The Vanguard System

The continued popularity for PFM restorations partially results from their ease of fabrication, their diversity of applications, their pleasing esthetics, their renown durability, without the need for expensive equipment or sophisticated technologies, and their ease of installation by dentists using traditional cements.

Additionally, PFM restorations can easily be modified chair-side by the dentist to assure a perfect fit without major concern of breaking or shattering.

A common characteristic of conventional PFM alloys is the inclusion of oxide forming elemental metals such as copper, zinc, tin, gallium, indium and even iron. The theory for the addition of these oxide formers is that porcelain, which is mostly composed of silicon oxides, will bond to a metal surface with an adherent oxide.

Empirical studies have shown that when oxide forming metals are added to ceramic alloy compositions, good adhesion of the porcelain results whereas alloys lacking oxide formers tend to have weaker porcelain adhesion resulting in debonding, cracking or chipping. Unfortunately most of the metal oxides tend to be dark. The processing of oxide containing ceramic alloys typically requires two coats of porcelain opaque to cover the dark color of these oxides and to form suitable bonding to the surface.

During the porcelain buildup and processing, the metals continue to oxidize under the porcelain. This oxidation gradually continues even after installation in the patient’s mouth.

After time, the continual oxidation of the metal leads to the formation of dark lines at the margins of the restoration. Over time these dark lines distract from the esthetics of the restoration and in rare cases can cause irritation at the gums.

The Vanguard System from Aurident represents a new concept in the generation of porcelain fused to metal restorations. This noble metal, castable ceramic alloy contains only precious metals. There are no oxide- forming metals in its formulation.

The lack of oxide formers is unique among ceramic alloys. Because this alloy does not form any oxides, two critical features become immediately evident. First, the hue and chroma of the overlying porcelain are comparable to the best all-ceramic systems because of the lack of interference from a metal oxide.

Secondly, the formation of black lines at the margins of the restoration is eliminated because the oxides that cause these lines are not present. The Vanguard alloy is highly cost effective.

With its low density, technicians can cast up to 35 units from each troy ounce of alloy so that the final cost of the restoration approaches that of lower cost, non-noble alloys.

Vanguard’s lack of oxide-forming metals requires that a bonder be
used to enhance the porcelain-metal bonding.

The Vanguard bonder provides two benefits to the finished restoration. First the porcelain adhesion to the bonder is exceptionally strong so that potential for chipping or debonding is substantially reduced.

Secondly, the bonder has a gold color that enhances the esthetics of the porcelain overlay.

The bonder, which comes in 2-gram jars, is mixed with a special liquid and will provide sufficient material to process approximately 100 copings or approximately 2.5 oz of the Vanguard alloy. The final component of the Vanguard System is the optional colorant that is used to create a 24k golden interior color (Fig. 3).

The Vanguard alloy is processed in a manner similar to other ceramic alloys by casting either using a gas-oxygen torch or induction casting furnace. The low density of the alloy requires one or more extra windings on the casting machine to develop sufficient centrifugal force to completely fill the mold.

Standard processes are used to remove castings from the investment and to remove sprues. Following the cleaning of the casting in alcohol, a light wash of the bonder is applied to the casting surfaces and fired (Fig. 2). Only one application of the porcelain opaque is required.

This is followed by a traditional porcelain buildup to the final restoration. Because Vanguard has no oxides and because the bonder has a golden color, the esthetics of the final restoration will satisfy the most demanding cosmetic requirements.

About the author

Bruce Spivack joined Aurident in 2002 as manager of sales and new product development. Spivack has a PhD in inorganic chemistry as well as an MBA in marketing and finance. He has an extensive background in the development and application of advanced ceramics, composites and other high technological materials as well as material science. At Aurident, Spivack also oversees several product lines, domestic and international sales and new product development.