title: Non-thermal atmospheric plasmas in dental restoration: improved resin adhesive penetration.
abstract: OBJECTIVE
  To investigate the influence of non-thermal plasma treatment on the penetration of a model dental adhesive into the demineralized dentine.
  
  
  METHODS
  Prepared dentine surfaces were conditioned with Scotchbond Universal etchant for 15s and sectioned equally perpendicular to the etched surfaces. The separated halves were randomly selected for treatment with an argon plasma brush (input current 6mA, treatment time 30s) or gentle argon air blowing (treatment time 30s, as control). The plasma-treated specimens and control specimens were applied with a model adhesive containing 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]-propane (BisGMA) and 2-hydroxyethyl methacrylate (HEMA) (mass ratio of 30/70), gently air-dried for 5s, and light-cured for 20s. Cross-sectional specimens were characterized using micro-Raman spectral mapping across the dentine, adhesive/dentine interface, and adhesive layer at 1-μm spatial resolution. SEM was also employed to examine the adhesive/dentine interfacial morphology.
  
  
  RESULTS
  The micro-Raman result disclosed that plasma treatment significantly improved the penetration of the adhesive, evidenced by the apparently higher content of the adhesive at the adhesive/dentine interface as compared to the control. Specifically, the improvement of the adhesive penetration using plasma technique was achieved by dramatically enhancing the penetration of hydrophilic monomer (HEMA), while maintaining the penetration of hydrophobic monomer (BisGMA). Morphological observation at the adhesive/dentine interface using SEM also confirmed the improved adhesive penetration. The results further suggested that plasma treatment could benefit polymerization of the adhesive, especially in the interface region.
  
  
  CONCLUSIONS
  The significant role of the non-thermal plasma brush in improving the adhesive penetration into demineralized dentine has been demonstrated. The results obtained may offer a better prospect of using plasma in dental restoration to optimize adhesion between tooth substrate and restorative materials.
authors.affiliation: University of Missouri-Kansas City School of Dentistry, 650 E 25th Street, Kansas City, MO 64108, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, MO 65211 USA.
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Yu
authors.affiliation: University of Missouri-Kansas City School of Dentistry, 650 E 25th Street, Kansas City, MO 64108, USA. Electronic address: Wangyo@umkc.edu.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000268:Adhesiveness; D001128:Argon / Q000737:chemistry*; D001713:Biphenyl Compounds / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002164:Camphor / Q000031:analogs & derivatives / Q000737:chemistry; D003804:Dentin / Q000648:ultrastructure*; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D009861:Onium Compounds / Q000737:chemistry; D063065:Organophosphonates / Q000737:chemistry; D058567:Photoinitiators, Dental / Q000737:chemistry; D058626:Plasma Gases / Q000737:chemistry*; D058105:Polymerization; D011897:Random Allocation; D019279:Resin Cements / Q000737:chemistry*; D013059:Spectrum Analysis, Raman / Q000379:methods; D013499:Surface Properties; D013997:Time Factors
chemical_list: D001713:Biphenyl Compounds; D008689:Methacrylates; D009861:Onium Compounds; D063065:Organophosphonates; D058567:Photoinitiators, Dental; D058626:Plasma Gases; D019279:Resin Cements; C454540:Scotchbond etchant; C031291:diphenyliodonium; D017438:Bisphenol A-Glycidyl Methacrylate; D001128:Argon; C005044:hydroxyethyl methacrylate; D002164:Camphor; C049840:2-(dimethylamino)ethyl methacrylate; C553149:camphorquinone
keywords: Dental adhesive; Dentine; Micro-Raman; Non-thermal atmospheric plasmas; Resin penetration