title: Impact of filler size and distribution on roughness and wear of composite resin after simulated toothbrushing.
abstract: OBJECTIVE
  Nanofilled composite resins are claimed to provide superior mechanical properties compared with microhybrid resins. Thus, the aim of this study was to compare nanofilled with microhybrid composite resins. The null hypothesis was that the size and the distribution of fillers do not influence the mechanical properties of surface roughness and wear after simulated toothbrushing test.
  
  
  METHODS
  Ten rectangular specimens (15 mm x 5 mm x 4 mm) of Filtek Z250 (FZ2), Admira (A), TPH3 (T),Esthet-X (EX), estelite sigma (ES), concept advanced (C), Grandio (G) and Filtek Z350 (F) were prepared according to manufacturer's instructions. Half of each top surface was protected with nail polish as control surface (not brushed) while the other half was assessed with five random readings using a roughness tester (Ra). Following, the specimens were abraded by simulated toothbrushing with soft toothbrushes and slurry comprised of 2:1 water and dentifrice (w/w). 100,000 strokes were performed and the brushed surfaces were reanalyzed. Nail polish layers were removed from the specimens so that the roughness (Ra) and the wear could be assessed with three random readings (µm). Data were analyzed by ANOVA and Tukey's multiple-comparison test (α=0.05).
  
  
  RESULTS
  Overall outcomes indicated that composite resins showed a significant increase in roughness after simulated toothbrushing, except for Grandio, which presented a smoother surface. Generally, wear of nanofilled resins was significantly lower compared with microhybrid resins.
  
  
  CONCLUSIONS
  As restorative materials suffer alterations under mechanical challenges, such as toothbrushing, the use of nanofilled materials seem to be more resistant than microhybrid composite resins, being less prone to be rougher and worn.
authors.affiliation: Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.
authors.forename: Gabriela Ulian de
authors.initials: GU
authors.lastname: Oliveira
authors.forename: Rafael Francisco Lia
authors.initials: RF
authors.lastname: Mondelli
authors.forename: Marcela
authors.initials: M
authors.lastname: Charantola Rodrigues
authors.forename: Eduardo Batista
authors.initials: EB
authors.lastname: Franco
authors.forename: Sérgio Kiyoshi
authors.initials: SK
authors.lastname: Ishikiriama
authors.forename: Linda
authors.initials: L
authors.lastname: Wang
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D003775:Dental Polishing; D003802:Dentifrices; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D036103:Nanotechnology; D010316:Particle Size; D012833:Siloxanes / Q000737:chemistry; D013499:Surface Properties; D057085:Tooth Wear / Q000209:etiology*; D014099:Toothbrushing / Q000009:adverse effects* / Q000379:methods
chemical_list: D003188:Composite Resins; D003802:Dentifrices; C507124:Estelite sigma; C466112:Esthet-X; C444701:Filtek Z250; C509998:Grandio; D008689:Methacrylates; D012833:Siloxanes; C113300:TPH hybrid; C479084:admira; C533204:filtek Z350