THE EVALUTION OF STRESS DISTRIBUTIONS IN 3 AND 5 UNIT DENTAL AND IMPLANT SUPPORTED FIXED ZIRCONIA RESTORATIONS: FINITE ELEMENT ANALYSIS

Purpose: In this study, it is aimed to compare the distribution of stress on anchorage and implants in 3-and-5-member-dental and implant supported zirconia restorations by using finite element analysis.Material and Method: Stress distribution formed in anchorage and implants as a result of chewing forces was analyzed in dental and implant (Astra Tech Microthread Osseo Speed, Sweeden) supported models of zirconia restoration with 5-member placed on the numbers of 43, 44, 45, 46 and 47 and with 3-member placed on the number of 45, 46 and 47.  The study was performed through static nonlinear analysis with the three-dimensional finite element analysis method.  Results: The highest and the lowest stress were respectively found on the number of 45 and 47 in 3-member dental supported model. The highest and the lowest stress in 5-membered dental-supported model were respectively found on the tooth of number 45 and on the root apex of the implant of number 43. Stress accumulation was observed in the cervical portion of the implant in implant-supported models. Stress accumulation in the tooth-supported model was found less than in implant-supported modelsConclusion: The extreme forces on the dental and implant-supported restorations with increased members can reduce survival rate of restorations in mouth. To prefer dental implants with larger diameter and longer length along with infrastructure like zirconia to design posterior implant-supported restorations can keep restorations in mouth for longer period

Effects of diode laser application on inflammation and mpo in periodontal tissues in a rat model

Objective: In this study, we aimed to histologically and immunologically evaluate the effect of diode laser treatment when applied adjunctive to scaling and root planing (SRP) in an experimental periodontitis model. Materials and methods: We used Wistar-Albino rats (n=60) with average weight of 230 g. Experimental periodontitis was induced by ligature at the right and left first mandibular molar teeth in all rats. After 11 days, the ligature was removed and rats were divided into two groups. The control group (n=30) received only SRP treatment, while the laser group (n=30) received a diode laser (GaAlAs, 810 nm, 1 W, 10 J, 20 s) treatment adjunctive to SRP. Ten rats in each group were sacrificed after 7, 15, and 30 days. Histopathological examination was performed in the left mandible of rats. Myeloperoxidase (MPO) was evaluated by western blot in the gingival specimens from the right mandible. Results:MPO levels in the laser group were statistically significantly lower compared with the control group (p≤0.05). There was no statistically significance at any time between MPO levels in the control group (p>0.05). MPO levels in the laser group at the 7th day were statistically significantly higher compared to the 15th (p≤0.05) and the 30th day (p≤0.05). Inflammatory cell infiltration decreased over time in both groups and was statistically significantly lower in the laser group than in the control group at all times (p≤0.01). Conclusions: Within the limits of this study, we suggest that diode laser application is an adjunctive treatment because it reduced inflammation and MPO when applied in addition to SRP. On the other hand, more studies are needed for the assessment of the effects of diode laser application to periodontal tissues

Comparison of the biochemical and radiological criteria for lumbar disc degeneration

Background The relationship between radiological degeneration criteria on lumbar magnetic resonance imaging (MRI) and both the keratan sulfate (KS) and chondroitin sulfate (ChS) levels was examined in disc material taken from patients undergoing lumbar disc herniation (LDH) surgery. To examine whether the biochemical and radiological degeneration criteria testing the reliability of radiological degeneration findings agreed and to evaluate the contribution of the KS/ChS ratio to disc form (protruding or extruding). Methods This was a prospective experimental cohort study. Using enzyme-linked immunosorbent assay, KS and ChS levels were measured in the degenerate nucleus pulposus taken from 71 patients with a diagnosis of LDH who underwent surgery. The degeneration levels and disc form (protruding or extruding) were determined according to the Pfirrmann five-stage grading system on preoperative T2-weighted lumbar MRIs. According to the Pfirrmann system, 28 patients were grade III and 43 were grade IV. The relationship between radiological criteria and the KS/ChS ratio was statistically evaluated. Results The KS levels (p=0.046) and the KS/ChS ratio (p=0.001) were significantly higher in grade IV patients than in grade III patients. However, there was no difference between the KS and ChS levels and the KS/ChS ratio when patients were classified as protruding or extruding according to their disc structure. Disc structure and biochemical degeneration indicators were not correlated. Conclusions The KS level and the KS/ChS ratio were high in patients with marked radiological degeneration on lumbar MRI, demonstrating the sensitivity and reliability of the Pfirrmann five-stage grading system for showing radiological degeneration

A retrospective evaluation of bifid mandibular canal prevalence of Southeastern Anatolia population by cone-beam computed tomography

Introduction: Bifid mandibular canal (BMC) is often detected incidentally on radiological examination and can be observed in unilateral or bilateral forms. The correct localization of the BMC plays an important role in the prevention of complications such as paresthesia, anesthesia, bleeding, traumatic neuroma, which may occur during or after surgical operations on the mandible such as sagittal split ramus osteotomy, impacted third molar tooth extraction, and dental implant surgery. Objective: This study aims to retrospectively evaluate the prevalence of bifid mandibular canal (BMC) in the Southeastern Anatolian population via Conical Beam Computed Tomography (CBCT). Material and Method: In this retrospective study, CBCT images of 615 patients, who applied to the Department of Oral and Maxillofacial Surgery in the Faculty of Dentistry at Dicle University, Turkey, for various reasons from 2015 to 2020, is evaluated and cases with bifid mandibular canals are examined. The prevalence evaluation is conducted by statistical analyses in terms of sex and laterality. Results: According to the analyses, the BMC prevalence did not constitute a significant difference in terms of the age variable (p>0.05). The incidence of unilateral BMC was higher than bilateral BMC (p<0.05; p=0.016). Additionally, the prevalence of BMC was higher in males compared to females (p<0.05; p=0.008). Conclusion: BMC, which can be detected more easily and frequently via CBCT technology, is an anatomical formation that should be taken into account during oral and maxillofacial practices

Karbon lifli polimer sargılı standart silindir beton numunelerin eksenel yük altındaki davranışlarının incelenmesi

Lif takviyeli polimer kompozitlerin betonarme yapılarda güçlendirme amaçlı olarak kullanımı son yıllarda oldukça yaygınlaşmıştır. Özellikle yüksek dayanımlı beton kullanılarak üretilen yapı elemanlarının yük etkisi altında sünek davranmasını sağlamak için, dışarıdan lifli polimer malzemeler kullanılarak sarılması alternatif bir güçlendirme yöntemi olarak öne çıkmaktadır. Yüksek çekme dayanımına sahip olan bu malzemeler, kolay uygulanabilmeleri ve hafif olmaları sebebiyle sıklıkla tercih edilmektedir. Bu çalışmada dayanımı 53.13-74.87 MPa arasında değişen silindir şeklindeki beton numuneler (tek veya çift kat) çift yönlü karbon lifli kumaş (CFRP) kullanılarak sarılmıştır. Söz konusu numunelerin eksenel basınç altında test edilmesiyle CFRP sargısının betonun basınç dayanımına ve sünekliğine olan etkileri araştırılmıştır. Ayrıca test edilen numunelere ait elde edilen gerilme-deformasyon ilişkileri literatürde mevcut olan CFRP ile güçlendirilmiş silindir numunelere ait modellerin sonuçları ile kıyaslanmıştır. Sonuç olarak CFRP sargılı numunelerin basınç dayanımlarında ve şekil değiştirme kapasitelerinde önemli artışlar elde edilmiştir. Özellikle çift kat CFRP sargılı durumda elde edilen gerilme-deformasyon değerlerinin, modellerden elde edilen değerler ile oldukça uyumlu olduğu gözlenmiştir

Investigation of the behavior of carbon fiber reinforced polymer confined standard cylinder concrete specimens under axial load

Lif takviyeli polimer kompozitlerin betonarme yapılarda güçlendirme amaçlı olarak kullanımı son yıllarda oldukça yaygınlaşmıştır. Özellikle yüksek dayanımlı beton kullanılarak üretilen yapı elemanlarının yük etkisi altında sünek davranmasını sağlamak için, dışarıdan lifli polimer malzemeler kullanılarak sarılması alternatif bir güçlendirme yöntemi olarak öne çıkmaktadır. Yüksek çekme dayanımına sahip olan bu malzemeler, kolay uygulanabilmeleri ve hafif olmaları sebebiyle sıklıkla tercih edilmektedir. Bu çalışmada dayanımı 53.13-74.87 MPa arasında değişen silindir şeklindeki beton numuneler (tek veya çift kat) çift yönlü karbon lifli kumaş (CFRP) kullanılarak sarılmıştır. Söz konusu numunelerin eksenel basınç altında test edilmesiyle CFRP sargısının betonun basınç dayanımına ve sünekliğine olan etkileri araştırılmıştır. Ayrıca test edilen numunelere ait elde edilen gerilmedeformasyon ilişkileri literatürde mevcut olan CFRP ile güçlendirilmiş silindir numunelere ait modellerin sonuçları ile kıyaslanmıştır. Sonuç olarak CFRP sargılı numunelerin basınç dayanımlarında ve şekil değiştirme kapasitelerinde önemli artışlar elde edilmiştir. Özellikle çift kat CFRP sargılı durumda elde edilen gerilme-deformasyon değerlerinin, modellerden elde edilen değerler ile oldukça uyumlu olduğu gözlenmiştir.The use of fiber reinforced polymer composites for strengthening in concrete structures has become quite prevalent in recent years. Especially, to provide ductile behavior from the structural elements that produced by using the high strength concrete under the load effects, the externally wrapping of these elements with using the fiber reinforced polymer materials comes into prominence as an alternative method for strengthening. These materials with high tensile strength can often be preferred due to their lightweight and easy to apply. In this study, cylinder-shaped concrete specimens with compressive strengths range between 53.13~74.87 MPa, are wrapped one or two layer with using bi-directional carbon fiber reinforced fabric (CFRP). These wrapped specimens were tested under the axial comprehensive loads and the effects of the CFRP wrapping on concrete strength and ductility was investigated. In addition, stress-strain relations obtained from the tested specimens were compared with the results of existing models for strengthened cylindrical specimen with CFRP in literature. As a result, a significant increase was obtained in the compressive strength and deformation capacity of CFRP wrapped specimens. Especially, it was observed that the stress-strain values obtained from the two layers CFRP wrapped specimens show good agreement with the values obtained from the models

Analysis of Carbon Fiber Polymer Confined Slender Reinforced Concrete Columns by Using Moment Magnification Method

Bu çalışmada, karbon lifli polimer sargılı yüksek dayanımlı çelik lifli ve lifsiz betonarme kolonların davranışları incelenmiştir. Bu amaçla hazırlanan 8 adet çelik lifli ve lifsiz karbon fiber sargılı betonarme kolon numuneler iki eksenli eğilme ve eksenel yük altında test edilerek taşıma gücü kapasiteleri ve yükdeplasman eğrileri belirlenmiş ve aynı kolon numunelerinin teorik olarak da analizi gerçekleştirilmiştir. Analizde beton basınç bölgesi için literatürde yer alan sargılı beton gerilme-şekil değiştirme modeli kullanılmıştır. Ele alınan kolon numunelerin beton basınç dayanımı 53,13~76,76 MPa arasında değişmektedir. Test edilen kolon numunelerine ait dayanım, dış merkezlik, karbon lifli polimer malzeme özellikleri ve narinlik etkisi parametreleri yapılan analizlerde incelenmiştir. Analizde, narinlik etkisi ACI-318 yönetmeliği tarafından önerilen Moment Büyütme Yöntemi' ne göre ele alınmıştır. Kolon numunelerin analizinden elde edilen sonuçların deneysel olarak elde edilen sonuçlarla uyum içinde olduğu gözlenmiştir.In this study, the behavior of carbon fiber polymer confined plain and steel fiber reinforced concrete columns were examined. For this purpose, carbon fiber polymer confined plain and steel fiber reinforced concrete column specimens were prepared and analyzed to determine the ultimate strength capacity and the load-deflection curves of columns. In the analysis, a stress-strain model for confined concrete was used for the concrete compression zone. Compressive strength of reinforced concrete column specimens are range from 53,13~76,76 MPa. In the analysis compressive strength, eccentricity, carbon fiber polymer material properties and parameters of slenderness effect were examined. In the analysis, slenderness effect of the column is taken into account by using Moment Magnification Method suggested by ACI-318 building code requirements for structural concrete. In conclusion the analysis and experimental results of carbon fiber reinforced polymer confined plain and steel fiber reinforced concrete columns have been achieved in good accurac

Rectangular stress block parameters for high-strength concrete columns subjected to biaxial bending and axial load

Sunulan çalışmada, yüksek dayanımlı beton için beton basınç bölgesinde kullanılan ve çeşitli yönetmeliklerce kabul edilmiş olan dikdörtgen gerilme bloğu modeli ve model parametreleri irdelenmekledir. Çalışma iki eksenli eğilme ve eksenel basınca maruz kolonların analiz ve tasarımı için beton basınç bölgesinde dikdörtgen dağılım modelini esas alan ve ikinci mertebe momentlerinden meydana gelen narinlik etkisinin de dahil edildiği bir yöntem ile ele alınmaktadır. Yöntemin geçerliliğini göstermek ve çeşitli yönetmeliklerce tanımlanmış olan dikdörtgen gerilme bloğu modelini ve model parametrelerini irdelemek amacı ile literatürde mevcut bir deneysel çalışma önerilen yönteme dayalı olarak geliştirilen bilgisayar programı ile analiz edilmiştir. Analiz sonuçlarının deneysel sonuçlarla uyumlu olduğu gözlenmiştir.In the presented study, the rectangular stress block model used in the concrete compression zone and its parameters accepted by various Standards for high-strength concrete have been examined. The study has been taken into account with a procedure based on the rectangular stress block in the concrete compression zone for the analysis and the design of columns, including slenderness effect due to the second order moments, under biaxial bending and axial load. An experimental study has been analyzed with a computer program based on the proposed method to demonstrate the effectiveness of the method and to examine the proposed rectangular stress block and its parameters defined by various Standards. A good degree of accuracy has been observed between the analysis and test results

TRACE METAL LEVELS IN VEHICLE AIR AND POLLEN FILTER DUSTS BY THE BCR EXTRACTION PROCEDURE

The availability of Cd, Co, Cr, Cu, Mn, Ni, Pb, Fe and Zn of dust from vehicle air and pollen filters were investigated by four-step BCR (European Community Bureau of Reference) sequential extraction procedure. The acid-soluble, reducible, oxidizable, residual extracts were measured by inductively coupled plasma-optical emission spectrometry (ICP-OES). The results indicated that both of air and pollen filter dusts contained higher concentration of Fe. To estimate the accuracy of the method the standard reference material BCR 701 was used. The results for recovery all the elements were found in the range 95.4-101.3%. The mean concentrations [mu g/g] of trace elements in dusts from air filters/pollen filters were: cadmium 16.72/17.56; cobalt 24.22/23.72; chromium 46.02/55.44; copper 44.92/37.67; iron 1868.03/1854.92; manganese 231.2/213.64; nickel 38.89/45.27; lead 60.99/67.17; zinc 199.58/201.25. The results obtained are in agreement with data reported in the literature