The esthetic dentist’s PFM

Oct. 1, 2006
As restorative dentists, we are constantly faced with the task of determining which restoration will best suit our patient.

As restorative dentists, we are constantly faced with the task of determining which restoration will best suit our patient. At times, the overriding concern is esthetics. In some cases, strength is our main concern. Based on our ability to achieve a dry field, the need for a restoration that can be conventionally cemented might drive our decision. Perhaps the subgingival location of a crown margin, or the unhealthy appearance of the gingiva, would dictate choosing a material that demonstrates less bacterial accumulation than any other material. This would include enamel.

When choosing a ceramometal crown for a particular patient, many dentists simply think in terms of ceramic materials. Almost no consideration is given to which metal substructure is most appropriate. Most clinicians have observed that all-ceramic restorations provide better esthetics than most ceramometal crowns placed on anterior teeth. The esthetic shortcomings of most ceramometal crowns, however, are almost always a result of the metal coping. On the other hand, many dentists have shown a reluctance to embrace all-ceramic restorations, either due to concerns about strength and longevity or concerns about having to bond the restoration rather than cement the restoration. As a result, anterior ceramometal restorations will continue to be prescribed in large numbers for quite some time.

The good news for ceramometal fans is that one product overcomes all of the objections listed above. Captek is an 88 percent gold composite alloy coping that serves as the substructure in a porcelain to Captek crown. Specifically, the gold composite alloy coping consists of approximately 88 percent gold, 4 percent platinum, 4 percent palladium, 3 percent silver, 1 percent iridium, and 1 percent ruthenium. The copings are fabricated, utilizing replicated master dies composed of a proprietary refractory material. A thin sheet of wax (Captek P) impregnated with platinum-palladium-gold alloy particles is utilized to coat the refractory die. The die is then placed in a porcelain oven. During this cycle, the alloy particles undergo a fusing process that creates a sintered, porous, solid metal coping while the wax is eliminated.

Upon removal from the oven, the solid platinum-palladium-gold coping is attached to the refractory die. Then another thin layer of wax (Captek G) containing 97 percent pure gold particles is placed over it. During the next firing cycle, the wax is again eliminated as the gold particles melt and infiltrate the pores in the underlying coping. During the melt-infiltration phase, the gold penetrates the entire width of the coping. This produces an internal and external gold surface.

Clinically, this internal and external gold surface is of tremendous benefit. Internally, the gold surface contacts the preparation. Due to its high nobility, the gold surface eliminates any potential for allergic or adverse reactions. Dr. Gordon Christensen remarked at a recent CRA Update course that nearly 50 percent of women will have some sort of allergic or adverse reaction to nonprecious metals. This reaction can take from seven to 10 years to develop. The implications of Dr. Christensen’s statement are clear. Why use nonprecious metals if a high-noble substitute with equal strength and superior esthetics is available?

Captek’s advanced gold alloy reduces the accumulation of harmful bacteria at the gum line by 90 percent as compared to natural tooth structure. Based on survey analysis data collected by J. Max Goodson at the Forsyth Dental Institute, Captek crowns exhibit less bacterial accumulation than either conventional full-coverage porcelain to high-noble crowns or high-noble, full-cast crowns. While this lower bacterial accumulation benefit might sound trivial, think about the hygiene exams you have done during the last five years. How many times have you asked your hygienist how Mr. Smith’s gums are doing, only to hear the words, “They look great except for around the teeth that have crowns”? It’s difficult enough to fool Mother Nature with a subgingival margin. Why not use material with a proven lower plaque and bacterial accumulation rate?

The ability to prepare the tooth in a conservative fashion is another clinical benefit of the Captek coping material. Chamfer, shoulder, knife-edged, or beveled preparations can be used with this coping. With an overall reduction of 0.5 to 1.0 mm at the margin, the coping promotes natural esthetics and helps eliminate over-contoured restorations. Since the coping is 88 percent gold, the resultant hue is a warm yellow color. Consequently, less opaque can be used. This results in a more lifelike restoration. The coping even can be cut short to the internal line angle of the margin. This allows the technician to build a true porcelain margin for the ultimate in esthetics.

Dr. Michael DiTolla is the Director of Clinical Research and Education at Glidewell Laboratories in Newport Beach, Calif. He lectures nationwide on both restorative and cosmetic dentistry. Dr. DiTolla has several clinical programs available on DVD through Glidewell. For more information on this article, or to receive a free copy of one of Dr. DiTolla’s clinical DVDs, e-mail him at [email protected].

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