Terminology, technology, and troubleshooting: curing lights

Terminology, technology, and troubleshooting: curing lights

Victoria L. Wallace

Welcome to the lazy days of summer! I guess hat is a saying that doesn’t pertain to dental offices, because I don’t seem to remember any summer lazy days in dentistry. Do you?

Like busy dental office schedules filling so quickly, so go the number of new choices dentists have to make when it comes to light curing units. Once again, it’s that constant change in technology.

New technology has once again arrived in the light curing unit arena. The newest trend in curing lights is LED–light emitting diode. Before we review the LED lights, let’s just take a minute to review our curing light options.


Quartz-Tungsten-Halogen lights seem to be the most common light cure source in today’s dental practice. Not only have they been used in the dental industry for many years, they are proven and relatively inexpensive.

Most commonly referred to as halogen lights, they are excellent for curing resins and have become a real workhorse in dentistry. Halogen lights produce a blue light by passing current through tungsten filament in a quartz bulb that contains halogen gas. We could really get into it, but this is not a research paper. The light is reflected and then goes through filters, producing a broad wavelength of light to cure resins. Due to the broad wavelength produced, halogen lights also produce some extra heat, but they always cure everything. Have you ever put the light guide on your fingernail? It gets very hot, fast.

The halogen lights also require maintenance. Bulbs degrade over time, lowering the output. The dental assistant should be using a curing radiometer to check the light periodically, especially if it is an older model. Newer models house a radiometer right in the unit, which is an excellent feature, as it is a constant reminder to check the light. The Optilux[TM] 501 by sds Kerr is just one example (Photo 1).


Halogen lights also have a fan to cool the unit. This is somewhat noisy and produces some vibration. It is important to remember halogen curing lights must not be turned off until the fan has stopped running, as it will overheat. The light guide must also be kept free of resin buildup on the end. Either use a sleeve cover to protect the light guide or use some acetone to remove any residue that has formed. Light guides can also break or fracture if dropped. Remember, light guides are autoclavable.

We’ve all used halogen lights and we all know how reliable they are. However, unless they are properly maintained and the output monitored, they could be a source of sensitivity due to uncured resin. If you look on the back of the radiometer it will instruct you to increase the cure time if the output is less than 400 mW/cm2.

PAC–Plasma Arc Curing

As we rolled into the late 1990s curing technology was revised. Dentists became very busy, and adhesive dentistry was the norm. Time was now an issue, and doctors wanted a faster cure. With plasma arc curing, they got it.

Plasma arc curing introduced a 3-5 second cure. Wow, what a time saver! They were cool, but not literally. They also produced heat, which sometimes would make the patient jump if they were not anesthetized.

PAC lights such as the Rembrandt Sapphire by Den-Mat (Photo 2) are also very popular for use with in-office whitening procedures.


PAC lights have a lot of moving parts housed in a fairly heavy metal type box. Some have a handle so they can be moved easily from room to room. The cord to the wand houses fiber optics, with the newer models being more flexible than in the past. PAC lights are also very expensive, starting at around $3000. PAC bulbs should last around 1000 hours. Good thing, as they cost around $700 to replace.

There were also some concerns with the first generation of PAC lights not curing all resins. The new models of PAC lights are said to cure everything.

LASER–Light Amplification by Stimulated Emission of Radiation

LASER curing units also became very popular. Light Amplification by Stimulated Emission of Radiation (LASER), or as most of us know it, argon laser–excited ions in an argon-filled chamber produce a light that is focused and passed through the handpiece. It is great technology as the cure is fast and virtually no heat produced. LASER curing units also have a very narrow wavelength, which may not cure all resins.

LASER technology is everywhere we look today. It is widely used in the medical field and is becoming more popular in dentistry. Due to the high cost of the LASER, it would not be an investment a doctor would make just to cure resins.

As technology progressed, so did the curing research. Output of curing lights always seemed to be the concern, but as the research came in, we were also taught that the wavelength produced by the light was of importance. Many new proprietary photo initiators only cured at certain wavelengths. As with all new technology, manufacturers made some adjustments to meet the needs of their customers.

LED–Light Emitting Diode

Now that you are up to speed on curing options, let’s talk about the future of curing.

Light emitting diode (LED) curing lights have many great features, which really benefit the dental assistant. Of course, they also benefit the clinician and the patient, but I am now looking at this as a dental assistant that is responsible for the equipment. I love the LED lights! Let me explain my excitement.

LED curing lights use semiconductors that are subjected to electricity and produce a blue light. It’s as simple as that! Well, not really or we would have had them years ago. Again, this is only basic information, not a research paper. The really great thing about the LED curing technology is that minimal heat is produced, therefore no fan is needed. No noise, no vibration and no waiting until the fan has shut off before turning off the unit. The patient doesn’t even know when the light is in the oral cavity.

Because the LEDs take less power to run, new battery operated models are available. They are easy to handle and easy to move from room to room. Most of the units are quite small compared to the other curing options. Cordless LED lights like the Elipar FreeLight 2 by 3M ESPE (Photo 3) sits in a base to be recharged. If you choose not to worry about recharging you may want to go with a corded unit like the Ultra-Lume LED 5 from UItradent (Photo 4). Humanitarian groups love the size and convenience of the LEDs when traveling to remote areas to perform dentistry.


Checking an LED light with a curing radiometer is not as important as it is with a halogen light if it is a corded unit. However, the same may not be true for cordless LEDs that are battery powered. As the battery wears down, the output can decrease. Please check with the manufacturer for its recommendation. If you choose to be on the safe side and check the output, sds/Kerr makes the Demetron L.E.D. Radio-meter (Photo 5) that is calibrated specifically for light emitting diodes that have a round end on the light guide.


Most of the manufacturers have a one- to two-year warranty. If you are purchasing a cordless unit, the batteries are usually lithium. Lithium batteries are more expensive, but last longer and are more environmentally safe. Also note that the warranty on the battery is usually only one year that is less time than the unit itself.

The LED curing lights are very convenient, but still relatively inexpensive. Most of the lights range from $700 to $1500. Make sure to ask what the return policy is when making the purchase. Most companies will allow 30 days to return if not satisfied. Another option is to ask if the representative has a loaner that your office can try out for a day or two. Try before you buy … always a smart move.

Ok, so the LED lights are convenient, long lasting, and a must have. What about the wavelength of the LEDs? Good question. Let’s go back to new technology. When something new is released, there may be some glitches, or bugs that need to be worked out. Nothing is perfect, and this is how the real world works. So when you find a problem, you research it and solve it, right? When the first generation of LED lights came out, we were all excited. However, some brilliant minds asked some good questions and realized that once again some of the photo initiators weren’t being polymerized.–primarily, photo initiators other than the traditional camphorquinone. So the manufacturers went back to the drawing/wavelength board to make the new LED technology work. However, the research is still taking place. As of the date of this article, there is only one LED light on the market that cures everything according to CRA Newsletter (June 2003) and Reality Publishing 2004 (Dr. Michael Miller). That is the Ultra-Lume LED 5 from Ultradent Products, Inc. (Photo 6). Therefore, my excitement about the lights. I also love the way it feels in my hand. It is so light–four ounces to be exact! The Ultra-Lume LED 5 also fits right in the handpiece holder, either on the doctor’s cart or the assistant’s cart (Photo 7). No worries about knocking it off the counter or dropping it, and if you do drop it, it won’t matter as the unit is very compact and durable.


Check with the manufacturer of the LED light you choose when it comes to using it for procedures such as in-office whitening that require long periods of constant exposure. Some recommend that you don’t use the LED in that manner.

Do the research; ask about the peaks for curing the products you use in your office. Your representative should have the answer for you. The sales rep should also know the wavelength of their LED light, and should be able to provide you a list of products that it may not cure.

You will hear more and more about LEDs in everyday life. You see them used in so many applications from car headlights, traffic signals, clocks, fun flashing pens, you name it. LEDs are a great step ahead in technology as they use a lot less energy and last a long time.

Next time your office is in need of a new curing unit, take some time to investigate the advantages of LED. The time you save in maintenance, and the convenience of moving them from room to room will make it a smart investment.

The next article will be about troubleshooting. If you have any questions or areas of interest you would like me to address, please e-mail me at: wvictoria@ultradent.com

Enjoy Life! Victoria

Victoria L. Wallace, CDA, RDA, has a varied dental assisting career that includes general dentistry, cosmetic/esthetic dentistry, lecturing and consulting. Currently she is Western U.S. University Relations Manager for Ultradent Products, Inc., and an independent practice organizer for dentists starting their own practices. Ms. Wallace is President of the Nevada Dental Assistants Association and a director of the ADAA Foundation.

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