Resin matrix system used in the composite shown below is:

Polyhedral Oligomeric Silsesquioxane (POSS): POSS molecules are 12-sided silicate cages produced from silane and functionalized to copolymerize with other monomers. POSS is a molecule-sized hybrid organic-inorganic oligomeric compound that can disperse homogeneously in compatible monomers and become covalently incorporated into cross-linked networks upon curing. Like the ormocer-type materials, the silicate cage structures provide a reinforcing function, but filler particles must also be included to achieve the balance of mechanical and other properties required for adequate performance as dental composites. Reference-Phillips’ Science of Dental Materials / Kenneth J. Anusavice - 11th Ed Pg:303