Reliability of Radiometers Measuring Different Light Curing Units

<>Objectives: The aim of this study was to examine the precision of light intensity measurements of  different radiometers with different light curing units (LCU).

<>Methods: The light intensity of 50 LED and halogen light curing units  was measured with four different radiometers (Spring light meter 3K (SL) [Spring Health Products], LED Demetron (LD) [Demetron Research Corporation], Curing Radiometer Model 100 P/N (CR) [Demetron] and bluephase meter (BM) [prototype; Ivoclar Vivadent AG]. Every measurement was repeated twice. As gold standard all LCUs were measured with an Ulbricht sphere (US). The reliability of the different radiometers was calculated using linear regression analysis with the US value as the independent variable.

Results:

Table 1: Slope of the regression curve (B), significance of Slope different from 1 (identity line) and standard deviation of the residual values (res stddev) including (n=114) and excluding(*) (n=68) LCUs without light guide.

Curing meter	B	identity p<0.05	res stddev	B*	identity* p<0.05	res stddev*
SL	1.82	sig.	304.0	1.8	sig.	294.2
LD	0.78	sig.	102.6	0.74	sig.	106.8
CR	0.74	sig.	164.7	0.84	sig.	144.2
BM	0.74	sig.	206.9	0.87	sig.	113.7

Conclusion: A correct light intensity measurement of LCU is important for an adequate control of the LCU and for a sufficient polymerization of restorative materials. Best consistency showed CR (identity became not significant from 1 when p<0.01) but it is limited to measurements up to 1000mW/cm². BM showed a good reliability when excluding the LCUs without light guide. SL overestimated the light intensity of high power  LCUs.