Reliability of a handheld radiometer in contrast to an Ulbricht-sphere

Objective: To evaluate the accuracy of measurement taken from different established and an innovative radiometer, which is able to consider the diameter of the light guide tip, compared with the Ulbricht sphere. Furthermore it should be determined if the accuracy of different radiometer decreases over a certain period of time.

Method: Therefore the power density [mW/cm2] of 8 different LED curing devices (Elipar FreeLight 2, Bluephase, Bluephase 16i, Mini LED, LEDemetronII, SmartlitePS, Translux PowerBlue, Radii) and 3 QTH-devices (Optilux 501, Elipar Trilight, Astralis 10) was evaluated with six different radiometers: LED-Radiometer/Kerr Demetron, Optilux-Radiometer/Kerr Demetron, LED-Radiometer/SDI, Coltolux-Radiometer/Coltene, Cure-Rite/DENTSPLY, Bluephase-Meter/ Ivoclar Vivadent, and the Ulbricht sphere (n =10).

Results: The mean power density [mW/cm2] determinated for the Bluephase-Meter was 74% of the mean density determinated by the Ulbricht sphere for the same devices. For the Cure-Rite this was 72 %, the LED-Radiometer/SDI showed 71 % of the mean Ulbricht sphere records, the Coltolux-Radiometer: 69 %, the Kerr Demetron LED-Radiometer 60 %, while the original Kerr Demetron Radiometer showed 55 % of the mean Ulbricht sphere values. Compared to the Ulbricht-sphere some Radiometer showed false positive values; the long-term test did not show any statistically significant deterioration over time (Wilcoxon Text, 5% level) for any device investigated. Over all tested curing devices, the new Bluephase-Meter showed recorded mean values which were closest to the Ulbricht sphere.

Conclusion: Due to the fact that the inner diameter of the light guide tips can not be considered in measurements with conventional handheld radiometers, they do not seem to be appropriate for comparative measurements of the power density of different curing devices. The new Bluephase meter is able to consider this inner diameter and therefore might be easier used for such a comparison which was only possible with the Ulbricht sphere so far.