Light cured composite materials are based on camphorquinone and other initiators such as phosphinoxides or germanium based initiators (Ivocerin). These initiators have different absorption spectra. Polywave based LED polymerization units use two different LED with emission maxima at 405 nm and 460 nm. The purpose of this study was to investigate the curing potential of polymerization units with different wavelengths at constant light intensity on composites initiated with different initiators.
Method:
Four different composites, based on Tetric Ceram (Ivoclar Vivadent) were initiated with 0.3% CC / 0.4% Amine, 1.0 % Irgacure 819, or 0.3% Ivocerin (Di-4-Methoxybenzoyl-diethylgermane), and in one composite a combination of all initiators was used. The composites were polymerized with LED units which had a emission maximum at 400 nm, 430 nm, 470 nm, 480 nm, 500 nm, and a light intensity of 800 mW/cm2 each. The following physical parameters were measured: Depth of cure (curing time 15 sec), and flexural strength according to ISO-4049.
Result:
Depth of cure and flexural strength measurements gave the following results: (different letters indicating significant differences in post-hoc comparisons after a multivariate ANOVA):
Depth of cure (mm)
LED-Wavelength (nm) |
CC/Amine |
Irgacure-819 |
Ivocerin |
All together |
400 |
2.55±0.05a |
2.15±0.05a |
2.90±0.03a |
3.02±0.02a |
430 |
2.70±0.04b |
2.27±0.02a |
3.46±0.04b |
3.24±0.03b |
470 |
3.13±0.05c |
0 |
2.06±0.06c |
3.25±0.05b |
480 |
3.22±0.04c |
0 |
1.64±0.02d |
3.21±0.05b |
500 |
2.69±0.05b |
0 |
0.49±0.03e |
2.84±0.04c |
Flexural strength (MPa)
LED-Wavelength (nm) |
CC/Amine |
Irgacure-819 |
Ivocerin |
All together |
400 |
96±11a |
72±2a |
99±3a |
121±5a |
430 |
93±12a |
63±8a |
94±4a |
112±7a |
470 |
115±6b |
0 |
92±10a |
116±6a |
480 |
101±6a |
0 |
55±7b |
105±10a |
500 |
93±7a |
0 |
0c |
114±7a |
Conclusion:
The absorption spectra of the initiator system has a significant influence on the curing potential of LED curing units emitting different wavelengths. The combined use of several initiators results in high flexural strength and depth of cure values at all investigated wavelengths.