Investigation of Bruxism wear behavior of titanium alloy biomaterials; experimental and 3D finite element simulation.

Bruxism can be defined as the process of direct contact with teeth and dental materials with an involuntary jaw-tightening movement. In this process, teeth and dental materials can be exposed to various damage mechanisms. This study aims to realize the mechanism of bruxism with finite element analysis and in vitro rotating chewing movement analysis. Within the scope of the study, cp-Ti, Ti-5Zr, and Ti-5Ta materials were subjected to wear tests in the finite element analysis and in vitro rotating chewing movement method under the determined Bruxism chewing test conditions. Test specimens with cylindrical geometry were exposed to a direct every-contact wear mechanism for 30 s under 150 N bruxism chewing bite force. The bruxism chewing cycle continued for 300 min at a frequency of 2 Hz. Microanalysis of the wear surfaces of the samples after the experimental study was carried out with Scanning Electron Microscopy. The results obtained within the scope of this study showed that the Bruxism wear resistance increased by adding zirconium and tantalum to pure titanium material. This result shows that pure titanium material, which is known to have poor wear resistance, can be improved with Zr and Ta alloys. It is clinically important that the success rate in the treatment process increases with the increase in wear resistance. However, the micro-cracks observed in the microstructure may have occurred in the sub-surface, which is a show of the fatigue wear mechanism.

Impact of chronic total occlusion in a non-infarct-related coronary artery on contrast-associated nephropathy in acute ST-elevation myocardial infarction.

OBJECTIVES: Co-existing chronic total occlusion (CTO) in a non-infarct-related artery (IRA) might serve as an important trigger of adverse outcomes in ST-segment elevation myocardial infarction (STEMI). Therefore, we planned to analyse the potential impact of non-IRA CTO on the evolution of contrast-associated nephropathy (CAN) in STEMI patients managed with primary percutaneous coronary intervention (P-PCI). METHODS: A total of 537 subjects with STEMI undergoing P-PCI during the first 12 h after the onset of their symptoms were enrolled in this retrospective study. The subjects were categorised based on the angiographic presence of non-IRA CTO. Moreover, the subjects were also divided into 2 groups based on their CAN status following P-PCI (CAN (+) and CAN (-)). RESULTS: Co-existing non-IRA CTO was demonstrated in 86 subjects (16%). During the hospitalisation period, we identified 81 (15.1%) subjects with CAN. Subjects with non-IRA CTO had a significantly higher incidence of CAN compared with those without (56 [12.4%] vs 25 [29.1%], respectively, p < 0.001). In a logistic regression analysis, an existing non-IRA CTO (odds ratio: 2.840, 95%CI: 1.451-5.558, p = 0.002), as well as age, haemoglobin, diabetes mellitus, creatinine, and white blood cell count, were independent of predictors of CAN. CONCLUSION: In STEMI patients managed with P-PCI, a co-existing non-IRA CTO had an independent association with the evolution of CAN.

Systemic Immune-Inflammation Index: A Novel Predictor of Coronary Thrombus Burden in Patients with Non-ST Acute Coronary Syndrome.

Background and Objectives: Excessive coronary thrombus burden is known to cause an increase in mortality and major adverse cardiac events (MACEs) in NSTE-ACS (non-ST acute coronary syndrome) patients. We investigated the association between the systemic immune-inflammation index (SII) and coronary thrombus burden in patients with non-ST segment elevation myocardial infarction (NSTEMI) who underwent coronary angiography and percutaneous coronary intervention (PCI). Materials and Methods: A total of 389 patients with the diagnosis of NSTEMI participated in our study. Coronary thrombus burden was classified in the TIMI (thrombolysis in myocardial infarction) thrombus grade scale and patients were divided into two groups: a TIMI thrombus grade 0-1 group (n = 209, 157 males) and a TIMI thrombus grade 2-6 group (n = 180, 118 males). Demographics, angiographic lesion images, coronary thrombus burden, clinical risk factors, laboratory parameters, and SII score were compared between the two groups. Results: The high thrombus burden patient group had a higher neutrophil count, WBC count, platelet count, and systemic immune-inflammation index (SII) (p < 0.001). The receiver operating characteristic (ROC) curve analysis showed that at a cutoff of 1103, the value of SII manifested 74.4% sensitivity and 74.6% specificity for detecting a high coronary thrombus burden. Conclusions: Our study showed that the SII levels at hospital admission were independently associated with high coronary thrombus with NSTEMI.

Investigation of two-body wear behavior of zirconia-reinforced lithium silicate glass-ceramic for biomedical applications; in vitro chewing simulation.

The aim of this work was to the investigate two-body wear behavior of zirconia-reinforced lithium silicate glass-ceramic and composite resins through in vitro chewing simulation. Two types of glass-ceramics (IPS e.max CAD; lithium disilicate, Vita Suprinity; zirconia-reinforced lithium silicate) and two types of composite resins (Filtek Supreme; nano-filled, Ivoclar Vivadent Heliomolar; micro-filled) were used. All specimens were exposed to two-body wear tests using a dual-axis computer-controlled chewing simulation. Each chewing simulation test procedure, Al2O3 ball with a diameter of 6 mm, was used as antagonist material. The mean volume loss and wear depth of all specimens after the chewing tests were determined with use non-contact 3 D profilometer. Zirconia-reinforced lithium silicate Vita Suprinity had significantly higher two-body wear resistance than lithium disilicate IPS e.max CAD glass-ceramic and other composite resins after chewing tests. While Vita Suprinity exhibited a homogeneous crystal microstructure, IPS e.max CAD glass-ceramic exhibited a structure with needle-shaped fine-grained crystals embedded in a glassy matrix. As a result, the homogeneous distribution of zirconia particles into the ceramic material will increase the two-body wear resistance through chewing simulation tests.

Influence of lubricating conditions on the two-body wear behavior and hardness of titanium alloys for biomedical applications.

Commercially pure titanium and titanium alloys are often preferred in biomedical applications due to their high biocompatibility behavior. However, the inadequate wear, fatigue and corrosion resistance of titanium alloys limit their use as a biomaterial in the human body. Furthermore, these alloys may contain such as aluminum and vanadium elements that can damage the nervous system. The aim of this in vitro study was to evaluate the influence of lubrication conditions on the two-body wear behavior of pure titanium, Ti-2.5Si-5Zr, Ti-5Si-5Zr, and Ti-6Al-4V using dual-axis computer-controlled wear simulator device. The mean wear volume loss of all test specimens after the two-body wear test procedures were determined to use a non-contact 3D profilometer. The alloys hardness and microstructures were evaluated using the Vickers indention method, scanning electron microscopy (SEM), X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analysis. The hardness of Ti-6Al-4V titanium alloy material was significantly greater than the other alloy materials and cp-Ti. The mean wear volume loss of Ti-5Si-5Zr test specimens was lower than the other test group specimens irrespective of lubrication conditions. It was concluded, the two-body wear resistance of the alloy formed with the addition of silica to the pure titanium is increased after both wear test procedures. However, for the test materials in this study considered, correlations between the two-body wear resistance and hardness were found to be insignificant.