title: Effects of bonding materials on the mechanical properties of enamel around orthodontic brackets.
abstract: OBJECTIVE
  To determine if the enamel around orthodontic brackets is significantly altered after demineralization followed by application of adhesives with and without fluoride-releasing ability.
  
  
  METHODS
  One hundred eight noncarious human premolars were divided into six groups of 18 each and exposed to a demineralization solution. Stainless steel brackets were bonded using two conventional composite resin etch-and-rinse systems, three self-etching primer (SEP) composite resin systems, and one resin-modified glass ionomer cement (RMGIC) system. One conventional and one SEP composite resin adhesive did not have fluoride-releasing ability, which was claimed for the other four adhesives. The elastic modulus and hardness of the enamel were determined with a nanoindenter at 10 equidistant depths ranging from 1-46 µm and at four regions: control (not exposed) enamel surface, under the adhesive, and at 50 µm and 100 µm from the bracket edges. Using the Kruskal-Wallis and Mann-Whitney U-tests (P < .0125 for statistical significance), these properties were compared at different regions.
  
  
  RESULTS
  The same behavior was observed for values of elastic modulus and hardness. Significant differences were found within approximately 21 µm of the enamel surface for etching with 35% phosphoric acid or priming with SEP, but only minimal changes occurred for the SEP adhesive. Increases in near-surface elastic modulus and hardness of enamel were found with the SEP adhesive and RMGIC with fluoride-releasing ability.
  
  
  CONCLUSIONS
  Clinical use of the fluoride-releasing adhesives investigated may prevent demineralization of enamel around brackets during orthodontic treatment.
authors.affiliation: Division of Orthodontics and Dentofacial Orthopedics, Department of Oral Growth and Development, Health Sciences University of Hokkaido, Hokkaido, Japan.
authors.forename: Naohisa
authors.initials: N
authors.lastname: Kohda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Iijima
authors.forename: William
authors.initials: W
authors.lastname: Brantley
authors.forename: Takeshi
authors.initials: T
authors.lastname: Muguruma
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Yuasa
authors.forename: Susumu
authors.initials: S
authors.lastname: Nakagaki
authors.forename: Itaru
authors.initials: I
authors.lastname: Mizoguchi
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000180:Acrylic Resins / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D001696:Biomechanical Phenomena; D002327:Cariostatic Agents / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry*; D003743:Dental Enamel / Q000473:pathology*; D004058:Diffusion; D055119:Elastic Modulus; D005459:Fluorides / Q000737:chemistry; D005899:Glass Ionomer Cements / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D016910:Orthodontic Brackets; D010756:Phosphoric Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013193:Stainless Steel / Q000737:chemistry; D017001:Tooth Demineralization / Q000473:pathology
chemical_list: D000180:Acrylic Resins; D000538:Aluminum Silicates; C519484:Beauty Ortho Bond; D002327:Cariostatic Agents; D003188:Composite Resins; D003722:Dental Alloys; D003738:Dental Cements; C095451:Fuji Ortho LC; D005899:Glass Ionomer Cements; D010756:Phosphoric Acids; D019279:Resin Cements; C429625:Transbond Plus Self-Etching Primer; C477790:Transbond XT; D013193:Stainless Steel; C030242:phosphoric acid; D005459:Fluorides