The aim of this study was to compare a fiber composite laminate (FCL) post core and a conventional cast post core system by using two different methods. The first method was a conventional fracture strength test, and the second was a finite elemental stress-analysis method (FEM). For the conventional fracture strength test, 20 extracted, human upper, central incisors were used. The teeth were decoronated, treated endodontically, and restored with two post core systems. After embedding the samples in resin blocks, a loading force was applied to the teeth at a crosshead speed of 5 mm/ min at an angle of 45 degrees to the long axis of the tooth. The data were recorded, and the results were compared by using the Mann-Whitney U test. There was no statistically significant difference between the two post systems (p > 0.05). For FEM analysis, a pseudo three-dimensional model of a maxillary central incisor, theoretically restored with either a cast post or an FCL, was used. The analysis was performed by using the structural analysis program (SAP90). FEM analysis showed that stress was accumulated within the cast post core system, and transmission of stress to supportive structures and the tooth was low. This is an advantage for tooth and supporting tissues. When the FCL post core system was evaluated by FEM, the results indicated that this system transferred stress to supportive structures and the tooth while stress accumulation within the post system was low. This is an advantage for the restoration but disadvantage for the supporting tissues.

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(i) Use of flowable composite resin under composite restorations had no effect on fracture resistance of root filled molar teeth with MOD preparations, (ii) use of polyethylene ribbon fibre under composite restorations in root filled teeth with MOD preparations significantly increased fracture strength.

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Stresses within roots increased with an increase in the number of the adhesive interfaces. Creation of a primary monoblock within the root canal either by an endodontic sealer or with an adhesive post-core system can reduce the stresses that occur inside the tooth structure.

The aim of this numerical analysis was to evaluate the amount and localization of stress that occurs with various materials used in implant-crown design under functional forces. Computer-aided design techniques and a finite-element stress analysis method were used for evaluation. A 4.1 x 10-mm implant placed in the mandibular second premolar area was simulated and analyzed. Simulation and analysis were performed with the use of COSMOS/M software and Pro/Engineer 2000i on a Dual Pentium III 1-GHz computer. Crown designs were as follows: porcelain fused to noble metal crown, porcelain fused to base metal crown, In-Ceram porcelain crown, and IPS Empress 2 porcelain crown. A 300-N vertical force was applied to the centric relation stop points of the crowns. The results of this study indicated that different types of restorative materials play an important role in the amount and distribution of the stresses in the superstructure and the implant. The highest stress values were observed in the IPS Empress 2 porcelain crown design (600 MPa). Porcelain fused to base metal and In-Ceram framework designs transferred less stress to abutment. Type of restorative materials used in implant crown designs are significant factors in the amount and distribution of the stresses on superstructure and implant under functional forces. Porcelain fused to base metal (149 MPa) and In-Ceram (173 MPa) crown designs induced higher von Mises stress values within the framework than porcelain fused to noble metal (108 MPa) and IPS Empress 2 (119 MPa) porcelain crown designs.