Interaction of resin-modified glass-ionomer cements with moist dentine.
OBJECTIVE
The objective of this study was to report on a novel phenomenon that occurs when resin-modified glass-ionomer cements (RMGICs) are bonded to moist human dentine.


METHODS
Dentine surfaces from extracted third molars were abraded with 180-grit SiC paper. Ten teeth were prepared for each of the two RMGICs tested (Fuji II LC, GC Corp. and Photac-Fil Quick, 3M ESPE). RMGIC buildups were made according to the manufacturers' instructions. After storage at 37 degrees C, 100% humidity for 24 h, the bonded specimens were cut occlusogingivally into 0.9 x 0.9 mm beams. Dentine surfaces bonded with the two RMGICs were examined along the fractured RMGIC/dentine interfaces. Additional beams fractured within the RMGICS and at 3 mm away from the interfaces were used as controls. The fractured beams were examined using scanning electron microscopy (SEM), field emission-environmental SEM (FE-ESEM) and transmission electron microscopy (TEM).


RESULTS
SEM and FE-ESEM revealed numerous solid spherical bodies along the RMGIC/dentine interfaces. By contrast, no spherical bodies could be identified within the RMGIC fractured 3 mm distant from the bonded interface. TEM and energy dispersive X-ray analyses performed on carbon-coated ultrathin sections showed that these solid spherical bodies consisted of a thin aluminum and silicon-rich periphery and an amorphous hydrocarbon core within the air voids of the original resin matrix.


CONCLUSIONS
The spherical bodies probably represent a continuation of GI reaction and poly(HEMA) hydrogel formation that results from water diffusion from the underlying moist dentine. Their existence provides evidence for the permeation of water through RMGIC/dentine interfaces.
Department of Paediatric Dentistry and Orthodontics, Faculty of Dentistry, Prince Philip Dental Hospital, University of Hong Kong, 34 Hospital Road, Hong Kong, SAR, China.
C K Y
CK
Yiu
F R
FR
Tay
N M
NM
King
D H
DH
Pashley
R M
RM
Carvalho
M R O
MR
Carrilho
D000535:Aluminum / Q000737:chemistry; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D001840:Dental Bonding; D003804:Dentin / Q000648:ultrastructure*; D004058:Diffusion; D004577:Electron Probe Microanalysis; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D011073:Polyamines / Q000737:chemistry; D011102:Polyhydroxyethyl Methacrylate / Q000031:analogs & derivatives* / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry*; D012117:Resins, Synthetic / Q000737:chemistry; D012825:Silicon / Q000737:chemistry; D017655:Silicon Compounds / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014867:Water / Q000737:chemistry
D017554:Carbon Compounds, Inorganic; C079765:Fuji II LC cement; D005899:Glass Ionomer Cements; C467912:Photac-Fil Quick; D011073:Polyamines; D019279:Resin Cements; D012117:Resins, Synthetic; D017655:Silicon Compounds; C056971:poly(2-hydroxyethyl methacrylate)-polyamine graft copolymer; D014867:Water; D011102:Polyhydroxyethyl Methacrylate; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D000535:Aluminum; C022088:silicon carbide; D012825:Silicon