Using the 3D Shade System in Color Matching Comparison: Easy Shade System vs. Visual Methods
Background
Today patients are very aware and esthetically conscious of color and can be very demanding when it comes to the esthetics of restoring a tooth. They might not know the technicality of the procedure but they can defi nitely judge the look of the restoration and how close it matches the adjacent tooth. The esthetic makeup of a restoration includes both shape and matching color of the adjacent tooth. Shade matching is one of the most important and critical factor in a successful and esthetically superior restoration.
The ability to correctly match shades of teeth to the shade guide is a major factor in the treatment process. As we move anteriorly the esthetic demands become greater. Patient demand is also higher for an exact replication of their restoration to their natural dentition especially if it is a single unit restoration. According to a 2002 survey in Dental Product Report, nearly half of the general practitioners changed their typical shade taking procedures for single unit anterior cases.1 Practitioners are now seeking computer technology to contribute to their every day procedures to eliminate the human errors. A new alternative form of shade selecting is the VITA Easyshade system. A hand held device using electronic optical measurements. The manufacturer claims that their device is superior in reading and analyzing color thus giving a color match reading that will be more accurate than the human eye. This technology is assumed to be repeatable and accurate eliminating the human errors with visual matching. Clinical shade matching has always been conducted by the operator or the dental auxiliary personnel. Patient’s feedback also play a major contributor in the color matching decision.
This study will evaluate the electronic color matching in comparison to the trained the human eye. The reading from each subject is compared and to the shade selected by the trained operator using the VITA 3D shade guide system and the data collected will be analyzed and compared to the VITA classic shade guide results.
Currently available electronic shade-matching devices are spectrophotometers, colorimeters, digital color analyzers, or combinations of these. Spectrophotometers are useful in the measurement of surface color. A prism disperses white light from a tungsten lament bulb in the spectrophotometer into a spectrum of wavelength bands between 10 and 20 nm.2 The amount of light refl ected from a specimen is measured for each wavelength in the visible spectrum.
Of all devices, a spectrophotometer is the most accurate for absolute color measurement. These instruments have a longer working life than colorimeters and are unaffected by object metamerism.2-4 Colorimeters are useful in quantifying color differences between specimens. These devices measure tristimulus values according to CIE illuminant and observer conditions.3,5
Colorimeters use photodiode filters to control light reaching the specimen. The light reflected from the specimen is then measured by a detector. Colorimeters are easier to use and are less expensive than spectrophotometers. However, repeatability may be poor due to aging of filters, and object metamerism can be a challenge to their accuracy.4,5
The Vita 3D-Master shade guide6,7 features a systematic colorimetric distribution of 26 shade tabs within the tooth color space.
The manufacturer purports that this shade guide demonstrates an equidistant distribution in the color space. The shade guide is organized into 5 primary value levels, with a secondary distribution based on chroma and hue. These value groups are arranged from lightest (value level 1) to darkest (value level 5), left to right. Intermediate shades can be achieved based on mixing formulas. The manufacturer advocates a 3-step process: value is determined first in making a shade determination, then the proper chroma and hue are determined. The selection process is simplified because the number of choices decreases throughout the 3-step procedure.6
The CIE L*a*b* (CIELAB) color space is a uniform color space derived from the tristimulus values of X, Y, Z, with L*, a*, and b* coordinates.13 It is one of the color spaces within the international standard color specification system by the CIE (Commission Internationale de l’Eclairage, or the International Commission on Illumination), and is useful for colorimetric assessments of natural teeth and dental restorative materials.
Dental Application
The prevalence of color defective vision in male dentists was found by Barna et al. to be 14%8, by Moser et al. to be 9.9%,9 and by McMaugh to be 8.2%.10 The prevalence of color defective vision in male dentists, being as much as 14%, supports the conclusions of different studies that every dentist as well as dental students along with dental auxiliaries should be tested for color deficient vision as well as their shade matching abilities be evaluated for accuracy.8,11,12 The ability to consistently match shades accurately can help reduce the number of unsatisfactory results which could lead to costly remakes.
Previous authors have recommended that dental students, dentists and auxiliaries be tested for color
discrimination.9,11-13 The Farnsworth 100-Hue test has been used in dental research studies as a screening test to rule out defective color vision subjects.14
The 100-Hue test is a sensitive and accurate test that is used widely and is considered the standard by which most other color discrimination tests are measured.15-17 The Easyshade is a relatively new system. The standard for clinical shade matching has always been the human eye. The machine will be analyzed for effectiveness as well as compared to specific operator’s abilities whose effectiveness in color analysis has been determined by using a simple color screening test. Hamad et al.18 stated that the use of the Vitapan 3D-Master shade guide significantly improved intrarater repeatability among general practitioners when compared with the Vita Lumin Vacuum shade guide (P_.0001). This improvement could be attributable to the color science information gained by the general practitioners after they used the organized and scientific approach associated with the Vitapan 3D-Master shade guide. This study will compare the results using the 3D Vita shade guide with the results using the Vita classic shade guide when using the Easyshade system.
Materials and Methods
The Vita-Vita test17 was used to identify two visual shade evaluators with a predetermined superior shade matching ability. The individuals were the evaluators to whom the Vita Easy Shade’s accuracy was compared. Expert observers were chosen to participate in the vita easy shade matching study. The Vita Easy Shade machine was used on 40 subjects to measure the central region of each subject’s left maxillary central incisor. Protocol consisted of mandating virgin non restored teeth without any gross signs of developmental intrinsic staining. The two visual evaluators selected a shade from the same area of the left maxillary central incisor for all subjects. The visual evaluators were instructed to focus only on the central portion of the tooth.
The evaluators analyzed the tooth first, and then the tooth was scanned by the machine. If the evaluators disagreed amongst the shade chosen, they were asked to retake the shade and come to a consensus of one shade. The machine tip was placed on the middle third of the tooth for shade analysis. The Vita Easyshade (Vita Zahnfabrik) is
an intramural dental spectrophotometer that provides CIE L*a*b* values in specific modes. This shade taking device (Vita Easyshade) comprises a base unit, a handpiece, and a fiberoptic cable assembly. There are 3 measuring modes: tooth, shade tab, and restoration. The appropriate mode must be selected prior to measuring, and data reported are mode specific. The accuracy of the Vita Easy Shade was based on the comparison of the results obtained compared to the shade chosen using the visual evaluation method. All readings on the Vita easy shade instrument were made by the same operator for consistency. Statistical analysis included comparison of the correct matches of the Vita Easy Shade to the standard matching technique the visual observers using a standard t-test. A 95% confidence interval was used in comparative analysis.
Discussion
Shade matching to adjacent teeth is one of the most difficult and important aspects of an esthetically successful restoration. The Vita Easy Shade system is a relatively new handheld device that uses electronic optical measurements of teeth. While the standard method for clinical shade matching is the human eye, different visual evaluators are able to match shades more or less effectively depending on multiple variables. This is why the Vita- Vita test was used to choose the best visual evaluators available. Also, shade matching was performed under similar conditions as well as during the same time of day. It was considered a “match” if the visual evaluator’s choice matched the machines’ reading.
Results
The results showed that the machine was accurate 97.5% of the time. However, at a 95% confi dence interval one can be certain that 95% of the time the machine will not perform below 92.7% matches the visual method. One can only infer that this machine is not absolutely reliable, but considerably accurate and should be used as an adjunctive shade matching method.
Conclusion
As more dentists realize the importance of a scientifi c approach to color matching in dentistry, manufacturers will continue to research and develop better digital equipment. Currently, the Vita Easy Shade instrument in combination with the 3D vita shade guide shows superiority in color matching and determination when compared to the Vita classic shade. Nevertheless, this machine is not a replacement for traditional methods. However, it is a defi nite adjunct to visual shade matching. The final question, regardless of which system used, visual or electronic, is “Does it match?” The final evaluation system for success or failure will be the patients’ and their peers’ visual methods. The art of dentistry will always rely on individual observation and interpretation, and adjunctive electronic instruments can only enhance this process and attempt make it more reliable.
References
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by Dr. Wael Abdulla, Dr. Waleed AlYaseen, Dr. Abdulaziz Sadeq
