title: Effect of acid etching time on bond strength of an etch-and-rinse adhesive to primary tooth dentine affected by amelogenesis imperfecta.
abstract: BACKGROUND
  Dentine affected by amelogenesis imperfecta (AI) is histologically altered following loss of the hypoplastic enamel and becomes hypermineralized, which would make bonding less predictable.
  
  
  OBJECTIVE
  This study examined the effect of etching time on the microtensile bond strength (microTBS) to AI-affected primary dentine.
  
  
  METHODS
  Flat coronal dentine surface was obtained from extracted AI-affected and noncarious primary molars. Teeth were etched either for 15 or for 30 s using 34% phosphoric acid. Prime & Bond NT (Dentsply De Trey), an etch-and-rinse adhesive, was applied to dentine surfaces, air-dried and light-cured, followed by composite build-ups. The bonded teeth were sectioned into beams of 0.8 mm(2) and stressed to failure under tension. Representative fractured beams from each group were examined under scanning electron microscopy.
  
  
  RESULTS
  The extended etching time had an adverse effect on the microTBS for the normal dentine, while no significant difference was found for AI-affected dentine. When the AI-affected dentine was etched for 30 s, the fracture occurred in the demineralized dentine at the base of the hybrid layer.
  
  
  CONCLUSIONS
  Bonding to AI-affected dentine compromised the bonding of the etch-and-rinse adhesive. The bonding could not be improved by increasing etching time.
authors.affiliation: Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong, Prince Philip Dental Hospital, 34 Hospital Road, Hong Kong. hiraishinoriko@yahoo.com
authors.forename: Noriko
authors.initials: N
authors.lastname: Hiraishi
authors.forename: Cynthia Kar Yung
authors.initials: CK
authors.lastname: Yiu
authors.forename: Nigel Martyn
authors.initials: NM
authors.lastname: King
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods*; D000567:Amelogenesis Imperfecta / Q000473:pathology*; D002648:Child; D001840:Dental Bonding / Q000379:methods*; D017742:Dental Care for Chronically Ill; D003793:Dental Restoration, Permanent / Q000379:methods; D003799:Dental Stress Analysis; D003804:Dentin / Q000002:abnormalities / Q000187:drug effects*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008963:Molar; D011109:Polymethacrylic Acids / Q000737:chemistry; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D014094:Tooth, Deciduous
chemical_list: D017220:Dentin-Bonding Agents; D011109:Polymethacrylic Acids; C425843:Prime and Bond NT