title: Influence of force location in orthodontic shear bond strength testing.
abstract: OBJECTIVE
  The purpose of the present study was to analyze the influence of debonding force location in shear bond strength testing of orthodontic brackets in vitro.
  
  
  METHODS
  Ninety extracted permanent bovine mandibular incisors were randomly divided into 3 groups of 30 specimens each. Teeth were bonded with stainless steel orthodontic brackets. Enamel surfaces were etched with 37% phosphoric acid for 30s and bonded with a composite adhesive. Debonding force measurements were performed with a universal testing machine. Location of the debonding force was: bracket base (group A), ligature groove (group B), occlusal bracket wings (group C).
  
  
  RESULTS
  Mean shear bond strength measurements were as follows: 22.70(4.23)MPa (group A), 11.52(2.74)MPa (group B), 9.44(2.96)MPa (group C). Analysis of variance indicated that there were significant differences in shear bond strength. Post-hoc Tukey tests showed that bond strength measurements of group A were significantly different from those of groups B and C. The adhesive remnant index also showed significant differences and ranged from a mean of 1.53 in group A to a mean of 2.10 in group C.
  
  
  CONCLUSIONS
  Debonding force location had a significant influence on shear bond strength measurements and bond failure pattern, indicating that this parameter needs to be taken into consideration for interstudy comparison of in vitro results.
authors.affiliation: Department of Orthodontics, University Hospital Hamburg-Eppendorf, Kieferorthopaedie, ZZMK, Pav. O 53, Martinistr. 52, D-20246 Hamburg, Germany. klocke@uke.uni-hamburg.de
authors.forename: Arndt
authors.initials: A
authors.lastname: Klocke
authors.forename: Bärbel
authors.initials: B
authors.lastname: Kahl-Nieke
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D001840:Dental Bonding; D017005:Dental Debonding / Q000379:methods*; D003799:Dental Stress Analysis; D008422:Materials Testing; D016910:Orthodontic Brackets; D011897:Random Allocation; D019279:Resin Cements; D033081:Shear Strength; D018709:Statistics, Nonparametric; D016019:Survival Analysis
chemical_list: D019279:Resin Cements; C477790:Transbond XT