If one or more of your teeth need to be restored with full coverage crowns, Dr. McArdle may recommend that all-gold crowns (as opposed to porcelain-fused-to-gold ones) be used should the teeth involved be in high stress areas. Teeth that Dr. McArdle's experience has shown tend to endure more severe wear include upper second molars (those in front of your wisdom teeth, if they are present) and most lower molars. One of the reasons these teeth suffer more stress when you bite or chew is because of their relative position in your mouth. A bite discrepancy can also account for excessive wear and tear, but even when such discrepancies have been harmonized (equilibrated or adjusted for), teeth in the posterior regions of your mouth undergo increased loads.
Your jaws are connected by joints that are very similar to hinges (the TMJs or Temperomandibular Joints) that are located just in front of your ears. Due to the principle of leverage, the closer your teeth are situated to these joints, the more force is generated on them. Think of a hinged nutcracker. When you want to open a nutshell with it, would you put the shell towards the end of its handles before you squeezed or further down at its hinge? You would put the nut down at the hinge where leverage will create greater cracking power, making the nutshell easier to split. In the same way, the porcelain covering of a porcelain-fused-to-metal crown is more likely to fracture in the high stress areas noted above, which are the closest to your jaw joints. If you grind your teeth while sleeping, as many patients do, the leveraged force on your teeth mentioned above is multiplied several fold at these elevated pressure locations in your mouth. Many times the porcelain fractures that result under these circumstances are not repairable, necessitating that your crown so fractured be redone.
This porcelain fracture (arrow) occurred less than one week after the crown was inserted, in a case
where the patient had been previoulsy advised to have a gold crown placed.
The same tooth with a cast gold crown in place after one year.
Luckily, the areas where your teeth bear these greater loads are not usually seen when you speak or smile, so all-gold crowns on those teeth do not typically present an esthetic problem. Dr. McArdle rarely, if ever, advises that all-gold crowns be used for any of your teeth forward of the molars on the lower or in front of the second molars on the upper. Some people (like Julia Roberts) can show their entire upper first molar on smiling, so Dr. McArdle only places gold crowns on these teeth in cases of extreme attrition.
Third types of crowns used in dentistry are called metal-free crowns and, as the name implies, are made entirely of porcelain with no underlying metal substructure. They are the most esthetic option available and produce a naturally beautiful smile when used on front teeth. However, Dr. McArdle believes that they should almost never be used on your back teeth because their lack of metal infrastructure makes them too weak to withstand the forces present in these areas. Some dentists do prescribe this type of crown for even molar teeth, but Dr. McArdle has seen too many failures in patients with this type of treatment who are new to our office to be able to propose these types of restorations to his patients of record.
A metal-free crown on a lower molar that fractured after only a few years of service, exposing its underlying tooth.
Another reason why gold based restorations work so well in your mouth is their compatibility with your gingiva (gum tissue). No dental restorative material is so well tolerated by your gums as gold. While other metal alloys used in porcelain-fused-to-metal crowns composed of nickel or beryllium can be irritating or even mildly toxic to your gingiva, gold produces no ill effects when properly placed. This is why when Dr. McArdle does restore your teeth with porcelain-fused-to-metal crowns, he will prescribe a gold alloy (such as Captek) as the underlying metal. This not only ensures the potential for optimal gum health, it also results in beautiful esthetics. The only tooth colored alternative to gold crowns that are nearly equivalent would be zirconia crowns that are in Dr. McArdle's estimation about 95% as effective.
IF YOU HAVE ANY QUESTIONS ABOUT THE RATIONALE FOR USING ALL-GOLD OR
GOLD ALLOY PORCELAIN-FUSED-TO METAL CROWNS, PLEASE ASK DR. MCARDLE.
