Pouzdanost primene konvencionalnih ključeva za određivanje boje zuba

Background/Aim. Color matching in prosthodontic therapy is a very important task because it influences the esthetic value of dental restorations. Visual shade matching represents the most frequently applied method in clinical practice. Instrumental measurements provide objective and quantified data in color assessment of natural teeth and restorations. In instrumental shade analysis, the goal is to achieve the smallest ΔE value possible, indicating the most accurate shade match. The aim of this study was to evaluate the reliability of commercially available ceramic shade guides. Methods. VITA Easyshade spectrophotometer (VITA, Germany) was used for instrumental color determination. Utilizing this device, color samples of ten VITA Classical and ten VITA 3D - Master shade guides were analyzed. Each color sample from all shade guides was measured three times and the basic parameters of color quality were examined: ΔL, ΔC, ΔH, ΔE, ΔElc. Based on these parameters spectrophotometer marks the shade matching as good, fair or adjust. Results. After performing 1,248 measurements of ceramic color samples, frequency of evaluations adjust, fair and good were statistically significantly different between VITA Classical and VITA 3D Master shade guides (p = 0.002). There were 27.1% cases scored as adjust, 66.3% as fair and 6.7% as good. In VITA 3D - Master shade guides 30.9% cases were evaluated as adjust, 66.4% as fair and 2.7% cases as good. Conclusion. Color samples from different shade guides, produced by the same manufacturer, show variability in basic color parameters, which once again proves the lack of precision and nonuniformity of the conventional method.Uvod/Cilj. Određivanje boje zuba u protetskoj terapiji predstavlja veoma važan zadatak jer utiče na prirodan izgled i estetsku vrednost zubnih nadoknada. Vizuelni metod određivanja boje zuba najčešće se koristi u kliničkoj praksi. Instrumentalna merenja pružaju objektivne i kvantifikovane podatke u proceni boje prirodnih zuba i restauracija. U instrumentalnoj analizi boje cilj je da se postigne najmanja moguća vrednost ΔE, što predstavlja najtačniji izbor nijanse. Cilj ovog istraživanja bio je da se utvrdi pouzdanost najčešće korišćenih ključeva za određivanje boje zuba. Metode. Za instrumentalni izbor boje korišćen je VITA Easyshade spektrofotometar (VITA, Germany). Uz pomoć ovog uređaja, analizirani su uzorci boja 10 VITA Classical i 10 VITA 3D - Master ključeva boja. Svaki uzorak boje analiziran je tri puta i ispitivani su osnovni parametri kvaliteta boje: ΔL, ΔC, ΔH, ΔE, ΔElc. Stepen poklapanje boje nadoknade sa ciljnom nijansom spektrofotometar izražava kroz tri ocene kvaliteta: good, fair i adjust. Rezultati. Nakon izvršenih 1 248 merenja keramičkih uzoraka boje, frekvencije ocena adjust, fair i good statistički su se značajno razlikovale između VITA Classical i VITA 3D - Master ključeva boja (p = 0.002). U VITA Classical ključu boja bilo je 27,1% ocene adjust, 66,3% fair i 6,7% ocene good. U VITA 3D - Master ključu boja bilo je 30,9% ocene adjust, 66,4% fair i 2,7% ocene good. Zaključak. Uzorci boje iz različitih ključeva boja proizvedenih od istog proizvođača, pokazuju varijabilnost u osnovnim parametrima boje, što ukazuje na nepreciznost i neuniformnost konvencionalne metode

Density functional theory calculation of the optical properties of graphene quantum dots

Graphene quantum dots (GQDs) are class of nanoparticles exhibiting unique and tunable electronic, optical, chemical and structural properties owing to their small size and quantum confinement and edge effects. GQDs most prominent characteristics are high photoluminescence, photostability, excellent photobleaching resistance, low citotoxicity, good biocompatibility, exceptional electrochemical activity and physicochemical stability, making them suitable for a wide range of applications, from biosensing and fluorescence bioimaging usage, photodynamic therapy, to optoelectronic, susteanable agricultural and environmental applications. Using density functional theory (DFT) we demonstrate that the optical properties of the GQDs can be sensitively tuned by its size, shape, edge configuration, attached chemical functionalities.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Promene biohemijskog sastava salive kod dijabetičara

Introduction: Diabetic patients, beside numerous acute and chronic complications, often have oral manifestations of the disease. Aim: The aim of the study was to establish changes in saliva of diabetic patients in relation to healthy population in order to use saliva in the disease monitoring, as well as the changes depending on the type of diabetes. Materials and methods: The study comprised 52 adult patients of both sexes and at the age between 18 and 79 with Diabetes mellitus type 1 and 2 who were treated at the Institute for endocrinology, diabetes and metabolic disorders of the Clinical center of Serbia. The control group consisted of 67 volunteers from Belgrade, students at the School of Dentistry, aged between 19 and 24. The whole of unstimulated and stimulated saliva was collected and biochemical parameters (glucose, total proteins, albumin, sodium and potassium) were determined by methods commonly used for serum. Results: The results showed that salivary potassium level was increased in saliva of diabetic patients, that of sodium and total proteins was decreased, and glucose and albumin did not show changes compared to the control group. Concentrations of total proteins and potassium were higher in patients with DM type 2, and sodium was higher in DM type 1 (p = 0.05). Conclusion: Diabetic patients often have changes in biochemical composition of saliva.Uvod: Kod obolelih od Diabetes mellitus-a (DM), pored brojnih akutnih i hroničnih komplikacija, dolazi i do poremećaja oralne homeostaze. Cilj: Cilj rada bio je da se utvrde promene u biohemijskom sastavu salive dijabetesnih bolesnika u odnosu na zdravu populaciju radi eventualnog korišćenja salive u praćenju toka bolesti, odnosno da se utvrde promene u salivi u odnosu na tip dijabetesa. Materijal i metode: Istraživanje je obuhvatilo 52 odrasla pacijenta oba pola, uzrasta 18-79 godina, obolelih od DM - tip 1 i tip 2, lečenih na Institutu za endokrinologiju, dijabetes i bolesti metabolizma Kliničkog centra Srbije. Kontrolnu grupu činilo je 67 dobrovoljaca iz Beograda, studenata Stomatološkog fakulteta u Beogradu, uzrasta 19-24 godine. Sakupljana je ukupna nestimulisana i stimulisana saliva, a biohemijski parametri (glukoza, ukupni proteini, albumin, natrijum i kalijum) određeni su referentnim metodama za serum. Rezultati: Dobijeni rezultati su pokazali da je u salivi obolelih od dijabetesa koncentracija kalijuma povišena, koncentracija natrijuma i ukupnih proteina snižena, a glukoze i albumina nepromenjena u odnosu na kontrolnu grupu. Koncentracije proteina i kalijuma više su kod obolelih od DM tip 2 nego kod DM tip 1, a koncentracija natrijuma viša je kod DM tip 1 (p = 0.05). Zaključak: Biohemijski sastav salive je ukazao na promene kod dijabetesnih bolesnika

Innovative modifications of graphene quantum dots for improved photodynamic therapy in antibacterial treatment

Considering the rising concern of antibiotic resistance, developing advanced antibacterial solutions is highly needed. The ability of graphene quantum dots (GQDs) to generate reactive oxygen species (ROS) upon light exposure made them promising candidates as agents in photodynamic therapy for combatting infections, including antibiotic-resistant strains. GQDs show versatile chemical, physical, and biological properties such as high fluorescent activity, resistance to photo-bleaching, low toxicity, excellent solubility, and biocompatibility. This research focused on exploring the ability of GQDs to produce singlet oxygen under blue light exposure. We used two singlet oxygen probes, 9,10-anthracenediylbis(methylene) dimalonic acid and 1,3-diphenylisobenzofuran to study photoinduced production radicals from several GQDs. To tune the ability of GQDs to generate ROS, we used gamma irradiation in two different media, the presence of L-cysteine and cyclopentanone. The results showed improvements in singlet oxygen production in both cases. However, the modification conducted with cyclopentanol showed notably higher efficacy in promoting singlet oxygen production. This research demonstrates the increasing significance of GQDs in discovering new methods to combat bacteria. The modification of GQDs with gamma irradiation leads to increased production of singlet oxygen enhancing the effectiveness of photodynamic therapy for treating infections.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Self-assembly of carbon based nanoparticles films by Langmuir-Blodgett method

Carbon nanoparticles are a class of materials with extraordinary properties. In the past three decades, four major types of carbon nanoparticles were synthesized and investigated: fullerenes, carbon nanotubes, graphene and carbon quantum dots. One of the main properties of such materials is their hydrophobic nature. At the same time, Langmuir–Blodgett (LB) method the for deposition of thin films of hydrophobic materials provides the possibility to design thin films of different carbon-based nanoparticles with special architectures and features enabling their usage in various fields, particularly in electronics and biomedicine. In this review, the state of art of LB thin films of four types of carbon-based nanoparticles and their application in electronics and biomedicine are presented. The breakthrough in this field was finally achieved by application of carbon quantum dots soluble in solvents optimized for LB deposition

The influence of tip sonication on structural and morphological properties of graphene

Although ultrasound is frequently used to disperse carbon nanomaterials in suitable solvents, the propagation of high-amplitude ultrasonic vibrations from the tip sonicator was found to be aggressive and has the potential to break down graphene sheets. Here, the effects of tip sonication time on structural and morphological properties of two types of graphene (graphene oxide and electrochemically exfoliated graphene) was investigated by UV-vis spectroscopy and Atomic Force Microscopy. It was found that the structural composition of the graphene was not affected by ultrasounds emitted from the tip sonicator even for the prolonged period of sonication (60 min). Microscopy analysis showed an increased portion of smaller graphene sheets in the sonicated samples for both types of graphene as a result of graphene sheet fragmentation caused by tip sonication

Fungicide sensitivity of selected Verticillium fungicola isolates from Agaricus bisporus farms

Five isolates of Verticillium fungicola, isolated from diseased fruiting bodies of Agaricus bisporus collected from mushroom farms in Serbia during 2002-2003, were studied. By observing their colony morphology under different growth conditions and their pathogenic characteristics, the isolates were identified as V. fungicola var. fungicola. The peat/lime casing was the primary source of infection. Testing of sensitivity to selected fungicides showed that all isolates were highly resistant to benomyl (EC50 values were higher than 200.00 mg/l), moderately sensitive to iprodione (EC50 values were between 11.93 and 22.80 mg/l), and highly sensitive to prochloraz-Mn (EC50 values were less than 3.00 mg/l)

Races and hosts of Pseudomonas syringae pv. tomato in Serbia

During the past few years, frequent appearance of bacterial speck of tomatoes was recorded in several tomato-growing regions in Serbia. A three-year survey of tomato fields in Serbia (2002-2004) resulted in the isolation of numerous bacterial strains, with 30 representative strains selected for further analyses. Based on the results of pathogenicity, biochemical, and physiological tests, all strains isolated from diseased tomato plants were identified as P. syringae pv. tomato. The identity of strains was confirmed by the polymerase chain reaction (PCR), since PCR products of expected size (650 bp) specific for coronatine-producing strains of P. syringae pv. tomato were amplified from all tested strains. Study of the host range of P. syringae pv. tomato strains originating from Serbia confirmed tomato as the sole host. The reaction of tomato differential cultivar Ontario 7710 showed that the Serbian strains belonged to races 0 and 1 of P. syringae pv. tomato

Plasmon induced enhancement of photoinduced antibacterial activity of graphene quantum dots

Due to the exponential growth of bacterial infection as well as resistance toward most antibiotics, the development of new materials for treatment is urgently needed. In recent years, graphene quantum dots (GQDs) have been identified as promising carbon nanomaterial for eco-friendly antibacterial applications due to their optical and chemical stability, non-toxicity, and biocompatibility. One of the reported GQD’s antimicrobial mechanisms is the photo-induced production of singlet oxygen (1O2). Under light exposure, GQDs transfer the energy to molecular oxygen from the surrounding medium. Oxygen molecules transform to their excited form 1O2, which causes oxidative stress in bacterial cells and reduces their viability. In this study, pristine GQDs were produced in an easy, one-step electrochemical top-down approach using graphite electrodes as a starting material. Carboxyl groups of GQDs are modified using a carbodiimide coupling reaction catalyzed by 1-ethyl-3- (3-dimethylaminopropyl)carbodiimide (EDC), with ethylenediamine (EDA) as an amine. In the next step, these NH2 terminated dots were decorated with gold nanoparticles (AuNPs) by the same EDC coupling procedure. Abillity of GQDs-AuNP nanocomposite to generate singlet oxygen upon blue light (470 nm) was investigated by UV-Vis spectroscopy and 9,10- anthracenediylbis-(methylene)dimalonic acid (ABDA) as selective 1O2 traping agent. After 2 hours of blue light illumination, the band at 420 nm charachterisic for ABDA was completly disaperided only in the presence of the GQD-AuNPs indicating good prooxidative potential of composite. Photoinduced antibacterial effects of GQD-AuNPs were studied using minimum inhibitory concentration (MIC) test which showed great antibacterial activity against several bacterial strains.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi