Efficiency of Various Light Initiators after Curing with Different Light-curing Units

Objectives: Camphoroquinone (CC) is the most commonly used light activated initiator in dental composites. Its absorption spectra fits perfectly into the emission spectra of halogen lamps. Newly introduced polymerization units like Argon Laser, Plasma lamps and LED have a narrower emission spectra, which covers (CC), but not other initiators, like Phenyl-Propane-Dion (PPD) or Acylphosphineoxides (APO), which absorb at lower wavelengths. The purpose of this study was to test the efficiency of LED, Halogen lamps, Plasma Lamps and Lasers on the curing ability of composites, formulized with different initiators (CC, PPD, and APO). Methods: Composites were made using the different initiators based on Bis-GMA, UDMA and D3MA in the monomer (25 w-%) and Ba-Silicateglass, Ytterbiumfluoride and Spherical mixed oxide in the filler (75 w-%). The composites were cured with an LED (Akeda), Argon Laser (AccuCure 3000), Halogen (Astralis 10) and Plasma Lights (Apollo 95 E). Eight rectangular molds (2 x 2 x 25 mm) were cured  (12 – 40 sec, depending on light source), stored at 37 °C in water for 24 hours and the flexural strength and modulus were measured with an Universal Testing machine. The data were analyzed by ANOVA, significance level was set at p=0.05. Identical letters indicate no statistical differences in the same row.

Results: Flexural Strength (FS) and Flexural Modulus (FM) measurements showed the following results (Numbers in MPa):