title: In vitro comparison of mechanical properties and degree of cure of a self-adhesive and four novel flowable composites.
abstract: OBJECTIVE
  To compare a self-adhesive with two low-shrinkage and two regular flowable resin-based composites (RBCs) in terms of degree of conversion (DC) as well as micromechanical (indentation modulus [E]; Vickers hardness [HV]) and macromechanical properties (flexural strength [σ], modulus of elasticity [Eflexural]).
  
  
  METHODS
  DC was investigated by an ATR-FTIR spectrometer at clinically relevant filling depths (0.1 mm, 2 mm, 4 mm, 6 mm bulk, 6 mm incremental) and irradiation times (10 s, 20 s, 40 s). Micro- and macromechanical properties were measured with an automatic microhardness indenter and a three-point bending test device after curing the specimens for 20 s and storing them in distilled water for 24 h at 37°C. Fillers were visualized using a field emission scanning electron microscope (FE-SEM). Results were evaluated using one-way ANOVA, Tukey's HSD post-hoc test, Pearson's correlation and a multivariate analysis (α = 0.05). A Weibull analysis was used to assess σ.
  
  
  RESULTS
  N'Durance Dimer flow (65.66%) reached the highest DC (at 2 mm depth, 20 s irradiation). In terms of macromechanical properties, EcuSphere-Flow (129.82 MPa) for σ and Synergy D6 Flow (3.74 GPa) for Eflexural reached the highest values. The highest micromechanical properties were measured for the self-adhesive RBC (Vertise Flow; E = 10.81 GPa, HV = 60.20 N/mm2). Reliability was highly influenced by filler weight (η2 = 0.77) and volume (η2 = 0.99) proportion.
  
  
  CONCLUSIONS
  In the present study, the self-adhesive RBC showed the highest reliability, highest DC (together with one of the low-shrinkage RBCs), and highest micromechanical properties as well as good macromechanical properties. Moreover, a curing time of 40 s and an incremental thickness not exceeding 2 mm appeared to be necessary for such results.
authors.affiliation: Department of Restorative Dentistry, Ludwig Maximillians University, Munich, Germany.
authors.forename: Pascal
authors.initials: P
authors.lastname: Czasch
authors.forename: Nicoleta
authors.initials: N
authors.lastname: Ilie
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D055119:Elastic Modulus; D005898:Glass / Q000737:chemistry; D006244:Hardness; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods; D008422:Materials Testing; D055595:Mechanical Phenomena; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites / Q000737:chemistry; D018583:Pliability; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D003188:Composite Resins; D008689:Methacrylates; C551012:N'Durance composite resin; D019279:Resin Cements; C111840:flowable hybrid composite; C485972:synergy compact resin cement; C581746:vertise flow; D014867:Water; C041979:2,2-bis-(4-(2-methacryloxyethoxy)phenyl)propane; D017438:Bisphenol A-Glycidyl Methacrylate