Not Your Father’s Nonprecious
Steven Pigliacelli, CDT, MDT
It’s amazing how much things change over the years, from technology and materials to attitudes. The greatest insult you could give a dental technician in the ’80s was to say, “These teeth look like white Chiclets.” (For those of you under 40, Chiclets are smooth, hard, square, white pieces of chewing gum.) Our goal was to make natural-looking, detailed, esthetic restorations with striations and crack lines shade A3.5 with orange gingival. Today, with the bleached white craze that has swept the nation, we in essence now make square, perfect white teeth. OK, they don’t look like Chiclets, but the desire for “natural,” stained, detailed teeth is almost gone. The same is true for the acceptance of base or nonprecious alloys.
Nonprecious alloy had the negative reputation of being the metal for knock out commercial labs. It was not easy to work with, and the grinding from it contained nickel, beryllium, rexillium, and other nondesirable elements. But it was cheap. Noble and high noble alloys were the standard for quality restorations but at a much higher price. For example, gold alloy is not only higher in price per dwt, but being a denser alloy requires more alloy per unit than noble or base alloy. So a porcelain-fused-to-gold crown is substantially higher priced than fused to noble or base alloy. These days, gold and palladium are at an extremely high cost due to situations that have nothing to do with dentistry. For example, palladium is heading toward $1,000 an ounce because of its use in catalytic converters.
We have seen the emergence of milled titanium and zirconia as alternatives to traditional alloys. In the case of cast implant bridges such as hybrids or bar overdentures, milled titanium has been a huge success. The frame is milled out of titanium without the need for gold cylinders or alloy, resulting in cost savings and better fitting prosthetics. There are porcelains that can be baked to titanium, but they are technique-sensitive and more difficult to use. In most cases, labs and dentists choose not to use milled titanium for anything but hybrids and removable prosthetics.
Milled zirconia is another option for ceramic restorations, but in the case of implants, many feel that the zirconia interface is not strong enough and cement titanium cylinders into the framework to act as the interface to the implants. Full contour zirconia bridges are just stained and not very esthetic. Many fear that zirconia wears too much on opposing dentition. Also, zirconia does not have the ability to be welded in the event of a frame not seating. Cast alloy and titanium, on the other hand, can be welded.
Another option that exists today is milled cobalt chrome. But isn’t cobalt chrome a nonprecious alloy? Doesn’t this contradict past feelings about nonprecious? Not exactly. Titanium is a nonprecious alloy, and we have been using it for years. Modern cobalt chrome does not contain the harmful elements such as nickel and beryllium. It is not cast but milled, just like titanium and zirconia. Working with milled cobalt chrome is no different from working with titanium – no grinding and dust splashing in your face and no torch-casting at very high degrees. One great advantage is that it can be sectioned and welded. It can have regular porcelain applied to it without fear of incompatible oxide layers and highly technique-sensitive procedures. It is safe to say that modern cobalt chrome is not your father’s nonprecious. It has been a standard in Europe for years and has no real negative effects in the mouth.
More importantly, cobalt chrome ends up being more cost-effective. A single cast-alloy, screw-retained crown cost is based on model, analog, gold cylinder, labor, and alloy. However, a single cobalt chrome, screw-retained crown is based on model, analog, labor, and cost of milled unit. The milled unit is not cheap, but considering a gold cylinder can cost as much as $250, the savings are guaranteed. When looking at a roundhouse on six implants, the overall savings can be more than $1,000 per frame.
At present, only a few milling facilities offer milled cobalt chrome – Panthera Dental, Straumann Cares from Straumann, Atlantis Isus from Atlantis, and CMC Technology Center from Schein. The cost per unit varies between these companies, and labs will charge what they feel is appropriate for the labor. But in the long run, we’re looking at a very reliable and cost-effective alternative to cast-alloy ceramic restorations, with a more guaranteed esthetic result.