title: Streptococcus mutans forms xylitol-resistant biofilm on excess adhesive flash in novel ex-vivo orthodontic bracket model.
abstract: BACKGROUND
  During orthodontic bonding procedures, excess adhesive is invariably left on the tooth surface at the interface between the bracket and the enamel junction; it is called excess adhesive flash (EAF). We comparatively evaluated the biofilm formation of Streptococcus mutans on EAF produced by 2 adhesives and examined the therapeutic efficacy of xylitol on S mutans formed on EAF.
  
  
  METHODS
  First, we investigated the biofilm formation of S mutans on 3 orthodontic bracket types: stainless steel preadjusted edgewise, ceramic preadjusted edgewise, and stainless steel self-ligating. Subsequently, tooth-colored Transbond XT (3M Unitek, Monrovia, Calif) and green Grengloo (Ormco, Glendora, Calif) adhesives were used for bonding ceramic brackets to extracted teeth. S mutans biofilms on EAF produced by the adhesives were studied using the crystal violet assay and scanning electron microscopy. Surface roughness and surface energy of the EAF were examined. The therapeutic efficacies of different concentrations of xylitol were tested on S mutans biofilms.
  
  
  RESULTS
  Significantly higher biofilms were formed on the ceramic preadjusted edgewise brackets (P = 0.003). Transbond XT had significantly higher S mutans biofilms compared with Grengloo surfaces (P = 0.007). There was no significant difference in surface roughness between Transbond XT and Grengloo surfaces (P >0.05). Surface energy of Transbond XT had a considerably smaller contact angle than did Grengloo, suggesting that Transbond XT is a more hydrophilic material. Xylitol at low concentrations had no significant effect on the reduction of S mutans biofilms on orthodontic adhesives (P = 0.016).
  
  
  CONCLUSIONS
  Transbond XT orthodontic adhesive resulted in more S mutans biofilm compared with Grengloo adhesive on ceramic brackets. Surface energy seemed to play a more important role than surface roughness for the formation of S mutans biofilm on EAF. Xylitol does not appear to have a therapeutic effect on mature S mutans biofilm.
authors.affiliation: Discipline of Orthodontics and Paediatric Dentistry, Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: Cindy S F
authors.initials: CS
authors.lastname: Ho
authors.affiliation: Discipline of Orthodontics and Paediatric Dentistry, Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: Yue
authors.initials: Y
authors.lastname: Ming
authors.affiliation: Discipline of Orthodontics and Paediatric Dentistry, Faculty of Dentistry, National University of Singapore, Singapore. Electronic address: kelvinfoong@nuhs.edu.sg.
authors.forename: Kelvin W C
authors.initials: KW
authors.lastname: Foong
authors.affiliation: Discipline of Oral Sciences, Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: Vinicius
authors.initials: V
authors.lastname: Rosa
authors.affiliation: Discipline of Oral Sciences, Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: Truong
authors.initials: T
authors.lastname: Thuyen
authors.affiliation: Discipline of Oral Sciences, Faculty of Dentistry, National University of Singapore, Singapore. Electronic address: jaya@nus.edu.sg.
authors.forename: Chaminda J
authors.initials: CJ
authors.lastname: Seneviratne
mesh_terms: D018441:Biofilms / Q000254:growth & development; D003738:Dental Cements / Q000378:metabolism; D006801:Humans; D008855:Microscopy, Electron, Scanning; D016910:Orthodontic Brackets / Q000382:microbiology*; D019279:Resin Cements / Q000378:metabolism; D013295:Streptococcus mutans / Q000187:drug effects / Q000254:growth & development*; D014993:Xylitol / Q000494:pharmacology*
chemical_list: D003738:Dental Cements; D019279:Resin Cements; C477790:Transbond XT; D014993:Xylitol