The curing light dilemma
GORDON J. CHRISTENSEN, D.D.S., M.S.D., Ph.D.
All general practitioners need curing lights for myriad curing tasks. Light-cured resin has become the state of the art during the past 25 years. It seems logical that the light-curing concept would have matured during that time, but it has not.
Without question, light-curing is desirable, but practitioners are confused about the most appropriate light-curing concept to use in their practices. Because of this confusion, some practitioners have continued to use older lights in spite of the advantages offered by some of the newer ones. The light-emitting diode, or LED, concept is challenging more established modes of curing, and some dentists are buying LED lights. And many practitioners who have purchased the even faster plasma arc curing, or PAC, lights are not willing to go back to the slower LED light-curing method.
Although there is continuing confusion on the subject among practitioners, a rational conclusion is that any of the current concepts available today will work adequately. The choice about which type of curing light to buy should be based on which of the various lights’ features suit the specific practitioner best. What is the state of the art in 2002?
This article explores the advantages and disadvantages of the various popular types of curing lights, and it makes suggestions about the most logical ways to make the decision about which curing light to use.
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CONVENTIONAL HALOGEN CURING LIGHTS
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Since the late 1970s, halogen lights (such as the Optilux 500, Kerr, a Division of Sybron Dental Specialties, Orange, Calif.) have been in constant use in dentistry. They have served the profession well, they are a known entity and they are easy-to-use, relatively reliable devices.
What are the advantages of conventional halogen curing lights?
- – Some cost less than other light systems.
- – They are based on a simple technology.
- – They generate little or no heat.
- – Their technology is well-known and nonthreatening.
What are the disadvantages of conventional halogen curing lights?
- – They have a slower cure time (about 15 seconds) than PAC lights (about three seconds) or some LED lights (a range of 10–20 seconds).
- – Most devices must be plugged into the house electricity.
- – The units are relatively large and cumbersome.
- – The lamps (bulbs) decrease in output over a period of use.
- – The lamps must be replaced frequently at moderate cost.
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ENHANCED HALOGEN LIGHTS
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In the last few years, there has been an emphasis on enhanced conventional curing lights to provide greater curing intensity and faster cure. The most obvious way this has been accomplished is by the use of light guides that diminish in size as they exit from the curing light. The Turbo Tip (Kerr) exemplifies this concept. Numerous enhanced halogen curing lights (such as the Optilux 501, Kerr) are on the market, and they have been popular choices for practitioners.
The main advantages of enhanced halogen lights:
- – They offer a faster resin cure.
- – They operate via a known, proven technology.
The main disadvantages of enhanced halogen lights:
- – They can generate heat during curing.
- – Some brands have a narrower-diameter light guide (curing tip) than conventional lights.
- – Most have a higher cost than conventional lights.
- – They offer a slower cure than PAC lights.
- – Most must be plugged into house electricity.
- – Most such units are relatively large and cumbersome.
- – Lamps decrease in output over time.
- – Lamps must be replaced frequently at moderate cost.
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LIGHT-EMITTING DIODE LIGHTS
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Recently, a new concept to dentistry, the LED, has entered the market. There have been significant sales promotions from the several companies selling LED lights. As a result of the promotions, dentists appear to be more confused than before. In spite of the confusion, sales of these lights has been good, and, with the exception of a poor start by one light that is now off the market, some dentists appear to be relatively satisfied with lights such as the Elipar FreeLight (3M/ESPE, St. Paul, Minn.), the NRG LED Curing Light (Dentsply Caulk, York, Pa.) and the GC E-Light (GC America, Alsip, Ill.).
Why would a dentist want an LED curing light? They have some apparent advantages:
- – LED lights are cordless, small and lightweight.
- – Diodes are long-lasting without the need for frequent replacement.
- – They generate no heat during curing.
- – They offer a moderate curing time of about 10 to 20 seconds.
- – They are quiet in operation.
LEDs have some disadvantages as well:
- – Their technology is new to dentistry, and the concept still is evolving.
- – Their curing time is slower than that of PAC lights and some enhanced halogen lights.
- – Their batteries must be recharged.
- – They cost more than do conventional halogen lights.
- – They offer a relatively low intensity.
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PLASMA ARC CURING LIGHTS
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These lights have been on the market for several years (two examples are PowerPAC [American Dental Technologies, Corpus Christi, Texas] and the Rembrandt Sapphire [Den-Mat, Santa Maria, Calif.]), and, in spite of continued enthusiastic acceptance by users, they have created considerable controversy. Some practitioners have reported that the rapid cure afforded by PAC lights causes damage to both resin-based composite restorations and the tooth preparations. Although this subject has been debated for several years, current clinical usage, as well as research, have disproved the allegations of damage caused by the faster lights.1 I have used PAC lights successfully for several years on hundreds of restorations.
What are the advantages of PAC lights?
- – Curing time averages three seconds for a typical shade A2 resin-based composite restoration.
- – The time savings observed with PAC lights amounts to a significant sum of money over a year’s use.
- – Short curing time makes overall procedures shorter and more integrated.
And what are the disadvantages of PAC lights?
- – Heat production during curing must be controlled by accurate timing of cure or reduction of heat by air cooling.
- – Their cost is high compared with that of other light-curing concepts.
- – Although lamps last many hours, when a lamp wears out or is broken, replacement of the lamp is costly.
- – Most of the devices are large, heavy and bulky.
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DISCUSSION AND SUGGESTIONS
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The type of curing light a dentist uses should be directly related to his or her needs and preferences. There is not a clearly superior light-curing technique. All currently popular curing lights have been shown to cure resin-based composite effectively in somewhat different modes. For dentists who are more time-oriented than others, the fastest curing of resin-based composite is effected by the PAC light. However, some practitioners wish to remain in a relatively safe situation with known technology, and they should choose conventional halogen or enhanced halogen lights. Some like the convenience and lack of heat offered by the LED concept, and this group may find greatest satisfaction with the LED technology.
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SUMMARY
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At this time, all the light-curing technologies on the market work adequately when used as directed by the manufacturers. The trend in the profession is to accept faster curing of resin-based composite. I agree completely. I have been using fast curing lights for many years, and I do not see any scientific or clinical reasons to change.
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Dr. Christensen is co-founder and senior consultant of Clinical Research Associates, 3707 N. Canyon Road, Suite No. 3D, Provo, Utah 84604, and is a member of JADA’s editorial board. He has a master’s degree in restorative dentistry and a doctorate in education and psychology. He is board-certified in prosthodontics. Address reprint requests to Dr. Christensen.
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FOOTNOTES
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The views expressed are those of the author and do not necessarily reflect the opinions or official policies of the American Dental Association.
Educational information on topics discussed by Dr. Christensen in this article is available through Practical Clinical Courses and can be obtained by calling 1-800-223-6569.
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REFERENCES
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- Clinical Research Associates. LED resin-curing lights: 2002 update. CRA Newsletter 2002; 26(3):3.
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CONVENTIONAL HALOGEN CURING...
ENHANCED HALOGEN LIGHTS
