Over the past 2 years, I have worked with Dr. Richard Price at Dalhousie University and BlueLight Analytics Inc. to investigate curing light differences using scientific measuring devices and dentist equipments. As a member of BlueLight Analytics scientific advisory board, I have seen data for the evaluation of more than 145 different models of curing lights from 42 manufacturers.
While irradiance is the most common and easiest techniquWhat e to measure curing light tip energy, it only provides a small piece of the puzzle for light curing composites. In fact, the in-office curing light radiometers have been shown to be unreliable.
Recently, more sophisticated instruments have been utilized to evaluate curing light irradiance and to describe the beam profile. Beam profile refers to the mapping of energy transmission at the surface of the light tip. Some lights deliver power evenly and uniformly over the light tip surface while others have hot and cold spots of energy delivery over the light tip surface delivering energy ununiformly.
The time-reducing competition among manufacturers is fierce; some claim to cure an increment of composite in one second, while others recommend 10-20 seconds. Dentists simply wish to know which curing light should I buy and how long should I light cure so that I am confident that my composites are properly polymerized?
Many curing lights exhibit a rapid drop in irradiance (75 percent or more) over that distance. The practitioner may purchase a seemingly “powerful” curing light that actually cures very little at the composite surface. Consider the high power Light D (center tip irradiance 7,000 mW/cm2) that delivers the same irradiance as the low power Light E at the clinically relevant distance of 8 mm.
Beam profile refers to the distribution of polymerizing blue light across the surface of the light guide tip. Many curing lights have an unevenly distributed blue light emission across the light tip; intense hot spots provide effective polymerization while intense cold spots do not.
Some curing lights can increase surface temperature up to 80° Celsius in just a few seconds. Other curing lights may increase pulpal temperatures dangerously, more than 5.5° Celsius, even when within recommended curing times. The risk of dangerous pulpal temperature increase is exacerbated when curing times are arbitrarily increased without concomitant heat management techniques such as increasing the waiting time and/or air cooling the tooth between polymerization cycles.
Even when using the same brand and model of curing light, in the same mode and for the same time, different curing light operators get very different results. This has been well demonstrated in studies using BlueLight’s MARC? Patient Simulator, a unique curing light operator-training device now used in dental schools throughout Europe and North America. MARC? is a laboratory-grade, clinically relevant light curing energy measurement tool. The light energy measuring sensors are embedded in a typodont head and provide immediate data collected by a chairside computer.