title: In vitro fracture resistance of fiber reinforced cusp-replacing composite restorations.
abstract: OBJECTIVE
  To assess the fracture resistance and failure mode of fiber reinforced composite (FRC) cusp-replacing restorations in premolars.
  
  
  METHODS
  Forty-five extracted sound upper premolars were randomly divided into three groups. Identical MOD cavities with simulated buccal cusp fracture and height reduction of the palatal cusp were prepared. In Group A two layers of resin impregnated woven continuous FRC (EverStick Net) were applied. In Group B one layer of unidirectional continuous FRC (EverStick) was used. In Group C no fibers were applied (control). Subsequently, all teeth were restored with resin composite (Clearfil Photo Posterior), subjected to thermocycling (6000 x 5-55 degrees C) and static load tests. Load until fracture was registered for each tooth. Simultaneously, fracture propagation was monitored using acoustic emission analysis (AE). Failure modes were visually assessed.
  
  
  RESULTS
  Weibull analysis revealed a characteristic strength and Weibull modulus (m) at 2364.8 N for Group A (m=8.9), 2437.9 N for Group B (m=5.9) and 2160.3N for Group C (m=13.6). Fracture loads were not significantly different (ANOVA, p>0.05). Teeth with FRC showed less fractures below the cemento-enamel junction (CEJ) (38% and 23% for Groups A and B, respectively) than teeth without FRC (93%) (chi-square, p<0.05). The control group showed the least AE energy signals.
  
  
  CONCLUSIONS
  The results suggest that glass FRC does not increase fracture load of premolars with cusp-replacing restorations. However, FRC has a beneficial effect on the failure mode. Woven fibers give more consistent results than unidirectional fibers.
authors.affiliation: Department of Oral Function and Prosthetic Dentistry, College of Dental Science, University Medical Centre Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. w.fennis@dent.umcn.nl
authors.forename: Willem M M
authors.initials: WM
authors.lastname: Fennis
authors.forename: Arzu
authors.initials: A
authors.lastname: Tezvergil
authors.forename: Ruud H
authors.initials: RH
authors.lastname: Kuijs
authors.forename: Lippo V J
authors.initials: LV
authors.lastname: Lassila
authors.forename: Cees M
authors.initials: CM
authors.lastname: Kreulen
authors.forename: Nico H J
authors.initials: NH
authors.lastname: Creugers
authors.forename: Pekka K
authors.initials: PK
authors.lastname: Vallittu
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D003188:Composite Resins / Q000737:chemistry*; D003737:Dental Cavity Preparation; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D005898:Glass; D006801:Humans; D008422:Materials Testing; D011897:Random Allocation; D013018:Sound Spectrography; D016019:Survival Analysis; D019228:Tooth Crown
chemical_list: D003188:Composite Resins; C009753:fiberglass; C092420:Clearfil Photo Posterior