title: Polymerization shrinkage assessment of dental resin composites: a literature review.
abstract: Composite restorations are widely used worldwide, but the polymerization shrinkage is their main disadvantage that may lead to clinical failures and adverse consequences. This review reports, currently available in vitro techniques and methods used for assessing the polymerization shrinkage. The focus lies on recent methods employing three-dimensional micro-CT data for the evaluation of polymerization shrinkage: volumetric measurement and the shrinkage vector evaluation through tracing particles before and after polymerization. Original research articles reporting in vitro shrinkage measurements and shrinkage stresses were included in electronic and hand-search. Earlier methods are easier, faster and less expensive. The procedures of scanning the samples in the micro-CT and performing the shrinkage vector evaluation are time consuming and complicated. Moreover, the respective software is not commercially available and the various methods for shrinkage vector evaluation are based on different mathematical principles. Nevertheless, these methods provide clinically relevant information and give insight into the internal shrinkage behavior of composite applied in cavities and how boundary conditions affect the shrinkage vectors. The traditional methods give comparative information on polymerization shrinkage of resin composites, whereas using three-dimensional micro-CT data for volumetric shrinkage measurement and the shrinkage vector evaluation is a highly accurate method. The methods employing micro-CT data give the researchers knowledge related to the application method and the boundary conditions of restorations for visualizing the shrinkage effects that could not be seen otherwise. Consequently, this knowledge can be transferred to the clinical situation to optimize the material manipulation and application techniques for improved outcomes.
authors.affiliation: Department of Conservative Dentistry and Periodontology, School of Dentistry, Ludwig-Maximilians-University Munich, Goethestr.70, 80336, Munich, Germany. kaisarly@dent.med.uni-muenchen.de.|Biomaterials Department, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt. kaisarly@dent.med.uni-muenchen.de.
authors.forename: Dalia
authors.initials: D
authors.lastname: Kaisarly
authors.affiliation: Department of Restorative Dentistry, University of Dammam, Dammam, Saudi Arabia.
authors.forename: Moataz El
authors.initials: ME
authors.lastname: Gezawi
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D008422:Materials Testing; D058105:Polymerization; D011140:Polyurethanes / Q000737:chemistry*; D055114:X-Ray Microtomography
chemical_list: D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D011140:Polyurethanes
keywords: Contraction stresses; Dental resin composites; Medical image registration; Micro-computed tomography; Polymerization shrinkage