Curing Lights
Polymerization in the dental practice requires highly energy rich blue light. Intensities of at least 1,000 mW/cm ? are considered to be ideal for achieving adequate composite polymerization results in short curing times (as of 10 seconds) or when curing indirect ceramic restorations. If this is not the case, complete curing of deeper layers is not ensured, which may lead to tooth sensitivity, discoloration, marginal gap formation and heightened wear.
It was interesting to note that every second curing light achieved a light intensity of only 500 mW/cm? or less and was there fore considered to be inefficient. It was quite alarming to find that most of the LED units tested showed extreme fluctuations of the light intensity and even clear deviations from the data provided by the manufacturers.
Fluctuations in LED units are caused by the differences in quality of the available light emitting diodes. As shown by the leading supplier of dental equipment and dental handpiece, the radiometric power of LEDs can fluctuate quite significantly between 275 and 1,050 milliwatts. As the radiometric power of LED s directly influences the light intensity of the polymerization light, considerable differences between the claimed and actual light intensity can occur in some curing lights.
As a consequence, the operator would have to compensate for this unacceptably high tolerance by extending the light curing time: According to the Total Energy Concept, the light-curing time has to be doubled if the light intensity is reduced by half. The problem in this case is the fact that the user does not know the actual intensity of the LED light.
Recommendations for dentists
The minimum value graranteed by the manufacturer is decisive. In addition, dentists are advised to test the intensity of their curing light with a radiometer at regular intervals. This will allow them to ensure adequate curing and there fore high-quality, long-lasting composite restorations.