Introduction: An important disadvantage of current dental resin composites is their polymerization shrinkage and production of microleakage. This shrinkage can cause tooth sensitivity, marginal discoloration, and secondary caries. The objective of this study was to review the effective factors on microleakage of methacrylate and silorane composites and compare them with each other.
This reviewed article was compiled and searched on library sources and Google scholar, Pubmed, ISI of science database, using the key words “Microleakage, Siloran-Based Composite, Methacrylate-Based Composite, Retentive Groove, Light Curing Technique,” from 1984 -2019.
Although it is not yet definitely clear, which methods of layering techniques (oblique, vertical, split) are more suitable, it seems that the layering technique has advantage over the bulkythat can effective in decreasing the shrinkage caused by polymerization and the resulting microlaekage.  It can also be concluded that silorane base composites have less shrinkage, but some factors such as cavity type, cavity extent, cavity margin distance to CEJ, type of silorane base  bonding system are also involves in their microleakage.  It seems the presence of retention grooves in the cavities seems useful, because it increases the bonding area and mechanical retention as well as decreases the marginal shrinkage due to polymerization and the resulting microleakage.
Conclusion: Finally, it can be said that microleakage cannot be stopped completely, and more studies, especially clinical studies, should be conducted to show the effects of these cases clinically.