Ensuring the Quality of Aesthetic Veneers With Digital Shade Analysis

In the September 2002 issue of Dentistry Today, I examined the importance color can have in the dental operatory, paying particular attention to the dimensions of color (hue, value, and chroma); the critical elements affecting color perception (the light source, the textures of the tooth, the environment, and the receiver); and finally, significant advancements in shade-matching technology. New technology makes quantifying color measurement easier, consistently more accurate, and in some cases more economical in both time and cost.

Digital shade analysis systems have been designed to eliminate the subjectivity of color analysis typically associated with traditional shade guides, and provide exact information for laboratory buildup and fabrication. With our current low-cost/low-technology visual assessment tool—the shade guide—hue and chroma are easily discerned, but value is not determined correctly. In fact, 75% of improper shade selection involves deviation in value.1

It is difficult for anyone to see the same color as identical across different illuminants and light levels. The fact is that the eye and brain use some great image-processing tricks to provide reasonable visual characterization. Human vision adapts to local illumination; based upon the color of whites or highlights, our minds accommodate to the scene. This adaptation is useful for most vision situations, but it can significantly impact our eyes’ ability to make objective color judgment. In addition, because of spatial contrasts, crooked, overlapped teeth often appear darker in more recessed regions, while more prominent teeth appear brighter.2

As consumer awareness for cosmetic dentistry increases, patients are demanding aesthetically pleasing restorative options. Therefore, a natural visual appearance of the restorations has become imperative, and the dental industry must continue to advance the field of aesthetic restorative dentistry by balancing the science of dentistry with the artistry of an individual smile.3

Advantages of coupling an aesthetic procedure with a digital shade analysis device (specifically, a colorimeter) include the following:

•Colorimeters provide a highly refined illumination area, with equal illumination across the whole measured area.

•Colorimeters are engineered to directly measure color as perceived by the human eye.

•A colorimeter filters light in three or four areas of the visible spectrum to determine the color of an object.

•Properly designed colorimeters can provide greater data efficiency, as they only store the needed three data points of hue, value, and chroma instead of the more basic 16+ data points of reflectance.4

PREOPERATIVE PATIENT EVALUATION

Figure 1. Extraoral preoperative view of patient’s smile. Notice composite veneers on teeth Nos. 5, 6, 7, 10, and 11 and interproximal defective composite restorations on the mesial and distal aspects of teeth Nos. 8 and 9. Tooth No. 3 is missing, and the patient’s smile exhibits an exaggerated Curve of Spee on the right side. Notice a slight diastema between teeth Nos. 8 and 9, which skews the balance and proportion of the anterior complement of teeth. Figure 2. Right lateral anterior view of teeth Nos. 6 through 8, showing marginal deterioration of composite resin veneer facings on teeth Nos. 6 and 7, and large discoloration of restoration No. 8, indicative of microleakage and recurrent decay. Note disproportion of individual tooth size of No. 7 compared with No. 8.
Figure 3. Intraoral full view in occlusion. Notice the disproportion of the maxillary six anterior teeth, as well as minimum overbite relationships of teeth. Figure 4. Intraoral full-mouth view slightly disarticulated, showing the exaggerated Curve of Spee (plane of occlusion), as well as missing tooth No. 3.
Figure 5. Intraoral left lateral anterior view of teeth Nos. 9 through 11, showing marginal breakdown of interproximal restorations and veneer facings. Tooth No. 10 exhibits inconsistent proportion to tooth No. 9, as well as contralateral tooth No. 7, respectively. Figure 6. Preoperative view of teeth Nos. 7 through 10 prior to composite mock-up to correct proportion of anterior teeth.
Figure 7. Postoperative view of teeth Nos. 7 through 10 after composite mock-up, showing correction and re-establishment of proper tooth dimensions and proportions. Figure 8. Patient’s smile view of composite mock-up, showing corrected proportion, reestablishment of correct incisal edge position, and alignment of cuspids toward the patient’s midline.
Figure 9. Incisal depth preparations of anterior teeth unilaterally to control quantitative evaluation of depth of preparation compared with contralateral side. Perception can easily be lost if complete mouth preparation is performed simultaneously. Figure 10. Preparation of anterior teeth, and hemostatic/tissue deflection material (Expasyl, Kerr Sybron) placed prior to impression making.

A 51-year-old white female was unhappy with her smile for various reasons. Her bonding was breaking down and the discoloration of her teeth left her uncomfortable with her smile. The patient presented with discoloration of bonding, disproportionate teeth, and excessive gingival display (Figure 1). The patient had failing composite veneers; teeth Nos. 5, 6, 7, 10, and 11 were classic examples of failed bonding. In addition, there were defective interproximal composite restorations on the mesial and distal regions of the teeth. The right anterior view displayed failing composite and disproportionate teeth. Teeth Nos. 6 and 7 showed marginal deterioration of composite resin veneer facings, and a large discoloration on tooth No. 8, highly indicative of microleakage and recurrent decay. Note the misalignment of tooth No. 7 compared with tooth No. 8 (Figure 2).

The intraoral full view displayed the inconsistencies of the six maxillary anterior teeth, as well as minimum overbite and overlapping relationships of the teeth (Figure 3). The patient’s smile was slightly disarticulated, showing an exaggerated plane of occlusion and missing tooth No. 3 (Figure 4). Figures 5 and 6 demonstrate the incorrect proportion of the anterior teeth.

TREATMENT PLAN

Based upon several stained teeth, worn bonding, several disproportionate teeth, and the patient’s demand for cosmetically pleasing veneers, the diagnosis was to cover the six defective composite restorations in the anterior region with a fully synthetic ceramic material, HeraCeram (Heraeus Kulzer). Figures 7 and 8 display the composite mock-up of the patient’s smile postoperatively, establishing the correct alignment of the cuspids toward the patient’s midline. HeraCeram was selected because the material creates an aesthetic veneer that exhibits strength, consistent reproducibility, high thermal stability, compatibility with all-ceramic-bonding alloys, and extreme versatility, creating a natural-looking restoration that meets the patient’s demand.

The incisal depth preparations of the anterior teeth were done unilaterally to control quantitative evaluation of preparation depth compared with the contralateral side (Figure 9). After tooth preparation, a hemostatic/tissue deflection material (Expa-syl, Kerr Sybron) was placed prior to taking the impression (Figure 10).

MATCHING COLOR

It is estimated that approximately 8% of men and slightly less than 1% of women have some degree of color vision deficiency, meaning that the particular shade that the dentist sees in the dental office may not appear to be the same to the technician working with the porcelain in the laboratory.5 A digital shot of the patient’s lower anterior teeth (Figure 11) was taken with the ShadeVision System (X-Rite, Inc) (Figure 12) to determine the appropriate hue, value, and chroma of the patient’s adjacent teeth in order to accurately design matching restorations.

The ShadeVision System is a colorimeter designed to measure and communicate accurate tooth shades. The system was developed to ensure that each dental prosthesis matches not just the tooth it replaces, but the teeth surrounding it. In the past, dentists and laboratory technicians have relied on the subjectivity of the human eye to determine tooth shade in restorative work. Today, ShadeVision’s technology allows the dentist to easily capture the precise color image and accurate colorimetric data of the patient’s teeth while precisely communicating the information to the dental laboratory in order to fabricate a matching prosthesis. In this case, the ShadeVision report displayed the shade tendencies from gingival to incisal, and the patient exhibited a D2 Vitapan classic shade at the cervical 1/3 to an A1 incisal 1/3 shade (Figure 13).

LABORATORY PROCEDURES

Figure 11. Clinical picture of lower anterior teeth that had been bleached/whitened prior to shade determination. Figure 12. ShadeVision System from X-Rite.
Figure 13. ShadeVision report—analysis of shade tendencies from gingival to incisal. Patient exhibited a D2 Vitapan classic shade at the cervical 1/3 to an A1 incisal 1/3 shade. Figure 14. Ceramic buildup of maxillary anterior teeth using a fully synthetic ceramic material (HeraCeram, Heraeus Kulzer) and employing the refractory die/connector paste technique. Cervical shade of D2 Vita classic was blended to an A1 incisal, as well as opal translucent porcelains used proximally with internal crack lines incorporated into the buildup process, because the patient’s natural teeth exhibited internal check lines as well.
Figure 15. Try-in of ceramic veneer No. 7. Note tooth preparation designs as well as internal crack lines seen on natural tooth No. 6. Teeth were cleaned with a chlorhexidine/pumice slurry, total-etch 37% phosphoric acid wash for 10 seconds, and disinfected, with OptiBond Solo (Kerr Sybron) as the definitive bonding resin system. Figure 16. One-week postoperative view 2X magnification, showing excellent tissue response as well as great optical properties of the synthetic ceramic veneers. Note the internal effects built into the ceramic restorations (ie, opalescent effects), as well as fine crack lines.
Figure 17. Black-and-white photo of finished case, showing excellent value matching of veneer restorations to lower anterior teeth. Veneers are virtually imperceptible from natural dentition. Figure 18. Close-up color photo of completed restorations, showing imperceptible color difference between restorations and natural dentition.
   
Figure 19. Extraoral smile view of patient after restoration. Note brightness yet vitality of veneer restorations, as well as correction of occlusal plane, smile curve, and individual tooth proportions, including golden proportion.

Accurate tooth-shade measurement and communication lie in the ability to measure color’s basic structure—visual light waves—and arrive at absolute numeric values that allow us to assign precise identities that correspond to industry references. Successful measurement requires precise control of both the illumination of the subject and a measurement instrument that is objective and accurate.6 Traditional shade selection techniques using conventional shade tabs are highly subjective by nature. When fabricating anterior restorations, even the most skilled technicians can experience difficulties and remakes that can prove expensive for the clinician and dental laboratory technician.7

Precise color communication between the dentist and the laboratory is integral to the development of aesthetic harmony and overall restorative success.8 Also, laboratory technicians who employ the use of digital shade-taking systems are realizing the benefits this technology can provide for quality control checks.9 In this case, it was determined that a cervical shade of D2 Vita classic blended to an A1 incisal was the appropriate shade match. To add to the natural beauty, opal translucent porcelains were used proximally with internal crack lines incorporated into the buildup process, because the patient’s natural teeth exhibited internal crack lines (Figure 14). With the ShadeVision System, the lab technician can put the finished restoration into the custom-made restoration holder, take a digital image of the restoration, and virtually try the restoration into place, to see if the color matches accordingly before it is sent back to the dentist.

PLACEMENT

After porcelain buildup was complete on the six veneers, the restorations were sent back to the dentist for final cementation. Figure 15 shows the try-in of ceramic veneer No. 7. For an optimal aesthetic and natural quality, internal crack lines were added (Figure 16). Teeth were cleaned with a chlorhexidine/pumice slurry, total-etch 37% phosphoric acid wash for 10 seconds, and disinfected, with OptiBond Solo (Kerr Sybron) as the definitive bonding resin system. Figure 17 was taken in black and white to show the value matching of veneer restorations to the lower anterior teeth.

CONCLUSION

By utilizing a cosmetically pleasing ceramic material, coupled with a digital shade analysis system, ideal aesthetic veneers can be achieved that match the hue, value, and chroma of the patient’s surrounding teeth, creating a natural-looking smile (Figures 18 and 19).


References

1. Sagars J. Shade matching for today’s dentist. Dent Econ. 2002;1:62-67.

2. Chu S. Precision shade technology: Contemporary strategies in shade selection. PPAD. 2002;14:78-83.

3. Chu S. The science of color and shade selection in aesthetic dentistry. Dent Today. 2002;9:86-89.

4. Hunter RS, Harold RW. The Measurement of Appearance. 2nd ed. Hoboken, NJ: John Wiley & Sons; 1987:290-302.

5. Tarnow D, Chu S. Digital shade analysis and verification: A case report and discussion. PPAD. 2001;13:129-136.

6. Aamodt K. Color science goes to the dentist. J Dent Technology. 2002;3:22-26.

7. Palmer R. Made in the shade. Dental Lab Products. 2002;4:28-30.

8. Chu S. Precision shade technology: Contemporary strategies in shade selection. PPAD.   2002;14:79-83.

9. LMT. True colors. Lab Management Today. May 14, 2002;18:14.



Dr. Chu is a recipient of the Columbia Dentoform Corporation Award in operative dentistry and fixed prosthodontics from the University of Pennsylvania and the Granger-Prudent Award for excellence in prosthodontics research from the Northeastern Gnathological Society in 1988. He has published numerous articles on implant, restorative, and aesthetic dentistry, tissue management, bleaching, and dental ceramics in national dental journals. Dr. Chu maintains a private practice in New York City, and has a part-time teaching appointment at New York University as a clinical associate professor, Department of Implant Dentistry and Postdoctoral Continuing Education series. He is director of the advanced and international aesthetic dentistry program at NYUCD.