title: Evaluating the Microshear Bond Strength and Microleakage of Flowable Composites Containing Zinc Oxide Nano-particles.
abstract: BACKGROUND
  Preventive resin restorations (PRR) are the conservative choice for the most common carious lesions in children. Thus, new age flowable resin composites with higher filler content are readily used. The aim of this study was to evaluate the microshear bond strength and microleakage of two flowable resin composites containing different percentages of nano zinc oxide (NZnO) particles, which have proven to have antimicrobial properties.
  
  
  METHODS
  This experimental in-vitro study was carried out in the Dental Material Research Center of Babol University of Medical Sciences in 2015. One nanohybrid and one nanofill flowable resin composite were chosen and modified with the incorporation of 1% and 3% Wt NZnO particles. Six groups (n=10, 0%, 1%, and 3%) of resin composite sticks on dental enamel (2×2mm) were prepared to be placed in the microtensile tester. The microshear bond strength magnitude (MPa) was recorded at the point of failure. A class I box (3×0.8×1 mm) was prepared on 60 premolars and filled using the resin composites (6 groups, n=10). The specimens were immersed in a 5% basic fuschin solution and sectioned bucco-lingually to view the microleakage using a stereomicroscope. One-way ANOVA and Tukey tests for microshear and Wilcoxon and Kruskal-Wallis tests for microleakage were used to analyze the data in the IBM SPSS Statistics version 22 software.
  
  
  RESULTS
  The bond strength of the 3% clearfill group significantly decreased while no significant change occurred in the bond strength in other groups. The Z-350 group had significantly lower microleakage as nanoparticles increased. No significant difference was observed in the clearfill group.
  
  
  CONCLUSIONS
  Up to 3% Wt incorporation of NZnO particles will not diversely alter the bond strength, but it will be beneficial in providing antimicrobial effects with lower microleakage rates.
authors.affiliation: Postgraduate Student, Department of Pediatric Dentistry, Faculty of Dentistry, Babol University of Medical Sciences, Babol, Iran.
authors.forename: Koorosh
authors.initials: K
authors.lastname: Teymoornezhad
authors.affiliation: Associate Professor, Dental Materials Research Center, Department of Operative Dentistry, Faculty of Dentistry, Babol University of Medical Sciences, Babol, Iran.
authors.forename: Homayoun
authors.initials: H
authors.lastname: Alaghehmand
authors.affiliation: Postgraduate Student, Department of Operative Dentistry, Faculty of Dentistry, Babol University of Medical Sciences, Babol, Iran.
authors.forename: Ghazaleh
authors.initials: G
authors.lastname: Daryakenari
authors.affiliation: Biostatistics and Epidemiology Department, Medicine School, Babol University of Medical Sciences, Babol, Iran.
authors.forename: Soraya
authors.initials: S
authors.lastname: Khafri
authors.affiliation: Assistant Professor, Dental Materials Research Center, Department of Pediatric Dentistry, Faculty of Dentistry, Babol University of Medical Sciences, Babol, Iran.
authors.forename: Mitra
authors.initials: M
authors.lastname: Tabari
keywords: Dental leakage; Flowable composite; Nanoparticles; Shear strength; Zinc oxide