Objective: three kinds of composite resin materials and glass fiber post comparative study of micro- tensile bond strength . Methods : 45 Parapost glass fiber posts were randomly divided into 3 groups , respectively, with three different composite resins : Clearfil AP-XTM, Ceram-X, ParaCore dual-cure composite resin cement post and core material made ​​of post and core samples , cut cross-section of the prepared sample specimen strip 1.0mm × 1.0mm for micro tensile strength test. The results : ParaCore micro- tensile bond strength with Ceram-X was significantly higher than AP-XTM (P <0.05), no ParaCore and micro- tensile bond strength Ceram-X with fiber pile significant difference (P> 0.05) . Conclusion : ParaCore and bonding properties Ceram-X and glass fiber post better, suitable for clinical use plastic core .
Keywords : fiber post ; micro- tensile bond strength ; composite resin
Ideal and dentin pile should have the same or similar elastic modulus, so that force can be evenly distributed along the entire length of the pile , and is conducive to the root surface conduction stress , reduce stress concentration. More teeth dental defects , higher stress levels within the root , if using a metal post and core restoration will produce stress concentration , greatly increases the risk of root fracture . Glass fiber post and dentin with similar elastic modulus, stress distribution, and contribute to the root surface conduction , thereby reducing root fracture . Currently resin plastic that can be used in clinical nuclear material type variety, ingredients, are quite different nature , on its evaluation and fiber post bonding effect is not one . In this study, a comparison test three kinds of micro- tensile bond strength of composite resin and glass fiber pile , choose plastic resin nuclear material for clinical reference.
1 Materials and methods
1.1 Materials Clearfil AP-XTM light-cured composite
    Resin (kuraraCo., Japan); porcelain Namics Ceram-X light-cured composite resin (DentsplyCo., USA); ParaCore high strength dual-cure composite resin post and core resin material (Coltène / WhaledentCo, USA.).
    Parapost glass fiber post (Coltène / WhaledentCo, Switzerland.); Spectrum800 curing light (DentsplyCo., USA); EZ-TEST500N micro tensile testing machine (Shi-madzuCo, Japan); SYJ-150 low speed diamond cutter ( Shenyang Branch crystal automation Equipment manufacturing Co., Ltd. ); SME-654 -type stereo microscope (NikonCo, Japan).
1.2 Methods
    1.2.1 Preparation of fiber post surface samples with 75% ethanol solution
    After cleaning liquid , surface treatment with a silane coupling agent PBA 1min, dried spare . The treated surface of the fiber pile is placed diameter of 10mm, a height of 10mm in the center of a cylindrical transparent mold [ 1 ] , the composite resin is filled into the mold , after full curing light curing lamp light from a plurality of directions ( both sustained 20sec) ensure adequate resin polymerization . Prepared post-core model immersed in artificial saliva , after 24h at 37 ℃ preservation , low-speed diamond cutter under running water and cut into strips cross section of 1.0mm × 1.0mm of specimens .
    1.2.2 Tensile bond strength test machine at the micro test sensor 500N, preload 5N, the tensile speed of 1.0mm/min maximum load tensile test specimen at break (N). Micro- tensile bond strength (MPa) = maximum fracture load (N) / specimen bonded area (mm2). Each sample 1.2.3 bonding interface fracture mode was observed to complete the test placed under the stereomicroscope (× 40) observed bonding interface fracture mode , fracture way into bond failure ( occur in the resin / fiber post bonding interface ) , cohesive failure ( ) and mixed in a resin or fiber damage occurred inside the pile ( both these two failure modes ) . Record fracture mode for each sample .
    1.2.4 Statistical analysis was performed using SPSS13.0 software for micro- tensile strength measurement results of samples in each group , univariate analysis of variance and q test (Newman-Keuls method ) .
2 Results
    Three kinds of micro- tensile bond strength of composite resin materials and the results of stereo microscope fracture mode results in Table 1, the results showed that the fracture mode 3 groups bonded specimens are destroyed ; micro- tensile bond strength of one-way ANOVA analysis are shown in Table 2 , analysis of variance P = 0.0088, according to α = 0.05 level can be considered as the overall mean of each group are not equal ; pairwise comparisons between groups q test are shown in Table 3 , the results show microtensile ParaCore with Ceram-X ''s bond strength was significantly higher than the AP-XTM (P <0.05), there was no significant difference (P ParaCore and micro- tensile bond strength Ceram-X with fiber pile > 0.05 ) .

Microtensile composite resin with glass fiber post Intensity
Click here to view all news photos easily form a chemical combination of epoxy resin and so on . On the other hand , the study will be formed between the elastic Ceram-X used in the composite resin is the largest and best relative mobility , the fibers having a small pile of bubbles , cracks relatively continuous and complete bonding interface , thereby get more ideal bond strength [ 9 ] . Therefore, this study table 2, Table 3 showed that the tensile strength of different composite resins micro different , ParaCore and micro- tensile bond strength Ceram-X was significantly higher than AP-XTM (P <0.05). The micro- tensile bond strength ParaCore and Ceram-X with fiber pile no significant difference (P> 0.05). Resin bonded together with fiber posts , composite body composed of three parts: the resin - bonded interface - fiber posts ( epoxy ) . If the epoxy resin and fracture toughness, bonding interface failure occurs . Conversely cohesive failure occurs within the material [ 10 ] . In this study, the fracture mode of analysis, three groups of micro tensile fracture type nuclear resin and fiber post bonding interface are destroyed . The reason to consider , such as can be excluded when the resin filling process such as nuclear formation of bubbles or test generation micro-cracking and other operational errors in the internal audit resin case , their breaking strength of these three core plastic resin and epoxy resin fiber post surfaces are much higher bond strength at break ( which micro- tensile bond strength largest ParaCore was 14.23 ± 3.86MPa).
In summary , polymerization shrinkage dual cure resin system is relatively small ; micro- tensile bond properties of nanometer processing resin and glass fiber composite pile can be improved, these two types of composite resins are guaranteed a strong adhesive force , is a clinical better choice of plastic cores.