Objectives: To study the rate of curing, three composites, Heliomolar^® (HEL) (Vivadent), Z100^™ (Z100) (3M), and Renew^® (REN) (Bisco) were investigated.  Method:Volumetric shrinkage was measured at 25^oC using the Acuvol^™ with an RG610 red filter. Results:Detailed kinetic studies for REN determined the effect of varying the light intensity (100mW - 500mW) and irradiation time (3sec - 30sec) on the rate of curing. This provided confirmation of the kinetic model described by Anseth et al. A measurement of the gel time of composites and a kinetic constant is reported. ANOVA followed by a Fisher's LSD test and Kruskall-Wallis tests were used for analysis of the data.

REN @ 500 mW	3 sec (n=6)	5 sec (n=4)	10 sec (n=3)	20 sec (n=7)	30 sec (n=5)
Gel Time (sec)	11.4±1.6	10.2±0.8	12.0±0.4	12.2±1.6	11.9±1.8
Kinetic Const.(min-1)	4.8±0.3	7.1±0.9	8.0±0.5	7.6±0.6	7.6±1.4

 

REN @ 20 sec irrad.	100 mW (n=3)	200 mW (n=3)	300 mW (n=3)	500 mW (n=7)
Gel Time (sec)	19.4±1.3	14.8±1.5	14.1±1.6	12.2±1.6
Kinetic Const.(min-1)	4.2±0.2	5.9±0.5	6.1±0.5	7.6±0.6

 

20 sec @ 500 mW	Z100 (n=4)	REN (n=7)	HEL (n=4)
Gel Time (sec)	8.9±0.8	12.2±1.6	15.3±1.0
Kinetic Const.(min-1)	8.9±0.8	7.6±0.7	5.0±0.3

Conclusion:The gel times follow the order of HEL > REN > Z100 at 20 sec and 500mW. Irradiation time has no significant effect on the gel time of REN.  Light intensity has a significant effect on the gel time of REN.