title: Effects of curing mode and moisture on nanoindentation mechanical properties and bonding of a self-adhesive resin cement to pulp chamber floor.
abstract: OBJECTIVE
  This study aimed to investigate the effect of dentin surface moisture and curing mode on microtensile bond strength (MTBS) and nanoindentation characteristics of a self-adhesive resin cement.
  
  
  METHODS
  Forty-four extracted human molars were distributed into four groups according to dentin surface moisture (dry or wet) and curing mode of the resin cement (light or chemical). Clearfil SA Cement (Kuraray Noritake Dental, Japan) was used for cementation of composite cores to the pulp chamber dentin. The specimens were sectioned into beams for MTBS test at the pulpal floor. Nanoindentation hardness and creep of the cement layer were measured under 100 mN load with 30s hold segment. Data were statistically analyzed using two-way ANOVA and Weibull distribution of MTBS (α=0.05).
  
  
  RESULTS
  Moisture, curing mode or their interaction did not significantly affect mean MTBS values that ranged 17.6-22.6 MPa (p>0.05); however, the lowest characteristic strength was found in moist chemically cured group. Hardness ranged 437-512 MPa, and was not affected by the experimental factors (p>0.05). Nanoindentation creep ranged 9.3-10.9% with the chemically cured groups showing the highest values, indicating lower cross-linking and deformation resistance of their polymer network.
  
  
  CONCLUSIONS
  Additional moisture on dentin surface did not contribute to adhesion of the anhydrous self-adhesive resin cement to dentin. Light-curing, despite attenuation through the composite core, was beneficial and improved nanoindentation creep resistance of the cement. The difference was not, however, reflected in the mean bond strength or hardness values.
authors.affiliation: Dental Material Research Centre and Department of Operative Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Horieh
authors.initials: H
authors.lastname: Moosavi
authors.forename: Ilnaz
authors.initials: I
authors.lastname: Hariri
authors.forename: Alireza
authors.initials: A
authors.lastname: Sadr
authors.forename: Suppason
authors.initials: S
authors.lastname: Thitthaweerat
authors.forename: Junji
authors.initials: J
authors.lastname: Tagami
mesh_terms: D000268:Adhesiveness; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry; D003786:Dental Pulp Cavity / Q000648:ultrastructure*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000648:ultrastructure*; D006244:Hardness; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D011176:Post and Core Technique / Q000295:instrumentation; D019279:Resin Cements / Q000737:chemistry*; D055116:Self-Curing of Dental Resins / Q000379:methods*; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: C469237:Clearfil Core; C581302:Clearfil SA; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D011109:Polymethacrylic Acids; D019279:Resin Cements; D014867:Water; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C069749:methacryloyloxydecyl dihydrogen phosphate