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.
Source= http://www.dental-picture-show.com/dentists-crowns/a-gold-crowns.html
