Browsing by Author "Imirzalioglu, Pervin"

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The Effect of Three Different Crown Heights and Two Different Bone Types on Implants Placed in the Posterior Maxilla: Three-Dimensional Finite Element Analysis
(2016) Cinar, Duygu; Imirzalioglu, Pervin; 27004295
Purose: The purpose of this study was to determine the amount and localization of functional stresses in implants placed in two different bone types (type 3 and type 4) with three different crown heights in the atrophic posterior maxilla using finite element analysis. Materials and Methods: A three-dimensional finite element model of the posterior maxilla was created from a computerized tomography image by using the Marc 2005 (MSC Software) program. Three different crown/implant ratios (1/1, 1.5/1, 2/1) in the first molar tooth zone were modeled. Type 3 and type 4 bone quality according to the classiication system of Lekholm and Zarb was created. The total oblique force of 300 N with a 30-degree angle was applied from the locations of the mesiobuccal cusp (150 N) and the distobuccal cusp (150 N) of first molar teeth. Results: For the implants, the highest stresses were observed around the implant neck at the crown/implant ratio of 2/1 (430.57 MPa). As the crown/implant ratio increased two times, the von Mises stresses increased at a rate of 47%. The highest tensile values exceeded the ultimate tensile strength of the cortical bone for all the designs. Also, the highest compressive values exceeded the ultimate compressive strength of the cortical bone in the 2/1 design for type 3 bone, and in the 1.5/1 and 2/1 designs for type 4 bone. As the crown/implant ratio increased from 1/1 to 2/1, the highest tensile value and the highest compressive value increased 13%. For the spongious bone, as the crown/implant ratio increased, the highest tensile value increased 42% and 85%, respectively. Tensile stresses increased at a rate of 26% in the 1/1 ratio, 30% in the 1.5/1 ratio, and 32% in the 2/1 ratio when the density of spongious bone decreased. Compression-related values also increased 34% in the 1/1 ratio, 35% in the 1.5/1 ratio, and 36% in the 2/1 ratio when the density of spongious bone decreased. Conclusion: Compressive and tensile stresses formed mostly at the alveolar bone around the implant neck that was cortical bone. Thus, it had to be preserved during the surgical procedures. Deformation due to the stresses had great importance for the type IV spongious bone due to the increase caused by the higher crown height levels.
Heat Transfer and Thermal Stress Analysis of a Mandibular Molar Tooth Restored by Different Indirect Restorations Using a Three-Dimensional Finite Element Method
(2017) Koycu, Berrak Celik; Imirzalioglu, Pervin; 26618930
Purpose: Daily consumption of food and drink creates rapid temperature changes in the oral cavity. Heat transfer and thermal stress caused by temperature changes in restored teeth may damage the hard and soft tissue components, resulting in restoration failure. This study evaluates the temperature distribution and related thermal stress on mandibular molar teeth restored via three indirect restorations using three-dimensional (3D) finite element analysis (FEA). Materials and Methods: A 3D finite element model was constructed of a mandibular first molar and included enamel, dentin, pulp, surrounding bone, and indirect class 2 restorations of type 2 dental gold alloy, ceramic, and composite resin. A transient thermal FEA was performed to investigate the temperature distribution and the resulting thermal stress after simulated temperature changes from 36 degrees C to 4 or 60 degrees C for a 2-second time period. Results: The restoration models had similar temperature distributions at 2 seconds in both the thermal conditions. Compared with 60 degrees C exposure, the 4 degrees C condition resulted in thermal stress values of higher magnitudes. At 4oC, the highest stress value observed was tensile stress (56 to 57 MPa), whereas at 60 degrees C, the highest stress value observed was compressive stress (42 to 43 MPa). These stresses appeared at the cervical region of the lingual enamel. The thermal stress at the restoration surface and resin cement showed decreasing order of magnitude as follows: composite > gold > ceramic, in both thermal conditions. Conclusions: The properties of the restorative materials do not affect temperature distribution at 2 seconds in restored teeth. The pulpal temperature is below the threshold for vital pulp tissue (42 degrees C). Temperature changes generate maximum thermal stress at the cervical region of the enamel. With the highest thermal expansion coefficient, composite resin restorations exhibit higher stress patterns than ceramic and gold restorations.
Three-dimensional finite element analysis of stress distribution in inlay-restored mandibular first molar under simultaneous thermomechanical loads
(2016) Koycu, Berrak Celik; Imirzalioglu, Pervin; Oezden, Utku Ahmet; 27041006
Functional occlusal loads and intraoral temperature changes create stress in teeth. The purpose of this study was to evaluate the impact of simultaneous thermomechanical loads on stress distribution related to inlay restored teeth by three-dimensional finite element analysis. A mandibular first molar was constructed with tooth structures, surrounding bone and inlays of Type II gold alloy, ceramic, and composite resin. Stress patterns on the restorative materials, adhesive resin, enamel and dentin were analyzed after simulated temperature changes from 36 degrees C to 4 or 60 degrees C for 2 s with 200-N oblique loading. The results showed that the three types of inlays had similar stress distribution in the tooth structures and restorative materials. Concerning the adhesive resin, the composite resin inlay model exhibited lower stresses than ceramic and gold alloy inlays. Simultaneous thermomechanical loads caused high stress patterns in inlay-restored teeth. Composite resin inlays may be the better choice to avoid adhesive failure.