Inside Dental Assisting

March/April 2011, Volume 7, Issue 2
Published by AEGIS Communications

Digital Photography and Shade Analysis

A leader in the field, Dr. Edward McLaren shares his insight on the value of dental assistants participating in these processes.

By Edward A. McLaren, DDS, MDC

Inside Dental Assisting (IDA): Dr. McLaren, do you think that dental assistants should learn how to do digital photography and shade matching?

Dr. McLaren: I think assistants should definitely be involved in the photography process, because many assistants have a very good eye for color, and many of them enjoy doing photography. I think photography is one of the fun things we get to do on a daily basis in dentistry. It can be very artistic, very expressive, and the final results can be especially satisfying when you get a nice esthetic result.

I believe that all dentists should train their assistants how to do all of the steps in the process of photography—preoperatively, intra-operatively, and postoperatively. More importantly, the assistant can definitely participate in taking the shade images and communicating the shades to the laboratory. With the high-end digital photography that is now possible today, you can take a very accurate image of the existing condition and tooth with shade guides. So I think that would be a great skill set for assistants to learn. In fact, when I teach photography courses, probably 25% of our students in our 1-day and 2-day shade and photography courses are dental assistants. And they seem to enjoy it more than the dentists, actually. It’s a great skill set, it’s a fun, additional responsibility that they enjoy, and if the dentist can delegate it, the practice can reap the rewards of increased production through increased patient treatment acceptance.

IDA: In your teaching center, how do dental assistants get involved in shade taking?

Dr. McLaren: As far as the actual shade-analysis aspect, I think that assistants should learn how to do that step-by-step process too. I always like to get one or two people’s feedback on what their perception of the shade was. I would still recommend that dentists take the shade themselves—especially if they’re doing anterior esthetics, they need to be able to see the shade for themselves. So my recommendation would be that they take it, and then have one or two auxiliaries take the shade too. And this is important: all the team members should take the shade independently—you don’t want one person to bias the other. If I saw an A2 or 2M2, let’s say, and announced that, the assistant would tend to want to see, or at least look for, that as well. I prefer, in fact, to take the shade and then have one of my trusted personnel take the shade without any bias from me, while I’m out of the operatory getting something else done, and then after we’ve both taken it we will compare what we both saw and see if it was different. That helps us sort of troubleshoot the process, and we tend to get a little bit closer to what we want our final result to be. I think it’s a fabulous thing to know how to do, and it’s also one of those fun things in dentistry versus having nothing to do but set-ups and "suck, spit." I hate to say that, but those are the less fun things to do that assistants have to do, although they are critical functions. So, I absolutely think that both photographic and shade analysis processes should be learned by dental assistants.

IDA: Do you think these responsibilities are commonly delegated to dental assistants, from what you’ve seen?

Dr. McLaren: I would say that it’s becoming more common than it used to be. Dentists tend to be perfectionists, so these are processes that dentists have a hard time delegating. Dentists who are more successful financially tend to be better delegators, because the more the dentist can delegate to auxiliary staff, the more production the practice can ultimately complete. In reality, what I see is that dentists don’t do a good job of delegating—I think primarily because, at the end of the day, it’s their business and they’re naturally protective of it. But for dentists who are open to the idea and able to let go of that responsibility at least a little bit, there’s incredible opportunity. It’s an incredible internal marketing tool if you have good photography of finished cases to present to potential new clients. It’s one of the most valuable things in my own practice growth that I can correlate to increased patient acceptance. This is a skill set that’s as or even more valuable as any other skill set for motivating patients to accept the dentistry we know they need. So while I would say it’s becoming common, it should be even more common.

IDA: How do you work with your dental assistants, either at UCLA or in your practice?

Dr. McLaren: I train my staff and my students too—because sometimes the staff isn’t available to me, they’re helping students—so I teach them how to do all the photography. That’s early on in the process. They all know how to do standardized images. Then we start to learn how to standardize it, streamline it, and simplify it to get to the absolute basics to get a great result. I’ve got it down to some very small variables that someone would need to know on a couple of basic camera settings, and a couple of flash positions, as well. Then, we delve into how to get the correct composition—the specific image you want. It’s actually pretty easy to learn how to get high-quality images. I delegate all of those tasks to my assistants, sometimes even before I meet the patient. Then we can have a dialogue. On the computer screen, I can actually bring up the images that the assistant has taken. With computer technology, with digital technology, it is so easy to get their images in the computer quickly and bring them up on a screen. And you start pointing things out to the patient—there’s a crack here, caries there. At that point, you’re not even proposing treatment yet. The patient asks what needs to be done to fix it. It comes down to everybody wants to fix it; it’s just a matter of whether they can afford it.

The beauty of digital photography is the ability to see the images immediately and get re-takes if necessary. We can see it right on the screen; yes, we got the shot we need, or no, we didn’t get it, we need to take it again—and the patient is still in the chair. With film, we didn’t have that ability. That’s the great equalizer of the digital world. Not that we get better images, it’s the instantaneous feedback.

When we do the shade analysis, I will visually take the shade myself and then I will have one or two other people do the same process. I might be off in another room anesthetizing somebody, returning a phone call, or some other task. Then we will compare our data, and once we are sure that it’s between two shades, for example, we will take the photography. Now, that’s one level of photography I might still do myself, because the positioning of the shade guides becomes very critical relative to the teeth. In other words, if I’m going to sit down and interpret in the laboratory the image that I took from the shade analysis process, if that image wasn’t done correctly it can create an error in perception. I still do that a fair amount of the time, especially when I’m working with different people all the time. But in a private dental office, dentists can—and should—keep training assistants on an ongoing basis until everyone is comfortable with the process, and the assistant is comfortable with the skill set required for the task, and then the assistant really can take over the process under the dentist’s supervision and guidance. Again, I would advise that the dentist should still review the images before the patient leaves the office just to make sure that the images have captured what you were looking for.

IDA: Is there anything else that you think dental assistants should know?

Dr. McLaren: I think it would be great for assistants to talk to their dentist about sending them to a course on shade taking, and learning to understanding a little bit about color. They don’t necessarily need to be a color scientist who knows all the nuances of wavelengths of light and things like that—unless of course, they want to—but they should definitely understand the basics of color and the qualities of color that we’re looking for, such as translucency, surface texture, and how these variables affect perception. I think dentists would find it valuable if their assistants took a photography course. As I said earlier, the dental assistants in my courses seem to be having more fun than the dentists. They see it as an added responsibility that makes them more valuable to the practice, but one that is also fun.

Principles of Shade Taking and Photography

In the following excerpt from his May 2010 Inside Dentistry article, "Shade Analysis and Communication: 2010," Dr. McLaren teaches several of the essential aspects of evaluating and communicating tooth color. To read the article in its entirety, visit www.dentalaegis.com/id.

Understanding Lighting and the Effect on Color Perception

The perception of color is affected by three primary factors: the character of the light, the observer, and the object being viewed. A change in the condition of any of the three will cause a change in the perception of color. Thus, differing viewing conditions, ie, changes in light or changes in position, can alter perception. It is impossible to try to match tooth color under every lighting and positional possibility. Thus, the clinician should try to match under the conditions that the restoration will most likely be viewed. Relative to tooth position, most people are viewed standing up at conversational distance, so this is the best position to place the patient to evaluate shade. Too often shade is taken with the patient lying back, which increases the chance of misperception. The reason this happens is the shade guides do not have the same optical properties as the natural tooth. In different viewing angles they look different; a perceived match from one viewing angle may not be a perceived match at another viewing angle. Therefore, the first rule of shade analysis is to take the shade with the patient sitting up, eye-to-eye at conversational distance.

Most shade guides were fabricated to match a standard in a 5,500 K light source. Shade guides do not have the same optical properties as natural teeth. This means they do not reflect light the same way in all lighting conditions as the corresponding shaded tooth would. Thus, visual shade matching should only be done in a lighting environment that is closest to 5,500 K. In the author's experience, if the shade guide is matched to teeth in a 5,500 K light then it will match well in most lights, but if it was matched in a strongly biased light (eg, blue) the restoration will only match in that light.

There are many other factors that could be discussed about controlling viewing conditions. The quantity of light and the hydration of the tooth are very important. Make sure when shade matching that there are no overt shadows on the teeth or shade guide and that the light is not too strong to create specular highlights (reflective white spots). Also, the teeth need to stay hydrated. Saliva dries fast, especially with cheek retractors in. It is important to wet both the teeth and the shade guide as differences in surface texture between both can create a misperception. Using the same liquid on both surfaces can neutralize this. The second rule of shade analysis is to use full-spectrum, color-correct lighting and keep the teeth adequately hydrated.

Understanding Color Parameters Critical to Dental Shade Analysis

A basic understanding of color terminology is necessary for one to be able to evaluate differences from the shade guide but also to communicate color to the ceramist. Color has been defined in many different ways. The most widely used color-ordering or descriptive system in dentistry was developed by Mussell.¹

He defined color to have three dimensions; hue, the specific wavelength of light energy that would be labeled as red, green, blue, and everything in between; chroma, the intensity, concentration, or amount of a given hue (eg, lighter yellow or deeper yellow); and value, which is the lightness or darkness of a color. In real terms, if more light reflects off an object and hits our eyes it will be perceived as brighter or higher in value; conversely, if less light reflects off an object and hits our eyes it will be perceived as darker or lower in value. There is a fourth dimension of color, translucency, that is important when evaluating tooth color because teeth are, by nature, translucent and translucency is directly related to the perception of value. When evaluating tooth color, the most important color dimension to match is the value and the translucent zones are a close second. Next in importance are the chroma zones present in the teeth being evaluated. The least important dimension of color relative to matching natural teeth is the hue. In natural teeth, the hue range is very narrow, and in the author's experience matching the specific hue is unimportant as long as value/translucency and chroma are closely matched.

Digital Photography for Shade Communication

The second part of the author's shade-taking technique is to record the value and chroma images using digital photography. The most important points are to use a digital SLR camera that allows interchangeable lenses; record shade images in RAW file format; and control exposure and white balance ideally with manual exposure at specific flash/subject distances.

There are four images necessary for shade communication. One image is taken with the two or three closest value shade tabs to the teeth being matched using the VITA 3D Master or the VITA Linearguide (Vident, www.vident.com). With the VITA Classical Guide (Vident), the four closest value tabs should be in the image. Remember, the goal is to have a range of value; ideally, one tab should be slightly higher in value and one slightly lower in value. The second image is with the two closest chroma matches to the teeth. Again, one tab is slightly higher in chroma and one slightly lower. The third image is an image with what is perceived as the closest value using a small piece of digital gray card that has been attached to the shade tab. Attach the digital gray card using white utility wax. This allows for correction of inherent color bias because all flashes have subtly different color temperatures; depending on the charge state of the flash capacitor, the color temperature of the flash also can be affected. The fourth image is of the hydrated prepared tooth with a closely matched shade tab in the image. This is for the ceramist to see the preparation color to be able to modify the build-up or core color as necessary to compensate for the preparation color.

It is absolutely critical to take all of the images with the shade guide and the teeth to be matched in the same vertical plane, as objects closer to the film plane will be perceived as brighter and objects farther away will be perceived as darker. The shade guide and the teeth should be wetted with a glaze liquid. The ceramist will use this photographic information to visualize contrasts between the shade guide and the natural teeth.

Reference

1. Munsell AH. A Color Notation. 12th ed. Baltimore, Md: Munsell Color Co; 1936.

About the Author

Edward A. McLaren, DDS
Director, Center for Esthetic Dentistry
Founder and Director
UCLA Master Dental Ceramist Program
Adjunct Associate Professor
Los Angeles, California

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