The aim of this article is comparison of polymerization shrinkage in two types of resin composites: Methacrylate base(Z250) and Silorane base(P90). Polymerization shrinkage is one of the most important factors in composite restorations failure, because of stress generated in tooth to composite restoration interface and gap formation that causes bacterial leakage and recurrent caries. Polymerization shrinkage is also affected by composite type.
Methods:
5 disk shape samples for each resin composites were placed in the centre of metallic ring bonded to glass slab. Top surface of ring was covered by glass cover slip. Lam and sample were placed on especial LVDT holder in order to light cured from bottom surface and measuring polymerization shrinkage .In this study, "Deflecting Disk" method was used for dimensional change measurement of resin composite.
Results:
Mean of polymerization shrinkage in silorane base composite(0.7%) is significantly lower than methacrylate base composite(2.3%). Shrinkage pattern is completely different in these two types of composite.This is due to the polymerization mechanism that is Ring Opening in silorane base and opening of oxiran loops compensate polymerization shrinkage.
Conclusions:
Amount of polymerization shrinkage and it’s pattern is different in silorane and methacrylate base composite.silorane base composites. Silorane base composite(P90) showed significantly less polymerization shrinkage than methacrylate base composite(Z250).