Esthetic Customizing of Full-Contour Zirconia Restorations
Eliminating the guesswork of zirconia stain infiltration
By Janet Jones, CDT
The use of CAM-milled full-contour zirconia as an indirect restorative material for the fabrication of crowns and bridges has been established firmly in dentistry as an alternative for metal-based restorations. As an indirect restorative material, zirconia dioxide accounts for an estimated 56.1% of all restorations fabricated in the US currently. Satisfying the requirements for strength, durability, and esthetics, monolithic restorations manufactured using digital technology are highly efficient and cost-effective to produce.
Once milled, monolithic zirconia restorations undergo a color infiltration process prior to sintering to provide a final life-like appearance. Although all the A-D VITA shades can be reproduced using zirconia coloring liquids, most are colorless and provide technicians with no visual guide on the amount of characterization applied. With the introduction of Wieland’s Zenostar VisualiZr Liquids (Ivoclar Vivadent, ivoclarvivadent.us), the guesswork of zirconia stain infiltration has been eliminated. The author has found the technique of adding VisualiZr liquid concentrates to the Zenostar Color Zr infiltration coloring liquids to be an effective and efficient technique for visually monitoring where and how much liquid has been applied in the characterization process. The post-sintered result is a gradual progression of shades, similar to a natural tooth.
Once the full-contour zirconia units are designed and milled, they will need to be removed from the milling blank. The author recommends that the bars holding the restoration within the blank be cut from the margin side of the restoration using cross-cut burs. Since the bars generally are located closer to the margins, using this technique provides a clear view for assuring the margins are not damaged during removal. Care must be taken to not apply too much pressure, as this will cause the units to break out prematurely and possibly damage the restoration.
Once the restoration is removed from the disc, a diamond impregnated rubber wheel or a similar instrument can be used for smoothing the bar attachment area. If desired, the occlusal anatomy can be carefully defined. Once the bar attachments are smoothed as much as possible, Pro-Art Polishing Wheels (Ivoclar Vivadent) can be used to further polish the surface of the restoration. Once complete, remove any grinding dust from milling by using a brush and air hose to clean the surfaces inside and out. Failure to clean thoroughly will result in rough white spots that will need to be removed after sintering. The restoration is now ready for the colorization process.
The author recommends using only a plastic brush for the application of the coloring liquids. The Zenostar VisualiZr liquid concentrates come in 3 colors: red for the dentin area; blue for the incisal; and yellow for the fissures. However, the concentrates can be mixed to create additional colors if needed. The liquid concentrate applied to the restoration completely burns out during the sintering process with no residue. It is recommended that a small amount (2 drops of VisualiZr liquid per 2 ml of Zenostar Color Zr) of the appropriate coloring liquid be poured into another container to avoid dipping the brush directly into the bottle (Figure 1). Any zirconia dust that may be on the brush could collect in the coloring liquid and contaminate it.
Begin the infiltration process of applying the coloring liquids to the restoration by applying the body shade (A-D) horizontally around the margin, both inside and out (Figure 2 and Figure 3). Then apply the body shade in a vertical direction to blend from the margin toward the cusp tips (Figure 4). The chroma is now applied to the occlusal table as desired, as well as the intaglio surface to achieve a depth of color on the occlusal fossae (Figure 5). The chroma should be carried fairly close to the cusp tip, to avoid a high value area in the occlusal one-third. Using the appropriate incisal shade, apply the coloring liquid to the cusp tips, ridges, and inner incisal area (Figure 6 through Figure 8). This can be accomplished in several applications, depending on the desired incisal effect. It also may be appropriate to use effect shades on the occlusal for additional customization—for example, brown in the depth of the occlusal pits to deepen the color.
Single-unit crowns should be sintered on their occlusal surfaces or on the facial surface for anterior crowns. Smaller bridges should be positioned so that the maximum number of units are touching the sintering platform, with care that the pontic is touching. If this is not possible, the bridge should be positioned on the facial of the pontic. Larger bridges should have a support milled to allow the arch to be sintered vertically.
Post-sintering, the restoration can be polished and the surfaces smoothed to achieve a highly esthetic final result (Figure 11).
The author has found that using Zenostar VisualiZr concentrates in combination with Zenostar Color Zr coloring liquids to characterize full-contour zirconia restorations is a highly effective and efficient technique that can save laboratories both time and money.
About the Author
Janet Jones, CDT, is a Technical Consultant for Ivoclar Vivadent in Amherst, New York.
For more information, contact:
ivoclarvivadent.us • 800-533-6825
Disclaimer: The statements and opinions contained in the preceding material are not of the editors, publisher, or the Editorial Board of Inside Dental Technology.