EFFECT OF MONOWAVE AND POLYWAVE LED TECHNOLOGY ON MICROHARDNESS, TEMPERATURE RISE AND LIGHT TRANSMISSION DURING POLYMERIZATION

Objectives: To investigate the microhardness, polymerization temperature and light transsmision of different bulk fill composite materials cured by polywave and monowave LED technology.
Methods: Eight groups (n=5) of Tetric EvoCeram Bulk Fill (Ivoclar Vivadent), X-tra fil (Voco), Filtek Bulk Fill Posterior (3M ESPE) and Tetric EvoCeram (Ivoclar Vivadent) were prepared in Teflon moulds (5 mm in diameter and 2 and 4 mm thick) and cured with polywave Bluephase Style, 1100 mW/cm², and monowave Bluephase Style M8, 800 mW/cm². Temperature of the samples during illumination was measured with T-type thermocouple, light transmission with Ocean Optics spectrometer and microhardness with Vickers tester.
Results: During polymerization with the monowave lamp maximal temperature rise was 6.2 °C at 2 mm and 5.2 °C at the depth of 4 mm, while these temperatures were 6.8 °C and 5.8 °C when using polywave lamp. Average temperature rise using polywave was significantly higher than with monowave (p<0.05) for all materials except Filtek. Microhardness was highest at the surface in comparison to 2 and 4mm depths for all tested materials while the greatest microhardness was found for X-tra fil at all depths. Average microhardness was greater when using monowave for Filtek Bulk Fill Posterior at 2 mm, Tetric EvoCeram Bulk Fill at surface and 2 mm and X-tra fil at 4 mm depth (p<0.05). The function of transmission vs. time shows much faster rise of transmission using the polywave lamp compared to the monowave. The saturation of transmission was reached at 2 mm but not at the depth of 4mm, for all samples and both lamps.
Conclusions: Polywave LED produced higher temperature while the microhardness was almost similar when using both lamps. Optical transmission data indicates that the polymerization is not finished directly after irradiation, but after 24 h, which can be confirmed by the microhardness tests (80 % assumption).