title: Effects of coating materials on nanoindentation hardness of enamel and adjacent areas.
abstract: Materials that can be applied as thin coatings and actively release fluoride or other bioavailable ions for reinforcing dental hard tissue deserve further investigation. In this study we assessed the potential of resin coating materials in protection of underlying and adjacent enamel against demineralization challenge using nanoindentation.
  
  
  
  Enamel was coated using Giomer (PRG Barrier Coat, PBC), resin-modified glass-ionomer (Clinpro XT Varnish, CXT), two-step self-etch adhesive (Clearfil SE Protect, SEP) or no coating (control). After 5000 thermal cycles and one-week demineralization challenge, Martens hardness of enamel beneath the coating, uncoated area and intermediate areas was measured using a Berkovich tip under 2mN load up to 200μm depth. Integrated hardness and 10-μm surface zone hardness were compared among groups.
  
  
  
  Nanoindentation and scanning electron microscopy suggested that all materials effectively prevented demineralization in coated area. Uncoated areas presented different hardness trends; PBC showed a remarkable peak at the surface zone before reaching as low as the control, while CXT showed relatively high hardness values at all depths.
  
  
  
  Ion-release from coating materials affects different layers of enamel. Coatings with fluoride-releasing glass fillers contributed to reinforcement of adjacent enamel. Surface prereacted glass filler-containing PBC superficially protected neighboring enamel against demineralization, while resin-modified glass-ionomer with calcium (CXT) improved in-depth protection. Cross-sectional hardness mapping of enamel on a wide range of locations revealed minute differences in its structure.
authors.affiliation: Tokyo Medical and Dental University, Cariology and Operative Dentistry Department, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan; Yanbu Dental Center, Saudi Ministry of Health, Al-Madina Health Region, Saudi Arabia.
authors.forename: Ehab Z
authors.initials: EZ
authors.lastname: Alsayed
authors.affiliation: Tokyo Medical and Dental University, Cariology and Operative Dentistry Department, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Ilnaz
authors.initials: I
authors.lastname: Hariri
authors.affiliation: Tokyo Medical and Dental University, Cariology and Operative Dentistry Department, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Syozi
authors.initials: S
authors.lastname: Nakashima
authors.affiliation: Tokyo Medical and Dental University, Cariology and Operative Dentistry Department, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shimada
authors.affiliation: King Abdulaziz University, Conservative Dental Sciences, P.O. Box 114759, Jeddah 21381, Saudi Arabia.
authors.forename: Turki A
authors.initials: TA
authors.lastname: Bakhsh
authors.affiliation: Tokyo Medical and Dental University, Cariology and Operative Dentistry Department, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
authors.forename: Junji
authors.initials: J
authors.lastname: Tagami
authors.affiliation: University of Washington School of Dentistry, 1959 NE Pacific St. B162, Seattle, WA 98195, United States. Electronic address: arsadr@uw.edu.
authors.forename: Alireza
authors.initials: A
authors.lastname: Sadr
mesh_terms: D002327:Cariostatic Agents; D003188:Composite Resins; D003430:Cross-Sectional Studies; D003743:Dental Enamel; D005459:Fluorides; D005899:Glass Ionomer Cements; D006244:Hardness; D006801:Humans; D019279:Resin Cements; D017001:Tooth Demineralization
chemical_list: D002327:Cariostatic Agents; D003188:Composite Resins; D005899:Glass Ionomer Cements; D019279:Resin Cements; D005459:Fluorides
keywords: Bioactive; Demineralization; Fluoride; Nanohardness; Nanoindentation