Inside Dental Technology
Maximizing Esthetics with Modifiers
Using the No Cut-Back Technique™ to create a more natural-looking restoration.
With the wide range of ceramic materials that manufacturers offer for creating highly esthetic restorations, technicians can sometimes overlook the importance of porcelain modifiers. These ceramic powders are the single most important product for transforming a generic-looking restoration into a more natural end result. The author has developed a technique that enhances esthetics without delaying production. By using porcelain powders that are readily available in most porcelain modifier kits, the technician can achieve an increased level of esthetics.
When the individual ceramist understands the dynamics of the porcelain being used, the process becomes simpler. This technique is based on the porcelain's amount of shrinkage. Once a ceramist has an understanding of the shrinkage factor, it then comes down to choosing the correct modifiers. On a daily basis, the author uses a number of staple modifiers, which include Blue Translucency, Mamelon Coral, White Opal Incisal, Grey Translucency, Mamelon Amber, Ivory, and Orange Occlusal (Figure 1). The specific use of each modifier will be demonstrated in the build-up technique.
The Role of Modifiers
Developed by the author, the No Cut-Back Technique can be applied to the fabrication of any type of framework that requires layered porcelain. It is very important to use high-quality brushes that maintain a fine tip after countless build-ups, such as the Takanishi #6 or the Ceramicus #6 (Renfert USA, www.renfert.com). In addition to this, using a high-quality wet tray, such as the Regis-Tray™ (SpectraFire, www.spectrafire.com), increases productivity while maintaining the consistent modeling characteristic of the porcelain (Figure 2). The ceramist can use either distilled water or a ceramic modeling liquid of choice.
Before starting the No Cut-Back Technique, always make sure that the contact areas are sealed with some type of die and stone conditioner/sealer. The demonstration build-up is shade A2. The opaque coping is now ready for the ceramic material to be applied (Figure 3). The build-up begins with applying the dentin layer on the lingual surface of the substructure. Always blot to control moisture from the facial aspect of the restoration. Create the mamelons by using the tip of the ceramic brush in an irregular pattern to create a more natural appearance (Figure 4).
Next, apply the facial dentin, matching it up with the mamelons already created with the lingual build-up (Figure 5). The ceramist will need to condense the ceramic material vigorously at this point, keeping in mind the shrinkage characteristics of the chosen porcelain. Once the internal modifiers are applied, blotting is the only technique that can be used to condense them. If the modifier ceramics are condensed too much, they will simply run together.
Apply the Mamelon Coral modifier on each tip of the previously built mamelons with the fine tip of the brush (Figure 6). Set the modifier on the tips of the mamelons by pulling the porcelain down toward the incisal one-half of the restoration. Apply Translucent Blue modifier between each of the mamelons and to the interproximal surfaces (Figure 7).
Returning to the lingual aspect of the restoration (Figure 8), apply the incisal porcelain in the same manner used to apply the dentin build-up (Figure 9). Create an uneven incisal edge, and then place lingual contours that correspond to adjacent teeth. Returning to the facial, begin placing the incisal porcelain two-thirds down the length of the restoration, matching it with the lingual porcelain already applied and keeping the incisal edge uneven (Figure 10).
In order to incorporate a more natural appearance into the restoration, opal translucent porcelain is added into the uneven areas of the incisal edge (Figure 11). It is also necessary to fill the incisal two-thirds of the interproximal areas. The last step before removing the restoration from the model is to highlight the middle of the gingival one-half with White Opal Incisal (Figure 12). This technique helps to accentuate the contour of the restoration.
Remove the restoration from the working model. At the gingival one-third, apply the next darker shade in the chroma spectrum (Figure 13). For example, if building an A1 restoration, apply A2 in this area. When building a B3 restoration, apply B4. The final step is to apply opal incisal translucent porcelain to the incisal edge down the axial wall to blend with the gingival one-third (Figure 14). The finished build-up is now ready to be fired in the porcelain furnace (Figure 15).
Once fired, the finishing process begins. Marking the contacts for adjustment with a permanent marker expedites the process (Figure 16). Choosing the proper grinding instruments for anterior restorations is essential. The three basic instruments include a smooth cutting wheel (Bredent, Diagen grinding wheel, www.xpdent.com), a smooth tapered diamond, and a course silicone polishing wheel (Figure 17). Remove either the mesial or distal section from the working model and begin adjusting the corresponding contact (Figure 18). Repeat this procedure for the other contact. Adjust for the path of insertion (Figure 19) before making any adjustments to the incisal length. When looking down on the incisal edge of the restoration, make the facial adjustments needed to bring the restoration into line with the adjacent teeth (Figure 20).
Once length and contour have been established, it is time to create the surface texture that will mimic the adjacent teeth in the mouth. There are many materials, powders, and techniques used for this procedure. One that is easily incorporated into any laboratory is the use of an indelible pencil. Rubbing the pencil on a piece of paper and then transferring some powder onto the index finger is sufficient to see the details. Lightly rub some of this material onto the adjacent teeth of the stone model to provide a visual aid to see the desired surface texture (Figure 21). Using diamond burs and a rubber wheel will also help to achieve a more natural surface texture.
Glazing and Polishing
The glazing process is somewhat more involved than one might think. Several different techniques are used in the dental technology industry. The most common is the use of a glazing powder. The second method includes creating an ideal surface with stones and diamonds and then incorporating a stain medium to create the surface texture in the glaze cycle. Making adjustments to the firing parameters also allows for surface texture to appear more natural. A third technique involves the use of stones, diamonds, and rubber wheels with a natural glaze cycle. After the restoration is glazed without the use of glaze powder, polish the surface with the aid of a mixture of diamond paste and Brasso® metal polish. This third method achieves the most natural final result of any of the described techniques.
Breaking It Down
While this technique demonstration involves a shade A2 restoration, the No Cut-Back technique can be incorporated into any restoration, regardless of shade the colors of the modifiers are the only things that change. Figure 24 shows the gradual changes from an A1 on the far left to an A4 on the right. The chosen modifiers increase in chroma as the restoration darkens by shade selection. A shade tab shows a very simplistic idea of the patient's shade.
In order to provide a better understanding of the procedure, the author segmented each shade with the selected modifiers. Starting with shade A1, Figure 25 illustrates the internal modifiers used at the incisal edge. The Coral mamelons, Translucent Blue modifier in between the mamelons, and the increased amount of incisal translucency incorporates the halo effect. Using Opal Translucent powders for lighter shades will not lower the value of the restoration as a clear translucent powder would. The White Opal placed at the gingival one-half is very subtle but will enhance the contour of the restoration.
The shade A2 restoration in Figure 26 primarily employs the same technique as the A1 build-up, with the only exception being the amount of incisal translucency used. The halo effect is still present but not as pronounced as in the shade A1 restoration. The intensity of the modifiers will increase as the shade darkens. When the restoration shade is A3, the modifiers will change (Figure 27). Mixing the mamelon shade Coral with mamelon shade Amber will start to increase the amount of chroma needed to reflect natural dentition. Blue translucency will stay the same except for a slightly thicker application. The incisal translucency created with Translucent Opal will be replaced with Translucent Neutral. The White Opal modifier at the gingival one-half is decreased. By placing Ivory modifier in the incisal areas when building the enamel layer, a check line begins to show. The mamelons will now have a show-through appearance at the incisal edge.
The modifiers used on an A3.5 (Figure 28) will once again change. Mamelon Amber will replace the Coral shade used previously, and Grey Translucent modifier will take the place of the Blue Translucent modifier. Occlusal Orange is applied at the cervical one-third to enhance chroma and replicate an aging tooth. The Ivory modifier is still present, but internal check lines will start to appear. There are several techniques that can be used to make internal check lines; those in Figure 28 were created using a yellow/white stain during the build-up process. The White Opal is no longer present at the gingival one-half and is replaced with a thicker amount of enamel porcelain.
The final shade of A4 (Figure 29) illustrates an older tooth that has increased in chroma at the incisal edge, with Occlusal Brown modifier showing through from the lingual and Grey Translucent modifier at the interproximals. Deeper and more internal check lines will be present. In the gingival one-third, the chroma is increased with Occlusal Orange and Occlusal Brown. A thick layer of clear translucent will be applied to the incisal edge down to the gingival one-third.
About the Author
Douglas J. Frye, CDT
Functional Esthetics Dental Lab Inc.