title: No evidence for the growth-stimulating effect of monomers on cariogenic Streptococci.
abstract: BACKGROUND
  In spite of contradicting results, the high susceptibility of composites for secondary caries is still often associated with the bacterial growth-stimulating effect of released methacrylate monomers. However, most studies that showed this effect were performed with techniques having inherent limitations (spectrophotometry).
  
  
  OBJECTIVE
  Therefore, our objective was to determine the effect of four methacrylate monomers (2-Hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEGDMA), ethylene glycol dimethacrylate (EGDMA), diethylene glycol dimethacrylate (DEGDMA)) on the growth of two caries-associated bacteria, Streptococcus mutans and sobrinus, and one non-cariogenic species, Streptococcus sanguinis, using TaqMan quantitative polymerase chain reaction (qPCR) to quantify bacterial DNA.
  
  
  METHODS
  Cultures were exposed to monomer solutions selected after spectrophotometric growth measurements. At baseline and predetermined time intervals, bacterial DNA was extracted and quantified with TaqMan qPCR. Biofilms grown in the presence of monomers were analyzed with scanning electron microscopy (SEM).
  
  
  RESULTS
  Spectrophotometry indeed showed increased growth rates of all three strains with 5 mM TEGDMA, EGDMA, and DEGDMA and increased total biomass of S. sanguinis with 5 mM TEGDMA. However, qPCR failed to show any growth-stimulating effect of these monomers on S. mutans and S. sobrinus. In contrast, some monomers exhibited a growth-inhibiting effect on S. sanguinis. SEM revealed extracellular matter in S. sobrinus and S. sanguinis biofilms, which might be attributed to polymer formation.
  
  
  CONCLUSIONS
  Techniques which quantify bacterial DNA are more appropriate to evaluate bacterial growth in the presence of monomers than spectrophotometry.
  
  
  CONCLUSIONS
  Even though methacrylate monomers did not affect the growth of cariogenic species, growth inhibition of S. sanguinis, a non-cariogenic antagonistic species, may lead to ecological shifts towards higher cariogenicity.
authors.affiliation: BIOMAT, Department of Oral Health Sciences, University of Leuven and Dentistry University Hospitals Leuven, Kapucijnenvoer 7, 3000, Leuven, Belgium.
authors.forename: Ivana
authors.initials: I
authors.lastname: Nedeljkovic
authors.affiliation: Center for Innovative Clinical Medicine, Okayama University Hospital, 2-5-1 Shikata-cho, Okayama, Kita-ku, 700-8558,, Japan.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Yoshihara
authors.affiliation: BIOMAT, Department of Oral Health Sciences, University of Leuven and Dentistry University Hospitals Leuven, Kapucijnenvoer 7, 3000, Leuven, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: De Munck
authors.affiliation: Oral Microbiology, Department of Oral Health Sciences, University of Leuven and Dentistry University Hospitals Leuven, Kapucijnenvoer 7, 3000, Leuven, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Teughels
authors.affiliation: BIOMAT, Department of Oral Health Sciences, University of Leuven and Dentistry University Hospitals Leuven, Kapucijnenvoer 7, 3000, Leuven, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Van Meerbeek
authors.affiliation: BIOMAT, Department of Oral Health Sciences, University of Leuven and Dentistry University Hospitals Leuven, Kapucijnenvoer 7, 3000, Leuven, Belgium. kirsten.vanlanduyt@med.kuleuven.be.
authors.forename: Kirsten L
authors.initials: KL
authors.lastname: Van Landuyt
mesh_terms: D018441:Biofilms / Q000187:drug effects; D003188:Composite Resins / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000032:analysis; D003731:Dental Caries / Q000382:microbiology*; D008689:Methacrylates / Q000494:pharmacology; D020366:Methylmethacrylate / Q000494:pharmacology*; D008855:Microscopy, Electron, Scanning; D011092:Polyethylene Glycols / Q000494:pharmacology; D011109:Polymethacrylic Acids / Q000494:pharmacology; D060888:Real-Time Polymerase Chain Reaction; D013053:Spectrophotometry; D013295:Streptococcus mutans / Q000187:drug effects*; D013298:Streptococcus sanguis / Q000187:drug effects*; D016986:Streptococcus sobrinus / Q000187:drug effects*
chemical_list: D003188:Composite Resins; D004269:DNA, Bacterial; D008689:Methacrylates; D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; D020366:Methylmethacrylate; D011092:Polyethylene Glycols; C005044:hydroxyethyl methacrylate; C004919:ethylene dimethacrylate
keywords: Bacterial growth; Dental composite; Methacrylate monomers; Oral streptococci; RT PCR; Spectrophotometry; Streptococcus mutans; Streptococcus sanguinis; Streptococcus sobrinus; qPCR