title: Model system for measuring the effects of position and curvature of fiber reinforcement within a dental composite.
abstract: OBJECTIVE
  The aim of this study was to compare the effect of fiber curvature and position on flexural strength (FS), toughness, and elastic modulus in a dental flowable composite test specimen.
  
  
  METHODS
  Test specimens made of composite resin (Denfil Flow) were reinforced with preimpregnated glass fibers (Interlig). Control specimens (group A) did not contain fiber reinforcement. Fibers were placed with different positions and orientations into the test specimens (2 mm x 2 mm x 25 mm) (groups B, C, D). The test specimens (n = 10) were stored in distilled water for 3 days at 37 degrees C before testing in a three-point loading test (ISO 10477) at a crosshead speed of 1 mm/min to determine FS, flexural modulus (FM), and toughness. Data were analyzed with 1-way analysis of variance and Tukey HSD (sigma= 0.05).
  
  
  RESULTS
  The FM varied from 4.7 +/- 0.5 to 6.7 +/- 0.5 GPa. The lowest flexural strength and toughness values in reinforced specimens resulted from compression side fiber reinforcement (132 +/- 12 MPa, 21 +/- 4 MJ) and the highest from curved fiber reinforcement (174 +/- 8 MPa, 83 +/- 28 MJ), though this was not statistically significant from tension-side reinforcement. Although the toughness of the curved reinforced group was significantly higher than other groups, the flexural strength of curved reinforcement was not significantly higher than tension-side reinforcement.
  
  
  CONCLUSIONS
  Position and fiber orientation influenced the flexural strength, FM, and toughness. The most effective in increasing toughness was curved placement of fibers.
authors.affiliation: Department of Fixed Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Nayereh
authors.initials: N
authors.lastname: Rashidan
authors.forename: Vahid
authors.initials: V
authors.lastname: Esmaeili
authors.forename: Marzieh
authors.initials: M
authors.lastname: Alikhasi
authors.forename: Sara
authors.initials: S
authors.lastname: Yasini
mesh_terms: D003188:Composite Resins; D019245:Compressive Strength; D003799:Dental Stress Analysis; D055119:Elastic Modulus; D005898:Glass; D006244:Hardness; D008422:Materials Testing; D018583:Pliability; D019279:Resin Cements; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; C503708:Denfil Flow; D019279:Resin Cements; C009753:fiberglass