title: Effect of novel restorative materials and retention slots on fracture resistance of endodontically-treated teeth.
abstract: OBJECTIVE
  The aim of this study was to evaluate the fracture resistance of endodontically-treated teeth restored with nano-hybrid composite resin, bulk-fill flowable and short fibre-reinforced-composite in the absence/presence of retention slots.
  
  
  METHODS
  One hundred and ten extracted non-carious human mandibular molars received endodontic treatment followed by mesio-occlusodistal (MOD) cavities with 3 ± 0.2 mm thicknesses of buccal and lingual walls. Teeth were divided into two main groups according to the retention slot preparation. The dove-tail retention slots were prepared on the middle of opposite buccal and lingual walls to create mechanical interlocking. Each group was further divided into four sub-groups according to restorative material types: control (no restoration), nano-hybrid composite resin (Filtek™ Z550), bulk-fill flowable (Filtek™ Bulk Fill) and short fibre-reinforced-composite (everX Posterior™). Restored teeth were subjected to compressive load at a strain rate of 1 mm/min. The data were statistically analysed using two-way ANOVA and Tukey's test for multiple comparisons.
  
  
  RESULTS
  The fracture resistance was significantly affected by the presence of the retentive slots and restorative material (p < 0.05). Restored teeth with retentive slots significantly increased the fracture resistance compared with restored teeth without retentive slots (p < 0.05). Short fibre-reinforced-composite with retentive slot cavities had significantly higher fracture resistance values compared with the other test groups (p < 0.05).
  
  
  CONCLUSIONS
  The preparation of retention slots may increase the fracture resistance of endodontically-treated teeth, especially, when restored with short fibre-reinforced composite. The use of short fibre-reinforced composite with retentive slots could be an alternative technique to prevent cuspal fracture on endodontically-treated teeth with MOD cavity.
authors.affiliation: a 1 Department of Restorative Dentistry, Faculty of Dentistry, Izmir Katip Celebi University , Izmir, Turkey.
authors.forename: Bilal
authors.initials: B
authors.lastname: Yasa
authors.affiliation: b 2 Department of Endodontics, Faculty of Dentistry, Ataturk University , Erzurum, Turkey.
authors.forename: Hakan
authors.initials: H
authors.lastname: Arslan
authors.affiliation: c 3 Department of Restorative Dentistry, Faculty of Dentistry, Sifa University , Izmir, Turkey.
authors.forename: Elif
authors.initials: E
authors.lastname: Yasa
authors.affiliation: d 4 Department of Pedodontics, Faculty of Dentistry, Izmir Katip Celebi University , Izmir, Turkey.
authors.forename: Merve
authors.initials: M
authors.lastname: Akcay
authors.affiliation: a 1 Department of Restorative Dentistry, Faculty of Dentistry, Izmir Katip Celebi University , Izmir, Turkey.
authors.forename: Huseyin
authors.initials: H
authors.lastname: Hatirli
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003737:Dental Cavity Preparation / Q000379:methods; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000379:methods*; D005898:Glass / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008963:Molar / Q000473:pathology; D053761:Nanocomposites / Q000737:chemistry; D010756:Phosphoric Acids / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D014082:Tooth Fractures / Q000503:physiopathology*; D019553:Tooth, Nonvital / Q000628:therapy*
chemical_list: C438313:Clearfil SE Bond; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; D010756:Phosphoric Acids; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D019279:Resin Cements; C009753:fiberglass; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; C074277:ethoxylated bis-phenol A dimethacrylate; D017438:Bisphenol A-Glycidyl Methacrylate; C069749:methacryloyloxydecyl dihydrogen phosphate; D019904:Polymethyl Methacrylate; C030242:phosphoric acid
keywords: Fracture resistance; MOD cavity; bulk-fill flowable; retentive slot; short fibre-reinforced composite