title: Influence of free-hand vs uniform irradiation on tensile bond strength in Er:YAG-lased dentin.
abstract: OBJECTIVE
  To compare effects of free-hand and mechanically applied uniform irradiation on tensile bond strength of 4-META/MMA-TBB resin to Er:YAG laser-irradiated dentin using an X-Y moving stage.
  
  
  METHODS
  Three different laser conditions were evaluated: 1.0 W, 100 mJ/pulse, 10 pps; 1.0 W, 50 mJ/pulse, 20 pps; 1.0 W, 33 mJ/pulse, 30 pps. Samples of bovine dentin were set on a moving stage and mechanically irradiated with an Er:YAG laser at a scanning speed of 1.0 mm/s or subjected to free-hand irradiation. The lased dentin surfaces were acid conditioned with 10% citric acid/3% ferric chloride for 15 s, rinsed, and dried. The surfaces were bonded to PMMA rods with 4-META/MMA-TBB resin, and mini-dumbbell-shaped bonded specimens were prepared. Tensile bond strength was measured and compared with the results for free-hand irradiated samples obtained under the same conditions in an earlier study. SEM observations of fractured surfaces after tensile bond testing were also performed.
  
  
  RESULTS
  A significant difference was found in tensile bond strength among the 3 laser settings in both free-hand and mechanically uniform irradiations. A comparison of free-hand laser irradiation and mechanically performed uniform laser irradiation revealed no significant difference under either laser condition (p > 0.05). SEM observation of the fractured surfaces showed no difference between the two irradiation methods under all laser conditions.
  
  
  CONCLUSIONS
  No significant difference was found in tensile bond strength between free-hand and mechanically irradiated dentin. Significant differences were found, however, with changes in laser setting in both groups.
authors.affiliation: Department of Operative Dentistry, Tokyo Dental College, Chiba, Japan.
authors.forename: Koya
authors.initials: K
authors.lastname: Aizawa
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kameyama
authors.forename: Junji
authors.initials: J
authors.lastname: Kato
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Oda
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Hirai
mesh_terms: D000180:Acrylic Resins; D000818:Animals; D001896:Boron Compounds; D002417:Cattle; D001840:Dental Bonding; D003799:Dental Stress Analysis; D003804:Dentin / Q000528:radiation effects* / Q000648:ultrastructure; D003806:Dentin Permeability; D053844:Lasers, Solid-State; D008768:Methylmethacrylates; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements / Q000737:chemistry; D013499:Surface Properties / Q000528:radiation effects; D013718:Tensile Strength
chemical_list: D000180:Acrylic Resins; D001896:Boron Compounds; D008768:Methylmethacrylates; D019279:Resin Cements; C476987:methylmethacrylate-tributylborane resin; C031172:4-META resin