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Öğe Clamp fixation to prevent unfolding of a suture knot decreases tensile strength of polypropylene sutures(Springer, 2012) Turker, Mehmet; Yalcinozan, Mehmet; Cirpar, Meric; Cetik, Ozgur; Kalaycioglu, BarisPurpose Although sutures evolved in last decade and the product spectrum broadened largely, they can be still classified into two: monofilament and multifilament. Sutures are the mainstay of orthopedic procedures like fascial closures, tendon repairs or tenodesis. In every repair, a suture loop is created. This suture loop is prone to failure due to suture elongation, knot slip and suture breakage. As the knot is the stress riser in a suture loop, the majority of acute loop failure occurs just adjacent to the knot. Monofilament sutures have higher bending stiffness and tendency to untie than multifilament sutures. The first throw of monofilament sutures have tendency to untie, which decrease loop tension and result in loss of achieved tissue approximation. Methods Although a common practice is to fix the first throw via a clamp before the locking one is tied, it can be hypothesized that a potential deforming effect can lead to a decrease in ultimate failure load of a monofilament suture loop. Results Fixing the first throw significantly reduced the ultimate failure load of monofilament nonabsorbable polypropylene sutures (Prolene) (62.2 +/- 8 N vs. 72.7 +/- 9 N, p = 0.019). The ultimate failure load achieved by monofilament sutures Polyglyconate (Maxon) and Nylon (Ethilon) and braided absorbable Polyglactin (Vicryl) were not affected by fixing the first throw. Conclusion Under microscopic examination, polypropylene sutures were found to be deformed by clamp fixation, while the others were not. Polypropylene sutures can be easily damaged when it is fixed by a clamp during knot tying. Presented data demonstrated that in real surgical situations clamp fixation of polypropylene knots can damage the suture loop and carry the risk of acute failure of repair site during early rehabilitation.Öğe Effect of Different Cavity Disinfectants on Shear Bond Strength of Composite Resin to Dentin(Quintessence Publishing Co Inc, 2009) Ercan, Ertugrul; Erdemir, Ali; Zorba, Yahya Orcun; Eldeniz, Ayce Unverdi; Dalli, Mehmat; Ince, Bayram; Kalaycioglu, BarisPurpose: The aim of this study was to evaluate the effect of different cavity disinfectants on dentin bond strengths of composite resin applied with two different adhesive systems. Materials and Methods: One hundred mandibular third molars were sectioned parallel to the occlusal surface to expose midcoronal dentin. The dentin surfaces were polished with waterproof-polishing papers The specimens were randomly divided into 5 groups of 20 each. In group 1, the specimens were not treated with any cavity disinfectants and served as control. From groups 2 to 5. dentin surfaces were treated with the following cavity disinfectants, respectively; 2% chlorhexidine solution, 2.5% NaOCl, 1% chlorhexidine gel, 3% H2O2. The specimens were then randomly divided into 2 subgroups including ten teeth each to evaluate the effect of different bonding systems Dentin bonding systems were applied to the dentin surfaces and the composite buildups were created After the specimens were stored in an incubator for 24 h. the shear bond strength was measured at a crosshead speed of 1 mm/min. The bond strength data were analyzed with one way analysis of variance and Tukey-HSD tests. Results: There was no significant difference between chlorhexidine gel and control groups regardless of the type of the bonding agent (p > 0.05). On the other hand, pretreatment with NaOCl, H2O2 or chlorhexidine solutions had a negative effect on the shear bond strength of self-etching bonding systems Conclusion: The findings of this study suggest that when NaOCl, H2O2 or chlorhexidine solution Eire used as a cavity disinfectant, an etch-and-rinse bonding system should be preferredÖğe EXTRUSION FORMING OF A DOUBLE BASE SOLID ROCKET PROPELLANT BY FINITE ELEMENT METHOD(Pamukkale Univ, 2007) Kalaycioglu, Baris; Dirikolu, M. Husnu; Celik, VeliIn this study, three dimensional modelling of extrusion forming of a double base solid rocket propellant is performed on Ansys (R) finite element simulation package. For the purpose of initial model construction and later comparisons with elastoviscoplastik model, the solid propellant is assumed to obey the elastic-plastic material response during the direct extrusion process. Taking into account the contact surface behavior with Coulomb friction and geometric and material nonlinearities, an incremental large large strain solution methodology has been adapted in the simulation. The hydrostatic pressure, stress, strain, and displacement values during extrusion of the solid rocket propellant are obtained from the simulation.Öğe Investigation of the design of a metal-lined fully wrapped composite vessel under high internal pressure(Taylor & Francis Ltd, 2010) Kalaycioglu, Baris; Dirikolu, M. HusnuIn this study, a Type III composite pressure vessel (ISO 11439: 2000) loaded with high internal pressure is investigated in terms of the effect of the orientation of the element coordinate system while simulating the continuous variation of the fibre angle, the effect of symmetric and non-symmetric composite wall stacking sequences, and lastly, a stacking sequence evaluation for reducing the cylindrical section-end cap transition region stress concentration. The research was performed using an Ansys (R) model with 2.91 volume, 6061 T6 aluminium liner/Kevlar (R) 49-Epoxy vessel material, and a service internal pressure loading of 22 MPa. The results show that symmetric stacking sequences give higher burst pressures by up to 15%. Stacking sequence evaluations provided a further 7% pressure-carrying capacity as well as reduced stress concentration in the transition region. Finally, the Type III vessel under consideration provides a 45% lighter construction as compared with an all metal (Type I) vessel.Öğe Revision of the failed pedicle screw in osteoporotic lumbar spine: Biomechanical comparison of kyphoplasty versus transpedicular polymethylmethacrylate augmentation(Turkish Joint Diseases Foundation, 2012) Derincek, Alihan; Turker, Mehmet; Cinar, Murat; Cetik, Ozgur; Kalaycioglu, BarisObjectives: In this study, we aimed to compare of kyphoplasty versus transpedicular polymethylmethacrylate (PMMA) augmentation biomechanically in the revision of the failed pedicle screw in osteoporotic lumbar spine. Materials and methods: Bone mineral density (BMD) of, lumbar vertebrae collected from four bovines were measured., Each vertebra was decalcified with hydrochloric acid solution to obtain osteoporotic specimens. Primary polyaxial pedicle screws, were inserted into the pedicles and pulled out until they failed. The pullout strength results of all specimens were recorded. Revision pedicle screws were randomly inserted into the same pedicles by either pedicle hole PMMA augmented (group 1) or kyphoplasty (Xvoid (TM)) PMMA augmented pedicle screws (group 2). The pullout strength results of all specimens were re-recorded. Results: The mean BMD significantly decreased from 1.686 +/- 227.9 g/cm(2) to 1.432 +/- 157.1 g/cm(2) following decalcification (p<0.001). In group 1, the mean pullout strength of primary screws significantly decreased from 3443 +/- 1086 N/m(2) to 2088 +/- 924 N/m(2) following pedicle screw augmentation (p=0.006). In group 2 the mean pullout strength of primary screws decreased from 3702 +/- 1063 N/m(2) to 3664 +/- 1057N/m(2) following kyphoplasty augmentation (p=0.934). Pedicle screw augmentation group achieved significantly lower pullout strength values than kyphoplasty pedicle hole augmentation group (p=0.002). Conclusion: Although pedicle hole PMMA augmentation is the gold standard for the failed screws in an osteoporotic bone, kyphoplasty augmented pedicle screw seems to be more effective method increasing the pullout strength.Öğe Stress Analysis of an Arbitrarily-Shaped Structure with an Irregularly-Shaped Hole using Digital Image Correlation(ELSEVIER, 2020) Kalaycioglu, BarisEngineering structures commonly have arbitrarily-shaped geometry and contain irregularly-shaped cutouts. The integrity of these structures is significantly influenced by the boundary stresses associated with these cutouts. This paper focuses on the evaluation of the stress of a complicated-shaped structure with an irregularly-shaped hole using a single measured displacement component. Digital Image Correlation (DIC) was utilized herein to record the in-plane displacements of the loaded structure. Considering the complications in providing solely analytical solutions for finite structures or numerical solutions in case of insufficient knowledge of the boundary and loading conditions, this paper demonstrates an effective hybrid technique of experimentally stress analyzing in such situations. Processing only one component of the in-plane displacement information with a stress function provides the full-field stresses, including the edges of the plate. Without the knowledge of the external loading conditions nor the need of physically differentiating the measured displacement to obtain strains, and hence stresses, the proposed hybrid technique simultaneously smoothes the recorded displacement information and evaluates the individual stresses full-field in a strong mechanics foundation (equilibrium and compatibility). To validate and support the proposed hybrid technique based on Airy stress function, the obtained results were compared with the those obtained through thermoelastic stress analysis, finite element analysis, and strain gauges.
