title: Distance and time effect on shear bond strength of brackets cured with a second-generation light-emitting diode unit.
abstract: OBJECTIVE
  The aims of this study were to evaluate increasing exposure times and distance between source (light-emitting diode) and adhesive composite on the shear bond strength (SBS) of stainless steel brackets.
  
  
  METHODS
  Stainless steel maxillary incisor brackets (3M Unitek, Monrovia, Calif) were bonded to the facial surfaces of 120 bovine incisors. The bond of each specimen in eight randomly divided groups was tested to failure using an Instron Universal Testing Machine (Instron Corp, Canton, Mass). The mode of failure was evaluated using the adhesive remnant index (ARI).
  
  
  RESULTS
  There were significant SBS differences between exposure times; 5-second exposures were significantly less than at 20-and 40-second exposures; SBS increased in a curvilinear fashion. Significant differences were recorded neither in the frequencies of ARI scores nor the SBS in relation to distance. Significant differences in the frequencies of ARI scores were observed when comparing the 5-second cure time to other time periods, indicating incomplete polymerization in the bracket base.
  
  
  CONCLUSIONS
  SBS increased with increasing time periods in a curvilinear fashion, with no difference between the distances evaluated from source to specimen.
authors.affiliation: Department of Orthodontics, Baylor College of Dentistry, Dallas, TX 75246, USA.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Gronberg
authors.forename: P Emile
authors.initials: PE
authors.lastname: Rossouw
authors.forename: Barbara H
authors.initials: BH
authors.lastname: Miller
authors.forename: Peter
authors.initials: P
authors.lastname: Buschang
mesh_terms: D000134:Acid Etching, Dental; D000268:Adhesiveness; D000818:Animals; D002417:Cattle; D001840:Dental Bonding; D003743:Dental Enamel / Q000648:ultrastructure; D003799:Dental Stress Analysis / Q000295:instrumentation; D008029:Lighting / Q000295:instrumentation*; D008422:Materials Testing; D016910:Orthodontic Brackets; D010756:Phosphoric Acids / Q000737:chemistry; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D011897:Random Allocation; D019279:Resin Cements / Q000737:chemistry* / Q000528:radiation effects; D033081:Shear Strength; D013193:Stainless Steel / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
chemical_list: D010756:Phosphoric Acids; D011108:Polymers; D019279:Resin Cements; C477790:Transbond XT; D013193:Stainless Steel; C030242:phosphoric acid