using a precious alloy to run on the order of 15% or so more than a non-precious one. In terms of dollar amount, that might be on the order of $100 to possibly even $200 more.

Insurance considerations.

Ask your dentist's office staff for information, some dental insurance plans may limit what types of alloys may be used. Or they may provide coverage at different rates for different classes of metals.

c) Metal allergies.

The potential for experiencing an allergic reaction to your crown's alloy (a relatively rare situation) is generally greater when a non-noble (base) alloy has been selected. But of course, it simply depends on exactly which metal you are allergic to. (See mentions above.)

d) Your dentist's preference.

Your dentist may have a strong opinion about which type of alloy should be selected for your new crown. Their concerns typically involve issues such as which is easiest for them to work with and which tends to give them the best and most predictable result.

  • Dentists usually prefer high-noble alloys.

A high noble (precious) alloy usually makes the best choice.

If given the situation where cost isn't a factor, it would be the rare case that selecting a high noble alloy for your new all-metal crown didn't make the best choice, hands down.

As mentioned above, it offers advantages related to crown fabrication, fit and biocompatibility that other classes of alloys don't. And if its added expense isn't a significant factor for you, then there are no disadvantages in choosing it.

As a final test, you might ask your dentist what they would choose for themselves or their mother. Expect to hear them say "high-noble gold alloy."

 
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