Polymerization shrinkage of cured dental composites with different resin matrices

The purpose of this study was to evaluate the polymerization shrinkage of cured silorane based composite (Filtek^TM P90) and methacrylate based composites (Filtek^TM Z350XT) nanofilled and (Filtek^TM Z250 XT) nanohybrid. A total of 45 specimens were prepared, they were divided into three main groups of 15 specimen for each according to the restorative material used (A); where “A1”: Filtek p90, “A2”: Filtek Z250XT and “A3”: Filtek Z350XT. A rectangular glass slab was used for polymerization shrinkage measurements .The composite materials were condensed incrementally in the mold and covered with celluloid strip, then cured for 40 seconds by LED light curing.  Four reference points were marked, then the distance between top and bottom of the uncured material (thickness of the specimen) was measured at each reference point,then the thickness of the specimen was repeatedly measured at the same reference points giving the measurements of the cured samples. The measurements were recorded using digital microscope. Results: It was found that there were statistically significant differences in maximum polymerization shrinkage between the same shade of the three resin formulations. Conclusion: Silorane based composites polymerized through ring opening polymerization is considered an excellent alternative to Bis GMA based composites regarding to their low shrinkage and polymerization stresses.