title: Light-Curing Volumetric Shrinkage in Dimethacrylate-Based Dental Composites by Nanoindentation and PAL Study.
abstract: Light-curing volumetric shrinkage in dimethacrylate-based dental resin composites Dipol® is examined through comprehensive kinetics research employing nanoindentation measurements and nanoscale atomic-deficient study with lifetime spectroscopy of annihilating positrons. Photopolymerization kinetics determined through nanoindentation testing is shown to be described via single-exponential relaxation function with character time constants reaching respectively 15.0 and 18.7 s for nanohardness and elastic modulus. Atomic-deficient characteristics of composites are extracted from positron lifetime spectra parameterized employing unconstrained x3-term fitting. The tested photopolymerization kinetics can be adequately reflected in time-dependent changes observed in average positron lifetime (with 17.9 s time constant) and fractional free volume of positronium traps (with 18.6 s time constant). This correlation proves that fragmentation of free-volume positronium-trapping sites accompanied by partial positronium-to-positron traps conversion determines the light-curing volumetric shrinkage in the studied composites.
authors.affiliation: Danylo Halytsky Lviv National Medical University, 69, Pekarska St., Lviv, 79010, Ukraine. boyko.olha@gmail.com.
authors.forename: Olha
authors.initials: O
authors.lastname: Shpotyuk
authors.affiliation: Centre for Innovation and Transfer of Natural Sciences and Engineering Knowledge, University of Rzeszow, 35-959, Rzeszow, Poland.
authors.forename: Stanislaw
authors.initials: S
authors.lastname: Adamiak
authors.affiliation: Danylo Halytsky Lviv National Medical University, 69, Pekarska St., Lviv, 79010, Ukraine.
authors.forename: Elvira
authors.initials: E
authors.lastname: Bezvushko
authors.affiliation: Centre for Innovation and Transfer of Natural Sciences and Engineering Knowledge, University of Rzeszow, 35-959, Rzeszow, Poland.
authors.forename: Jozef
authors.initials: J
authors.lastname: Cebulski
authors.affiliation: Danylo Halytsky Lviv National Medical University, 69, Pekarska St., Lviv, 79010, Ukraine.
authors.forename: Maryana
authors.initials: M
authors.lastname: Iskiv
authors.affiliation: Jan Dlugosz University in Czestochowa, 13/15, Armii Krajowej St., 42200, Czestochowa, Poland.|Vlokh Institute of Physical Optics, 23, Dragomanov St., Lviv, 79005, Ukraine.
authors.forename: Oleh
authors.initials: O
authors.lastname: Shpotyuk
authors.affiliation: Lviv State University of Life Safety, 35, Kleparivska St., Lviv, 79007, Ukraine.
authors.forename: Valentina
authors.initials: V
authors.lastname: Balitska
keywords: Composites; Filler; Light curing; Nanoindentation; Positron annihilation; Trapping