title: A Comparative Evaluation of Microleakage of Two Low-Shrinkage Composites with a Conventional Resin Composite: an In Vitro Assessment.
abstract: BACKGROUND
  Polymerization shrinkage stress in composite restorations may lead to microleakage. Clinical methods such as using low-shrinkage composites have been suggested to overcome this problem; however, there are controversies about their efficiency in decreasing the microleakage.
  
  
  OBJECTIVE
  This in vitro study was conducted to compare the microleakage of two low-shrinkage resin composites with a conventional one.
  
  
  METHODS
  Fifty class V cavities of 2.5×3×2 mm (depth× length× width) were prepared in the buccal surfaces of intact bovine incisor teeth with the incisal margin on the enamel and gingival margin on the cementum. The teeth were randomly divided into 5 groups. In group 1, Clearfil APX (conventional) with SE Bond was used in 2 layers (Kuraray; Japan). In group 2, GC Kalore (low -shrinkage) with GC UniFil Bond was applied in one layer (GC Company). In group 3, the material of group 2 was applied in two layers. In group 4, FiltekP90 (low -shrinkage) with P90 System adhesive was applied in one layer (3M ESPE). In group 5, the materials of group 4 were applied in two layers. The samples were thermocycled and immersed in 0.5% fuchsin solution for 24h. The restorations were sectioned in buccolingual direction. Then they were evaluated for microleakage by using a stereomicroscope and scored as 0, 1, 2, and 3 and then Kruskal-Wallis test was used (p< 0.05).
  
  
  RESULTS
  The groups were not significantly different regarding the microleakage in the coronal and cervical margins (p< 0.423 and p< 0.212, respectively); however, the Filtek P90 yielded the best results. In all groups, except group 5 (p= 0.018), the cervical margins had greater microleakage than the coronal margins.
  
  
  CONCLUSIONS
  The results suggested that low-shrinkage resin composites may not reduce the marginal microleakage. The proper use of conventional resin composites may offer comparable clinical results.
authors.affiliation: Dept. of Operative and Esthetic Dentistry, Faculty of Dentistry, Guilan University of Medical Sciences, Rasht, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Tavangar
authors.affiliation: Dept. of Operative and Esthetic Dentistry, Faculty of Dentistry, Guilan University of Medical Sciences, Rasht, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Tayefeh Davalloo
authors.affiliation: Dept. of Operative and Esthetic Dentistry, Faculty of Dentistry, Guilan University of Medical Sciences, Rasht, Iran.
authors.forename: Farideh
authors.initials: F
authors.lastname: Darabi
authors.affiliation: Dentist, Rasht, Iran.
authors.forename: Mahsa
authors.initials: M
authors.lastname: Karambin
authors.affiliation: Dept. of Reconstructive Sciences, University of Connecticut Health Center, School of Dental Medicine, Farmington, USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Kazemi
keywords: Dental Bonding; Microleakage; Resin Composites