Bonding of contemporary glass ionomer cements to dentin.
OBJECTIVE
The objective of this study was to investigate the microtensile bond strength (microTBS) of contemporary glass ionomer cements (GIC) to sound coronal dentin.


METHODS
Three specimen teeth were prepared for each material tested: Fuji IX GP (GC), ChemFlex (Dentsply) and Ketac-Molar Aplicap (ESPE). GIC buildups were made according to the manufacturers' instructions. After being stored at 37 degrees C, 100% humidity for 24h, the teeth were vertically sectioned into 1x1mm beams for microTBS evaluation. Representative fractured beams were prepared for scanning (SEM) and transmission electron microscopic (TEM) examination.


RESULTS
Results of the microTBS test were: Fuji IX GP (12.4+/-8.6MPa), ChemFlex (15.0+/-9.3MPa) and Ketac-Molar Aplicap (11.4+/-7.7MPa). One-way ANOVA and a multiple comparison test showed that ChemFlex had a statistically higher microTBS (p<0.05). SEM fractographic analysis showed that the predominant failure modes were interfacial and mixed failures. The GIC side of the fractured beams revealed dehydration cracks, a high level of porosity, and voids with an eggshell-like crust. TEM analysis of the demineralized dentin sides of the fractured beams revealed the presence of an intermediate layer along the GIC-dentin interface. This zone was present on the fractured dentin surface in the case of interfacial failure, and beneath GIC remnants in specimens that exhibited a mixed failure mode.


CONCLUSIONS
The findings suggest that the bonding of GIC to dentin is not weak and that the microTBS values probably represent the weak yield strengths of GICs under tension.
Yip
H K
HK
Faculty of Dentistry, The University of Hong Kong, Hong Kong, SAR, China. hkyip@hkusua.hku.hk
Tay
F R
FR
Ngo
H C
HC
Smales
R J
RJ
Pashley
D H
DH
D000134:Acid Etching, Dental; D000180:Acrylic Resins / Q000737:chemistry; D000268:Adhesiveness; D000704:Analysis of Variance; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D003890:Desiccation; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006801:Humans; D006813:Humidity; D008422:Materials Testing; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D015999:Multivariate Analysis; D016062:Porosity; D013223:Statistics as Topic; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors
D000180:Acrylic Resins; C410563:ChemFlex; D003764:Dental Materials; D017220:Dentin-Bonding Agents; D005899:Glass Ionomer Cements; C424245:Ketac-Molar Aplicap; C110713:fuji IX; C006903:carbopol 940