Evaluation of stress in three different fiber posts with two-dimensional finite element analysis

Introduction: The primary function of corono-radicular post is to provide retention for the core and to reinforce and to replace the remaining coronal tooth structure. There is considerable controversy regarding optimal choice of the material. An ideal post system should exhibit fracture resistance higher than the average masticatory forces. Finite elemental analysis (FEA) method facilitates precise analysis of the distribution and magnitude of stresses at any point of complex and irregular structures. Thus, this FEA study has been undertaken to evaluate the fracture stress distribution patterns in three fiber posts, viz., carbon, glass fiber, and everStick with an FEA. Materials and Methods: The FE stress analysis was performed with the FE software program (CATIA). Three two-dimensional FEA models of central incisor were simulated, and elastic moduli and Poisson's ratio of all the materials were fed to the software. For all the models, a 200 N vertical force was applied on the lingual surface of the tooth at an angle of 45°. Stress concentration and distribution were evaluated and noted down for all the models. To evaluate the stresses within the restored tooth, the modified von Mises failure criterion was used. The equivalent stresses found in the tested models were compared with the tensile strength of the respective materials. Contact stresses in the luting cement–dentin interface were calculated. Results: Finite element method revealed that maximum stress concentration was at the point of stress application. The stress value was highest in carbon fiber post followed by glass fiber post and least stresses found in everStick post. Maximum stress was observed at the labial surfaces of crown. However, the stress values and distribution were more homogenous in everStick post. Conclusion: The present findings suggest that everStick post has uniform stress distribution within tooth structure.

An analysis of failure mode of teeth restored with fiber-reinforced posts under the condition of bony resorption / 대한치과보철학회지

STATEMENT OF PROBLEM: Fiber-reinforced posts have lower modulus of elasticity than titanium post or cast post-core. With this similar elasticity to that of dentin, fiber-reinforced posts have been known to have a tendency to reduce the risk of root fracture. However, there were few studies on the teeth restored with fiber-reinforced posts under the condition of reduced periodontal support. PURPOSE: The purpose of this study was to evaluate the fracture strength and failure mode of endodontically treated teeth restored with fiber-reinforced posts and titanium posts under the condition of reduced periodontal support. MATERIAL AND METHOD: Extracted human maxillary incisor roots were divided into 3 groups (group 1 : carbon fiber post, group 2 : glass fiber post, and group 3 : titanium alloy post). After coronectomy and endodontic treatment, teeth were restored with each post systems and resin core according to the manufacturer's recommendation. Then, teeth with simulated periodontal ligament were embedded in the acrylic resin blocks at the level of 4 mm below the cemento-enamel junction. Each specimen was exposed to 105 load cycles with average 30 N force in 36.5 degrees C water using a computer-controlled chewing simulator. Loads were applied at 45.angle to the long axis of the teeth. After cyclic loading, teeth were subjected to a compressive load until failure at a crosshead speed of 0.5 mm/min. Fracture strength (N) and failure mode were examined. The fracture strength was analyzed with one-way ANOVA and the Sch ffe adjustment at the 95% significance level. RESULTS AND CONCLUSION: The results were as follows. 1. There was no statistically significant difference in the mean fracture strength among the groups ( P>0.05). 2. Carbon fiber post and glass fiber post group showed less root fracture tendency than control group. 3. All specimens with root fractures showed fracture lines above the level of acrylic resin block, except for only one specimen in group 3.

A STUDY ON THE FRACTURE STRENGTH OF TEETH RESTORED WITH A CARBON FIBER POST UNDER CYCLIC LOADING / 대한치과보철학회지

In the restoration of endodontically treated teeth, carbon fiber post was recently introduced. The purpose of this in vitro study was to investigate the fracture strength of teeth restored with a preFabricated carbon fiber post in comparison with teeth restored with a prefabricated titanium post & custom cast gold post after cyclic loading in the different environment. A total of 30 recently extracted human central incisors of similar dimension with crowns removed were used. All teeth were placed into acrylic blocks and every steps for post and core fabrication were made according to manufacture s instruction. The post length and core dimensions were standardizd. All teeth were divided into 6 groups 1) carbon fiber post / atmosphere, 2) titanium post / atmosphere, 3) gold post / atmosphere, 4) carbon fiber post / wet, 5) titanium post / wet, 6) gold post / wet. Carbon fiber post and titanium post were cemented in place using resin cementt and cores were fabricated with Ti-Core. Custom cast gold post was made from Dur clay pattern resin and cemented using resin cement, too. All specimens were thermocycled 10,000 times. After 50,000 cyclic loading, failure strength was measured using Instron testing machine. KruskalWallis test followed by Mann-Whitney test was used to compare the mean fracture strength. Results were as follows 1. All specimens showed lower fracture strength in wet environment after cyclic loading than in atmosphere condition, but did not reveal a significant difference. 2. There was no significant difference between carbon fiber post specimen and titanium post spec imen in the same environment. 3. Gold cast post specimen showed significant different greater fracture strength than those of others in the same environment. 4. Carbon fiber post specimen showed no root fracture.