A hollow inner plunger (100) for use within a syringe-in-syringe mixing systemfor mixing a two-part dental composition. The hollow inner plunger includesa body having a continuous cylindrical wall (102) defining an internal chamber(108) for containing a first component (HOa). The body (100) includes a proximalend (104) and a distal end (106). A sealing plug and rupturable membrane (116)are disposed at the distal end of the body, and the sealing plug and rupturablemembrane (116) are integrally formed together as a single piece (e.g., formedof a single piece of elastomeric material). An associated syringe-in-syringemixing system (124) includes a first plunger (126), the hollow inner plunger(100), and a syringe barrel (128) configured to contain a second component (HOb).When assembled, the first plunger (126) is slidably disposed within the hollowinner plunger (100), and the hollow inner plunger (100) is slidably disposedwithin the syringe barrel (128). The two components (110a, 110b) are initiallyseparated by the rupturable membrane (116).
