Written by Lorin Berland, DDS Sunday, 30 June 2002 19:00
Today’s standards for natural-looking anterior dental prostheses that are stable and aesthetic are high. Modern dentistry demands mastery of the best techniques, equipment, and materials to re-create nature with durable restorations. Replacing a maxillary anterior tooth poses a challenge for even the most adept cosmetic dentist. In this critical smile zone, you must restore both aesthetics and function to a high degree, while working around limitations such as preservation of tooth structure, the periodontal architecture, and exact color match including shade, hue, chroma, and value.1
There are a variety of restorative options from which to choose, including removable retainers, different types of fixed bridges, and implants. Whatever the choice, a high degree of skill and knowledge of technique and materials must be employed to ensure a successful outcome with a good prognosis, because this area is highly visible and under careful scrutiny with every smile.2
|Figure 1. Patient congenitally missing tooth No. 7.|
This task presents even more of a challenge for a younger patient needing a front tooth replaced. I have seen many such cases, including a 12-year-old girl who was congenitally missing tooth No. 7 (Figure 1). This patient was too young to consider an implant. She had just completed orthodontic treatment. She and her parents were concerned about traumatizing the adjacent virgin teeth in preparation for a traditional three-unit bridge. The large pulp horns associated with young teeth are a major concern when planning preparation design. To ensure that such a young patient shows no signs of wearing a prosthesis, the best in restorative materials must be used to create the most natural pontic with minimal visibility of any retainers. Even with these limitations, the aesthetics, function, and retention must be optimal. For this patient, my choice of treatment was the porcelain-bonded fixed bridge with retainer wings.3 I have used this type of bonded bridge in at least 20 cases over the past 12 years, and all of them are still in place and functioning well.
The porcelain-bonded fixed bridge is ideal in a case such as this, which involves replacing only one tooth, with no mobility on the abutment teeth, and with optimal abutment teeth with proper height and normal function. The retainers for such a bridge require a much more conservative preparation design than the traditional PFM bridge, and consist of lingual wings that are virtually invisible from the facial view and almost invisible from the palate. The bridge is highly retentive when using the best adhesive resin cement, and its strong connectors between the pontic and the abutments allow some flexure while still retaining strength in the face of stress and fracture forces.4
COLOR MATCH AND THE SHADEEYE NCC
|Figure 2. ShadeEye NCC Chromameter.|
In a case that involves replacing a missing front tooth, we face the ultimate dental challenge. Color choice is obviously an extremely critical factor in aesthetically perfect tooth reproduction.5 The ShadeEye NCC Chromameter (Shofu) is designed to identify the exact base shade of the tooth being measured for accurate reproduction (Figure 2). Faulty shade taking and consequential faulty restoration remakes are both costly and frustrating, but are routine because of the inherent inconsistency in shade taking, not to mention the variable influence of surrounding colors and lighting. To complicate matters, color perception varies from individual to individual. Furthermore, communication of this perceived color between the dentist and the lab technician can be difficult. The outside variables that influence human subjective interpretation of color are greatly reduced with the ShadeEye NCC.
The ShadeEye NCC is a highly accurate electronic shade-taking device, and is designed to interact with the operator to identify the most precise, aesthetic shade match possible, and communicate this information to the laboratory for duplication. The ShadeEye NCC can read even the smallest differences in tooth shade that make shade taking difficult. It expresses this difference in numerical form to make it clear and easy to understand, and more importantly, communicates this color information to the lab technician in unambiguous numerical values. The ShadeEye NCC prints out the exact shade, hue, and value of the tooth to be reproduced, and also gives a “recipe” for color reproduction using the Shofu Vintage Halo Porcelain System. This computer-generated information provides a precise communication tool between the dentist and the lab technician, allowing for perfect tooth reproduction.
HOW ABOUT RED?
The universal scientific standard formula for quantifying and expressing color is the L*a*b* color space paradigm. Tooth colors are found in the upper lightness area of the yellow-red range in the L*a*b* color space. The ShadeEye NCC colorimeter expresses tooth shades numerically according to this L*a*b* color measurement space. Being a tri-stimulus colorimeter, it reads color similar to the human eye, yet performs even better as it gives precise color measurement. When combining the computer-generated recipe derived from the universal L*a*b* standard for color measurement with the Shofu Vintage Halo Porcelain System, you can create the most natural-looking, beautiful restorations. Shofu’s opacious dentin materials have excellent masking ability due to the sub-micron particle technology that allows the porcelain to refract light. By utilizing Shofu’s basic layering technique with its porcelain, you can create absolutely natural-looking restorations.
STEP BY STEP USE OF THE SHADEEYE NCC
Look at the tooth to be measured to observe the color and characteristics—this should be performed as a first observation. Turn the Unit “ON.”
Place a clean Contact Tip on the ShadeEye NCC, turn the ShadeEye NCC unit “ON,” and calibrate according to instructions.
With the Contact Tip in the proper position, press the measurement switch button. The ShadeEye NCC will flash. Wait for the green ready light to illuminate, and repeat. Usually only three flashes are necessary, and the ShadeEye NCC LED will display “333” and begin printing. Depress the “DISPLAY” button on the handheld unit and the ShadeEye NCC will print the “recipe.”
Second Observation and Verification
To verify agreement of the shade measurement and a second observation of characteristics of the tooth, select the recommended Vintage Halo shade tabs noted in the printed recipe, place them in the Gumy, and observe them next to the tooth measured (and the tooth to be reproduced if different than the measured tooth). Take a digital picture for a more accurate duplication.
Recording and Communication of Shade Information
On the laboratory prescription, note the following information:
(a) The tooth from which the shade measurement was taken.
(b) The location on the tooth where the shade measurement was taken.
(c) Note if the middle third of the tooth is lower in chroma than the cervical third. If shade is 3, then 2.5 is 1/2 shade lower in chroma.
(d) Incisal characteristics and qualities.
(e) Drawings and/or photos are helpful in communicating existing or desired characteristics.
|Figure 3. Photograph of Shofu shade tabs placed in Gumy next to natural teeth for accurate lab reproduction.|
Along with the Shofu shade slip prescription, I like to send a digital photograph of the shade tabs in the Gumy placed next to the unprepared and prepared teeth, to capture the natural characteristics of the tooth to be duplicated. In this case, the patient’s shade slip recorded A1/hue R2.6 The appropriate shade tabs were inserted into the Gumy that matched the patient’s gingival color and placed next to her adjacent teeth to be color matched. A digital color photograph was taken using a Kodak DC290 zoom digital camera, and printed on Kodak paper using the Kodak 1200 medical image printer. This image was forwarded to the laboratory along with the Shofu shade slip (Figure 3).
|Figure 4. Shofu Contemporary Cutting Kit.||Figure 5. Round bur used to initiate preparations.|
|Figure 6. Coarse diamond removes undercuts.||Figure 7. Fine diamond smoothes preparations.|
|Figure 8. Conservative preparations for bridge with lingual wings.|
Next, the adjacent teeth were prepared for retainer wings on the respective mesial and distal surfaces using the Shofu Contemporary Cutting Kit (Figure 4). A small round diamond bur (0872-1) was used to outline the margins of the preparations (Figure 5). Round-end tapered diamonds (0836C-1 coarse and 0836V-1 superfine) were used to remove any undercuts and create parallel axial walls (Figures 6 and 7). With the latest adhesive materials on the market, excellent retention is possible without invasive preparations, and a very conservative design was employed (Figure 8). After the preparations were satisfactory, an Impregum (3M ESPE) polyether impression was taken using a Premier anterior triple tray. Because polyether is hydrophilic, the teeth were not desiccated, and the set around the preps and in the tray resulted in even better “wetting” for improved adaptation to the abutments.7
CREATING THE PONTIC SITE
|Figure 9. Bident Bipolar Electrosurgical Unit.||Figure 10. Bident tip No. 3201 used to contour pontic tissue space.|
|Figure 11. Bident tip No. 3302 creates smooth surface.||Figure 12. Gentle Gel placed to promote healing.|
To create the illusion of a natural tooth, every detail must be considered, from the choice of the material and shade for the pontic, to even the soft tissue surrounding the pontic.8 For the pontic to appear as if it is growing out of the surrounding periodontium, you must carefully plan the way it sets into the contour of the gum tissue. Because the edentulous space in this case never housed an actual tooth, a dimpled pontic site was needed to create the illusion of a tooth growing out of the gum. This challenge proved simple and fast using the Bident Bipolar Electrosurgical unit (Figure 9). This device is currently the standard in neurosurgery, and has been adapted for use in dentistry. There is no burning, excessive bleeding, or unpleasant odors, and the tissue heals very well. Tissue charring and shrinkage, as well as heat and current spread, are reduced. Separate cutting and coagulation controls permit precise individual power adjustments at a quarter of the wattage required for monopolar electrosurgery. This case required two different tips, Nos. 3201 and 3302, to create the desired surface and remove tissue tags to leave a smooth, aesthetic tissue pontic area (Figures 10 and 11). Gentle Gel (Bident), a topical ointment containing aloe vera and tea tree oil, was applied to the gums to promote healing (Figure 12).
|Figure 13. Clear matrix for provisional tried on.||Figure 14. Matrix filled with autocure bis-acrylic resin.|
|Figure 15. Facial view of bridge seated on model.||Figure 16. Lingual view of bridge seated on model.|
Temporization for this patient posed a challenge. Even though the patient had lived with this edentulous space up until now, I wanted to give her a transitional restoration that was easy to fabricate but would be durable and aesthetic enough to wear until the seating appointment. In order to fabricate a template, I took an alginate impression and built the missing tooth with composite. From this model, I vacuum formed a clear 0.02-mm splint and verified the fit (Figure 13). After filling the template with an A-1 autocure bis-acrylic temporary crown and bridge material (Protemp, 3M ESPE), I seated it on the teeth and let the resin completely set (Figure 14). The excess material was removed and the resin area cleaned, with the pontic remaining in the clear stint. This transitional was easy and comfortable to place, and the patient now had a provisional that both replaced her missing tooth and acted as an orthodontic retainer until her next appointment.
In the laboratory, this case was a little trickier than most because I wanted the added strength of an “imbedded” metal frame. As you can see in the final results, the lab did an excellent job. The only hint of the supportive metal frame inside is a small sprue dot on the distolingual (Figures 15 and 16).9
|Figure 17. Pontic tissue site healed and ready for seating of bridge.||Figure 18. Shofu Contemporary Polishing Kit.|
|Figure 19. Final photograph.|
When the patient returned for her seating appointment, the gingival tissue had healed perfectly, and she was ready for seating of her final restoration (Figure 17). The splint containing the transitional was removed to try on the fixed bonded bridge. After inspecting the fit and margins on the models, I seated the bridge intraorally to verify the margins, occlusion, and aesthetics. The gums had healed nicely. In a case involving a missing anterior tooth, the laboratory removes a touch of stone so the pontic will create a slight blanching of the tissue when it’s seated.
Applying alloy primer and lightly air-drying prepared the restoration. The preparations were etched with 37% phosphoric acid, vigorously rinsed, and gently air-dried. Single Bond (3M ESPE) was applied to the teeth in three to four coats, and gently air-dried until the preps were dry but glossy. The restoration was then bonded in place using Rely-X Arc Resin Cement (3M ESPE). While applying firm finger pressure, the luting agent was allowed to fully set for 4 minutes, and the excess was removed. The cement was further cured with the Virtuoso light (Den-Mat). Occlusion was adjusted, interproximal areas were cleaned, and the entire restoration was polished using the Shofu Contemporary Polishing Kit (Figure 18), which included six shapes of fine and superfine T and F diamonds and six ceramiste cups and points from pre- to ultra-polish.
In this case, the fixed bonded bridge with retainer wings provided an aesthetic and durable choice to replace a missing tooth without placing unnecessary trauma on the abutment teeth (Figure 19).10 In my experience, this type of restoration has proven retentive, functional, and highly aesthetic. New shade-matching and electrosurgery technologies have made the bonded bridge even better.
The author would like to thank Westbrook & Associates for the excellent lab work described in this article.
1. Lerner JM. Restoring anterior aesthetics and occlusion. Dent Today. 1999;18:78-81.
2. Hornbrook D. Communication: the key to aesthetic success. Profiles Dent. 1999;2:6-7.
3. Meyenber KH, Imoberdorf MJ. The aesthetic challenges of single tooth replacement: a comparison of treatment alternatives. Pract Periodont Aesthet Dent. 1997;9:727-735.
4. Bichacho N, Magne M. Controlled restorative treatment of compromised anterior dentition. Pract Periodont Aesthet Dent. 1998;10:723-727.
5. Ubassy G. Shape and Color: The Key to Successful Ceramic Restorations. Carol Stream, Ill: Quintessence Publishing; 1993.
6. Christensen G. An accurate shade evaluation instrument for Shofu Vintage Halo Porcelain. CRA. 2000;24(4).
7. Phillips K, Lepe X, AW TC, Johnson GH. Accuracy of Impregnum Penta and Impregnum Penta Soft with disinfection. Poster 3875 presented at IADR; April 2000.
8. Fienman RA. Conservative anterior tooth replacement using etched porcelain pontics. Pract Periodont Aesthet Dent. 1991;3:21-25.
9. Gleghorn T, Westbrook P. Aesthetics in anterior crown and bridge. Dent Today. 1998;17:56-58,60-61.
10. Barrack G, Bretz WA. A long-term prospective study of the etched-cast restoration. Int J Prosthodont. 1993;6:428-434.
Dr. Berland has practiced in the Dallas Arts District since 1982. He lectures nationally on building a practice using cosmetic dental strategies, marketing, materials, and techniques. For a preview and information about “The Latest and Greatest In Cosmetic Dentistry Today: A Full Mouth Rehab in Two Appointments,” visit the website http://www.lorinberland.com. Dr. Berland can be reached at (214) 999-0110.
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