title: Bioactive glass fillers reduce bacterial penetration into marginal gaps for composite restorations.
abstract: OBJECTIVE
  Bioactive glass (BAG) is known to possess antimicrobial and remineralizing properties; however, the use of BAG as a filler for resin based composite restorations to slow recurrent caries has not been studied. Accordingly, the objective of this study was to investigate the effect of adding 15wt% BAG to a resin composite on bacterial biofilms penetrating into marginal gaps of simulated tooth fillings in vitro during cyclic mechanical loading.
  
  
  METHODS
  Human molars were machined into approximately 3mm thick disks of dentin and 1.5-2mm deep composite restorations were placed. A narrow 15-20 micrometer wide dentin-composite gap was allowed to form along half of the margin by not applying dental adhesive to that region. Two different 72wt% filled composites were used, one with 15wt% BAG filler (15BAG) and the balance silanated strontium glass and one filled with aerosol silica and silanated strontium glass without BAG (0BAG-control). Samples of both groups had Streptococcus mutans biofilms grown on the surface and were tested inside a bioreactor for two weeks while subjected to periods of cyclic mechanical loading. After post-test biofilm viability was confirmed, each specimen was fixed in glutaraldehyde, gram positive stained, mounted in resin and cross-sectioned to reveal the gap profile. Depth of biofilm penetration for 0BAG and 15BAG was quantified as the fraction of gap depth. The data were compared using a Student's t-test.
  
  
  RESULTS
  The average depth of bacterial penetration into the marginal gap for the 15BAG samples was significantly smaller (∼61%) in comparison to 0BAG, where 100% penetration was observed for all samples with the biofilm penetrating underneath of the restoration in some cases.
  
  
  CONCLUSIONS
  BAG containing resin dental composites reduce biofilm penetration into marginal gaps of simulated tooth restorations. This suggests BAG containing composites may have the potential to slow the development and propagation of secondary tooth decay at restoration margins.
authors.affiliation: School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, Oregon, USA.
authors.forename: D
authors.initials: D
authors.lastname: Khvostenko
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Hilton
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, Oregon Health & Science University, Portland, OR, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Ferracane
authors.affiliation: College of Dental Medicine, Midwestern University, Glendale, AZ, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Mitchell
authors.affiliation: School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, Oregon, USA. Electronic address: jamie.kruzic@oregonstate.edu.
authors.forename: J J
authors.initials: JJ
authors.lastname: Kruzic
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D018441:Biofilms; D019149:Bioreactors; D003188:Composite Resins / Q000737:chemistry*; D003731:Dental Caries / Q000382:microbiology* / Q000517:prevention & control; D003737:Dental Cavity Preparation; D003763:Dental Leakage; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods*; D005898:Glass / Q000737:chemistry*; D006801:Humans; D066298:In Vitro Techniques; D008855:Microscopy, Electron, Scanning; D008963:Molar; D011140:Polyurethanes / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D011140:Polyurethanes
keywords: Bioactive glass; Biofilm; Marginal gap; Resin composite; Secondary caries; Streptococcus mutans