title: Effect of resin-based materials on fracture resistance of endodontically treated thin-walled teeth.
abstract: BACKGROUND
  Composite resins are recommended for root reinforcement, but little information exists about self-adhesive resin cements that eliminate the acid etching and bonding steps.
  
  
  OBJECTIVE
  The purpose of this study was to compare the fracture resistances of teeth restored with 2 different diameters of cast and fiber posts and to evaluate the effectiveness of increasing internal root thickness with 2 resin-based materials to reinforce thin-walled teeth.
  
  
  METHODS
  Ninety maxillary incisors were endodontically treated and divided into 9 groups. In the first 4 groups, teeth were restored with tapered end cast (C1.3 and C1.7) and fiber (F1.3 and F1.7) posts of 1.3 and 1.7 mm diameters. In the other 5 groups, the root canals were enlarged to simulate the thin-walled teeth and restored with low viscosity composite resin with fiber posts of 1.3 and 1.7 mm diameters (LF1.3 and LF1.7), self-adhesive resin cement with fiber posts of 1.3 and 1.7 mm diameters (SF1.3 and SF1.7), and cast posts of 4 mm diameter that fit in post spaces (C4). Teeth were loaded to fracture at a 135-degree angle to their long axis. Data were analyzed with 2-way ANOVA and the Tukey HSD test (α=.05).
  
  
  RESULTS
  Significant difference (P<.001) existed between the fracture resistances of the teeth restored with cast (C1.3, 588.4 ±72.7 N) and fiber (F1.3, 375.3 ±53.8 N) posts of 1.3 mm diameter; however, no significant difference was found between 1.3 and 1.7 mm post diameters. The teeth restored with the resin-based materials with fiber posts, groups SF1.3 (331.6 ±135.2 N), SF1.7 (535.7 ±134.4 N), LF1.3 (432.1 ±120.3 N) and LF1.7 (563.8 ±128.8 N), demonstrated fracture resistance values similar to or higher than those of the teeth restored with the fiber posts, groups F1.3 (375.3 ±53.8 N) and F1.7 (461.8 ±98.4 N). The parallel-sided cast posts C4 (799.8 ±228.9 N) of 4 mm diameter demonstrated the highest fracture resistance of all groups (P<.001).
  
  
  CONCLUSIONS
  The fracture resistance of the teeth increased as the elastic modulus of the posts increased but was not affected by small diameter variations of the posts. The resin-based materials were able to preserve and reinforce the remaining tooth structures.
authors.affiliation: Department of Prosthetics, Faculty of Dentistry, Istanbul University, Istanbul, Turkey. mcbalkaya@yahoo.com
authors.forename: Mehmet Cudi
authors.initials: MC
authors.lastname: Balkaya
authors.forename: Ilda Sinem
authors.initials: IS
authors.lastname: Birdal
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003442:Crowns; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003786:Dental Pulp Cavity / Q000473:pathology; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000473:pathology; D055119:Elastic Modulus; D006801:Humans; D007180:Incisor / Q000473:pathology; D008689:Methacrylates / Q000737:chemistry; D010969:Plastics / Q000737:chemistry; D011076:Polycarboxylate Cement / Q000737:chemistry; D011176:Post and Core Technique / Q000295:instrumentation; D019279:Resin Cements / Q000737:chemistry; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods; D013314:Stress, Mechanical; D013499:Surface Properties; D013871:Thiones / Q000737:chemistry; D014082:Tooth Fractures / Q000503:physiopathology*; D014092:Tooth Root / Q000293:injuries; D019553:Tooth, Nonvital / Q000503:physiopathology / Q000628:therapy*
chemical_list: D000180:Acrylic Resins; C521707:Alloy Primer; D002858:Chromium Alloys; C581302:Clearfil SA; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D010969:Plastics; D011076:Polycarboxylate Cement; D019279:Resin Cements; D013871:Thiones; C005506:polycarbonate