"Researchers at the University of Colorado investigated and developed a unique monomer chemistry that significantly reduced polymerization shrinkage and increased the initial double bond concentration of the monomer and the degree of conversion achieved during polymerization. (Ge, Lu) They accomplished this by developing a novel diluent monomer based on dimer acid chemistry when compared with conventional diluents and Bis-GMA resins. Recently this dimer chemistry conversion technology was incorporated into a new low-shrink high monomer conversion composite resin, N’Durance (Septodont). The volumetric shrinkage of Bis-GMA nano-hybrid based composites have a range of 1.85-3.00% while the dimer acid chemistry, N’Durance, has a reported polymerization shrinkage of 1.27%. (Bracho-Troconis) High radiopacity and wear resistance are two qualities a composite resin must have. With N’Durance, the use of optimized nano-fillers of Ytterbium Fluoride, Barium glass and silica make this composite easy to distinguish in radiographs and provide for wear resistance similar to existing nano filled composites. (Bracho-Troconis) With this significantly lower volumetric shrinkage and non-stick formulation with N’Durance, well- adapted composite resin restorations are more easily achievable. Side benefits of this new chemistry include extremely low water sorption and solubility which contributes to color stability (no color shifting), marginal integrity and stain resistance of the composite. This same dimer acid high conversion chemistry is used for the N’Durance Dimer Flow flowable composite resin."