title: Nd:YAG laser irradiation of etched/unetched dentin through an uncured two-step etch-and-rinse adhesive and its effect on microtensile bond strength.
abstract: OBJECTIVE
  To evaluate whether Nd:YAG laser irradiation of etched and unetched dentin through an uncured adhesive affected the microtensile bond strength (µTBS).
  
  
  METHODS
  Flat dentin surfaces were created in 19 extracted human third molars. Adper Single Bond (SB) adhesive was applied over etched (groups 1 to 3) or unetched dentin (groups 4 to 6). The dentin was then irradiated with a Nd:YAG laser through the uncured adhesive, using 0.75 or 1 W power settings, except for the control groups (groups 1 and 4). The adhesive was light cured and composite crowns were built up. After 24 h, the teeth were sectioned into beams, with cross-sectional areas of 0.49 mm2, and were stressed under tension. Data were statistically analyzed using two-way ANOVA and Tukey's test (α = 5%). Dentin surfaces of fractured specimens and the interfaces of untested beams were observed under scanning electron microscopy (SEM).
  
  
  RESULTS
  Acid etching, laser irradiation, and their interaction significantly affected bonding (p < 0.05). Laser irradiation did not improve bonding of etched dentin to resin (p > 0.05). However, higher µTBS means were found on unetched lased dentin (groups 5 and 6), but only in comparison to group 4, where neither lasing nor etching was performed. Groups 4 to 6 showed the lowest µTBS means among all groups tested (p < 0.05). Laser irradiation did not change the characteristics of the hybrid layers created, while solidification globules were observed on lased dentin surfaces under SEM.
  
  
  CONCLUSIONS
  Laser irradiation of dentin through the uncured adhesive did not significantly improve the µTBS in comparison to the suggested manufacturer's technique.
authors: Health Sciences Institute, School of Dentistry, Flamboyant Campus, UNIP, Goiânia, Goiás, Brazil. fabriciocastro.odontogo@unip.br
authors: Fabrício L
authors: FL
authors: Castro
authors: Marcelo F
authors: MF
authors: Andrade
authors: Josimeri
authors: J
authors: Hebling
authors: Rosane F
authors: RF
authors: Lizarelli
mesh_terms: D000134:Acid Etching, Dental; D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate; D001840:Dental Bonding; D003799:Dental Stress Analysis; D003804:Dentin / Q000528:radiation effects* / Q000648:ultrastructure; D003806:Dentin Permeability / Q000528:radiation effects*; D017220:Dentin-Bonding Agents; D006801:Humans; D053844:Lasers, Solid-State; D055115:Light-Curing of Dental Adhesives; D008855:Microscopy, Electron, Scanning; D018709:Statistics, Nonparametric; D013718:Tensile Strength
chemical_list: D017220:Dentin-Bonding Agents; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate