Nanoleakage types and potential implications: evidence from unfilled and filled adhesives with the same resin composition.
OBJECTIVE
To compare nanoleakage patterns of an unfilled (OS; One-Step), a 6 wt% spherical silica-filled (OSs; One-Step Plus) and a 15 wt% glass-filled (OSg) version of a two-step, acetone-based self-priming adhesive. Permeability of bonded dentin treated with OS and OSs was also examined.


METHODS
Deep, coronal dentin from extracted third molars were etched and bonded using these adhesives. One-mm thick sections were immersed in 50 wt% ammoniacal silver nitrate (pH 9.5) for 24 hours. Unstained, undemineralized sections were examined by TEM. The permeability of dentin bonded with OS and OSs were investigated at 20 cm of H2O hydrostatic pressure and compared with the osmotic conductance determined with 4.8 M CaCl2 at zero hydrostatic pressure. Composite-dentin beams bonded with OS, OSs and OSg that were fractured after microtensile bond testing were examined by SEM.


RESULTS
Two types of nanoleakage patterns were recognized along the resin-dentin interfaces. The reticular type consisted of discontinuous islands of silver deposits and was exclusively seen in hybrid layers. The spotted type consisted of isolated silver grains and was evident throughout the hybrid and adhesive layers in OS. These two patterns were seen to variable extents in the two filled adhesive versions OSs and OSg and their distribution was independent of one another. OS and OSs bonded dentin were permeable to fluid filtration. However, part of this fluid movement was due to the permeability of the adhesive layer, as demonstrated by osmotic fluid conductance in the absence of hydrostatic pressure. Fractographic analysis revealed denuded collagen fibrils within fractured hybrid layers that were indicative of incomplete resin infiltration.
Tay
Franklin R
FR
Department of Dental Materials, University of Siena, Italy. kfctay@hknet.com
Pashley
David H
DH
Yiu
Cynthia
C
Cheong
Celine
C
Hashimoto
Masanori
M
Itou
Kousuke
K
Yoshiyama
Masahiro
M
King
Nigel M
NM
D000096:Acetone / Q000737:chemistry; D000134:Acid Etching, Dental; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003763:Dental Leakage / Q000145:classification*; D003806:Dentin Permeability; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D019234:Dentinal Fluid / Q000737:chemistry; D006801:Humans; D006874:Hydrostatic Pressure; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology; D009995:Osmosis; D010539:Permeability; D012822:Silicon Dioxide / Q000737:chemistry; D016622:Silver Staining; D013718:Tensile Strength
C103506:Bis-GMA, BPDM, HEMA dental-bonding resin; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D000096:Acetone; D012822:Silicon Dioxide