title: A comparison of two different methods and materials used to repair polycarbonate crowns.
abstract: OBJECTIVE
  The aim of this study was to evaluate the bond strength and crown-repair material interface of polycarbonate crown repaired using flowable resin composite and hybrid resin composite following two different surface preparations.
  
  
  METHODS
  The facial surfaces of fifty-two polycarbonate crowns were flattened and roughened. Specimens were then divided into four test groups. A bonding agent alone (Groups 1 and 2) or a combination of methylmethacrylate (MMA) + bonding agent (Groups 3 and 4) was applied to the prepared surfaces. Then either a flowable (Groups 1 and 3) or a microfilled hybrid (Groups 2 and 4) resin composite was placed on the surfaces. Forty-eight of the original fifty-two specimens were used for shear bond strength testing. Failure types (adhesive, cohesive, and mixed) were evaluated. The remaining four specimens, one from each group, were used for crown-resin composite interface analysis using a scanning electron microscope (SEM).
  
  
  RESULTS
  There were significant differences in both mean shear bond strength values and failure types (P<0.05). The SEM evaluation revealed a close interface relationship in Groups 3 and 4.
  
  
  CONCLUSIONS
  MMA monomer application on a polycarbonate crown prior to application of an adhesive agent improved the shear bond strength of the repair material.
authors.affiliation: Department of Prosthetic Dentistry, Faculty of Dentistry, University of Atatürk, Erzurum, Turkey. yyilmaz25@atauni.edu.tr
authors.forename: Asude
authors.initials: A
authors.lastname: Yilmaz
mesh_terms: D000096:Acetone; D000704:Analysis of Variance; D003188:Composite Resins; D003442:Crowns; D001840:Dental Bonding / Q000379:methods*; D017269:Dental Prosthesis Repair / Q000379:methods*; D003799:Dental Stress Analysis; D008422:Materials Testing; D020366:Methylmethacrylate; D008855:Microscopy, Electron, Scanning; D011076:Polycarboxylate Cement; D011109:Polymethacrylic Acids; D019279:Resin Cements; D033081:Shear Strength; D018709:Statistics, Nonparametric; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D011076:Polycarboxylate Cement; D011109:Polymethacrylic Acids; D019279:Resin Cements; C444444:prime and bond 2.1; C452226:tetric flow composite resin; C112192:valux plus; D000096:Acetone; D020366:Methylmethacrylate; C005506:polycarbonate