title: Riboflavin-ultraviolet-A-induced collagen cross-linking treatments in improving dentin bonding.
abstract: OBJECTIVE
  To evaluate the collagen cross-linkers, riboflavin-ultraviolet-A (RF/UVA) and glutaraldehyde, with regard to their efficacy in cross-linking the dentinal collagen and improving dentin bonding.
  
  
  METHODS
  Glutaraldehyde and different RF/UVA protocols (0.1%RF/1-minUV, 0.1%RF/2-minUV, and 1%RF/1-minUV) were first evaluated by gel electrophoresis to determine their abilities of collagen cross-linking. The mechanical properties of acid-etched dentin receiving these cross-linking treatments were examined in either dry or wet condition by a nanoindentation test. Fifteen teeth with exposed occlusal dentin received the microtensile bond strength (μTBS) test. The teeth were primed either with RF/UVA or glutaraldehyde, followed by adhesive treatment and composite restorations, and then cut into resin-dentin microbeams. Half of the microbeams received the μTBS test after 24h, and the other half received test after 5000 thermocycles. Nanoleakage at the bond interface was examined under TEM. The alignments of collagen fibrils in the hybrid layers were also defined by an image analysis.
  
  
  RESULTS
  Gel electrophoresis showed that glutaraldehyde induced strong collagen gelation, while RF/UVA generated milder collagen cross-linking. Glutaraldehyde, 0.1%RF/2-min-UVA, and 1%RF/1-minUV showed higher stiffness compared to untreated and 0.1%RF/1-minUV in wet condition. All the crosslinking treatments improved early μTBS, but 0.1%RF/2-minUVA treatment maintained high μTBS after theromocycles. Under TEM, glutaraldehyde-treated dentin showed dense and enclosed collagen network on the adhesive interface. 0.1%RF/2-minUVA showed the least nanoleakage, and this could be associated with the suspended collagen fibrils in the hybrid layer.
  
  
  CONCLUSIONS
  0.1%RF/2-minUVA treatment enhanced resin-dentin bond possibly through enhancing the stiffness and maintaining the expanding collagen matrix in the hybrid layer.
authors.affiliation: Institute of Oral Medicine, National Cheng Kung University, Tainan, Taiwan.
authors.forename: Yung-Show
authors.initials: YS
authors.lastname: Chiang
authors.forename: Yuh-Ling
authors.initials: YL
authors.lastname: Chen
authors.forename: Shu-Fen
authors.initials: SF
authors.lastname: Chuang
authors.forename: Ching-Ming
authors.initials: CM
authors.lastname: Wu
authors.forename: Pal-Jen
authors.initials: PJ
authors.lastname: Wei
authors.forename: Chang-Fu
authors.initials: CF
authors.lastname: Han
authors.forename: Jui-Che
authors.initials: JC
authors.lastname: Lin
authors.forename: Hsiao-Tzu
authors.initials: HT
authors.lastname: Chang
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D024042:Collagen Type I / Q000737:chemistry* / Q000648:ultrastructure; D003188:Composite Resins / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D003763:Dental Leakage / Q000145:classification; D003764:Dental Materials / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D055119:Elastic Modulus; D005976:Glutaral / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D046529:Microscopy, Electron, Transmission; D019279:Resin Cements / Q000737:chemistry; D012256:Riboflavin / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
chemical_list: D024042:Collagen Type I; D003188:Composite Resins; D003432:Cross-Linking Reagents; D003764:Dental Materials; D017220:Dentin-Bonding Agents; C444701:Filtek Z250; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; D014867:Water; D005976:Glutaral; D012256:Riboflavin