Derangement of composite filler distribution inside syringe-type delivery systems

Used and almost emptied syringes of two brands of composites contained material close to the pestle-head that appeared to be more granular and dry, as compared to the composite obtained from unused syringes. The present results suggest that a derangement of filler and matrix phases occurred inside the used syringes when compared to unused controls. Stress imposed on the composite material inside the unused syringes resulted in a comparable derangement of filler and matrix phases. Although this derangement was limited, the effect could contribute to intra- and interlaboratory scattering of data.