Filtek Silorane by 3M ESPE

In 2007, 3M ESPE launched a new resin-based composite, Filtek Silorane (FS), and its adhesive system. Both the composite and the adhesive system contain a unique resin monomer based on the combination of siloxanes and oxiranes so it is apparent where the term "silorane" comes from. The polymerisation of FS differs from methacrylate-based composites and adhesives and is claimed to result in reduced polymerisation shrinkage. The cationic polymerisation of FS occurs via the ring opening of the C-O-C epoxide group which ends up in less reduction in molecule distances compared to the free radical polymerisation of methacrylate-based composites. In the latter, monomer interaction via methacrylate C=C groups results in the greater reduction of inter-molecular distances and subsequently greater polymerisation shrinkage.

Most recent studies have shown reduced shrinkage and shrinkage stress and strain for FS compared to methacrylate-based composites. Microleakage and nanoleakage were also reported for FS. Ongoing studies will reveal other properties of FS that may affect its clinical performance.

The dedicated adhesive system is designed to bridge the gap between hydrophilic dentine and hydrophobic FS composite. It contains the Primer and the Bond in separate bottles which are cured as separate layers, unlike any other two-step self-etch adhesive system, where primer and bond are mixed before curing. In Filtek Silorane adhesive system, these layers are not visible on SEM but can be detected using micro-Raman spectroscopy (Santini & Miletic, 2008) At the BSDR symposium on Dental materials it was reported, that after 6 months of storage, the type of failure for FS changes from the adhesive to cohesive as the fracture occurs within the adhesive system. The intermediate zone between FS Primer and Bond of about 1 micron may be the weak link in the failure mechanism and certainly needs further investigation.