title: In vitro fracture resistance of endodontically-treated maxillary premolars.
abstract: Many endodontically-treated teeth require quick, simple, low-cost restorations. This study evaluated the effect of horizontal pins and flowable composites on the fracture resistance of endodontically-treated maxillary premolars directly restored with resin composite. In this in vitro study, 64 intact human maxillary premolars, extracted for orthodontic reasons, were randomly divided into four groups of 16. Standard access cavities were prepared in such a way that the buccal cusp had a buccolingual thickness of 3 mm measured at the height of contour. The palatal cusp was reduced to 1.5 mm coronal to CEJ. The specimens were prepared as follows: Group 1: resin composite restoration without horizontal self-threading pins or flowable composite (control group). Group 2: resin composite restoration without horizontal self-threading pins but with a 2 mm thickness of the flowable composite. Group 3: resin composite restoration with two horizontal self-threading pins in the buccal cusp but without flowable composite. Group 4: resin composite restoration with two horizontal self-threading pins in the buccal cusp and flowable composite with a thickness of 2 mm. Subsequent to thermocycling, all specimens were loaded to failure. The data were analyzed using a two-factor ANOVA test (alpha = 0.05). The maximum mean of fracture resistance was in Group 1 (632.86 +/- 119.46 N), and the minimum value was related to Group 3 (533.49 +/- 168.07 N). There was not a statistically significant difference between the groups (p > 0.05).
  
  
  CONCLUSIONS
  Neither horizontal pin placement nor flowable composite had a significant effect on increasing the fracture resistance of endodontically-treated maxillary premolars restored with composite.
authors.affiliation: Department of Operative Dentistry, School of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran. soskoee@hotmail.com
authors.forename: Siavash Savadi
authors.initials: SS
authors.lastname: Oskoee
authors.forename: Parnian Alizadeh
authors.initials: PA
authors.lastname: Oskoee
authors.forename: Elmira Jafari
authors.initials: EJ
authors.lastname: Navimipour
authors.forename: Shahriar
authors.initials: S
authors.lastname: Shahi
mesh_terms: D000134:Acid Etching, Dental; D001641:Bicuspid / Q000473:pathology*; D003188:Composite Resins / Q000737:chemistry; D003737:Dental Cavity Preparation / Q000379:methods; D003743:Dental Enamel / Q000648:ultrastructure; D003772:Dental Pins; D003793:Dental Restoration, Permanent / Q000295:instrumentation / Q000379:methods*; D003804:Dentin / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006801:Humans; D008437:Maxilla; D012390:Root Canal Therapy; D013314:Stress, Mechanical; D014082:Tooth Fractures / Q000503:physiopathology*; D019553:Tooth, Nonvital / Q000628:therapy*
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; C467913:Filtek Flow; C444701:Filtek Z250; C111840:flowable hybrid composite