title: Improvement of exposure times: effects on adhesive properties and resin-dentin bond strengths of etch-and-rinse adhesives.
abstract: OBJECTIVE
  This study evaluated the effect of prolonged polymerization times on the microtensile resin-dentin bond strength (μTBS), degree of conversion of adhesive films (DC) and silver nitrate uptake (SNU) for an ethanol/water- (Adper Single Bond 2, [SB]) and an acetone-based (One Step Plus, [OS]) etch-and-rinse adhesive.
  
  
  METHODS
  Thirty caries-free extracted molars were included in this study. The occlusal enamel of all teeth was removed by wet grinding the occlusal enamel on 180-grit SiC paper. Adhesives were applied according to the manufacturer's instructions, but they were light cured for 10, 20 and 40 s at 600 mW/cm2. Bonded sticks (0.6 mm2) were tested in tension (0.5 mm/min). Two bonded sticks from each tooth were immersed in an ammoniacal solution of silver nitrate (24 h), photodeveloped (8 h), and analyzed by SEM. The DC of the adhesives was evaluated under Fourier Transformed Infra-Red spectroscopy (FTIR). Data for each property were analyzed by two-way ANOVA and Tukey's test (α = 0.05).
  
  
  RESULTS
  Statistically higher μTBS and DC were observed for SB and OS when both adhesives were light cured for 40 s in comparison with 10 s. For OS, the μTBS in the 20- and 40-s groups did not differ statistically, while for SB it did. Higher prolonged exposure times did not prevent nanoleakage within the hybrid layer for all groups regardless of the adhesive.
  
  
  CONCLUSIONS
  This study supports the hypothesis that exposure times longer than those recommended can improve the degree of conversion of adhesive films and the immediate resin-dentin bonds. The prolonged curing times (20 and 40 s) for polymerization of simplified adhesives resulted in an increase in the degree of conversion of the adhesive films and resin-dentin bond strengths but did not reduce the nanoleakage within the hybrid layer.
authors: School of Dentistry, Department of Restorative Dentistry, University Estadual de Ponta Grossa, Ponta Grossa, PR, Brazil.
authors: Sabrina Queji
authors: SQ
authors: Ferreira
authors: Thays Regina
authors: TR
authors: Costa
authors: Celso Afonso
authors: CA
authors: Klein-Júnior
authors: Maria de
authors: Md
authors: Accorinte
authors: Márcia Margarete
authors: MM
authors: Meier
authors: Alessandro Dourado
authors: AD
authors: Loguercio
authors: Alessandra
authors: A
authors: Reis
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000268:Adhesiveness; D000704:Analysis of Variance; D001840:Dental Bonding; D003738:Dental Cements; D003763:Dental Leakage; D003799:Dental Stress Analysis; D003804:Dentin; D017220:Dentin-Bonding Agents; D006244:Hardness; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008422:Materials Testing; D008689:Methacrylates; D008963:Molar; D044367:Phase Transition; D019279:Resin Cements; D012834:Silver / Q000378:metabolism; D012835:Silver Nitrate / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D018709:Statistics, Nonparametric; D013718:Tensile Strength; D013997:Time Factors
chemical_list: C554641:Adper single bond 2; C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; D003738:Dental Cements; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D019279:Resin Cements; C000212:ammoniacal silver; D012834:Silver; D012835:Silver Nitrate