• The Journal of Advanced Prosthodontics
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• v.7 no.1
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• pp.15-20
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• 2015

PURPOSE. The aim of this study was to evaluate whether the push-out bond strength varies between oval and circular fiber posts, and to examine the effect on the resin cement thicknesses around the posts. MATERIALS AND METHODS. Eighteen mandibular premolar roots were separated into two groups for oval and circular fiber posts systems. Post spaces were prepared and fiber posts were luted to the post spaces. Roots were cut horizontally to produce 1-mm-thick specimens. Resin cement thicknesses were determined with a metallographic optical microscope and push-out tests were done. RESULTS. No significant differences were observed in terms of push-out bond strength between the oval and circular fiber posts (P>.05) The resin cement thicknesses of the oval posts were greater than those of the circular posts group in the coronal, middle and apical specimens (P<.05). CONCLUSION. In the light of these results, it can be stated that resin cement thickness does not affect the push-out bond strength.

• The Journal of Advanced Prosthodontics
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• v.5 no.4
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• pp.434-439
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• 2013

PURPOSE. The aim of the present study was to evaluate the effects of posts with different morphologies on stress distribution in an endodontically treated mandibular premolar by using finite element models (FEMs). MATERIALS AND METHODS. A mandibular premolar was modeled using the ANSYS software program. Two models were created to represent circular and oval fiber posts in this tooth model. An oblique force of 300 N was applied at an angle of $45^{\circ}$ to the occlusal plane and oriented toward the buccal side. von Mises stress was measured in three regions each for oval and circular fiber posts. RESULTS. FEM analysis showed that the von Mises stress of the circular fiber post (426.81 MPa) was greater than that of the oval fiber post (346.34 MPa). The maximum distribution of von Mises stress was in the luting agent in both groups. Additionally, von Mises stresses accumulated in the coronal third of root dentin, close to the post space in both groups. CONCLUSION. Oval fiber posts are preferable to circular fiber posts in oval-shaped canals given the stress distribution at the postdentin interface.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.1
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• pp.1-9
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• 2006

Purpose: The purpose of this study was to evaluate the efficacy and substitute possibility of a newly developed flowable composite resins as a luting cement for translucent fiber post. Material & Method: Two kinds of 12 mm translucent fiber Post (D.T. Light-Post (Bisco, USA) and FRC Postec (Ivoclar vivadent, Liechtenstein) was inserted into the teflon mold (7 mm diameter, 9 mm long) and Filtek-Flow (3M ESPE. USA), a light activated flowable composite resin, was polymerized for 60 seconds through the post. Also, the post was cut from the tip to 9 mm, 6 mm, 3 mm, and Filtek-Flow was light cured according to each length. For comparison, 60 seconds light-cured and 24 hours self-cured two dual cured resin cement (Duo-cement (Bisco, USA) and 2 Panavia-F (Kuraray, Japan)) samples were prepared as control group. Also cavities (1 mm in width, 1 mm in depth and 12 mm in length) were prepared using acrylic plate and aluminum bar, and flowable composite resin was flied and light cured by the diffused light from the fiber post's side wall. The degree of polymerization was measured according to the distance from curing light using Vickers' hardness test. Result: Within the limitation of this study, the following conclusions were drawn: 1. Vickers' hardness of light cured dual cured resin cement and flowable composite resin decreased from Panavia-F, Filtek-Flow and Duo-cement accordingly (p<0.05). In the dual curing resin cement, light curing performed group showed higher surface hardness value than self cured only group (p<0.05). 2. Surface hardness ratio (light cured through fiber post /directly light cured) of D.T. Light-Post using Filtek-Flow showed about 70% in the 6 mm deep and about 50% in the 12 mm deep FRC Postec showed only 40% of surface hardness ratio. 3. Surface hardness ratio by diffused light from the post's side wall showed about 50% at 6 mm and 9 mm deep, and about 40% at 12 mm deep in D.T. Light-Post. However, FRC Postec showed about 40% at 6 mm deep, and almost no polymerization in 9 mm and 12 mm deep.

• The Journal of Advanced Prosthodontics
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• v.9 no.3
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• pp.170-175
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• 2017

PURPOSE. The aim of the present study was to evaluate the fracture resistances of zirconia, cast nickel-chromium alloy (Ni-Cr), and fiber-composite post systems under all-ceramic crowns in endodontically treated mandibular first premolars. MATERIALS AND METHODS. A total of 36 extracted human mandibular premolars were selected, subjected to standard endodontic treatment, and divided into three groups (n=12) as follows: cast Ni-Cr post-and-core, one-piece custom-milled zirconia post-and-core, and prefabricated fiber-glass post with composite resin core. Each specimen had an all-ceramic crown with zirconia coping and was then loaded to failure using a universal testing machine at a cross-head speed of 0.5 mm/min, at an angle of 45 degrees to the long axis of the roots. Fracture resistance and modes of failure were analyzed. The significance of the results was assessed using analysis of variance (ANOVA) and Tukey honest significance difference (HSD) tests (${\alpha}=.05$). RESULTS. Fiber-glass posts with composite cores showed the highest fracture resistance values ($915.70{\pm}323N$), and the zirconia post system showed the lowest resistance ($435.34{\pm}220N$). The corresponding mean value for the Ni-Cr casting post and cores was reported as $780.59{\pm}270N$. The differences among the groups were statistically significant (P<.05) for the zirconia group, as tested by ANOVA and Tukey HSD tests. CONCLUSION. The fracture resistance of zirconia post-and-core systems was found to be significantly lower than those of fiber-glass and cast Ni-Cr post systems. Moreover, catastrophic and non-restorable fractures were more prevalent in teeth restored by zirconia posts.

• The Journal of Advanced Prosthodontics
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• v.8 no.2
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• pp.158-166
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• 2016

PURPOSE. The aim of this study was to determine the fracture resistance and the mode of fracture of endodontically treated teeth restored with different fiber posts and all-ceramic crowns. MATERIALS AND METHODS. Two glass fiber reinforced post systems in two different sizes and polyethylene fiber ribbon in two different thicknesses (n=10) were used. The specimens, restored with all-ceramic crowns, were subjected to a compressive load (in N) delivered at a 130-degree angle to the long axis until a fracture could be noted. The results were analyzed statistically with a One-Way ANOVA test (P<.05). RESULTS. Statistically significant differences were observed between the mean fracture resistance values of Postec, Snowlight, and Kerr Connect thin specimens (P<.0095). The Postec results (395.70 N) were found to be significantly higher than the others. No statistical difference was observed among the thick specimens (P<.2657). The mean fracture resistance values of the Snowlight thick samples were found to be higher than those of the Snowlight thin samples. The specimens were always fractured around the cemento-enamel junction at the palatinal side. No post fracture was observed for the thin Snowlight and Kerr Connect specimens or for the thick Postec and Kerr Connect specimens. Among the common failure types of the specimens, the worst was observed to be the root fracture failure. The highest post dislodgement failure result (80%) was obtained from the thin Kerr Connect specimen. CONCLUSION. In terms of optimizing fracture resistance, the fiber post size selection should be done according to the forces applied to the restored teeth.

• The Journal of Advanced Prosthodontics
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• v.6 no.3
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• pp.194-199
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• 2014

PURPOSE. This study evaluated the depth of cure of resin composite cured by light through a translucent fiber post. MATERIALS AND METHODS. The opaque plastic tubes in various lengths of 2, 4, 6, 8, 10, 12, 14 mm. were filled with resin composite in which two different translucent fiber posts were inserted into the center and photo-polymerized for 40 seconds. The degree of conversion of the cured composite at bottom surface were examined using Fourier transform infrared attenuated total reflection spectrometer (FTIR/ATR) at 0.1, 0.5 and 1.0 mm apart from the post surface. RESULTS. The degree of conversion of the 0.1 mm, 0.5 mm, 1.0 mm apart from the post surface was highest at the 2 mm level and continuously decreased when the distance from the light source was increased and drastically decreased when the depth from the top of the post was greater than 4-6 mm. For each level, the highest degree of conversion was at 0.1 mm from the post surface and decreased continuously when the distance apart from the post surface was increased. CONCLUSION. The quantity of light transmission depends on the type of post and the light transmission capability of the post, especially after 4-6 mm depth and the area further apart from the post surface, are insufficient for clinical light activation of resin composite.

• Computers and Concrete
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• v.17 no.1
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• pp.67-86
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• 2016

Strengthening as well as correcting unsightly deflections of reinforced concrete (RC) beam may be accomplished by retrofitting. An innovative way to do this retrofitting that is proposed in this study utilizes turnbuckle to apply external post-tensioning. This Turnbuckle External Post-Tensioning (T-EPT) was experimentally proven to improve the serviceability and load carrying capacity of reinforced concrete beams. The T-EPT system comprises a braced steel frame and a turnbuckle mechanism to provide the prestressing force. To further develop the T-EPT, this research aims to develop a numerical scheme to analyze the structural performance of reinforced concrete beams with this kind of retrofitting. The fiber method analysis was used as the numerical scheme. The fiber method is a simplified finite element method that is used in this study to predict the elastic and inelastic behavior of a reinforced concrete beam. With this, parametric study was conducted so that the effective setup of doing the T-EPT retrofitting may be determined. Different T-EPT configurations were investigated and their effectiveness evaluated. Overall, the T-EPT was effective in improving the serviceability condition and load carrying capacity of reinforced concrete beam.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.900-909
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• 2002

Fibers play a role to increase the tensile strength and cracking resistance of concrete structures. The post cracking behavior must be clarified to predict cracking resistance of fiber reinforced concrete. The purpose of this study is to develop a realistic analysis method for the post cracking behavior of synthetic fiber reinforced concrete members. For this purpose, the cracked section is assumed to behave as a rigid body and the pullout behavior of single fiber is employed. A probabilistic approach is used to calculate effective number of fibers across crack faces. The existing theory is compared with test data and shows good agreement. The proposed theory can be efficiently used to describe the load-deflection behavior, moment-curvature relation, load-crack width relation of synthetic fiber reinforced concrete beams.

• Restorative Dentistry and Endodontics
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• v.39 no.4
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• pp.303-309
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• 2014

Objectives: Hydrogen peroxide ($H_2O_2$) surface treatment of fiber posts has been reported to increase bond strength of fiber posts to resin cements. However, residual oxygen radicals might jeopardize the bonding procedure. This study examined the effect of three antioxidant agents on the bond strength of fiber posts to conventional and self-adhesive resin cements. Materials and Methods: Post spaces were prepared in forty human maxillary second premolars. Posts were divided into five groups of 8 each: G1 (control), no pre-treatment; G2, 10% $H_2O_2$ pre-treatment; G3, G4 and G5. After $H_2O_2$ application, Hesperidin (HES), Sodium Ascorbate (SA) or Rosmarinic acid (RA) was applied on each group respectively. In each group four posts were cemented with Duo-Link conventional resin cement and the others with self-adhesive BisCem cement. Push-out test was performed and data were analyzed using 2-way ANOVA and tukey's post-hoc test (${\alpha}=0.05$). Results: There was a statistically significant interaction between the cement type and post surface treatment on push-out bond strength of fiber posts (p < 0.001, F = 16). Also it was shown that different posts' surface treatments significantly affect the push-out bond strength of fiber posts (p = 0.001). $H_2O_2$ treated posts (G2) and control posts (G1) cemented with Duo-link showed the highest ($15.96{\pm}5.07MPa$) and lowest bond strengths ($6.79{\pm}3.94$) respectively. Conclusions: It was concluded that $H_2O_2$ surface treatment might enhance the bond strength of fiber posts cemented with conventional resin cements. The effect of antioxidants as post's surface treatment agents depends on the characteristics of resin cements used for bonding procedure.

• 대한치과보철학회:학술대회논문집
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• 2001.11a
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• pp.63-63
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• 2001