By C. Mike Meek / DDS / FAGD
Dr. Mike Meek says, “Admit it … single-front-tooth cases scare us as dental practitioners …” In his quest to take on challenging anterior restorative cases with a consistent, standard protocol for anterior dental photography, Dr. Meek explains how the use of cross-polarizing filters for shade description completely changed his tooth shade communication for the better.
Admit it … single-front-tooth cases scare us as dental practitioners—so much so that it is not uncommon to hear dentists joke that there is no such treatment plan, only two-front-teeth cases! I realize that this is just a joke, but I also have thought the same thing myself from time to time. A single-front-tooth crown is the great bet we make with our patients. But to win that bet, we have to get the appearance of that crown close enough to the surrounding natural teeth in one or two delivery appointments to please the patient, without using so much chair time that the case becomes unprofitable … and the patient has a magnifying mirror!
Years ago, I began a quest to standardize and accessorize my anterior dental photography protocol so that I could take on these challenging cases with confidence. For the longest time, I tried a variety of images to find a consistent routine for anterior composite, crown, veneer, and dental implant cases. I took ambient light photos, black and white frames, super-macro, and deployed many different Photoshop tricks and adjustments. Over time, I developed a complicated method for communicating shade that was good for a little more than two-thirds of my cases. I was content, yet still hungry for a more consistent technique to communicate shade and to make that single central a two-visit crown procedure!
In 2015 I was doing some research when I stumbled upon the use of cross-polarizing filters for shade description in dentistry, and my interest was piqued. I looked further and learned that the use of cross-polarization frames for shade determination has been part of dentistry as far back as 1996. (1, 2), yet it seems to have drifted out of use due to the advent of digital photography. I wondered, could this particular imaging technique be the silver bullet to my shade communication woes?
What is cross-polarized reflective photography?
When we hear “polarized,” we think sunglasses. Well, polarized sunglasses reduce glare by one step—linear polarization. The gates of the polarized lens are oriented either horizontally or vertically, but not both. This filters the light waves moving in either the east/west or north/south directions as they pass through the lens and to your eyes.
Cross-polarization is a two-step filtering process using two linear polarizer filters—one on the flash oriented either horizontally or vertically, and one on the lens oriented 90 degrees off the axis of the flash filter. This causes the light illuminating the teeth to be filtered for one direction of light wave; then the reflected light is organized in the contrasting direction as it passes through the filter/lens combo and is recorded by the DSLR sensor.