J Korean Acad Conserv Dent.  2008 Jan;33(1):45-53. 10.5395/JKACD.2008.33.1.045.

Comparison of the elastic modulus among three dentin adhesives before and after thermocycling

• Chang J
• Lee IB
• Cho BH
• Kim HY
• Son HH

• KMID: 1986749
• DOI: http://doi.org/10.5395/JKACD.2008.33.1.045

Abstract

The purpose of this study was to determine the effects on the elastic moduli of the adhesive and the hybrid layer from thermocycling. Twenty one human molars were used to create flat dentin surfaces. Each specimen was bonded with a light-cured composite using one of three commercial adhesives (OptiBond FL [OP], Clearfil SE Bond [CL], and Xeno III [XE]). These were sectioned into two halves and subsequently cut to yield 2-mm thickness specimens; one specimen for immediate bonding test without thermocycling and the other subjected to 10,000 times of thermocycling. Nanoindentation test was performed to measure the modulus of elasticity of the adhesive and the hybrid layer, respectively, using an atomic force microscope. After thermocycling, XE showed a significant decrease of the modulus in the adhesive layer (p < 0.05). Adhesives containing hydrophilic monomers are prone to hydrolytic degradation. It may result in the reduced modulus of elasticity, which leads to the mechanically weakened bonding interface.

Keyword

Adhesive layer; hybrid layer; hydrophilic monomer; modulus of elasticity; nanoindentation; thermocycling

MeSH Terms

Adhesives
Chimera
Dentin
Dentin-Bonding Agents
Elastic Modulus
Humans
Molar
Resin Cements
Adhesives
Dentin-Bonding Agents
Resin Cements

Figure

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  Figure 1 Schematic of specimen preparation. Two adjacent 2-mm sections were used for nanoindentation before and after thermocycling.

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  Figure 2 Schematic of load-depth curve in nanoindentation.

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  Figure 3 Comparative mean elastic moduli of three adhesive systems on the adhesive layer at the immediate bonding and the thermocycled stage.

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  Figure 4 FE-SEM micrographs of bonded interface. Arrows indicate the representative indentations on the adhesive layer of OP (A) and the hybrid layer of CL (B) after thermocycling. Cracks propagated from the contact point were exibited on the indentation surface. Some indentation marks seemed to be elastically recovered after unloading without leaving permanent defects.

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