Inorganic and Prepolymerized Filler Analysis of Four Composite Resins

Objectives: To determine the filler content by weight percentage of four resin composites and to examine the morphology, size and elemental distribution of the filler particles. Methods: Four commercially available light-cured resin composites (Kalore, Filtek LS, Aelite LS and IPS Empress Direct) were evaluated for filler content by weight using ashing in air and acetone dilution techniques. Ten specimens, 0.5g each, were analyzed for each material and technique.  Specimens for ashing were heated to 650^oC for 30 min. For the acetone dilution the specimens were diluted, centrifuged and decanted. In addition, SEM evaluation and Energy Dispersive X-ray Spectroscopy (EDS) analysis were performed to determine morphological characteristics and elemental distribution, respectively. Filler percentages were compared against manufacturer’s data and statistically analyzed by one way-ANOVA, Pearson Correlation, Tukey Multiple Comparison and Independent t-Tests. Results: Filler percentage by weight for Aelite LS, Filtek LS, Empress Direct and Kalore from ashed in air were: 86.44%, 77.86%, 72.17% and 70.62%, and from acetone dilution: 85.05%, 75.56%, 78.88% and 77.73%, respectively.  Mean values for all materials were significantly different for both ashing and acetone dilution. Aelite LS had significantly higher filler content for both techniques. Kalore had significantly lower filler content for ashing (70.62%) and Filtek LS for acetone dilution (75.55%). Manufacturer reported filler content for Aelite LS (88%) and Filtek LS (76%) approximated the study results for both techniques, while Kalore (82%) and IPS Empress Direct (79%) were only similar for acetone dilution, indicating higher content of prepolymerized particles. Morphological examination showed spherical shaped particles for Aelite LS and splintered and irregular shaped particles for all other materials. Conclusions: Aelite LS had the highest filler content for both ashing and acetone dilution. Values for filler content by weight using the acetone dilution were closer to manufacturer reported values.