title: Influence of increment thickness on light transmission, degree of conversion and micro hardness of bulk fill composites.
abstract: This study evaluated characteristics of light transmission, degree of monomer conversion and surface microhardness of bulk fill, conventional and fiber-reinforced resin based composites (RBCs) through different incremental thicknesses of resin composite. Working hypotheses was that there are differences in transmission of blue light through RBCs of different kinds and that the thickness of the increments influence the degree of monomer conversion of RBCs. Six bulk fill, three conventional nanohybrid, one short fiber reinforced and one flowable RBCs were evaluated. For each material, four different incremental thicknesses (1, 2, 3 and 4 mm) were considered (n = 5). The specimens were prepared in cylindrical Teflon molds that are open at the top and the bottom sides and cured for 40 s by applying the curing unit. After curing process, the specimens were ground with a silicon carbide paper with a grit size of 1200 and 4000, and then stored dry at 37 °C for 24 h. Light transmission, degree of monomer conversion, surface microhardness were measured and data were analyzed using ANOVA (p = 0.05). There were differences in light transmission of resin composites of various types and brands. Low-viscous bulk fill and short fiber-reinforced RBCs presented higher light transmission compared to resin composites of higher viscosity. Reduced light transmission and lower surface microhardness and DC % at bottom side of the specimen suggests that more attention needs to be paid to ensure proper curing of the resin composite in deep cavities.
authors.affiliation: Department of Biomaterials Science and Turku Clinical Biomaterials Centre, TCBC, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, 20520, Turku, Finland.|Department of Restorative Dentistry and Periodontology, Institute of Dentistry, Libyan International Medical University, Benghazi, Libya.
authors.forename: Sufyan
authors.initials: S
authors.lastname: Garoushi
authors.affiliation: Department of Biomaterials Science and Turku Clinical Biomaterials Centre, TCBC, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, 20520, Turku, Finland.|City of Turku Welfare Division, Oral Health Care, Lemminkäisenkatu 2, 20520, Turku, Finland.
authors.forename: Pekka
authors.initials: P
authors.lastname: Vallittu
authors.affiliation: Department of Biomaterials Science and Turku Clinical Biomaterials Centre, TCBC, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, 20520, Turku, Finland. akikazu_dds@msn.com.|Department of Crown and Bridge, The Nippon Dental University School of Life Dentistry at Tokyo, 1-9-20 Fujimi, Chiyoda-ku, Tokyo, 102-0071, Japan. akikazu_dds@msn.com.
authors.forename: Akikazu
authors.initials: A
authors.lastname: Shinya
authors.affiliation: Department of Biomaterials Science and Turku Clinical Biomaterials Centre, TCBC, Institute of Dentistry, University of Turku, Lemminkäisenkatu 2, 20520, Turku, Finland.
authors.forename: Lippo
authors.initials: L
authors.lastname: Lassila
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D006244:Hardness; D066298:In Vitro Techniques; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
chemical_list: D003188:Composite Resins
keywords: Bulk fill composite; Depth of cure; Fiber-reinforced composite; Light transmission; Micro hardness