The Influence of Water Sorption of Dental Light-Cured Composites on Shrinkage Stress

Abstract

The contraction stress generated during the photopolymerization of resin dental composites is the major disadvantage. The water sorption in the oral environment should counteract the contraction stress. The purpose was to evaluate the influence of the water sorption of composite materials on polymerization shrinkage stress generated at the restoration-tooth interface. The following materials were tested: Filtek Ultimate, Gradia Direct LoFlo, Heliomolar Flow, Tetric EvoCeram, Tetric EvoCeram Bulk Fill, Tetric EvoFlow, Tetric EvoFlow Bulk Fill, X-tra Base, Venus BulkFil, and Ceram.X One. The shrinkage stress was measured immediately after curing and after: 0.5 h, 24 h, 72 h, 96 h, 168 h, 240 h, 336 h, 504 h, 672 h, and 1344 h by means of photoelastic study. Moreover, water sorption and solubility were evaluated. Material samples were weighted on scale in time intervals to measure the water absorbency and the dynamic of this process. The tested materials during polymerization generated shrinkage stresses ranging from 6.3 MPa to 12.5 MPa. Upon water conditioning (56 days), the decrease in shrinkage strain (not less than 48%) was observed. The decrease in value stress in time is material-dependent.

Novel Urethane-Dimethacrylate Monomers and Compositions for Use as Matrices in Dental Restorative Materials

“…Some researchers have shown that a certain water uptake can be beneficial by compensating for the volumetric contraction resulting from polymerization [11]. For this, the volume increase and the water sorption should be balanced by the volume reduction caused by polymerization shrinkage [43]. Therefore, a value of 40 µg/mm 3 was established as the maximum WS value for the resin-based dental materials, as given in the ISO standard 4049 [35].…”

Influence of composite type and light irradiance on color stability after immersion in different beverages

“…The “interaction theory” and the “free volume theory” (hole‐free volume). In the former, water diffuses and attaches to polymer chains via hydrogen bonds (bond water) . The latter assumes that water penetrates into nanopores, without any chemical interaction with polymer chain (unbond water) and depends on the macromolecular packing density .…”

“…30 The latter assumes that water penetrates into nanopores, without any chemical interaction with polymer chain (unbond water) and depends on the macromolecular packing density. 30 The quantity of sorbed water depends on the available equilibrium hole-free volume, the physicochemical affinity of network polymer groups to water, and the resistance of polymer chains to a swelling deformation stress. This could be the reason that exists color differences in RC after immersion in water (Table 4).…”

Color stability of bulk‐fill composites immersed in different drinks

“…Fillers were thought to minimalize the volume of resin matrices, thus reducing the sorption and solution of resin-based materials. 7,28 Comparing the filler loads of bulk-fill composites, Filtek Bulk had the lowest filler loading by volume (58.4%), compared to Tetric N-Ceram Bulk (61%) and SonicFill (66.8%). But, in spite of their filler loadings, when the SonicFill specimens immersed in coffee (ΔE = 5.22) and Tetric N-Ceram Bulk specimens immersed in red wine (ΔE = 4.22) showed more intense and unacceptable discolorations compared to Filtek Bulk Fill after 1-month immersion period.…”