title: Influence of cross-head speed on resin-dentin shear bond strength.
abstract: OBJECTIVE
  To evaluate the influence of different cross-head speeds on shear bond strength test on the dentin surface.
  
  
  METHODS
  One hundred and twenty extracted bovine incisors were embedded in polystyrene resin. The specimens were prepared by wet grinding with 320-, 400- and 600-grit Al2O3 paper exposing dentin. After the application of the adhesive system Single Bond (3M) to etched dentin, the composite resin Z-100 (3M) was applied and light cured. The specimens were randomly assigned to four groups (n=30). The shear bond strength tests were performed with an EMIC DL 500 universal testing machine at four different cross-head speeds: 0.50 (A); 0.75 (B); 1.00 (C); and 5.00 mm/min (D).
  
  
  RESULTS
  The mean values of shear bond strength in MPa (SD) were: A, 11.78 (3.91); B, 11.82 (4.78); C, 16.32 (6.45); D, 15.46 (5.94). The data were analyzed with one-way ANOVA and Tukey's test (alpha=0.05). The results indicated that A=B<C=D. The fracture pattern was evaluated by visual analysis in a stereomicroscope (25x). The percentage of fractures that occurred at the adhesive interface were: A, 92.5%; B, 91.6%; C, 70.0%; D, 47.0%. The Student's t-test to percentages (alpha=0.05) indicated that there were no significant differences among A, B and C; A and B differed from D, and there was no significant difference between C and D.
  
  
  CONCLUSIONS
  Different cross-head speeds may influence the shear bond strength and the fracture pattern in dentin substrate. Shear bond strength using cross-head speeds of 0.50 and 0.75 mm/min should be preferred.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry of Piracicaba, University of Campinas, Av. Limeira 901, Caixa Postal 52, Piracicaba, Brazil.
authors.forename: A T
authors.initials: AT
authors.lastname: Hara
authors.forename: L A
authors.initials: LA
authors.lastname: Pimenta
authors.forename: A L
authors.initials: AL
authors.lastname: Rodrigues
mesh_terms: D000134:Acid Etching, Dental; D000268:Adhesiveness; D000704:Analysis of Variance; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D008422:Materials Testing; D011897:Random Allocation; D012822:Silicon Dioxide; D013223:Statistics as Topic; D013314:Stress, Mechanical; D013499:Surface Properties; D015040:Zirconium
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents; C083568:Z100 composite resin; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; D015040:Zirconium