title: Effects of increased exposure times of simplified etch-and-rinse adhesives on the degradation of resin-dentin bonds and quality of the polymer network.
abstract: One of the reasons for resin-dentin degradation is poor polymerization of the adhesive layer. This study evaluated the effect of prolonged polymerization times on the immediate and 6-month resin-dentin bond strengths, silver nitrate uptake, and polymer quality of etch-and-rinse adhesives. Thirty extracted teeth were obtained, and a flat dentin surface was exposed on each tooth. Adhesives (Adper Single Bond 2 and One Step Plus) were applied to the dentin surface of these teeth and light-cured for 10, 20, or 40 s at 600 mW cm(-2) . Bonded sticks (0.6 mm(2) ) were tested in tension (0.5 mm min(-1) ) and analyzed, after immersion in 50% silver nitrate, using scanning electron microscopy. The polymer quality of adhesive films was evaluated using thermogravimetric analysis. Statistically higher bond strengths were observed for both adhesives when light-cured for 40 s. Degradation of dentin bonds occurred under all experimental conditions but it was less pronounced for adhesives light-cured for 40 s. Longer exposure times reduced silver nitrate uptake for Adper Single Bond 2. Solvent retention and the amount of residual monomer were statistically lower when both adhesives were light-cured for 40 s. Although longer exposure times than those recommended cannot prevent degradation of the dentin bonds, they can increase bond strength, probably because of the removal of an increased amount of solvent and the presence of a lower amount of residual monomer.
authors.affiliation: School of Dentistry, Department of Restorative Dentistry, University Estadual de Ponta Grossa, Ponta Grossa, PR, Brazil. reis_ale@hotmail.com
authors.forename: Alessandra
authors.initials: A
authors.lastname: Reis
authors.forename: Sabrina Q
authors.initials: SQ
authors.lastname: Ferreira
authors.forename: Thays R F
authors.initials: TR
authors.lastname: Costa
authors.forename: Celso A
authors.initials: CA
authors.lastname: Klein-Júnior
authors.forename: Márcia M
authors.initials: MM
authors.lastname: Meier
authors.forename: Alessandro D
authors.initials: AD
authors.lastname: Loguercio
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins; D045662:Dental Etching / Q000379:methods*; D003799:Dental Stress Analysis; D003804:Dentin; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D055115:Light-Curing of Dental Adhesives; D008689:Methacrylates / Q000737:chemistry; D058105:Polymerization; D011108:Polymers / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry*; D012835:Silver Nitrate / Q000737:chemistry; D018709:Statistics, Nonparametric; D013499:Surface Properties; D013718:Tensile Strength; D013818:Thermogravimetry; D013997:Time Factors
chemical_list: C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D011108:Polymers; D019279:Resin Cements; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate; D012835:Silver Nitrate