Effects of coating materials on nanoindentation hardness of enamel and adjacent areas

Ehab Z. Alsayed, Ilnaz Hariri, Syozi Nakashima, Yasushi Shimada, Turki A. Bakhsh, Junji Tagami, Alireza Sadr

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


Objectives 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. Methods 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 2 mN load up to 200 μm depth. Integrated hardness and 10-μm surface zone hardness were compared among groups. Results 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. Significance 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.

Original languageEnglish
Pages (from-to)807-816
Number of pages10
JournalDental Materials
Issue number6
Publication statusPublished - Jun 1 2016
Externally publishedYes


  • Bioactive
  • Demineralization
  • Fluoride
  • Nanohardness
  • Nanoindentation

ASJC Scopus subject areas

  • General Materials Science
  • General Dentistry
  • Mechanics of Materials


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