Papers by Keyword: Polymerization Shrinkage

Abstract: Polymerization shrinkage of composite filling materials still becomes one of the most important features which decreases strength properties of reconstructed teeth crowns. From among various methods to reduce that disadvantageous phenomenon which are used in a dental practice sandwich filling processing of crown cavity seems to be the most effective one. The paper presents the results of the strength examination of the influence of the different ways of layered polymerization processing on the mechanical properties of modern hybrid micro composite material with regards to the following quantities: compressive strength, strain to fracture, modulus of elasticity and work to fracture.

Abstract: The finite element analysis is presented in this paper in order to investigate the influence of interphase properties on restored-tooth structure due to polymerization shrinkage of resin-based composite. The restoration-tooth interface is simulated using plane elements of varying material properties and thicknesses. The stress and displacement within restored-tooth structure built-up from the polymerization shrinkage of the restorative composite were computed accounting for the time-dependent, visco-elastic behaviour of the composite. It was found that a correlation exists between material and geometry properties at the restoration-tooth interface and higher shrinkage stresses on interphase due to polymerization shrinkage. The development trend of residual stress from polymerization shrinkage in the restored-tooth structure was discussed and forecasted.

Abstract: The finite element analysis is presented in this paper in order to investigate residual stress distribution in the interphase of restoration-tooth structure due to polymerization shrinkage of resin-based composite. The restoration-tooth interface is simulated using plane elements of varying material properties and thicknesses. The stress within restored-tooth structure built-up from the polymerization shrinkage of the restorative composite were computed accounting for the time-dependent, visco-elastic behaviour of the composite. A sensitivity study is performed to examine the relative influence of geometric and material parameters of interphase on the shrinkage stress development. It was found that a correlation exists between material and geometry properties at the restoration-tooth interface and higher shrinkage stresses on interphase due to polymerization shrinkage. The development trend of residual stress from polymerization shrinkage in the restored-tooth structure was discussed and forecasted. The varying material and geometry properties of restoration-tooth interface seem to have conclusive effect on the interfacial stress system, as well as on the longevity of the restoration. From the purely mechanical point of view, this can result in interfacial debonding.

Abstract: The purpose of this paper is to investigate the influence of interphase properties on restored-tooth structure due to polymerization shrinkage of resin-based composite. The stress within the restored tooth structure built up from the polymerization shrinkage of the restorative composite was computed accounting for the time-dependent and viscoelastic behavior of the composite. A sensitivity study was performed to examine the relative influence of geometric and material parameters of an interphase on the shrinkage stress development. It was found that a correlation exists between material and geometry properties at the restoration-tooth interface and higher shrinkage stresses were located at the interphase due to polymerization shrinkage. The varying material and geometry properties of restoration-tooth interface seemed to have a conclusive effect on the interfacial stress system, as well as on the longevity of the restoration.

Abstract: The polymerization shrinkage of light-cured composite resin, a dental restoration material, was studied using three different experimental methods. Digital image correlation method was used to examine the shrinkage deformation on the free surface of artificial cylindrical cavities. X-ray CT images and the digital image correlation were employed to measure the shrinkage deformation in the cavities. The shrinkage force was measured at the floor of the cavity using a load-cell, and evaluated as functions of time and the depth of the cavity.

Abstract: This work presents results of research on compressive strength, microhardness, polymerization shrinkage and water sorption of some specially developed composite materials for dental fillings. The investigated powder fillers were divided into two groups: fluorine-based fillers, such as fluoridated glass, strontium fluoride, ytterbium fluoride and additives of improved mechanical characteristics such as nanosilica and polyethylene. The influence of fluoride ion source on the properties of the composite materials was evaluated. Tests were performed just after the material polymerization and, additionally, after seven, thirty and sixty days. Some small differences between composites were observed.

Abstract: This study explores degree of vinyl conversion (DVC), polymerization shrinkage (PS) and shrinkage stress (PSS) of the experimental amorphous calcium phosphate (ACP) composites intended for use as an endodontic sealer. Light-cure (LC), chemical cure (CC) or dual-cure (DC; combined light and chemical cure) resins comprised urethane dimethacrylate (UDMA), 2-hydroxyethyl methacrylate (HEMA), methacryloyloxyethyl phthalate (MEP) and a high molecular mass oligomeric co-monomer, poly(ethyleneglycol)-extended UDMA (PEG-U) (designated UPHM resin). To fabricate composites, a mass fraction of 60 % UPHM resin was blended with a mass fraction of 40 % as-made (am-ACP) or ground ACP (g-ACP). DVC values of copolymer (unfilled UPHM resin) and composite specimens were determined by infrared spectroscopy. Glass-filled composites were used as controls. PS and PSS of composites were determined by dilatometry and tensometry, respectively. LC copolymers attained extraordinary high DVC values at 24 h post-cure (95.7 %), compared to CC (52 %) and DC (79.3 %) copolymer specimens. While the DVC values of LC and DC am-ACP composites were reduced between 5 and 10 %, DVC values of DC g-ACP composites increased almost 8 % compared to the corresponding copolymers. High DVC attained in LC composites was, expectedly, accompanied with high PS values (on average 7 vol%). However, PSS developed in LC and especially DC composites did not exceed PSS values seen in other UDMA-based composites. Based on this initial evaluation, it is concluded that, DC, g-ACP filled UPHM composite shows promise as an endodontic sealer. However, further physicochemical evaluations, including water sorption, mechanical stability and ion release as well as a leachability studies need to be performed before this experimental material is tested for cellular responses and, eventually recommended for clinical utility.