Curing Lights: something you should know before buying (one)

The selection of a curing light that fits your style of practicing remains one of the most important equipment purchases you will make. If you have an active restorative practice, it is a device that you use virtually every time you treat a patient. The right light can help you achieve success, while the converse is true–the wrong light can make your efforts more tedious and your results less consistent.

Curing lights allow us to initiate the polymerization reaction “on demand” for a vast array of materials. However, there is, perhaps, more misinformation and hype regarding this type of equipment compared to just about anything else we use on a daily basis. Most of these controversies center on how long you have to cure specific types of restorations as well as how deep you can cure specific types of materials.

Manufacturers continue to make outlandish claims of their curing capabilities, most of which fall into the”too good to be true”category. An example is the claim that a new light can accomplish a“5mm depth of cure in 3 seconds”. Please don’t be fooled by these ads – you absolutely, positively cannot cure a composite in three seconds. Period. End of discussion.

If you undercure a restoration, for example, you may not even be aware of the negative sequelae for years. Therefore, selecting a curing light and using it properly can greatly affect the performance and longevity of your restorations.

Types of Curing Lights

Halogen

Use a halogen bulb as the source of light.

  • + Reliable – long track record
  • + Cures all materials due to wide bandwidth (400nm-510nm)
  • – Requires a cord due to power consumption
  • – Cooling fans are necessary and can be noisy

Bulb is really an aluminum oxide, high pressure vessel, which contains highly energized xenon gas (plasma) under 150psi. The inside shape is specific to reflect light arcing between two electrodes. Arc is only about 1mm long, enabling a very focused beam.

  • + Very fast (when a small tip is used)
  • – Expensive
  • – Large base units
  • – May not cure all materials
  • – Requires a cord that may be liquid-filled, may be stiff and can degenerate over time

Generates light when energy is applied to an atom raising an electron to a higher, unstable energy level. Electron will return to stable level by releasing light through a medium of argon gas.

  • + Fast
  • – Very expensive
  • – Large base units
  • – Small tips
  • – May not cure all materials
  • – Require a cord due to power consumption
LED (Light Emitting Diode)

Special diodes (electronic devices that restrict current flow chiefly to one direction) that emit light when connected in a circuit.

  • + Cordless or corded
  • + Lightweight
  • + Small
  • + Long battery life due to the low power usage
  • – May not cure all materials
  • – Some have poor and/or no selection of tips
  • – May shut down due to overheating during long curing intervals
Are Halogen Lights Obsolete?

With all the buzz these days over LEDs (one estimate is that 90% of all new lights being purchased in the U.S. are LEDs), the old reliable halogen curing light seems destined for the archives. It has been castigated for being heavy, still tethered to the base unit with a cord, noisy due to its fan, and possessing old technology.

On the other hand, LEDs are being touted as being on the leading edge of technology for numerous consumer and business applications. Along with nanotechnology, LEDs are blazing hot and getting hotter by the minute. It is difficult to dispute the attraction of LED curing lights.

Nevertheless, while we acknowledge the obvious appeal of these lights, some of them, especially the simpler versions, have significant drawbacks. The most significant ones are lack of timers, small tips, and the inability to cure beyond 3-4 minutes.

The lack of a timer may be viewed as just a nuisance, but it could lead to serious undercuring if you lose track of the beeps and/or how many times you have had to reactivate a light that automatically cuts off after 10 seconds.

In the same regard, small tips force you to overlap your curing area. Not only does this take longer, but you could inadvertently miss a section of the restoration, leaving an undercured area. And, since many of these lights do not have fans, their heat sinks are only effective for a few minutes. This is not an issue if your service mix is typically single restorations, but could be a significant problem when you are seating multiple indirect restorations such as veneers. With each veneer requiring at least 40 seconds (and that’s a bare minimum – 60 seconds is more reasonable), you would be out of luck trying to cure more than four veneers at a time.

Of course, then there is the issue of LEDs not being able to cure all materials. There is no doubt that the vast majority of light-cured materials can be fully polymerized with an LED. However, the few materials that cannot be cured with an LED mandate that you still have a halogen around for these contingencies. This may be just a nuisance as long as you know which material falls into this category, but it won’t compromise patient care. But what if you don’t know that a material can’t be cured properly with an LED? More than likely, it will still get pretty hard, but its degree of cure will be compromised along with its long-term performance.

The obvious solution to this problem is to buy an LED light that is capable of curing all materials. Unfortunately, only a few of them have this capability and it may require using a special tip. Therefore, it is still somewhat of a guessing game and you just have to hope that you don’t guess wrong.

This brings us back to halogen lights, which have something that it will take LEDs a long time to duplicate: a solid track record. Introduced just about 25 years ago, halogen lights have been the mainstay for curing resin-based materials. What you see is what you get – without any unpleasant surprises. And while many lights along the way have been introduced with various bells and whistles to make them stand out from the crowd, probably the only relatively new design is possessed by the Swiss Master, with its water cooling and monster light bulb. But with a price tag at the top of the food chain, it is clearly not for everyone.

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