title: Non-destructive characterization of voids in six flowable composites using swept-source optical coherence tomography.
abstract: OBJECTIVE
  The aim of this study was to evaluate the void frequency (V(F)) and void volume (V(V)) in different flowable composites using swept-source optical coherence tomography (SS-OCT).
  
  
  METHODS
  Standard class I cavities were prepared and filled with six different flowable composites: Clearfil Majesty LV (MJ; Kuraray), MI Flow (MW; GC), MI Fil (ML; GC), Beautifil flow plus (BF; Shofu), Palfique Estelite low flow (EL; Tokuyama) and Surefil SDR flow (SF; Dentsply). The restorations were scanned under OCT. The OCT tomograms were analyzed and average V(F) and V(V) per restoration for each composite were calculated. Scanning electron microscope (SEM) was used to observe the structure of each composite. In addition, the flowability of the materials was evaluated measuring the displacement of each material placed up-right on a glass slide. V(F) and V(V) obtained by OCT were also compared to those calculated using micro-computed tomography (micro-CT).
  
  
  RESULTS
  Kruskal-Wallis ANOVA and Mann-Whitney U tests revealed significantly different V(F) and V(V) values (p<0.05) among the composites. Voids ranging from 35 to 785 μm in diameter were detected in OCT tomograms. MJ showed highest V(F) and V(V) values followed by MW, but ML, BF, EL and SF showed no significant difference. Filler volume in composites showed a positive correlation with void formation, but flowability did not show a specific trend. Micro-CT evaluation validated the V(F) and V(V) calculation by OCT, with a significant correlation in void size (p<0.001, r=0.94).
  
  
  CONCLUSIONS
  The results of this study indicate the reliability of SS-OCT for real-time void characterization of composite materials and restorations. Void formation in flowable composites is material dependent.
authors.affiliation: Cariology and Operative Dentistry, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Amir
authors.initials: A
authors.lastname: Nazari
authors.forename: Alireza
authors.initials: A
authors.lastname: Sadr
authors.forename: Mohammad Ali
authors.initials: MA
authors.lastname: Saghiri
authors.forename: Marc
authors.initials: M
authors.lastname: Campillo-Funollet
authors.forename: Hidenori
authors.initials: H
authors.lastname: Hamba
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shimada
authors.forename: Junji
authors.initials: J
authors.lastname: Tagami
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Sumi
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry*; D003737:Dental Cavity Preparation; D003793:Dental Restoration, Permanent / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: D003188:Composite Resins