IADR Abstract Archives
Effect of Experimental Blue and Violet LCUs on Physical Properties of a CQ/TPO Resin Composite
Objectives: To evaluate degree of conversion (DC), knop microhardness (KH) and polymerization shrinkage (PS) of a CQ/TPO composite after light-curing by different experimental light curing units (LCU): blue, violet and conventional.
Methods: 3 groups were analyzed regarding different LCUs: G1 (violet), G2 (blue) and G3 (conventional: violet+blue). Emitted power of each LCU was measured using a NIST-traceable thermopile; spectral irradiant output by a integrating sphere and a spectroradiometer; and distribution of the emitted power over the light tip with a modified laser beam profiling instrument. Narrow bandpass filters restricted the light passing to isolate the blue (460nm) and violet (410nm) ranges. Resulting light images were mapped and applied to similar locations on the top surface of the samples. Cylindrical composite specimens were made separately for each test (7mm diameter, 2mm thick). DC evaluation (n=15) was performed by a Fourier transform infrared spectroscopy (FTIR), and values were analyzed at the bottom of the samples. KH (n=12) was evaluated in 4 different points, according to the LCU chips (blue and violet), in a microhardness tester at top and bottom. PS (n=6) was performed by micro-computed tomography (μCT); 2 scans were done (uncured and cured), and data were imported into 3D-image reconstruction software for analysis. Data were submitted to statistical analysis.
Results: G1 showed the lowest % of DC (p<0.05), while G2 and G3 were not significantly different (p>0.05). KH showed different results according to locations and to LCUs (p<0.05); where violet light irradiated, a higher decrease in hardness with depth was observed, while where blue light irradiated, light was maintained along the depth; conventional LCU generally showed higher hardness in all positions. Concerning PS, G1 showed higher shrinkage on regions closer to the top, and a significant drop within depths, while G2 showed consistent PS values among depths; G3 also showed decreased values along depths, where as deep as it gets, less PS is showed.
Conclusions: Due to the non-uniform irradiance distribution across the emitting light tips of the different LCUs, different patterns of DC, KH and PS was observed among them inside the composite mass, which can result in potential disadvantageous outcomes in the long term of restorations.
Methods: 3 groups were analyzed regarding different LCUs: G1 (violet), G2 (blue) and G3 (conventional: violet+blue). Emitted power of each LCU was measured using a NIST-traceable thermopile; spectral irradiant output by a integrating sphere and a spectroradiometer; and distribution of the emitted power over the light tip with a modified laser beam profiling instrument. Narrow bandpass filters restricted the light passing to isolate the blue (460nm) and violet (410nm) ranges. Resulting light images were mapped and applied to similar locations on the top surface of the samples. Cylindrical composite specimens were made separately for each test (7mm diameter, 2mm thick). DC evaluation (n=15) was performed by a Fourier transform infrared spectroscopy (FTIR), and values were analyzed at the bottom of the samples. KH (n=12) was evaluated in 4 different points, according to the LCU chips (blue and violet), in a microhardness tester at top and bottom. PS (n=6) was performed by micro-computed tomography (μCT); 2 scans were done (uncured and cured), and data were imported into 3D-image reconstruction software for analysis. Data were submitted to statistical analysis.
Results: G1 showed the lowest % of DC (p<0.05), while G2 and G3 were not significantly different (p>0.05). KH showed different results according to locations and to LCUs (p<0.05); where violet light irradiated, a higher decrease in hardness with depth was observed, while where blue light irradiated, light was maintained along the depth; conventional LCU generally showed higher hardness in all positions. Concerning PS, G1 showed higher shrinkage on regions closer to the top, and a significant drop within depths, while G2 showed consistent PS values among depths; G3 also showed decreased values along depths, where as deep as it gets, less PS is showed.
Conclusions: Due to the non-uniform irradiance distribution across the emitting light tips of the different LCUs, different patterns of DC, KH and PS was observed among them inside the composite mass, which can result in potential disadvantageous outcomes in the long term of restorations.