Study On Nanoleakage And Microtensile Bond Strengths Of Resin-dentin Interfaces

Nanoleakage was originally used to describe microporosities within hybrid layers that allow silver nitrate penetration to occur in the absence of gap formation between bonding agent and the tooth structure. Nanoleakage is one of the important indexes to evaluate the bonding interface besides microleakage. The introduction of nanoleakage renders it possible to evaluate the bonding interface at ultrastructural level. Nanoleakage is a common phenomenon for most introduced commercial adhesive systems and it's inevitable when applying these materials and using routine bonding techniques. The causes for nanoleakage and effects of influence factors on it vary according to different materials or research methods used by different researchers. Eelectronical microscopy has been used to evaluate nanoleakage, but it is difficult to use Transmission Electron Microscope (TEM) directly because of the difficulty of ultra-thin section of undecalcified dentin, which limits the application of TEM. Microtensile bond strengths (MTBS) can much more reflect the true bonding strength between dentin and adhesive due to small bonding areas and overwhelming fractured surface at interfaces. Microtensile test method has been replacing traditional bonding test methods and is becoming a main means to evaluate dentin bonding strength.In this thesis, we studied and evaluated the effects of three factors (curing time, vacuuming and thermocycling) on the nanoleakage and MTBS of three commercial dental adhesive systems (Adper Prompt, U-Bond and OptiBond). Dentin bonding specimens were decalcified then observed under TEM. Then TEM images were subjected to image analysis by NIH Image PC. Leakage scores of each restoration were calculated as the percentage of the total area of hybrid layer that was penetrated by silver nitrate. At the same time MTBS was tested after three treatments. The objectives of this study were to establish method to evaluate nanoleakage after decalcification of dentin with EDTA solution, to analyze the...