title: Immediate polymerization shrinkage in light cured restorative resins.
abstract: The purpose of this study was to evaluate the immediate polymerization shrinkage of restorative resins following activation with different amounts of light energy. The composites used were: Z-100 (3M-ESPE), Z-250 (3M-ESPE), Ariston pHc (Ivoclar-Vivadent), Filtek P-60 (3M-ESPE), SureFil (Dentsply), Tetric Flow (Ivoclar-Vivadent), Silux Plus (3M-ESPE) and F-2000 (3M-ESPE). The percentage shrinkage after an 80-second activation was determined by means of a capillary mercury dilatometer The power of the light beam that reached the unpolymerized material was regulated at 350 mW/cm2 (Group I) or 275 mW/cm2 (Group II) positioning the end of the light source (XL-3000, 3M-ESPE) either in contact with or 5 mm from the dilatometer stopper. Four measurements were taken for each material and experimental condition, reading the dilatometer scale one minute after light activation. Data were recorded as percentage volumetric shrinkage as a function of the material volume calculated from the specimen mass and density. Analysis of variance and Tukey's test were used for statistical evaluation. Shrinkage was found to be significantly greater in Group I - 1.43% (0.43) - than in Group II -1.04 % (0.38). Some significant differences were found among some of the products. A reduction in polymerization shrinkage occurred concomitantly with the reduction in light activation energy and varied according to the organic content and the physical and chemical characteristics of each material.
authors.affiliation: Department of Dental Materials, School of Dentistry, University of Buenos Aires, Argentina. vanesaines@hotmail.com
authors.forename: Vanesa I
authors.initials: VI
authors.lastname: Rodríguez
authors.forename: Pablo F
authors.initials: PF
authors.lastname: Abate
authors.forename: Ricardo L
authors.initials: RL
authors.lastname: Macchi
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D008027:Light; D044367:Phase Transition; D018709:Statistics, Nonparametric
chemical_list: D003188:Composite Resins