Objectives: To evaluate the reliability of different light curing meters (LCM) and to analyse parameters of light curing units (LCUs) that could influence the accurateness of measurement.
Methods: The light intensity of 220 LCUs was measured with four different light curing meters (Curing Radiometer, Demetron (CR), Light curing meter 3K, Spring (LM), LED Rediometer, Demetron (LR) and Bluephase meter (BM)) and the calibrated Ulbricht sphere (US) as reference. Statistical analysis were performed over all LCUs with z-test and Bonferroni-correction. Regarding the accuracy of LCM measuring LED and halogen LCUs and LCUs with (n=194) and without (n=26) light guides respectively, Wilcoxon rangsum-test was applied (a=0.05).
Results: Including all LCUs (n=220) in measurements, only CR showed a good corelation to the measurements of US. All other LCMs showed significant different values, whereas the highest discrepancy was found for LM. Evaluating differences in measurements of LED (n=150) and halogen (n=70) LCUs only BM showed a statistical difference in accurateness, whereas a better correlation in measurements was found for LED LCUs. Regarding measurements of LCUs with and without light guides there was a significant difference for LM and BM. Interestingly the values of LM without light-guides correlated better to US whereas it was inverse for BM.
Conclusion: A correct measuring of light intensity is of interest for daily practice as light intensity is correlated to curing properties of composite materials. However only CR showed a good correlation to the standard measurements of US. The other LCMs where more or less dependent from LCU properties like lamp type and light guide. However, some manufacturers of LCMs clearly exclude some LCUs from measurements as it is mentioned for BM and LCUs without light-guide.