Crowns (Caps)

Procedure Details
Types and Variations of Crowns Available
Gold CrownsVS. Porcelain Crowns

There is much more to this topic than the steps actually taken to perform this procedure. The TYPE of crown selected is much more a concern for me when I am making a diagnosis and this decision makes a huge difference when it comes to longevity and esthetics. The terms “crown” and “cap” describe the very same thing. A crown is a metal (usually gold) or porcelain "helmet"  that covers and protects a tooth.

The Procedure Includes:

1. Reshaping the tooth.
2. Making an impression of the tooth and surrounding teeth.
3. Making a temporary crown to fit on the tooth for several weeks.
4. The impression is sent to a lab where the dental laboratory technician makes the actual crown. The crown that fits over the stone model is made to very precise tolerances.
5. At the second appointment, the temporary crown is easily lifted off, the final crown is tried into position, adjusted and final cemented to place.

Both gold and porcelain crowns have their place in dentistry. There are advances being made continually in this area of dentistry. The ability to bond crowns and especially all porcelain crowns to the tooth structure itself is one such improvement. New porcelains that are less abrasive to opposing teeth is another such improvement.

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Variations and Descriptions of Crowns Available

a. Gold Crowns

• Full gold crowns - cover the entire tooth to the gum line.
• Gold onlays - equal strength as full crown BUT less tooth reduction and edges that do not go all the way to the gum line.
• Gold inlays - gold castings that replace only the areas where a typical filling would be placed.

     b. All-Porcelain Crowns

• No metal under porcelain. These are most often used for front teeth. These can be placed on molars as well but  personally I am suspect of their longevity and a porcelain fused to metal crown can be done very esthetically.

     c. Porcelain/Gold Combination Crowns

• Porcelain fused to metal crowns - thin metal casting is first made, porcelain applied over the entire surface. No metal is placed at the gumline where the teeth are viewed - this is referred to as a porcelain margin.
• These are extremely esthetic when prepared and made correctly.

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Gold Crowns VS. Porcelain Crowns

This an area that you won't find discussed by many dentists nor at many places on the web yet I find it the cornerstone to the restorative part of my practice. "Restorative" refers to primarily placing crowns as required on weak and broken teeth. Naturally most people have negative thoughts about "gold" in their teeth. They think of it as old technology and very unaccepable in appearance. As far as technology goes, there have been advances in the metals combined with gold to improve its properties and dental cements have made huge progress in helping gold (and all crowns) stay in place much better. When it comes to the appearance of gold I would NEVER place a crown in an unacceptable visual area. I would never try to "talk" a 24 year old woman into gold in areas that would show in a smile. Yet I WOULD try to convince this same attractive woman into have gold placed on very back molars where it would out last porcelain and NO ONE could ever see it.

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WHY GOLD ???

What a good question. Even within this website there is a "cosmetic dentistry" area. I even show cases that have all porcelain and porcelain-to-metal crowns. So what gives? Well, first off we're speaking about gold on back teeth and most specifically, the molars. Second, taking off  perfectly good enamel just to cover it back with something that looks like enamel stopped making sense to me. Third, where necessary, tooth colored materials can be used on the front side of crowns so that metal won't appear in the smile line. Fourth, experience is a great teacher, it takes time to really develop a philosophy of practice. There are many philosophies to choose from, one famous philosopher - Hippocrates - cautioned physicians that their main goal was to "do no harm". Seeing failures and finding incredible mentors I got to the point where I knew I would only have gold restorations in my mouth and in the mouths of my family, I could then do no different for my patients. Fifth, (and VERY important) I always educate the patient to the benefits before proceeding with this or any other therapy, ultimately, it is the patient's decision as to how to restore their teeth.. Read on and I think you'll begin to see why I feel the way that I do.

When polled on the subject, dentists overwhelmingly respond that if their own teeth are being restored with crowns, they want restorations that include the least  tooth preparations along with the most forgiving restorative materials (gold), yet statistics show that more than 90% of crowns placed in America today are porcelain-to-metal. How is it then that dentists routinely place in their patients mouths that which they would not accept in their own mouths?

The average crown placed today has an expected life span of less than 5 years. Five years! How can this be? The answer, in a nutshell is that partial coverage tooth preparation procedures have been abandoned in favor of more aggressive procedures using unacceptable materials because it is easier to teach, easier to do, and in the minds of the dentists doing this work, more acceptable to patients.

There are two basic premises that hold true for restorative dentistry: (1) be as conservative as possible in removing tooth structure, and (2) use biologically acceptable materials. Crown and bridge dentistry is yielding to the demands of esthetics. There is much damage being done by the overuse of porcelain coverage on back teeth. This is a problem that is created by dentists who, for the most part, are trying to do something good for their patients.

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Why is it that I and others say gold on back teeth is more acceptable than porcelain? This question has many answers.

1. When an excellent gold restoration is done it is most often performed as a partial coverage restoration, what this means is that the tooth is not reduced nearly as much as for placing porcelain. Instead, anywhere possible, good enamel and tooth structure is left. (Image 1 and 2 below)
2. Reduction of a tooth for a porcelain-to-metal crown is much more severe than for metal alone. This also tends to produce more nerve problems than partial coverage crowns. When asked in 1970 what the major cause of root canal therapy was, Dr. Maury Massler, one of the fathers of modern root canal therapy, responded without hesitation, "the porcelain-to-metal crown!"
3. Partial coverage also stays away from the gums and therefore less irritation is present. Many times around porcelain crowns, there are bleeding gums that stay continuously irritated and can eventually lead to periodontal (gum) disease problems.
4. Porcelain (no matter how polished it seems) is 16 times more abrasive than enamel! This is because porcelain (glass) is an inherently fragile material, so alumina has been added to the ceramic for increased strength. This is essentially the same material we use in the laboratory for sand blasting. If a single porcelain crown opposes a natural tooth, a gold crowns or filling material, it will immediately begin to destroy that surface. (Image 3 below)
5. Gold castings are more accurate in their fit to the prepared tooth. Conversely, porcelains shrink as much as 20% during application.
6. Longevity - gold restorations will be in service much longer than most porcelain-to-metal crowns. (Image 4 below)

As a footnote, there is not a significant fee difference between the porcelain-to-metal and partial coverage gold crowns.

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Photos courtesy Tom Colquitt, DDS and William McHorris, DDS