June 2009 | Dental Products Report
Clinical 360°: Cosmetic/restorative

The take-aways

LED curing lights offer a variety of advantages over traditional QTH curing lights.
Less heat is generated by LEDs, meaning less potential for pulpal thermal damage.

State-of-the-art cure

How LED technology continues to transform light-curing capabilities.

by Dr. Gary Radz

The author experiences great results with Kerr’s DEMI LED curing light.

The set-up

“Since adhesive dentistry went ‘light cured’ in the 1980s, many dental materials require some form of light activation. Halogen lights have been the standard because of the broad range of wavelengths covered to stimulate photoinitiators in the materials. There is a ‘new kid on the block’ taking over the curing light market: LED. Dr. Radz discusses the benefits of light curing with LED technology.”—Dr. Robert Lowe, Team Lead

Many dental materials are dependant on a light-curing process to establish the final form of the material. Through the years, dentistry has used various light sources to perform the light-activation of these light-dependant products.

For years the most popular form of light-curing technology has been quartz-tungsten-halogen (QTH); laser light and plasma arc light have found their way to the dental marketplace as well. Lasers and plasma arc, although effective for light curing, never really caught on with the dental masses, most likely because of their size and price. This left QTH lights as the industry standard. For an acceptable price a dentist could purchase a dependable light source that was a reasonable size and could effectively cure light-sensitive materials.

The dental industry, meanwhile, continued to look for an even better light source for light curing dental materials. The introduction of light-emitting diodes (LED) to dentistry has made a significant impact in a short period of time.

Heat wave
The primary reason LED light sources have been pursued is because the wavelength of LED light (460 um to 490 um) is almost identical to the peak wavelength (470 um) for the activation of the photoinitiator camphorquinone (CQ). CQ is the photoinitiator found in most light-activated dental materials.

This picture demonstrates a light cure in progress, performed by the author, using his DEMI LED curing light.

This is a benefit over QTH lights because although the QTH lights have a broader wave spectrum, this broader spectrum generates more energy, therefore more heat. LEDs are the most efficient devices available in their ability to convert electrical current into light of the correct wavelength.1 LEDs are approximately 10% efficient, while the other sources are much less than 1% efficient. This means there is far less heat generated in an LED unit than in the others,2 so there is less potential for pulpal thermal damage.

The QTH light-curing units require large fans to dissipate the heat built up within the unit itself. This leads to the creation of a large and loud piece of equipment. LED light-curing units still have to dissipate heat, but because the amount of heat is so much less, this heat dissipation can be done with smaller heat syncs and/or, smaller, quieter fans and other noiseless and lightweight methods. This provides the potential to make a silent and smaller piece of dental equipment.

Energy efficient

“The life of LEDs is far beyond what a practice would require from it. The typical dental practice will use a curing light 100-200 hours per year.”

Because LEDs generate less energy, they require less energy to run the light-curing unit itself. This has led the way to small, cordless light-curing units able to run on rechargeable batteries.

LED light-curing units have a significant advantage over QTH when it comes to life expectancy of the light source itself. A typical QTH light bulb has a life expectancy of about 100 hours. LED light comes from an array of LEDs positioned within the light and can have a life expectancy of tens of thousands of hours. And while LEDs cannot be changed like QTH bulbs, the working life of LEDs is far beyond what a practice would require from it. The typical dental practice will use a curing light 100-200 hours per year.3 The likelihood of changing a QTH bulb numerous times before the life of an LED comes to its end is definite.

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Personal preferences

Since the first round of LED curing lights hit the market, development has continued in an effort to make a good thing even better. Of the growing number of LED dental curing lights available, Kerr’s DEMI LED, the third generation of the Demetron family of curing lights, caught my attention.

SDI North America’s Radii Plus curing light with whitening attachment.

Dual-Use Technology

Can your curing light also be an effective tool in whitening procedures? With LED technology and the right attachments —yes!

SDI North America now offers a full-arch bleaching LED attachment to augment the Radii Plus curing light. The attachment operates at a safe temperature of about 98.6°F, and reportedly does not emit harmful ultraviolet light.

Able to work with most in-office tooth whiteners, the unit, when attached to an optional lightweight bleaching stand, can be lifted up, moved and positioned exactly where it is needed

Size. Demetron’s LED I and the LED II both won extensive awards when introduced, including REALITY’s product of the year (in 2004 and 2006). The one negative comment I often heard was that the units were too large and heavy for a LED light. The size issue was based primarily on the need for a very large battery to produce enough energy for this powerful light.

The DEMI was created in response to the market’s comments and suggestions and what people did not like in the earlier versions of Demetron’s LED units. The DEMI light is now, reportedly, one of the smallest and lightest LED curing lights available.

Through new advancements, Demetron also has been able to reduce the internal circuitry and fan to reduce the overall size of the light as well as use smaller, more powerful, rechargeable batteries.

Energy modes. Current LED curing light systems use a ramp mode and/or a consistent high output mode. A ramp mode has the drawback of a longer curing time. A consistent high output mode produces a lot of energy and heat, but this can have a negative effect on the intrapulpal temperature and/or the LED chip.

With the DEMI, Kerr engineers kept an important benefit of the Demetron LED II: Periodic Level Shifting (PLS). PLS allows for the increase in average source output while minimizing internal heat generation.3 By reducing the duration that the LED chip is driven to high levels, the total heat generated is less than the “critical” amount, so effective output levels are increased for a short duration.4

The DEMI’s output is 1,100 mW/cm2, but during each second of light curing the light energy is pulsed up to 1,330+ mW/cm2. This allows for maximum energy output without damaging the LED chip or generating excess external heat.

There is the ability to have a 5-, 10- or 20-second cure. There is a low battery indicator and an easy to use and find on/off button.

Time. Because PLS technology is so energy efficient it is possible to reduce curing times in some cases.

Internal company data demonstrates that the DEMI curing light is capable of curing most composites 4 mm deep in just 5 seconds. This is a significant improvement in LED curing light performance because it begins to demonstrate that LED curing is not only equal to QTH light curing, but able to surpass it.

Ergonomics. The “Star Trek phaser” shape of the DEMI is the result of extensive hands-on user studies. Feedback was used to create a unit with an easy-to-use shape and accessible button positions.

Retrofitting. The DEMI is designed to accept most previously manufactured Demetron light guides. This way, a favorite light guide from your 10-year-old Demetron 501 can be used with the newer model.

It can work for you

The DEMI light is the culmination of a wide range of LED light curing research and real user feedback. I consider it “state of the art” for my practice. I encourage you to do the research and find a LED light that you can rely on.

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