Crowns – The Advantages and Disadvantages of Different Materials

 In this post, I’ll compare the advantages/disadvantages of each of the crown materials discussed last week.

Gold crowns

Prior to when porcelain became available in dentistry, the gold crown was the standard material used.

The advantages include:

• A very accurate fit – possibly the most accurate fitting crown dentists have ever used.
• An even wear coefficient – Gold crowns wear at a rate very close to that of enamel – in other words, over time enamel against gold will wear each other down evenly, similar to enamel against enamel.
• Esthetics and appearance – Depending on where it is used and who is looking at the crown – gold can be a plus or a minus.
• Kinder to the tooth – A gold crown generally needs less tooth reduction because gold can be made very thin and less reduction is more kind to the tooth.
• Easier to position – The gold crown is placed on the tooth with traditional cement which is easy for the dentist to place and clean up.
• Strength – Finally, a gold crown is very strong since it won’t chip or break as some porcelains or ceramics can.

Overall gold is an excellent choice.

Disadvantages include:

• Cost – Today, cost of gold crowns is a major disadvantage since the price of gold has greatly increased and insurance will not cover the additional cost difference between a gold crown and a standard crown, so you must pay the difference.
• Esthetics and appearance – As mentioned above, depending on where it is used and who is looking at the crown, gold can be a plus or a minus.

Metal/Porcelain Fusion Crowns – A porcelain fused to metal crown is the standard crown made in dentistry today.

Advantages of this type of crown:

• Strength – It has good strength because of the metal layer covering the tooth
• Esthetics – It has good esthetics because of the porcelain bonded to the metal.
• Ease of positioning – A porcelain to metal crown is placed on the tooth with cement just like a gold crown is placed. A porcelain to metal crown fits the tooth accurately, although not as highly accurate as a gold crown.

Disadvantages of this type of crown:

Edges that may become exposed – Esthetics can sometimes be a problem if the margin of the crown at the gum-line becomes exposed due to gum recession, since there is often has a dark line at the edge of the margin.
Esthetics can also be compromised at times because the metal layer must be hidden by using extra porcelain layers to hide the metal before adding esthetic porcelain.
May be less natural looking – Porcelain to metal crowns do not allow light to shine through like a real tooth or ceramic crown, so achieving a natural look is more difficult.
Greater tooth reduction – A porcelain crown requires more tooth reduction compared to a gold crown, so it is not as kind to the tooth. Since the porcelain to metal crown is the standard crown used today, it is the most economical of the crowns available.

Glass Ceramic Crowns and Glass-Free Ceramic Crowns​ – These are the most esthetic crowns made today.

Advantages:

Esthetics – Glass ceramic crowns like lithium disilicate crowns have no metal, so they are very esthetic. There is no metal portion, so the esthetics are better than with the porcelain to metal crown.
Strength – The glass ceramics are also very strong, so they can be made thinner than porcelain to metal crowns.
Kinder on teeth – Since these crowns can be made thinner, it translates to less reduction and trauma to the tooth.
Additional strength – To make the ceramic crowns even stronger, these crowns can be bonded to the tooth instead of cemented on. Cementing a crown to a tooth is like placing two glass slabs together with water in between. The glass slabs are very hard to separate, but they are not bonded together. Bonding to a tooth is more like using super glue to hold the slabs together. It is a much stronger connection. The combination of a stronger material and added bonding strength mean the ceramic crowns are stronger than the porcelain to metal crowns.

Disadvantages:

Bonding is more difficult for the dentist to do however, so it takes more time and effort.
Cost is a disadvantage of the ceramic crowns. The lab cost to the dentist is higher than the porcelain to metal crowns, so the cost to the patient is higher. The extra time needed to bond the ceramic crowns can also increase the cost.

Glass-free ceramic crowns

Glass-free ceramic crowns such as zirconia crowns offer yet another option and have some unique advantages/disadvantages. As with the glass ceramic crowns, glass free crowns have no metal.

Advantages:

Highest strength – because of their comparable strength, glass-free ceramic crowns make them a good choice for back teeth.
Attachment options – Glass free crowns can be cemented or bonded to the tooth just like glass ceramic crowns

Disadvantages:

Less esthetic than glass ceramic crowns – Although stronger than the glass ceramic crowns, these crowns are not quite as esthetic as the glass ceramic crowns.
Fit – Because of the way they are made, glass free crowns are not quite as accurate fitting to the tooth as glass ceramic or porcelain to metal crowns. The fit does not compromise the crown, however.

Overall, it should be noted that most of these comparisons reflect choices for crowns made for back teeth. To get the highest esthetic results for a front tooth, a crown will have a ceramic portion for a majority of the crown and a porcelain layer placed over the visible surface. The porcelain layer is more esthetic than the ceramic portion and will achieve best esthetic result.

To sum it all up:

A standard porcelain to metal crown will be fairly esthetic, fairly strong, cost effective and less kind to the tooth.
Ceramic crowns will be esthetic to very esthetic, strong, more kind to the tooth and less cost effective.
A gold crown will be kind to the tooth, very strong, esthetic or not (depending on your perception), and less cost effective.
Porcelain to metal crowns and ceramic crowns will wear an opposing tooth more, meaning they will grind away more of the opposing enamel than a natural tooth or gold crown would.

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