When light passes through tooth structure, it can be reflected, refracted, absorbed, or transmitted by all of the layers of a tooth. This varying optical distinctiveness gives the natural tooth a multicolor or polychromatic effect. Making a restoration that looks like a natural tooth requires knowledge, skill, and understanding of color science.
This column attempts to give dental hygienists the tools for understanding related terms, as well as the steps encompassing shade-taking. We can evaluate shade selection and incorporate this skill in our hygiene repertoire.
Some terms to know include the following:
Hue is an attribute of color that is often confused with color itself. The hue is the name of a family of colors, a general (not specific) name. The hue is responsive and provides the visual sensation based on the various wavelengths of light. The wavelengths — from shortest to longest — are violet, blue, green, yellow, orange, and red.
Chroma may be defined as the strength or purity of the hue. The term "saturation" is frequently used instead of "chroma" and the two are largely interchangeable. Other synonyms are "intensity" and "concentration." Pale colors, also known as pastels, are of low chroma; intense, strongly hued colors have a high chroma. Let me share an analogy that I find to be helpful. Imagine a glass of red wine. Now add water to the wine. The chromatic part of the wine will decrease in intensity as more water is added, but the hue remains the same.
Steps to Shade Taking:
• What does the client want? Natural appearing or bright "Hollywood" white?
• Note the client's complexion and hair color. Restorations may appear lighter on those with dark hair and dark/olive complexions as compared with the same shade on those with blonde hair and fair complexions.
Take the stump shade when prepped teeth are hydrated (prior to final impression). This will help the laboratory determine the opacity of the base porcelain (ingot).
Drape the client with a neutral gray bib or towel when taking the shade. It neutralizes the color perception of the eyes.
• Color is dependent on light, and light sources have an influence on color. Utilize color-corrected lighting. As an added value, offices can also use a shade matching light (such as Shade Wand by Authentic Products) to negate the effect of different light outlets.
• Learn to use a computerized chroma meter or spectrophometers that are available on the market. The devices may aid in the shade taking, documentation, and communication. For examples, take a look at ShadeEye NCC (www.shofu.com), ShadeScan System (www.cynovad.com), and X-Rite ShadeVision System (www.sullivanschein.com).
• Send photos of the client, including pre-operative, of the stump shade next to prepped teeth, and of the provisionals. It helps the ceramist put a face to the artwork they are creating!
There are many intricacies involved with color and shade-taking. Take the time to better understand the skill required. Its importance is that this knowledge is added to the arsenal of hygiene tools, further bridging hygiene with restorative services. It also makes learning mutually beneficial for the dental professional and the client being served.Kristine A. Hodsdon, RDH, BS, is a coach with Hygiene Mastery, as well as an international speaker, author, and software developer. She can be contacted about speaking or coaching at (888) 347-4785 or by e-mail at [email protected] or [email protected]. Visit her on the Web at www.pre-d.com and www.hygienemastery.com.