DPR’s guide for successful light curing practices

January 3, 2014
Stan Goff

Issue 1

3M ESPE scientist Joe Oxman recently was interviewed by DPR Editor in Chief Stan Goff and shared his vast knowledge on curing lights, dental materials and technology.

3M ESPE scientist Joe Oxman recently was interviewed by DPR Editor in Chief Stan Goff and shared his vast knowledge on curing lights, dental materials and technology.

Last month we published Part 1 of the interview. Here we bring you Part 2.

Click here to learn more with our exclusive infographic on curing lights.

DPR: How does 3M ESPE work with its customer base to develop products?

Joe: One thing we do extensively is engage and interact with dental professionals. We literally talk to thousands of dentists globally every year. We’ve asked about potential opportunities like bulk filling of composite.

In principle most love the concept, however, they express two possible concerns: Number 1, am I getting adequate curing from top to bottom? And No. 2, how do I know that the material is sufficiently low shrinkage to avoid potential issues like post-operative sensitivity, microleakage and fracture of the tooth structure?

We have to do our homework and not launch a bulk cure composite until we’ve done a tremendous amount of compelling research. We try not to be premature when launching potentially game-changing products.

The trend of faster,more efficient procedure continues to develop traction from leading opinion leaders such as Gordon Christensen. He and others routinely  articulate the need for  faster, better and easier materials.

RelyX Luting Plus cement is another great example of a product that has used light curing to provide a novel clinically beneficial benefit. RelyX Luting Plus is paste/paste automixing resin modified glass ionomer luting cement.

3M ESPE always been a leader in the crown and bridge cementation category. Customers have continued to ask for products in this category that can be faster and more efficient from start of mixing to the final crown seating..

So for example, when dentists are cementing a crown, they fill it with the cement seat it on the prep and then remove the residual uncured cement that comes out around the margins. Most cements require waiting for the material to reach a gel or partially cured state that typically takes 2-3 minutes.

Dentists articulated the need for an approach to expedite this step, So we recently added a simple 5 second light-activated tack cure feature that provides immediate clean up around the margin without overcuring. Our customers love this simple cure on demand timesaving feature.

Another interesting class light activated systems could be called smart materials. …A number of years ago, we developed a new and novel technology that we have incorporated  into a variety of light curable materials such as dental sealants and orthodontic bracket adhesives. Interestingly these materials are pink when they are applied.

The color provides contrast when placed on the tooth structure so that it’s extremely easy to see and then when you light cure the material transforms from pink to essentially colorless. It’s a visual placement  indicator that irreversibly changes color indicating that that you’ve cured the material. It’s another example of how light activation of dental materials provides some unique clinical benefits.The light is the activator or the trigger for the on demand end result.

DPR: What should clinicians look for in a curing light?

Joe:  There’s also a trend towards the introduction of higher intensity lights into the marketplace. Traditionally lights were in the range of about 400 to 1200mW/cm2. Now we are beginning to see a significant number of ultra high intensity LEDs with outputs as high as 4000 mW/cm2.

The question that needs to be asked is more light necessarily better? Another key question is if you have a greater output does that necessarily mean that you can reduce the cure for a proportionally shorter period of time? And what about the potential heat from these high intensity lights?

Most of the curing lights today generate acceptable amounts of heat, however, the very high intensity lights of approximately 2000 mW/cm2 or greater may provide significant heat output that could have a negative clinical outcome.

It’s the age old question of if you have higher intensity lights can you cure for a shorter amount of time? It certainly seems reasonable and plausible…that if one provides you with double the light intensity then perhaps one should be able to light cure for half the time.

The key take home message from several researchers is that the exposure time is more important than the intensity. I’m not saying the intensity is unimportant, however, if you examine many recent scientific studies they collectively agree that there is some minimum light exposure independent of the intensity.. Certainly, there are other key factors such as the shade and opacity of the material being cured.

Be cautious about claims that may be too good to be true. For example, there are manufacturers of ultra high intensity lights, that may recommend  curing for 2-3 seconds.  The current data from the scientific experts would argue against those recommendations.

The message is that there are some inherent limitations with the current chemistry that require some specified minimum light exposure.  This is important to ensure that you cure materials as effectively at the top and the bottom.

Most of the thought leaders are currently saying that you probably shouldn’t be curing your materials for less than 10 seconds independent of intensity. That’s the minimum under the best set of conditions. As a consequence, you may wish to avoid super high intensity lights due to the excessive heat generation that could potentially result in a negative clinical outcome.

Furthermore, if you don’t cure composites adequately, the material may have reduced properties, higher wear, increased staining and more extractables. Adequate curing time is absolutely critical to achieving a long term clinical result.

DPR: What else can dentists do to help them get the most out of this technology?

Joe: In the end, I suggest that you follow the instructions of the manufacturer of the material. A manufacturer of the curing lights may say go ahead and cure for 2 seconds, however, they may not actually manufacture the light curable materials. I think it is best to heed the advice of the company that is selling the light curable materials.

In terms of communicating with their patients, there are several key messages.  First and perhaps most important is that the light itself is safe. There is no ultraviolet light but rather visible light. It’s the light we can actually see with the naked eye. It’s safe and there is no danger in the light itself to the patient.

Secondly, explain to them the materials are purely being activated or hardened by the light source. Light activation allows the dentist to place the shapeable material in a time frame that’s sufficient for  achieving the proper anatomy. Upon completion, the material can be rapidly transformed from a soft state to a hard tooth like state with a relatively brief light exposure. … also called cure on demand

The use of light curing has now been around in dentistry for close to 40 years and I wouldn’t even venture to guess how many millions of clinical placements have occurred using light activation.

DPR: Can this technology continue to get better?

Joe: I think there’s a realization today that curing lights can be improved. The light output of today’s lights overall is quite good and relatively uniform. But there is always room for improvement. Ultimately we’d like to further optimize the current lights by improving uniformity of the light output across the entire light guide surface.

The most significant trend and technical advancement during the last years has been the transformation from corded halogen lights to cordless, battery operated LEDs …a trend we predicted nearly twenty years ago in a similar article …that’s become a reality.

So now the question becomes, what’s next? With LEDs technology continuing to advance,  they will likely become even more energy efficient and as a result even smaller. At some point you may be curing your materials with a light that’s the size of laser pointer.

Perhaps the lights of the future will also be intelligent or smart lights.  They may be self adjusting to tell you when the material is adequately cured. There will be no guessing or concerns about sufficient curing independent of the material.

And perhaps the curing lights of the future will serve more than one purpose. Today some of the blue lights are also used to activate bleaching material…tomorrow,  they may be used to characterize carious lesions, or locate previously restored dentition.

Our responsibility and culture at 3M is to identify innovative solutions that address our customers articulated and unarticulated needs.