Cuspal movement and microleakage in premolar teeth restored with posterior filling materials of varying reported volumetric shrinkage values

It would appear that a reduction in the manufacturers' reported volumetric polymerisation shrinkage for Z100 (4.0%) to below 3% for Filtek Z250™, P60 and Admira, resulted in a significant reduction in the associated cuspal strain on the MOD cavity. The diluent triethyleneglycol dimethacrylate (TEGDMA) increases the polymerisation shrinkage of Z100 resin-based composite due to an increased concentration of carbon-to-carbon double bonds (CC). The replacement of TEGDMA with urethane dimethacrylate (UDMA) and Bis-EMA in Filtek Z250™ and P60, decreases the polymerisation shrinkage stress by increasing the cross-linking of polymer networks. However, no group was identified as producing less gingival microleakage at the cervical dentine cavosurface margin when the cavities were sectioned and examined, regardless of the reported variations in cuspal strain and the associated volumetric polymerisation shrinkage values.