by Paul Feuerstein, DMD
We are now looking at a new group of ceramics for restorations. Many of them are made in dental labs using CAD/CAM, and the materials seem to be getting stronger and stronger.
I will review many of these in upcoming articles, but I've been asked about the esthetics of many of the new materials. They do come in various shades, but some of the very robust materials are cut out of a monochromatic block and then stained and glazed.
Some allow for a "cut back" process where the substructure is ground off and porcelain or other materials can be layered on for better esthetics. The results are quite different from hand-built porcelain where you can layer several shades internally and externally.
In addition, some of the new CAD ceramics lack the translucency required for delicate anterior restorations. Nevertheless, the technology has allowed us to create a veneer that – although a bit opaque – can be thinned to 0.2 or 0.3 mm and be strong enough to be hammered into a 2x4 without breakage.
Sometimes we as dentists care more about this shading than patients do. There are countless times when we struggle with a lower molar to get the precise gradient from occlusal to gingival, as well as compensating for things such as gray stain from amalgam.
We insert these masterpieces, yet often have patients pull their cheeks way out and shine a light on the molar and say, "Gee, it isn't white" or "Why is it yellow on the side?" (Then it is time to bang your head against the wall.) Another common scenario is when you're taking a shade and the patient says, "Don't worry, Doc. It's in the back and no one will see it anyway."
Through the years, we've seen electronic products that can copy the shade of a natural tooth. These, for the most part, use spectroscopy. This is the process used in a hardware store to match paint. In fact, X-Rite, the company that makes these machines, had a good system to match tooth colors. Unfortunately, the company has stopped making the product.
Olympus Corporation also came into this arena a couple of years ago but also dropped out. Other companies have come and gone, and there are only a couple left standing. One is from MHT in Great Britain called SpectroShade. There is not a lot of visibility of this product in the U.S. This company is also involved in a new intraoral scanner called Clon 3D that I will report on soon.
The current market leader is Vident, which makes the VITA Easyshade. This product has evolved nicely, and the company continuously makes improvements based on dentist feedback. It is small and simple to use with a 3 mm tip that is placed on a section of the tooth. In seconds, it shows the VITA shade (classic and 3-D) on a small LCD screen.
The default software tells the operator to take three spot shades – incisal (occlusal), middle, and gingival – which are displayed. There are also settings to take a shade from a shade guide, as well as an existing crown that has different translucency than the natural tooth.
Of course, the human eye may often be better than any electronic wizardry. The problem sometimes occurs when you take a shade in different lighting. Many offices have fluorescent ceiling lights while others take a shade with the chair light on. For many years, dentists have ordered Vita-Lite fluorescents that are 5,500ºK (natural light). They are still available. But be careful, as ballasts have changed in new installations. Check with the salesperson if you have the right end/pin size.
There are also now CFL 5500 replacements for incandescents (list price $17). During a sunny day, it is possible to take a patient to a window (hopefully not tinted) but you cannot always count on that. AdDent corporation just released the Rite-lite 2, a small light source with a "window" that you can put in front of the patient's mouth, illuminate the mouth, and take the shade. This shade not only is 5,500º K, but it is also two other settings, incandescent (3,200º K) and ambient room light (3,800º K).
Many offices like to send photos to dental labs with the shade tab in place. This way the lab can get a better sense of how close the tooth is to the actual shade guide. It is often difficult to say the tooth is "a little lighter than A2 but darker than A1." PhotoMed has just introduced a polarizing filter (polar_eyes) that takes the shiny flash reflection off the facial of the tooth and helps get a more accurate shade photo.
We are constantly trying to simulate Mother Nature. I hope some of these ideas are helpful.
Paul Feuerstein, DMD, installed one of dentistry's first computers in 1978, teaching and writing about technology since then while practicing general dentistry in North Billerica, Mass. He maintains a website (www.computersindentistry.com), Facebook page (Paul-Feuerstein-DMD-Dental-Technology), is on Twitter (@drpaulf), and can be reached via email at [email protected].
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