The Evaluation Of Factors Affecting Retention Of Several Prefabricated Posts Using Push-out Tests

It is very common that the metal posts and cores as well as crowns are oftenused to restore the teeth that are badly defected. However, the cast metalposts have many disadvantages such as erosion, hypersensitivity, tending tocause root fracture, and would do harm to aesthetics. Recently, fiber postsare more and more popular for they would lead to more successful resultsthan cast posts and cores. In addition, the failure of teeth restored by fiberposts are often because of the debonding of cement between posts and rootcanals. This paper is to evaluate push-out strength of posts and root canalsusing different posts and bonding systems. In this way, the effect of differentfactors on bonding strength would be clear, which will provide proof toprosthetic theory of post and cores.PartⅠThe Evaluation of Factors Affecting Retention ofTwo Fiber Posts Using push-out TestObjective: To investigate shear bond strength between different fiber postsand root canals using different adhesive systems.Method: 24 intact extracted maxillary central incisors were sectionedperpendicular to the long axis at a point of 2mm-occlusal to the buccalcement-enamel junction (CEJ) and then endodontically treated. Posts(C-post, Aestheti-plus) were placed using different adhesive systems (onestep-plus/C&B cement, Rely X Unicem) respectively. The push-out test wasperformed on different sections of the root. The data were recorded andanalyzed with split-plot ANOVA.Results: Aestheti-plus showed higher push-out strengths than that of c-post.Total-etch adhesive systems resulted in higher strength than that of self-adhesive one. Bond strengths of the post decreased gradually from crownsection to apical section.Conclusion: shear bond strength of fiber posts were affected by manyfactors, it is necessary to choose the proper adhesive systems in coincidencewith the restorative goals.PartⅡThe Evaluation of Factors Affecting Retention of TwoPrefabricated Posts Using push-out TestObjective: To investigate shear bond strength between differentprefabricated posts and root canals using different adhesive systems.Method: Another group of 12 intact extracted maxillary central incisorswere sectioned perpendicular to the long axis at a point of 2mm-occlusal tothe buccal cement-enamel junction (CEJ) and then endodontically treated.The impression of C-post was made using silicon, and then the semi-noblemetal posts with the same size of C-post were cast from the wax pattern. Posts(C-post, semi-noble metal post) were placed using different adhesivesystems (one step-plus/C&B cement, Rely X Unicem)respectively. Thepush-out test was performed on different sections of the root. The data wererecorded and analyzed with split-plot ANOVA.Result: The push-out strengths were(MPa): 11.14±1.26, 5.04±0.94,13.62±1.16, 7.80±1.36. Prefabricated metal post showed higher push-outstrengths than c-post. Total-etch adhesive systems resulted in higherstrength than the self-adhesive ones. Bond strengths of the post decreasedgradually from crown section to apical section.Conclusion: It is necessary to choose the proper adhesive systems incoincidence with the restorative goals. Shear bond strength of different postswere affected by many factors such as the types of posts, the cement usedand region of the root canals.PartⅢ: The Evaluation of Factors Affecting Retention ofFiber Posts and Prefabricated Metal Posts Using push-out TestObjective: To investigate shear bond strength between differentprefabricated posts of the same size and root canals using different adhesivesystems.Method: The total 3 groups of 36 teeth as described in partⅠand partⅡwere done root canal therapy and then were cut into thin slices. After the push-out test being done, all the data were analyzed with the Stata toevaluate the push-out strengths using different posts(C-post, Aestheti-plusand prefabricated metal post) and different adhesive systems(onestep-plus/C&B cement, Rely X Unicem) respectively.Result: The push-out strengths were (MPa): 11.14±1.26, 5.04±0.94,11.82±1.16, 6.72±1.02, 13.62±1.16, 7.80±1.36. Prefabricated metal postshowed higher push-out strengths than aestheti-plus, while the latter showedhigher value than C-post. Total-etch adhesive systems resulted in higherstrength than the self-adhesive ones. To sum it, it is a best choice tocombine the prefabricated metal post with the total-etch adhesive system inrestoring teeth.Conclusion: Many factors including the material of the post, the type of theadhesive systems, and different sections of the root canal can affect thepush-out strengths while using the same-size post.