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Citation Count: 1
Adaptive Stimulus Design for Dynamic Recurrent Neural Network Models
(Frontiers Media Sa, 2019) Doruk, R. Ozgur; Zhang, Kechen; Electrical-Electronics Engineering
We present an adaptive stimulus design method for efficiently estimating the parameters of a dynamic recurrent network model with interacting excitatory and inhibitory neuronal populations. Although stimuli that are optimized for model parameter estimation should, in theory, have advantages over nonadaptive random stimuli, in practice it remains unclear in what way and to what extent an optimal design of time-varying stimuli may actually improve parameter estimation for this common type of recurrent network models. Here we specified the time course of each stimulus by a Fourier series whose amplitudes and phases were determined by maximizing a utility function based on the Fisher information matrix. To facilitate the optimization process, we have derived differential equations that govern the time evolution of the gradients of the utility function with respect to the stimulus parameters. The network parameters were estimated by maximum likelihood from the spike train data generated by an inhomogeneous Poisson process from the continuous network state. The adaptive design process was repeated in a closed loop, alternating between optimal stimulus design and parameter estimation from the updated stimulus-response data. Our results confirmed that, compared with random stimuli, optimally designed stimuli elicited responses with significantly better likelihood values for parameter estimation. Furthermore, all individual parameters, including the time constants and the connection weights, were recovered more accurately by the optimal design method. We also examined how the errors of different parameter estimates were correlated, and proposed heuristic formulas to account for the correlation patterns by an approximate parameter-confounding theory. Our results suggest that although adaptive optimal stimulus design incurs considerable computational cost even for the simplest excitatory-inhibitory recurrent network model, it may potentially help save time in experiments by reducing the number of stimuli needed for network parameter estimation.
Citation Count: 78
Amine grafted silica supported CrAuPd alloy nanoparticles: superb heterogeneous catalysts for the room temperature dehydrogenation of formic acid
(Royal Soc Chemistry, 2015) Yurderi, Mehmet; Bulut, Ahmet; Caner, Nurdan; Celebi, Metin; Kaya, Murat; Zahmakiran, Mehmet; Chemical Engineering
Herein we show that a previously unappreciated combination of CrAuPd alloy nanoparticles and amine-grafted silica support facilitates the liberation of CO-free H-2 from dehydrogenation of formic acid with record activity in the absence of any additives at room temperature. Furthermore, their excellent catalytic stability makes them isolable and reusable heterogeneous catalysts in the formic acid dehydrogenation.
Citation Count: 7
Applying Emmert's Law to the Poggendorff illusion
(Frontiers Research Foundation, 2015) Talasli, Umur; Inan, Asli Bahar; Department of Psychology
The Poggendorff illusion was approached with a novel perspective, that of applying Emmert's Law to the situation. The extensities between the verticals and the transversals happen to be absolutely equal in retinal image size, whereas the registered distance for the verticals must be smaller than that of the transversals due to the fact that the former is assumed to occlude the latter. This combination of facts calls for the operation of Emmert's Law, which results in the shrinkage of the occluding space between the verticals. Since the retinal image shows the transversals to be in contact with the verticals, the shrinkage must drag the transversals inwards in the cortical representation in order to eliminate the gaps. Such dragging of the transversals produces the illusory misalignment, which is a dictation of geometry. Some of the consequences of this new explanation were tested in four different experiments. In Experiment 1, a new illusion, the tilting of an occluded continuation of an oblique line, was predicted and achieved. In Experiments 2 and 3, perceived nearness of the occluding entity was manipulated via texture density variations and the predicted misalignment variations were confirmed by using a between-subjects and within-subjects designs, respectively. In Experiment 4, tilting of the occluded segment of the transversal was found to vary in the predicted direction as a result of being accompanied by the same texture cues used in Experiments 2 and 3.
Citation Count: 15
Assessment of depression, anxiety, and social support in the context of therapeutic abortion
(Wiley, 2019) Topal, Cansu Akdag; Terzioglu, Fusun; Nursing
Purpose The purpose of this study is to determine the levels of anxiety, depression, social support, and nursing care needed by women undergoing therapeutic abortion. Designs and Methods Sixty women were administered a sociodemographic form, the Hospital Anxiety Depression Scale and the Multidimensional Perceived Social Support Scale. Results More than half of the women experienced anxiety (61.7%). Anxiety scores were high (10.8 +/- 3.7), and most of the women had depression (85.0%). Social support from family and friends of the women decreased the women's anxiety and depression levels significantly; social support from their partners also decreased the women's anxiety levels (P < 0.05). Practice Implications Support from family and friends after therapeutic abortion is a fundamental affective variable on anxiety scores.
Citation Count: 4
Assessment of nitrogen excess in an agricultural area using a nitrogen balance approach
(I W A Publishing, 2005) Muhammetoglu, H; Muhammetoglu, A; Soyupak, S
A pilot study has been initiated to develop an approach for quantification of nitrogen excesses from agricultural activities that involve greenhouse farming in Kumluca Plain, Turkey. Detailed calculations utilizing the nitrogen balance method (NBM) were carried out at nine different locations within the plain over a time period of one year. The major contributing factors and governing operative mechanisms taken into consideration were nitrogen application rates both as organic and chemical fertilizers, irrigation water to application practices, and nitrogen uptake by plants. The adopted approach yielded valuable information such as plant nitrogen uptake efficiencies, excess nitrogen, leaching rates and leachate nitrogen concentrations. Further, a site specific multiple linear regression model has been developed to estimate the ratio (N-leachate/N-groundwater) as a function of independent variables: farming age, excess nitrogen application and SEEPAGE Index Number. The negative sign of the model parameters implies that the ratio (N-leachate/N-groundwater) decreases as values of the independent variables increase. The adopted approach and the obtained results can beneficially be applied to similar sites to establish basic parameters of irrigation and fertilizer application operations.
Citation Count: 36
Atmospheric Pressure Plasma Surface Treatment of Polymers and Influence on Cell Cultivation
(Mdpi, 2021) Sasmazel, Hilal Turkoglu; Alazzawi, Marwa; Alsahib, Nabeel Kadim Abid; Metallurgical and Materials Engineering
Atmospheric plasma treatment is an effective and economical surface treatment technique. The main advantage of this technique is that the bulk properties of the material remain unchanged while the surface properties and biocompatibility are enhanced. Polymers are used in many biomedical applications; such as implants, because of their variable bulk properties. On the other hand, their surface properties are inadequate which demands certain surface treatments including atmospheric pressure plasma treatment. In biomedical applications, surface treatment is important to promote good cell adhesion, proliferation, and growth. This article aim is to give an overview of different atmospheric pressure plasma treatments of polymer surface, and their influence on cell-material interaction with different cell lines.
Citation Count: 13
Attachment Style, Openness to Experience, and Social Contact as Predictors of Attitudes Toward Homosexuality
(Routledge Journals, Taylor & Francis Ltd, 2020) Metin-Orta, Irem; Metin-Camgoz, Selin; Department of Psychology
Considerable research has shown that people generally hold more negative attitudes toward homosexuals. Given this fact, it is important to understand psychological and social correlates of homophobia. With this purpose, the present study investigates attachment styles, openness to experience, and social contact in relation to attitudes toward homosexuals. The findings show that being female, having prior contact with homosexuals, and scoring high in openness to experience predict more favorable attitudes toward homosexuals. The supplementary analyses also support the moderating effect of secure attachment on the relationship between openness to experience and attitudes toward homosexuals. The present study not only extends the related research by examining the interactive effects of attachment style and personality trait, but also provides important implications for researchers, educators, or managers in terms of reducing anti-homosexual attitudes in diverse settings.
Citation Count: 0
Author Correction: Using urine FTIR spectra to screen autism spectrum disorder
(Nature Portfolio, 2024) Sarigul, Neslihan; Bozatli, Leyla; Kurultak, Ilhan; Korkmaz, Filiz; Physics Group
[No Abstract Available]
Citation Count: 2
Avoiding contingent incidents by quadrotors due to one or two propellers failure
(Public Library Science, 2023) Altinuc, Kemal Orcun; Khan, Muhammad Umer; Iqbal, Jamshed; Mechatronics Engineering
With the increasing impact of drones in our daily lives, safety issues have become a primary concern. In this study, a novel supervisor-based active fault-tolerant (FT) control system is presented for a rotary-wing quadrotor to maintain its pose in 3D space upon losing one or two propellers. Our approach allows the quadrotor to make controlled movements about a primary axis attached to the body-fixed frame. A multi-loop cascaded control architecture is designed to ensure robustness, stability, reference tracking, and safe landing. The altitude control is performed using a proportional-integral-derivative (PID) controller, whereas linear-quadratic-integral (LQI) and model-predictive-control (MPC) have been investigated for reduced attitude control and their performance is compared based on absolute and mean-squared error. The simulation results affirm that the quadrotor remains in a stable region, successfully performs the reference tracking, and ensures a safe landing while counteracting the effects of propeller(s) failures.
Citation Count: 4
Beyond expectations: disease duration and psychological burden in psoriatic arthritis
(Springer Heidelberg, 2023) Kilic, Gamze; Kilic, Erkan; Tekeoglu, Ibrahim; Sargin, Betul; Cengiz, Gizem; Balta, Nihan Cuzdan; Nas, Kemal
This study aims to investigate the relationship between disease duration and psychological burden in PsA and to identify the risk factors associated with psychological distress. Patients with PsA who met CASPAR classification criteria enrolled by Turkish League Against Rheumatism (TLAR)-Network. Patients were categorized into three groups based on disease duration: early stage (< 5 years), middle stage (& GE; 5, < 10 years), and late stage (& GE; 10 years). All patients underwent clinical and laboratory assessment using standardized protocol and case report forms. The associations between psychological variables and clinical parameters were assessed by a multivariate analysis. Of the 1113 patients with PsA (63.9% female), 564 (%50.7) had high risk for depression and 263 (%23.6) for anxiety. The risk of psychological burden was similar across all PsA groups, and patients with a higher risk of depression and anxiety also experienced greater disease activity, poorer quality of life, and physical disability. Multivariate logistic regression revealed that female gender (OR = 1.52), PsAQoL (OR = 1.13), HAQ (OR = 1.99), FiRST score (OR = 1.14), unemployment/retired (OR = 1.48) and PASI head score (OR = 1.41) were factors that influenced the risk of depression, whereas the current or past enthesitis (OR = 1.45), PsAQoL (OR = 1.19), and FiRST score (OR = 1.26) were factors that influenced the risk of anxiety. PsA patients can experience a comparable level of psychological burden throughout the course of their disease. Several socio-demographic and disease-related factors may contribute to mental disorders in PsA. In the present era of personalized treatment for PsA, evaluating psychiatric distress can guide tailored interventions that improve overall well-being and reduce disease burden.
Citation Count: 52
Biomechanical comparison of implant retained fixed partial dentures with fiber reinforced composite versus conventional metal frameworks: A 3D FEA study
(Elsevier, 2011) Erkmen, Erkan; Meric, Gokce; Kurt, Ahmet; Tunc, Yahya; Eser, Atilim
Fiber reinforced composite (FRC) materials have been successfully used in a variety of commercial applications. These materials have also been widely used in dentistry. The use of fiber composite technology in implant prostheses has been previously presented, since they may solve many problems associated with metal alloy frameworks such as corrosion, complexity of fabrication and high cost. The hypothesis of this study was that an FRC framework with lower flexural modulus provides more even stress distribution throughout the implant retained fixed partial dentures (FPDs) than a metal framework does. A 3-dimensional finite element analysis was conducted to evaluate the stress distribution in bone, implant-abutment complex and prosthetic structures. Hence, two distinctly different models of implant retained 3-unit fixed partial dentures, composed of Cr-Co and porcelain (M-FPD model) or FRC and particulate composite (FRC-FPD model) were utilized. In separate load cases, 300 N vertical, 150 N oblique and 60 N horizontal forces were simulated. When the FRC-FPD and M-FPD models were compared, it was found that all investigated stress values in the M-FPD model were higher than the values in the FRC-FPD model except for the stress values in the implant-abutment complex. It can be concluded that the implant supported FRC-FPD could eliminate the excessive stresses in the bone-implant interface and maintain normal physiological loading of the surrounding bone, therefore minimizing the risk of peri-implant bone loss due to stress-shielding. (C) 2010 Elsevier Ltd. All rights reserved.
Citation Count: 0
Blood metal analysis of plasmas from donors with and without SARS-CoV-2 using laser-induced breakdown spectroscopy and logistic regression
(Optica Publishing Group, 2024) Melikechi, Noureddine; Adler, Helmar G.; Safi, Ali; Landis, Joshua E.; Pourkamali-Anaraki, Farhad; Eseller, Kemal Efe; Xia, Weiming; Department of Electrical & Electronics Engineering
Research on the correlation between metal levels in blood and Covid-19 infection has been conducted primarily by assessing how each individual blood metal is linked to different aspects of the disease using samples from donors with various levels of severity to Covid-19 infection. Using logistics regression on LIBS spectra of plasma samples collected pre- and postCovid-19 pandemic from donors known to have developed various levels of antibodies to the SARS-Cov-2 virus, we show that relying on the levels of Na, K, and Mg together is more efficient at differentiating the two types of plasma samples than any single blood alone.
Citation Count: 0
CB65 and novel CB65 liposomal system suppress MG63 and Saos-2 osteosarcoma cell growth in vitro
(Taylor & Francis Ltd, 2024) Zorba, Basak Isil; Boyacioglu, Oezge; Caglayan, Tugba; Recber, Tuba; Nemutlu, Emirhan; Eroglu, Ipek; Korkusuz, Petek
Curable approaches for primary osteosarcoma are inadequate and urge investigation of novel therapeutic formulations. Cannabinoid ligands exert antiproliferative and apoptotic effect on osteosarcoma cells via cannabinoid 2 (CB2) or transient receptor potential vanilloid type (TRPV1) receptors. In this study, we confirmed CB2 receptor expression in MG63 and Saos-2 osteosarcoma cells by qRT-PCR and flow cytometry (FCM), then reported the reduction effect of synthetic specific CB2 receptor agonist CB65 on the proliferation of osteosarcoma cells by WST-1 (water-soluble tetrazolium-1) and RTCA (real-time impedance-based proliferation). CB65 revealed an IC50 (inhibitory concentration) for MG63 and Saos-2 cells as 1.11 x 10(-11) and 4.95 x 10(-11) M, respectively. The specific antiproliferative effect of CB65 on osteosarcoma cells was inhibited by CB2 antagonist AM630. CB65 induced late apoptosis of MG63 and Saos-2 cells at 24 and 48 h, respectively by FCM when applied submaximal concentration. A novel CB65 liposomal system was generated by a thin film hydration method with optimal particle size (141.7 +/- 0.6 nm), polydispersity index (0.451 +/- 0.026), and zeta potential (-10.9 +/- 0.3 mV) values. The encapsulation efficiency (EE%) of the CB65-loaded liposomal formulation was 51.12%. The CB65 and CB65-loaded liposomal formulation releasing IC50 of CB65 reduced proliferation by RTCA and invasion by scratch assay and induced late apoptosis of MG63 and Saos-2 cells, by FCM. Our results demonstrate the CB2 receptor-mediated antiproliferative and apoptotic effect of a new liposomal CB65 delivery system on osteosarcoma cells that can be used as a targeted and intelligent tool for bone tumors to ameliorate pediatric bone cancers following in vivo validation.
Citation Count: 3
Characteristic features of thermoluminescence in neodymium-doped gallium sulfide
(Wiley, 2018) Guler, I.; Isik, M.; Ahmedova, F.; Guseinov, A.; Gasanly, N.; Department of Electrical & Electronics Engineering
The thermoluminescence (TL) of neodymium-doped gallium sulfide (GaS:Nd) single crystals was measured from 10 K to room temperature with various heating rates between 0.2 and 1.0 K/sec. Two peaks centered at 70.9 K and 116.0 K were observed when using a heating rate of 0.8 K/sec. Initial rise and curve fitting methods were used to obtain information on trap activation energies. Activation energies of 94 and 216 meV were found for two analyzable peaks. The heating rate dependencies of TL intensities revealed that one of the observed peaks showed normal behavior according to the one trap-one recombination model, whereas the other model showed anomalous heating rate behavior. TL experiments were also carried out at different illumination temperatures from 10 to 32 K; maximum peak temperature remained almost the same at various illumination temperatures. This behavior indicated that the revealed trapping centers are single, discrete levels. The TL glow curves of undoped GaS crystals were also investigated and the effect of Nd doping on the TL characteristics of crystals is discussed in the manuscript.
Citation Count: 17
Characteristics and outcomes of carbapenemase harbouring carbapenem-resistant Klebsiella spp. bloodstream infections: a multicentre prospective cohort study in an OXA-48 endemic setting
(Springer, 2022) Isler, Burcu; Ozer, Berna; Cinar, Gule; Aslan, Abdullah Tarik; Vatansever, Cansel; Falconer, Caitlin; Ergonul, Onder
A prospective, multicentre observational cohort study of carbapenem-resistant Klebsiella spp. (CRK) bloodstream infections was conducted in Turkey from June 2018 to June 2019. One hundred eighty-seven patients were recruited. Single OXA-48-like carbapenemases predominated (75%), followed by OXA-48-like/NDM coproducers (16%). OXA-232 constituted 31% of all OXA-48-like carbapenemases and was mainly carried on ST2096. Thirty-day mortality was 44% overall and 51% for ST2096. In the multivariate cox regression analysis, SOFA score and immunosuppression were significant predictors of 30-day mortality and ST2096 had a non-significant effect. All OXA-48-like producers remained susceptible to ceftazidime-avibactam.
Citation Count: 0
Clinical and Laboratory Evaluation of Acute Pericarditis Associated with Antinuclear Antibodies Positivity
(Bentham Science Publ Ltd, 2023) Dursun, Ali Dogan; Saricam, Ersin; Erdem, Hakan; Sariyildiz, Gulcin Turkmen; Ozyer, Esref Umut; Bozkurt, Engin; Cantekin, Omer Faruk; Anesthesia Program; Basic Sciences
Background Up to 30% of patients with acute pericarditis develop recurrent pericarditis. Acute pericarditis may be a manifestation of an underlying systemic autoimmune disease. Therefore, we evaluated the characteristics of patients with acute pericarditis according to antinuclear antibodies (ANA) positivity/negativity. Methods Participants with acute pericarditis and negative ANA (n=29), recurrent pericarditis with positive ANA (n=30) and healthy controls (n=11) were examined. The groups were compared using serum parameters (ANA, C-reactive protein, leucocyte count, erythrocyte sedimentation rate, total antioxidant status, nitric oxide (NO), and oxidative stress index (OSI)) and imaging techniques (electrocardiogram, echocardiography, cardiovascular magnetic resonance, and venous Doppler ultrasound). Results In females, acute pericarditis associated with ANA occurred more frequently (p<0.001). ANA-positive acute pericarditis had significantly lower NO and OSI (p<0.05 and p<0.001, respectively) and pericardial inflammation on magnetic resonance. We found a pulmonary embolism in one patient with positive ANA. Slow venous flow (SVF) occurred more often in acute pericarditis associated with ANA than in the ANA-negative group on venous ultrasound (p<0.05). The prevalence of positive ANAs was 1.6 times higher among SVF patients than in controls. Conclusion This study suggests that acute pericarditis associated with ANA is more common in middle-aged females. SVF and lower oxidative stress tests were more common in patients with ANA-associated acute pericarditis. Acute pericarditis associated with ANA could be considered as a hypercoagulable state. Therefore, all newly diagnosed pericarditis patients (especially females) should be checked for ANA positivity. Awareness of this coexistence should be promptly addressed to establish management strategies.
Citation Count: 0
Clinical Characteristics of Patients with Intraocular Lens Calcification after Pars Plana Vitrectomy
(Mdpi, 2023) Bopp, Silvia; Ozdemir, Huseyin Baran; Aktas, Zeynep; Khoramnia, Ramin; Yildirim, Timur M.; Schickhardt, Sonja; Ozdek, Sengul; Surgical Sciences
Aim: To determine the clinical risk factors that may increase the occurrence of intraocular lens (IOL) calcification in patients who had undergone pars plana vitrectomy (PPV). Methods: The medical records of 14 patients who underwent IOL explantation due to clinically significant IOL opacification after PPV were reviewed. The date of primary cataract surgery, technique and implanted IOL characteristics; the time, cause and technique of PPV; tamponade used; additional surgeries; the time of IOL calcification and explantation; and IOL explantation technique were investigated. Results: PPV had been performed as a combined procedure with cataract surgery in eight eyes and solely in six pseudophakic eyes. The IOL material was hydrophilic in six eyes, hydrophilic with a hydrophobic surface in seven eyes and undetermined in one eye. The endotamponades used during primary PPV were C2F6 in eight eyes, C3F8 in one eye, air in two eyes and silicone oil in three eyes. Two of three eyes underwent subsequent silicone oil removal and gas tamponade exchange. Gas in the anterior chamber was detected in six eyes after PPV or silicone oil removal. The mean interval between PPV and IOL opacification was 20.5 +/- 18.6 months. The mean BCVA in logMAR was 0.43 +/- 0.42 after PPV, which significantly decreased to 0.67 +/- 0.68 before IOL explantation for IOL opacification (p = 0.007) and increased to 0.48 +/- 0.59 after the IOL exchange (p = 0.015). Conclusions: PPV with endotamponades in pseudophakic eyes, particularly gas, seems to increase the risk for secondary IOL calcification, especially in hydrophilic IOLs. IOL exchange seems to solve this problem when clinically significant vision loss occurs.
Citation Count: 8
Colorimetric detection of ultrathin dielectrics on strong interference coatings
(Optical Soc Amer, 2018) Ayas, Sencer; Bakan, Gokhan; Ozgur, Erol; Celebi, Kemal; Torunoglu, Gamze; Dana, Aykutlu; Department of Electrical & Electronics Engineering
Metal films covered with ultrathin lossy dielectrics can exhibit strong interference effects manifested as the broad absorption of the incident light resulting in distinct surface colors. Despite their simple bilayer structures, such surfaces have only recently been scrutinized and applied mainly to color printing. Here, we report the use of such surfaces for colorimetric detection of ultrathin dielectrics. Upon deposition of a nanometer-thick dielectric on the surface, the absorption peak red shifts, changing the surface color. The color contrast between the bare and dielectric- coated surfaces can be detected by the naked eye. The optical responses of the surfaces are characterized for nanometerthick SiO2, Al2O3, and bovine serum albumin molecules. The results suggest that strong interference surfaces can be employed as biosensors. (C) 2018 Optical Society of America
Citation Count: 0
Comparison of Amiodarone Loading Dosage in the Treatment of Postoperative Atrial Fibrillation: High Versus Standard Dose Treatment
(Bentham Science Publ Ltd, 2024) Saricam, Ersin; Ocal, Arslan; Iscanli, Murat Dogan; Bozkurt, Engin; Ilkay, Erdogan; Cantekin, Omer Faruk
Background Postoperative atrial fibrillation (POAF) is associated with poor outcomes, including hemodynamic instability, stroke, myocardial infarction, and death. In hemodynamic stable patients, the rhythm-control strategy is more advantageous than rate control. Current standard intravenous amiodarone administration has limited success and a delayed effect; the acute success rate is 44% (8-12 h to several days).Purpose The aim of this study was to evaluate the effectiveness of higher amiodarone loading dosage to restore sinus rhythm in patients with POAF after noncardiac surgery.Methods This is a prospective, randomized, controlled single-center study. The study included 39 patients with POAF, divided into group I (n=27) (intravenous 600 mg amiodarone loading dosage over 2 h and infusion of 50 mg/h over a 24-h period) and group II (n=12) (standard protocol; 300 mg of bolus intravenously in 30 min and infusion of 50 mg/h over a 24-h period). The primary endpoint of the study was a restoration of sinus rhythm at the 24th hour.Results Baseline clinical, laboratory and echocardiographic characteristics of both groups were similar. The patients with higher loading amiodarone dosage had earlier restoration of sinus rhythm (2.38 +/- 1.41 vs 8.66 +/- 2.87 h, respectively; p=0.015). There was no significant difference in achieving sinus rhythm at the 24th hour between both groups.Conclusion Higher loading amiodarone dosage increased early conversions to sinus rhythm compared with standard amiodarone protocol in patients with POAF.
Citation Count: 18
Comparison of biomechanical behaviour of maxilla following Le Fort 1 osteotomy with 2-versus 4-plate fixation using 3D-FEA Part 2: Impaction surgery
(Churchill Livingstone, 2009) Atac, M. S.; Erkmen, E.; Yucel, E.; Kurt, A.
The aim of the second part of this Study was to evaluate the mechanical behaviour of 2- versus 4-plate fixation and bony structures after Le Fort I impaction surgeries using three-dimensional finite element analysis (3D-FEA). Two 3D-FEA models were created to fixate the impacted maxilla at the Le Fort I level as 2-plate fixation at the piriform rims (IMP-2 model) and 4-plate fixation at the zygomatic buttresses and piriform rims (IMP-4 model). The IMP-2 model contained 225 664 elements and 48 754 nodes and the IMP-4 model consisted of 245 929 elements and 53 670 nodes. The stresses in each maxillary model were computed. The models were loaded on one side, at the molar-premolar region, in vertical, horizontal and oblique directions to reflect the chewing process. It was concluded that the use of 4-plate fixation following Le Fort I advancement Surgery provides fewer stress fields on the maxillary bones and fixation materials than 2-plate fixation from a mechanical point of view.

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