All curing lights are not created equal

April 3, 2015

In dental practices around the globe, resin-based dentistry has drastically increased over the last few decades because more patients desire tooth-colored restorations.

In dental practices around the globe, resin-based dentistry has drastically increased over the last few decades because more patients desire tooth-colored restorations.

Resins are now being used extensively as both a direct restorative material and as a cement for utilization of indirect procedure. The vast majority of resins being utilized today require polymerization reactions initiated by blue visible light.1 Unfortunately, proper polymerization of resin-based materials cannot be assured simply because a blue-colored light happens to be coming out of a curing unit when the switch has turned on.

A major concern in dentistry today is that restorations are undercured because curing lights may not be performing properly, even when light is being emitted from the tip. In a 2005 study, 214 curing lights were tested in a private dental office in Toronto, and only 10 percent of these lights were able to get composite resin to its desired relative hardness.2 

Related reading: How to know if you're using the right curing light

It is important to understand the most critical point of achieving proper polymerization is at the deepest portion of any given preparation. A hard top surface does not necessarily indicate that the entire volume of the restoration has been properly polymerized, and insufficient polymerization can lead to reduced bond strength, increased wear and breakdown at the margins, decreased biocompatibility of the resin restoration and increased bacterial colonization of the resin in the restoration.3

In order to combat these issues, any member of the dental team that is responsible for curing resin restorations must be properly trained on the best practices of polymerizing resin with blue visible light. In addition, offices must invest in a properly manufactured curing light that has the technological properties to achieve proper polymerization of resin materials, without causing harm to the patient or dental team member. Thankfully, many reputable manufacturers have invested in the proper research and development to create superb LED curing lights that meet these objectives. In particular, one manufacturer has taken its highly rated light and leveraged the platform of this light by adding optional tips that make the light more versatile for an array of procedures.

Pride Institute's "Best of Class" 2014: Ultradent VALO curing light is capable of polymerizing all light-cured materials

Continue reading on Page 2 ...

Foundational technology
The minimum criteria for any curing light should be that it has the proper amount of power striking a specific surface area (irradiance) and that it emits the correct wavelength of light to cure any resin that is being used in a practitioner’s office. Claims of high power are not enough to ensure adequate curing. It is very important to take into account the relevant amount of irradiance in clinical practice. Ideally, the tip of the light should be as close to the resin being cured as possible. As the light moves away from the surface being cured, the diversion of the light beam increases and the power striking the critical surface to be cured decreases. This decrease in irradiance at the critical surface leads to a decrease in the likelihood of proper polymerization. To combat this issue, Ultradent has manufactured its VALO® curing light with three key benefits.

1. The shape of the light is similar to a very low profile intraoral camera, allowing access to any part of the dentition in both children and adults. This allows the practitioner or team member to put the light in close proximity to the resin that is going to be cured.

2. The light beam emitted from the tip is highly collimated, and its irradiance measured 782 mW/cm2 on standard mode at 9mm when independently tested by the American Dental Association.1 Note that 400 mW/cm2  is the minimum irradiance that is needed to allow resin materials to polymerize.

Related reading: DPR's guide for successful light curing practices

3. The light has a multitude of LEDs at its tip, allowing resin materials with photo-initiators in the 405nm, 445nm and 465nm to be activated. It is known that camphorquinone is the primary photo-initiator found in most dental resins, so two LEDs in the 465nm range are included in the tip, while single LEDs are present for the 405nm and 445nm range to activate other photo-initiators that are evident in some dental restorative materials.

Leveraging the technology
It is without question that the primary role of a curing light is to adequately achieve a high level of resin polymerization; however, in an ideal world, a curing light would also have other uses to add a more favorable return on the investment. Taking this into consideration, Ultradent has created a series of simple magnetic lenses that can easily be put onto the VALO curing light and further aid the dental team in everyday practice. Three that are particularly helpful include the PointCure, TransLume and Black Light lenses.

PointCure lens
Traditional halogen curing lights offered the ability to use a small tacking tip to cure a small diameter of resin cement during veneer delivery. This tacking technique made cleanup of resin cement much easier. With the advent of LED curing lights, tips were generally fixed in place and the ability to decrease the radius of irradiance was not possible with the vast majority of lights. This issue paired with the high power output of LED lights tended to make veneer cementation cleanup more difficult. To combat this issue, Ultradent’s PointCure lens can be easily placed so that a tack curing technique can be used.

Related reading: DPR's guide to curing lights, material activation

TransLume lens
One of the big benefits of high intensity light is the ability to transilluminate tooth structure and act as an adjunctive device to help identify fractures and proximal demineralization. Over time, a few standalone products have been produced by manufacturers to aid in this capacity. But, if the red or green TransLume lens is attached to the VALO curing light, a similar functionality is possible-making VALO a useful, multipurpose device.

Black Light lens
One of the most difficult things to do in dentistry is to identify residual composite resin when removing a failing restoration, orthodontic bracket, resin attachment used for clear aligner therapy or spot bonded provisional restoration. To help overcome this issue, the Black Light lens was created so that when it is placed over the VALO tip several residual composites fluoresce, allowing easier identification and decreasing the chance of healthy tooth structure removal.

Resin dentistry is here to stay; however, resin dentistry is highly dependent upon proper polymerization. Thankfully, the industry understands that proper polymerization is a must, and many very good products exist from reputable manufacturers. The VALO curing light by Ultradent meets all the criteria to allow for successful polymerization of composites, while being nearly indestructible and having the ability to add specialized lenses that allow the light to be a multifunctional device.  

References
1. dentalmaterials 29 ( 2013 ) 605–617.
2. El-Mowafy OM, El-Badrawy WA, Lewis DW, et al. Intensity of quartz-tungsten-halogen light-curing units used in private practice in Toronto. J Am Dent Assoc. 2005;136:766-773.
3. Seth S, Lee CJ, Ayer CD. Effect of instruction on dental students’ ability to light cure a simulated restoration. J Can Dent Assoc. 2012;78:c123.

About the author
Dr. Parag R. Kachalia is the vice chair of simulation, technology and research and is team leader within the University of the Pacific’s prestigious complex and esthetic rehabilitation program. He is a fellow of the American Dental Education Association’s leadership institute and American College of Dentists. He lectures extensively in the areas of technology and reconstructive dentistry and maintains a private practice in San Ramon, Calif., with his wife, Dr. Charity Duncan.

Related reading: Are you sure about your cure?