title: Filler morphology of resin-based low-viscosity materials and surface properties after several photoactivation times.
abstract: OBJECTIVE
  This study aimed to characterize the morphology of filler particles and to analyze the effect of shortened and extended photoactivation times on hardness (VHN) and cross-link density (CLD) of resin-based low-viscosity materials.
  
  
  METHODS
  Sixteen commercially available materials were tested: four fissure sealants (Alpha Seal, Fluroshield Yellowed, Bioseal and Fluroshield White) and 12 flowable composites (Opallis T, Permaflo T, Opallis A2, Natural Flow A2, Master Flow A2, Permaflo A2, Filtek Z350 A2, Natural Flow O, Master Flow OA2, Opallis OA3.5, Filtek Z350 OA3, Opallis OP) at six curing times (10 s, 20 s, 30 s, 40 s, 50 s and 60 s). Specimens were fabricated (n = 5), analyzed by Scanning Electron Microscopy, by VHN and by CLD.
  
  
  RESULTS
  Unimodal and multimodal filler particles sizes with spherical and irregular shapes were observed. Unfilled materials were also detected. There were no differences among curing times for either VHN or CLD. Opallis A2 and Opallis OA3.5 showed the highest VHN at all curing times, whereas Master Flow A2 and Master Flow OA2 presented the lowest VHN. Opallis A2 presented the highest CLD at all curing times and Alpha Seal showed the lowest CLD.
  
  
  CONCLUSIONS
  Filler particle morphology differed among the resin-based low-viscosity materials tested. The shortest photoactivation time tested could yield similar VHN and CLD means to those provided by the most extended photoactivation time.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, University of Pernambuco, Camaragibe, Pernambuco, Brazil.
authors.forename: Boniek Castillo Dutra
authors.initials: BC
authors.lastname: Borges
authors.forename: Gabriela Voany Galdino
authors.initials: GV
authors.lastname: Bezerra
authors.forename: Janaína de Almeida
authors.initials: Jde A
authors.lastname: Mesquita
authors.forename: Talles Rodrigo Santiago Freitas
authors.initials: TR
authors.lastname: Silva
authors.forename: Clodomiro
authors.initials: C
authors.lastname: Alves-Júnior
authors.forename: Isauremi Vieira de Assunção
authors.initials: IV
authors.lastname: Pinheiro
authors.forename: Rodivan
authors.initials: R
authors.lastname: Braz
authors.forename: Marcos Antônio Japiassú Resende
authors.initials: MA
authors.lastname: Montes
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D003432:Cross-Linking Reagents; D006244:Hardness; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D018709:Statistics, Nonparametric; D013499:Surface Properties; D013997:Time Factors; D014783:Viscosity
chemical_list: D003188:Composite Resins; D003432:Cross-Linking Reagents