The Canadian dental clinician and researcher Richard Price at Dalhousie University in Halifax has spent the better part of the past few decades studying curing light technology. In an interview with Dental Tribune he shared his advice on how to light cure properly and explained why polymerisation lights are so important for the success of your dental office.
 

Thank you for this opportunity to discuss the undercuring of dental resins. The problem as I see it is that most dentists have never been taught about the importance of proper light curing or what to look for in a good curing light. Even the cheapest light and the sloppiest technique will produce a resin restoration that is hard to touch. The problem is that the dentist cannot determine whether the bottom or the inside of the restoration has been adequately cured. An under-cured restoration is weaker and more prone to fracture, the bond strength to the tooth is reduced or even non-existent, post-operative sensitivity occurs, the color stability of the resin is compromised, and more chemicals are released into the body from the partially cured resin. These are all very undesirable outcomes of inadequate light curing, and none of them need to occur.

Curing lights are defined as medical devices, and only approved medical devices should be used on patients. If we look at Ivoclar Vivadent’s curing lights, they are not only approved medical devices, but they are also functional, ergonomic, reliable and thoroughly tested according to international standards. Furthermore, the broad emission spectrum of Bluephase lights means that they will cure all known dental resins and bonding systems.

In addition to the new Polyvision technology, the light's high power and irradiance can cure both direct and indirect resin restorations. Depending on the thickness of the indirect restoration, the light can photocure the resin cement used to bond most indirect restorations to the tooth. I like to use the high output settings to photopolymerize the resin under my indirect restorations and the regular output settings for my direct resin restorations.

The Polyvision feature should assist clinicians in achieving reliable curing results by automatically detecting unwanted movement of the light tip away from the tooth. When it detects movement, it alerts the operator using vibration or an acoustic signal and automatically increases or interrupts the curing exposure cycle.

Ivoclar Vivadent recognizes that the success of its resin-based products depends on adequate light curing. Consequently, it makes excellent curing lights.

Manufacturers often state that their light has a high irradiance. This may be true, but the power output may be rather low. How can this be? I think that the way the international standards are written is the cause of a significant problem when describing lights. These standards require the manufacturer to measure the total power from the light and then divide this power by the area of the light tip. This means that to deliver the same irradiance, a light with a 7mm diameter light tip need only produce half the power of a light with a 10mm diameter light tip (area of a 7mm diameter tip is half that of a 10 mm tip). In addition, this method provides a single irradiance value that is an averaged value across the tip; however, there are often hot spots of high irradiance and areas where the irradiance is rather low across the light tip. I see this all the time in budget lights.

In contrast, the current range of Bluephase lights delivers an exceptionally uniform light output. Certain models of Bluephase lights also include a radiometer in the charging base, and an integrated tester makes it easy to test the light every day. I know that may seem unnecessary to some, but if you only test your light once a week or once a month, what will you do when the light fails the test, because it will fail at some point? Are you going to recall and redo all of the restorations you placed since the last successful test?

When light curing, I recommend the following steps:

For Class II situations, I also cure from the buccal and lingual aspects after the matrix band is removed. 

I use the same technique for indirect restorations, but I usually use a tacking tip first, clean up the excess cement and then light-cure with the tip in contact with the indirect restoration.

Disinfect the light using the manufacturer’s recommended disinfectant. Some disinfectants can damage the light.

Check that the end of the curing light tip is clean and has no chips, cracks or cured resin on it. Using a barrier over the light helps with infection control and prevents resins from bonding to the light. However, extra care needs to be taken for optimised functioning of Polyvision Technology when there is an infection control barrier over the light tip of the Bluephase PowerCure, and G4 light. In these cases, the best option is to use two hands and hold the light tip over the restoration and watch what you are doing with that light tip.

Dr. Price is a prosthodontist and the director of digital dentistry at Dalhousie University in Halifax in Canada. He received his BDS from the University of London in England in 1979 and his DDS from Dalhousie’s Faculty of Dentistry in 1988. He completed his specialty training at the University of Michigan in 1984 and his Doctorate in Oral Technology and Dental Materials at the University of Malmö in Sweden in 2001. He is actively involved in teaching light curing and researching dental resins and has authored more than 190 peer-reviewed articles, and co-authored the chapter on light curing in the 7th edition of Sturdevant’s textbook, Art and Science of Operative Dentistry.

Dr. Price organises symposia on light curing in dentistry. Consensus statements based on these symposia help dentists to deliver the best dental restorations for their patients and have been published in English, French, German, Spanish and Portuguese.