Abstract
Polymer networks are considered to be largely affected by water and chemical absorption from environment. Objective: The aim of this study was to evaluate the hygroscopic expansion of bulk-fill composite. Material and Methods: Fifteen disks (5 in each group) with different thickness(4mm/2mm) of Tetric N-Ceram Bulk Fill composite(TB) and Tetric N-Ceram composite(TN) were made according to the manufacturer’s instruction and stored in deionized water. The length of each specimen was recorded using a digital micrometer at baseline and at the end of 24 h, 1, 2, 4, 12 weeks intervals. Repeated measure ANOVA and Tukey HSD were used to determine the effect of variables. At 12 weeks, the mean hygroscopic expansion after water immersion ranged between 0. 33±0.09mm for TN to 0.41±0.07mm for TB with 2mm thickness. Repeated measure ANOVA revealed a significant increase in hygroscopic expansion over time (P<0.05). Results: The results indicated that at 24hours and 2weeks there was a significant difference among TN and TBwith 4mm thickness (p=0.007 and p=0.023, respectively). The other differences were not significant. Hygroscopic expansion affected by the type of composite and the passing of time. Conclusion: The results showed that the time taken to reach stabilization in hygroscopic expansion was shorter for TN in comparison with TB. For 2mm thickness equilibrium was attained earlier. KeywordsWater; Expansion; Composites; Polymerization; Bulk-fill.
Highlights
Polymer networks are considered to be largely affected by water and chemical absorption from environment
An understanding of the rate and extent of hygroscopic expansion due to water sorption of these materials is of considerable significance [9]
Dimensional changes of restorative materials caused by hygroscopic expansion can be verified by a variety of test methods such as: hydrostatic or Archimedes principle [11,12,13]; model cavities cut in brass in which the hygroscopic expansion of the material was expressed by the displacement force generated caused by water sorption[5]; the ability of materials in reducing the marginal gap [14]; measuring the relaxation of setting shrinkage shear stress [15]; measuring the length of specimens by means of an electrical or a computer-controlled laser micrometer or a microscope [16,17].In this study hygroscopic expansion of composites was evaluated by digital micrometer with measurement accuracy of one micron
Summary
Polymer networks are considered to be largely affected by water and chemical absorption from environment These effects may create biological, volumetric (plasticization, softening) and chemical changes (oxidation, hydrolysis) [1,2,3,4]. Expansion resulting from water sorption can be a clinically desirable phenomenon if it doesn’t go over the shrinkage value, as further stresses could be resulted in debonding, crack and crazing in enamel surrounding the cavity preparation [5]. These changes may causes undesirable effects including softening of the resin matrix, resin degradation, reduction of stainresistance and internal stress [6]. Water sorption may deteriorate mechanical properties of polymers, such as the modulus of elasticity, yield strength and produce changes in yield/ deformation mechanisms [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
