The Tensile Bond Strengths Of Dentin Bonding Agents To Non-caries Sclerotic Dentin

Most of the existing studies on dentin adhesion were based on normal dentin structures. However, the non-normal dentin, such as non-caries sclerotic dentin of wedge-shaped defect, is often encountered in clinic. Non-caries sclerotic dentin is different from normal dentin in composition and structure. Sclerotic dentin is a special substrate we must treat in the process of restoring tooth, whose histological structure and mechanical properties are different with normal dentin. Therefore, the deficient penetrability of sclerotic dentin may restrict its bonding performance.In the present study, the micro-tensile bond strengths of four dentin adhesive agents (Contax, Clearfil TRI-S Bond, Xenoâ…¢and Prime & Bond NT) to non-caries sclerotic dentin were evaluated. The efficiency of pre-etching with 37% phosphate acid on dentin was testified And the long-term bonding performance of non-caries sclerotic dentin was also evaluated by in vitro thermal cycling.The results were drawn as follows,1. The SEM observation on the micro-structure of non-caries sclerotic dentin showed that, the surface of sclerotic dentin was over- mineralized. There were a mass of rhombohedral, whitlockite crystallites in the dentin tubes. Neither etching nor treatment by adhesive can remove these blocked sclerotic casts from dentin tubes.2. The micro-tensile bond strengths between composite and non-caries sclerotic dentin treated by four different adhesives showed that, there was no significant difference between the effect achieved by Contax, Clearfil TRI-S Bond and Prime & Bond NT. While the bond strength of Xenoâ…¢to sclerotic dentin was significantly lower than the others.3. When the self-etched adhesives (Contax, Clearfil TRI-S Bond) were used for the surface treatment of sclerotic dentin, adding phosphoric acid etching significantly improved the bond strength; When Xenoâ…¢adhesive was used for the surface treatment of sclerotic dentin, phosphoric acid etching had no effect on the bond strength.4. When the self-etched adhesives (Contax, Clearfil TRI-S Bond) were used for the surface treatment of sclerotic dentin, the results of thermal circlings showed that, for Contax, 5,000 times thermal circlings did not weakened the bond strength, while the bond strength after 10,000 times thermal circlings significantly lower than that before circling; for Clearfil TRI-S Bond, 5,000 times thermal circlings significantly weakened the bond strength, while 10,000 times thermal circlings weakened it further. For both Contax and Clearfil TRI-S Bond, the failures occurred in the hybrid layer increased as the times of thermal circling increased.5. The observation of field emission-scanning electron microscope (FE-SEM) on the failure modes showed that, most of the failures were mixed failure consisted of dentin, hybrid layer and resin composite.