title: Analysis of surface roughness and surface free energy characteristics of various orthodontic materials.
abstract: BACKGROUND
  The purpose of this study was to analyze the differences in surface characteristics of various orthodontic materials; this might provide valuable information on bacterial adhesion to orthodontic materials.
  
  
  METHODS
  Surface roughness (SR) and surface free energy (SFE) characteristics of 5 orthodontic adhesives (2 composites resins, 2 resin-modified glass ionomer cements, and 1 compomer), 5 bracket materials (2 stainless steel, 1 monocrystalline sapphire, 1 polycrystalline alumina, and 1 plastic) and bovine incisors were investigated by using confocal laser scanning microscopy and the sessile drop method.
  
  
  RESULTS
  There were significant differences in SR and SFE characteristics among orthodontic materials. Bovine incisors showed the roughest surface, and monocrystalline sapphire showed the smoothest surface. However, there were only small variations in SR (less than 0.3 mum) among the materials, except for bovine incisors. In contrast to SR, there were big differences in SFE characteristics among materials. Generally, bracket materials showed lower SFE--specifically, dispersive and polar components on their surfaces--than orthodontic adhesives. Resin-modified glass ionomer cements had the highest SFE, dispersive component, and polarity; these conditions are more favorable for bacterial adhesion.
  
  
  CONCLUSIONS
  This study suggests that SFE characteristics can influence bacterial adhesion to orthodontic materials more than SR, and bracket materials might have less favorable SFE characteristics for bacterial adhesion than orthodontic adhesives.
authors.affiliation: Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Hyo-Beom
authors.initials: HB
authors.lastname: Ahn
authors.forename: Sug-Joon
authors.initials: SJ
authors.lastname: Ahn
authors.forename: Shin-Jae
authors.initials: SJ
authors.lastname: Lee
authors.forename: Tae-Woo
authors.initials: TW
authors.lastname: Kim
authors.forename: Dong-Seok
authors.initials: DS
authors.lastname: Nahm
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001422:Bacterial Adhesion; D002417:Cattle; D020770:Compomers / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003738:Dental Cements / Q000737:chemistry*; D003743:Dental Enamel / Q000648:ultrastructure*; D005899:Glass Ionomer Cements / Q000737:chemistry; D007180:Incisor / Q000648:ultrastructure; D016910:Orthodontic Brackets; D013499:Surface Properties; D013816:Thermodynamics
chemical_list: D020770:Compomers; D003188:Composite Resins; D003738:Dental Cements; D005899:Glass Ionomer Cements