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Dental esthetics are increasingly important, and as a result, accurate shade selection has become an integral part of daily dental practice. Esthetic appearance is an essential parameter for patient acceptance of and satisfaction with dental restorations. One of the tasks most dentists and technicians underestimate is shade communication. Beyond that, color assessment and reproduction remain two of the most challenging aspects of esthetic dentistry. Tooth shade selection is one of the key parameters in fabricating an esthetically successful restoration.1 Shade-matching technologies have been developed in an effort to increase the success of color matching, communication, reproduction, and verification in clinical dentistry, and, ultimately, to increase the efficiency of esthetic restorative work within dental practices.2
Communication between dentists and their technicians is vital to creating an efficient workflow and ensuring that patients receive the best possible treatment. This is a working relationship that needs clear communication, respect, and reasonable expectations. Technicians are essential when it comes to material selection and esthetic outcomes. Dentists should make a point to involve technicians from the very beginning of a treatment planning process.
This article will explore various techniques and technologies for color-matching restorations. Technology has significantly advanced this process, making it more efficient and accurate. However, even after the technology-based information is analyzed, it must be communicated to the technician for indirect restorations.3 The instruments and technologies discussed throughout this article are predominantly intended for shade analysis; however, this information alone may be insufficient for the technician to adequately interpret the shade information provided. Many of the methods described in this article can be combined in order to ensure the best possible communication between dentist and technician.4 Digital photographs, visual shade tabs, new technologies, and a systematic protocol for referencing shade information can all be used together to best ensure an esthetically pleasing color-matched restoration.
Shade and Light
Shade is a combination of three factors: hue, chroma, and value. Hue is what distinguishes one color from another. Dentin is the primary source of hue. Chroma describes the intensity of the color, or hue, and distinguishes a strong color from a weak color. Chroma is affected by the thickness and mineralization of dentin. Finally, value is the quality by which one distinguishes light from dark colors. Typically, as a tooth ages, its value decreases because the ratio of reflectively absorbed light is decreased compared with younger teeth.
Light is the most important factor in dental photography; reflection, pitch, and yaw can all change depending on light. Shade matching should be performed using standardized ideal daylight conditions with a correlated color temperature range of 5,000 K (D50) to 7,500 K (D75).5 These color temperatures are desired because of their universal nature and broad spectrum of wavelengths.6 However, since the color temperature of daylight is always changing, it may be difficult to rely on natural lighting to provide ideal conditions. In fact, research has shown that natural light does not necessarily produce better results than color-correcting artificial light.7,8 Handheld lights designed specifically for color matching in dentistry are available and may be a better option than complete reliance on natural daylight or office lighting.9,10
Color Matching: Visual vs Instrumental
Dental work, especially cosmetic dentistry, has a host of challenges, and limitation in the technology available in a practice can complicate procedures further. Technology advances can have a positive impact on dentistry for both patients and dentists, especially in the quality of treatments and the simplification of procedures.11 Unfortunately, each dental color-matching machine has its own limitations.12 For example, there may be variation within the distribution in the color space, manufacturing errors, and gradual changes in tab colors, and the range of shades available may not cover the complete range of natural tooth colors.13 All these problems can lead to errors in the evaluation results of dental color-matching machines.
Color measurement in clinical dentistry can be categorized into two groups: instrumental and visual.14 Visual color determination is when a dentist uses a shade guide (Figure 1). There are also a variety of instrumental aids on the market to determine color. These include devices to help create consistency in shading and devices that take snapshots of teeth and create color maps.
Although choosing a tab from a shade guide may seem simple, it is actually very difficult to get a good match due to the complicated interactions between light and tooth. The visual method may provide inconsistent results due to not only background color, light source, and shade guides, but also physiological and psychological factors.15-17 Furthermore, there are reports of color inconsistency even among shade guides from the same manufacturer.18,19
The first step in a conventional visual color-determining process is to determine the shade before the tooth dehydrates, using natural light. Recent studies show that ambient light is used by the majority of dentists during visual shade matching.20 The patient is then draped, and any lipstick is removed to minimize nearby influencing colors. The value of the patient's tooth is assessed, and shade tabs are used to choose dominant hue and chroma. A shade map is then drawn with differing translucencies, and the shade tabs are compared under varying conditions and angles.
Dental shade-matching instruments have been created to reduce or overcome the imperfections and inconsistencies of traditional visual shade matching. Instrumental color measurement systems, such as MicroShade powered by ShadeWave® (MicroDental, microdental.com), Vita Easyshade® Advance intraoral spectrophotometer (Vita, vita-zahnfabrik.com), Crystaleye (Olympus, Olympus-global.com), and Shade-X™ (X-Rite, xritephoto.com), are imaging spectrophotometers that provide complete measurements of both natural and prosthetic tooth coloring under any environmental conditions.21,22
Complete tooth surface measurement devices give a color map of the gingival, body, and incisal shades for the fabrication of direct or indirect restorations. These systems provide a virtual shade overlay of the proposed tab onto the digital image on the computer screen of the tooth measured for visual reference and assessment by the clinician and/or technician. Using these technologies and software, a dentist can objectively evaluate and determine ideal tooth shading based on topographical color mapping (Figure 2). This is useful for situations in which the color a dentist is trying to match may actually be a combination of various shades that can only be achieved by mixing different ceramic powders. Spectrophotometers, colorimeters, and imaging systems are useful technological tools in color analysis for direct and indirect restorations.2 They aid in the communication for indirect restorations as well as reproduction and verification of shade.2 The reproducibility of instrumental shade matching has been found to be much higher than that of standardized visual methods.23
However, not all instrumental aids are equally helpful. Some mappings are 2-dimensional and do not necessarily take into account the shape, texture, thickness of the restoration, type of abutment, and different core material.24 This may affect color-matching in an obvious way.
Studies have shown that different metal substructures and different porcelains can significantly affect the final color of the restoration.25Thickness, layering, and physical translucency can contribute to overall color shifting of restorative materials.26 For example, zirconia is a common restoration material, but as a highly reflective material, it tends to appear too bright in a patient's mouth. Some technology is able to take into consideration the material's conditions and create a shade map specific to zirconia.
These newest spectrophotometers can also help with tissue and stump shading. The dentist simply selects the area to mimic in the patient's mouth, and that area is calibrated and mapped using the technology and software. This information is then communicated to a technician to create an ideal fit. The final color of an all-ceramic restoration is a merging of the underlying tooth structure or core and the ceramic material. The color of the final restoration cannot match the shade selected from a shade guide unless this modification is taken into account. Therefore, a stump or base tooth preparation shade needs to be obtained and transmitted to the technician.27
The benefits for the dentist's office from this advanced spectrophotometric technology are threefold: the technology saves time in taking shades, saves money due to reducing the need for fewer shade remakes and adjustments, and eliminates influences of surrounding colors and lights.
Another important factor in the communication between dentists and laboratory technicians is the photography. Digital cameras represent the most basic approach to electronic shade-taking, still requiring a certain degree of subjective shade selection with the human eye.28 When using digital cameras, the author's recommendation is to put the F-stop on 25, the shutter speed to 1/200, the ISO to 200, the white balance to flash, spot metering, the magnification to 1:2.5-3, a high-resolution jpeg, and manual focus, the latter of which is imperative. MicroShade powered by Shadewave uses a special reference shade tab that includes three areas (absolute black, white, and a neutral grey) as well as two Vita shade tabs as additional color references. After the photo is color-corrected in the software, an algorithm matches specific areas in the photo, chosen by the user, with a database in the program. In case of a misalignment of the reference shade tab in the photo, the areas will wash out and result in incorrect color-correcting of the photo. The reference shade tab must always be placed in a correct 30-degree angle facing upward toward the camera lens. The optional shade arm will fixate the reference tab in the optimal angle and distance to the camera lens.29
A shade arm is a camera attachment that holds the shade tab at a specific distance, height, and angle and provides consistent lighting (Figure 3). The shade arm not only maintains optimal positions, but also balances the weight of the camera by using the pistol grip held in the user's fist as opposed to the unbalanced camera grip. With a digital single-lens reflex (DSLR) body, the main advantage is that any number of "interchangeable lenses" with different focal lengths can be fitted, removed, and refitted to suit the photographer's needs and requirements.30
Another alternative is mobile dental photography, which is becoming more popular as smartphone technology advances.30 The technological development is particularly promising for general practitioners who may not be able to invest in expensive, complex digital impressioning devices.11 A dentist can use a cell phone to take photographs with the aid of technology such as a Smile Lite mobile dental photography device (Smile Line, smileline.ch). The device has three groups of light-emitting diodes (LEDs); each scope can be lit up and dimmed individually; and the device has diffusers that create soft light and polarizing filters to eliminate glare. HASS BIO America's COCO Lux® (HASS BIO America, hassbioamerica.com) is another natural daylight solution that aids in mobile dental photography.31
The emphasis on esthetically pleasing restorations has prompted the dental industry to continuously strive to improve with regard to esthetic detail. By using today's shade-matching technology, the subjectivity of color assessment can be minimized, and accurate diagnosis of a restoration's shade can be more easily communicated. The above-mentioned methods are not mutually exclusive. Whenever possible, both instrumental and visual color-matching method should be used because they complement each other and can result in pleasing esthetic outcomes.
About the Author
Karsten Klimmek, MDT, AAACD, LVIFT
Karsten Klimmek has more than 20 years of experience as a dental technician, having become a Master Dental Technician at the Institute of Dental Technology in Germany.
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