Mechanical properties of ion-releasing restorative materials.

PURPOSE: To evaluate and compare the laboratory compressive strength (CS), flexural strength (FS), and diametral tensile strength (DTS) of Cention Forte and three bulk fill restorative materials. METHODS: A total of 168 specimens were prepared following the manufacturers' instructions and standards for testing CS, FS, and DTS. Mechanical properties of Cention Forte (LC-Cent) were compared to three commercial bulk-fill materials for posterior restorations: Fuji IX Extra (Fuji), Tetric PowerFill (TPF), and Equia Forte HT (Equia). The tests were performed 24 hours after storage in distilled water on a universal testing machine at a crosshead speed of 0.75 mm/minute. Strength values (MPa) were calculated and statistically analyzed by one-way ANOVA and Tukey's post hoc test (P< 0.05). RESULTS: Analysis showed significant differences between tested materials for CS, FS, and DTS (P= 0.0001). LC-Cent showed the highest mean value for FS (112.8 MPa) with a significant difference compared to Fuji and Equia. DTS (49.2 MPa) of LC-Cent was significantly higher than all tested materials. TPF showed the highest mean value (180 MPa) for CS but without significant difference compared to LC-Cent. CLINICAL SIGNIFICANCE: Ion-releasing material Cention Forte, according to obtained results, may serve as a viable alternative for posterior restorations compared to conventional bulk-fill restorative materials.

Outage Analysis of Unmanned-Aerial-Vehicle-Assisted Simultaneous Wireless Information and Power Transfer System for Industrial Emergency Applications.

In the scenario of a natural or human-induced disaster, traditional communication infrastructure is often disrupted or even completely unavailable, making the employment of emergency wireless networks highly important. In this paper, we consider an industrial Supervisory Control and Data Acquisition (SCADA) system assisted by an unmanned aerial vehicle (UAV) that restores connectivity from the master terminal unit (MTU) to the remote terminal unit (RTU). The UAV also provides power supply to the ground RTU, which transmits the signal to the end-user terminal (UT) using the harvested RF energy. The MTU-UAV and UAV-RTU channels are modeled through Nakagami-m fading, while the channel between the RTU and the UT is subject to Fisher-Snedecor composite fading. According to the channels' characterization, the expression for evaluating the overall probability of outage events is derived. The impact of the UAV's relative position to other terminals and the amount of harvested energy on the outage performance is investigated. In addition, the results obtained based on an independent simulation method are also provided to confirm the validity of the derived analytical results. The provided analysis shows that the position of the UAV that leads to the optimal outage system performance is highly dependent on the MTU's output power.

Hydroxyapatite-based dental inserts: Microstructure, mechanical properties, bonding efficiency and fracture resistance of molars with occlusal restorations.

This study aimed to (1) comparatively analyze properties of Sr- and Mg-substituted hydroxyapatite (HAP)-based dental inserts; (2) evaluate insert bonding to restorative materials, and (3) evaluate the effect of doped HAP inserts on fracture resistance (FR) of human molars with large occlusal restorations. By ion-doping with Sr or Mg, 3 insert types were obtained and characterized using XRD, SEM, Vickers hardness and fracture toughness. Shear bond strength (SBS) was determined between acid etched or unetched inserts and following materials: Maxcem cement (Kerr); Filtek Z250 (3M) bonded with Single Bond Universal (SBU; 3M) or Clearfil Universal (Cf; Kuraray). Modified Class I cavities were prepared in 16 intact molars and restored using insert + composite or composite only (control) (n = 8/group). FR of restored molars was determined by static load until fracture upon thermal cycling. Fracture toughness was similar between Sr/Mg-doped inserts (0.94-1.04 MPam-1/2 p = .429). Mg-doped inserts showed greater hardness (range 4.78-5.15 GPa) than Sr6 inserts (3.74 ± 0.31 GPa; p < .05). SBS for SBU and Cf adhesives (range 7.19-15.93 MPa) was higher than for Maxcem (range 3.07-5.95 MPa) (p < .05). There was no significant difference in FR between molars restored with insert-containing and control restorations (3.00 ± 0.30 kN and 3.22 ± 0.42 kN, respectively; p > .05). HAP-based inserts doped with Mg/Sr had different composition and mechanical properties. Adhesive bonding to inserts resulted in greater bond strength than cementation, which may be improved by insert acid-etching. Ion-doped HAP inserts did not affect FR of restored molars. In conclusion, HAP-based dental inserts may potentially replace dentin in large cavities, without affecting fracture resistance of restored teeth.

Influence of Aging on the Flexural Strength of PLA and PLA-X 3D-Printed Materials.

The three-point bending test is a valuable method for evaluating the mechanical properties of 3D-printed biomaterials, which can be used in various applications. The use of 3D printing in specimen preparation enables precise control over material composition and microstructure, facilitating the investigation of different printing parameters and advanced materials. The traditional approach to analyzing the mechanical properties of a material using a three-point bending test has the disadvantage that it provides only global information about the material's behavior. This means that it does not provide detailed insight into the local strain distribution within the material. However, the 2D Digital Image Correlation (DIC) method offers additional insight, especially in terms of strain localization. DIC is an optical technique that measures full-field displacements and strains on the surface of a sample. PLA and enhanced PLA-X material were utilized to create three-point bending samples. The aim of this paper was to analyze and compare the influence of aging on the mechanical properties of PLA and enhanced PLA-X materials using three-point bending coupled with the DIC method. The results showed statistically significant differences between the PLA and PLA-X, for both the new and aged materials. The aged PLA samples had the highest average value of maximal force around 68 N, which was an increase of 8.8% compared to the new PLA samples. On the other hand, the aged PLA-X material had an increase of 7.7% in the average maximal force compared to the new PLA-X samples. When comparing the two materials, the PLA samples had higher maximal force values, 6.2% for the new samples, and 7.3% for the aged samples. The DIC results showed that both the new PLA and PLA-X samples endured higher strain values at Points 1 and 2 than the aged ones, except for the aged PLA-X sample at Point 2, where the new sample had higher strain values. However, for the first 5 min of the experiment, both materials exhibited identical behavior, after which point significant differences started to occur for both materials, as well as at Points 1 and 2. A more profound comprehension of the biomechanical characteristics of both PLA and PLA-X material is essential to enhance the knowledge for potential biomedical applications. The DIC method was found to be a powerful tool for analyzing the deformation and failure behavior of samples and for complementing the traditional approach to material testing.

Compressive strains and displacement in a partially dentate lower jaw rehabilitated with two different treatment modalities.

BACKGROUND: Understanding of the biomechanical consequences of the stresses generated to the supporting bone during occlusal loading is significant for improving the design and clinical planning process in partial edentulism therapy. OBJECTIVE: The aim of this study was to analyse the distribution of strain and displacement on the partially dentate lower jaw rehabilitated with an partial denture (RPD) and to compare it to the strain and displacement distribution on a partially dentate lower jaw rehabilitated with a cantilever fixed partial denture (FPD). MATERIAL AND METHODS: The experimental models were a partially dentate mandible with full-arch PFM crowns and RPD and a partially dentate mandible rehabilitated with a full-arch cantilever FPD. Strains and displacement were measured using the Digital Image Correlation Method. RESULTS: Displacement values of the first experimental model ranged from 0.31 to 0.54 mm with strains from 1.35 to 2.34%. Analysis of the second experimental model results showed displacement values from 0 to 0.34 mm, while strains were in the range of 0-1.40%. CONCLUSION: Higher displacements and strains of bone tissue were observed below the RPD, especially in the region of the distal abutment and distal portion of the free-end saddle. Strains within bone and the bone-denture contact area were mostly influenced by the teeth and denture vertical displacement.

Optical aspect of deformation analysis in the bone-denture complex.

The aim of this study was to register and measure any deformation of mandible models under load. The method for full field measurement of strain is done by using the ARAMIS three-dimensional image correlation system. The system uses two digital cameras that provide a synchronized stereo view of the specimen and the results show the complete strain field during the tests. The biggest deformation values were just under the working force of the biggest intensity 500 N, and for the region of the lower second premolar the deformation is 625 microm. The following study is presented that highlight the use of stereometric measuring system for modern research. It is shown that this measuring methodology can capture the trends of the experiments.

Emerging Standards and the Hybrid Model for Organizing Scientific Events During and After the COVID-19 Pandemic.

Since the beginning of 2020, the coronavirus disease (COVID-19) pandemic has dramatically influenced almost every aspect of human life. Activities requiring human gatherings have either been postponed, canceled, or held completely virtually. To supplement lack of in-person contact, people have increasingly turned to virtual settings online, advantages of which include increased inclusivity and accessibility and a reduced carbon footprint. However, emerging online technologies cannot fully replace in-person scientific events. In-person meetings are not susceptible to poor Internet connectivity problems, and they provide novel opportunities for socialization, creating new collaborations and sharing ideas. To continue such activities, a hybrid model for scientific events could be a solution offering both in-person and virtual components. While participants can freely choose the mode of their participation, virtual meetings would most benefit those who cannot attend in-person due to the limitations. In-person portions of meetings should be organized with full consideration of prevention and safety strategies, including risk assessment and mitigation, venue and environmental sanitation, participant protection and disease prevention, and promoting the hybrid model. This new way of interaction between scholars can be considered as a part of a resilience system, which was neglected previously and should become a part of routine practice in the scientific community.

The effect of time on mechanical properties of biocompatible photopolymer resins used for fabrication of clear dental aligners.

Clear dental aligners are used for treating orthodontic anomalies (misaligned teeth, inappropriate contact between upper and lower teeth etc.), minor irregularities and bruxism. Using additive manufacturing technologies clear dental aligners are made of biocompatible photopolymer, using a vat photopolymerization technology. One of problems in application is the change of aligner material properties after production, including strength and elongation at failure. This can cause different sequence of tooth displacement which will not correspond to the planned therapy. In this paper three types of material testing are conducted i.e., tensile, compressive and three-point bending testing on specimens of 1 (24 h), 3 (72 h), 5 (120 h) and 7 (168 h) days old. Mechanical properties, such as tensile, compressive and flexural strength and strain at failure are monitored in order to show the effect of time on biocompatible photopolymer resin.

Determination of the Actual Stress-Strain Diagram for Undermatching Welded Joint Using DIC and FEM.

This paper presents new methodology for determining the actual stress-strain diagram based on analytical equations, in combination with numerical and experimental data. The first step was to use the 3D digital image correlation (DIC) to estimate true stress-strain diagram by replacing common analytical expression for contraction with measured values. Next step was to estimate the stress concentration by using a new methodology, based on recently introduced analytical expressions and numerical verification by the finite element method (FEM), to obtain actual stress-strain diagrams, as named in this paper. The essence of new methodology is to introduce stress concentration factor into the procedure of actual stress evaluation. New methodology is then applied to determine actual stress-strain diagrams for two undermatched welded joints with different rectangular cross-section and groove shapes, made of martensitic steels X10 CrMoVNb 9-1 and Armox 500T. Results indicated that new methodology is a general one, since it is not dependent on welded joint material and geometry.

International Scientific Collaboration Is Needed to Bridge Science to Society: USERN2020 Consensus Statement.

Scientific collaboration has been a critical aspect of the development of all fields of science, particularly clinical medicine. It is well understood that myriads of benefits can be yielded by interdisciplinary and international collaboration. For instance, our rapidly growing knowledge on COVID-19 and vaccine development could not be attained without expanded collaborative activities. However, achieving fruitful results requires mastering specific tactics in collaborative efforts. These activities can enhance our knowledge, which ultimately benefits society. In addition to tackling the issue of the invisible border between different countries, institutes, and disciplines, the border between the scientific community and society needs to be addressed as well. International and transdisciplinary approaches can potentially be the best solution for bridging science and society. The Universal Scientific Education and Research Network (USERN) is a non-governmental, non-profit organization and network to promote professional, scientific research and education worldwide. The fifth annual congress of USERN was held in Tehran, Iran, in a hybrid manner on November 7-10, 2020, with key aims of bridging science to society and facilitating borderless science. Among speakers of the congress, a group of top scientists unanimously agreed on The USERN 2020 consensus, which is drafted with the goal of connecting society with scientific scholars and facilitating international and interdisciplinary scientific activities in all fields, including clinical medicine.

3D Digital Image Correlation Analysis of the Shrinkage Strain in Four Dual Cure Composite Cements.

The introduction of resin-based cements and an adhesive-bonding system in daily dental practice has given the opportunity to increase the retention of previously conventional cemented restorations and the optimal results in esthetic. This experimental study employed the 3D Digital Image Correlation Method (3D-DIC) for detecting shrinkage strain in four dual cured composite cements. The aim was to visualize measure, analyze, and compare strain fields in four resin-based cements using the 3D-DIC method. A total of 72 samples were divided into 4 groups considering variations in sample types, diameter, and thickness. Four types of composite cements: RelyX U200 (3 M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Multilink Automix (Ivoclar Vivadent, Schaan, Liechtenstein), and SeT PP (SDI, Australia) were used. Each type had diameters of 3 mm, 4 mm, and 5 mm, respectively, combined with two different values of thickness: 1 mm and 2 mm. Thickness had an important role on strain detected in all tested materials showing higher strain in samples with 2 mm thickness compared to 1 mm samples. Shrinkage strain values were the highest in Set PP samples indicated the possibility of undesirable de-bonding.

Local deformation fields and marginal integrity of sculptable bulk-fill, low-shrinkage and conventional composites.

OBJECTIVE: To compare strain and displacement of sculptable bulk-fill, low-shrinkage and conventional composites as well as dye penetration along the dentin-restoration interface. METHODS: Modified Class II cavities (N=5/group) were filled with sculptable bulk-fill (Filtek Bulk Fill Posterior, 3M ESPE; Tetric EvoCeram Bulk Fill, Ivoclar Vivadent; fiber-reinforced EverX Posterior, GC; giomer Beautifil Bulk, Schofu), low-shrinkage (Kalore, GC), nanohybrid (Tetric EvoCeram, Ivoclar Vivadent) or microhybrid (Filtek Z250, 3M ESPE) composites. Strain and displacement were determined using the 3D digital image correlation method based on two cameras with 1µm displacement sensitivity and 1600×1200 pixel resolution (Aramis, GOM). Microleakage along dentin axial and gingival cavity walls was measured under a stereomicroscope using a different set of teeth (N=8/group). Data were analyzed using analyses of variance with Tukey's post-test, Pearson correlation and paired t-test (α=0.05). RESULTS: Strain of TEC Bulk, Filtek Bulk, Beautifil Bulk and Kalore was in the range of 1-1.5%. EverX and control composites showed 1.5-2% strain. Axial displacements were between 5µm and 30µm. The least strain was identified at 2mm below the occlusal surface in 4-mm but not in 2-mm layered composites. Greater microleakage occurred along the gingival than axial wall (p<0.05). No correlation was found between strain/displacements and microleakage axially (r2=0.082, p=0.821; r2=-0.2, p=0.605, respectively) or gingivally (r2=-0.126, p=0.729, r2=-0.278, p=0.469, respectively). SIGNIFICANCE: Strain i.e. volumetric shrinkage of sculptable bulk-fill and low-shrinkage composites was comparable to control composites but strain distribution across restoration depth differed. Marginal integrity was more compromised along the gingival than axial dentin wall.

Effects of a low-shrinkage methacrylate monomer and monoacylphosphine oxide photoinitiator on curing efficiency and mechanical properties of experimental resin-based composites.

This study investigated the degree of conversion, depth of cure, Vickers hardness, flexural strength, flexural modulus and volumetric shrinkage of experimental composite containing a low shrinkage monomer FIT-852 (FIT; Esstech Inc.) and photoinitiator 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO; Sigma Aldrich) compared to conventional composite containing Bisphenol A-glycidyl methacrylate (BisGMA) and camphorquinone-amine photoinitiator system. The degree of conversion was generally higher in FIT-based composites (45-64% range) than in BisGMA-based composites (34-58% range). Vickers hardness, flexural strength and modulus were higher in BisGMA-based composites. A polywave light-curing unit was generally more efficient in terms of conversion and hardness of experimental composites than a monowave unit. FIT-based composite containing TPO showed the depth of cure below 2mm irrespective of the curing light. The depth of cure of FIT-based composite containing CQ and BisGMA-based composites with either photoinitiator was in the range of 2.8-3.0mm. Volumetric shrinkage of FIT-based composite (0.9-5.7% range) was lower than that of BisGMA-based composite (2.2-12% range). FIT may be used as a shrinkage reducing monomer compatible with the conventional CQ-amine system as well as the alternative TPO photoinitiator. However, the depth of cure of FIT_TPO composite requires boosting to achieve clinically recommended thickness of 2mm.

Profile for body fat percentage of Serbian working population, aged from 18 to 65, measured by multichannel bioimpedance method / Perfil del porcentaje de grasa corporal de la población activa serbia, de 18 a 65 años, medido por el método de bioimpedancia multicanal

SUMMARY: Obesity prevalence and trends of PBF related to age were defined on a sample of 8100 people among whom, 4955 were male (Age = 31.2 ± 10 yr) and 3145 were female (Age = 32.1 ± 11.3 yr). Body structure measurements were performed using a standardized method of multichannel bioimpedance analysis (BIA), using a body structure analyzer - InBody 720. The total sample was divided into two subsamples according to sex, where every subsample was divided into five different age groups.The mean PBF values of the Male total sample were 18.2 ± 8.0 % and the female total sample was 28.3 ± 9.2 %. Results of Kruskal-Wallis ANOVA with Dwass-Steel-Critchlow-Fligner post-hock showed that there are statistically significant differences (p < 0.001) between all age groups among themselves except groups 50 - 60 and 60 - 65 (p = 0.09). Analysis of obesity prevalence according to the PBF indicator in different age groups revealed the existence of statistically significant (p < 0.001) trends of increasing obesity with age, both in men and women. Based on the result of this study, it can be concluded that most of the Serbian working population are in the range of normal PBF values, excluding the male 30-39.9 yr and female 60-65 yr age categories as groups which are more prone to obesity levels.

RESUMEN: La prevalencia de obesidad y las tendencias de PBF relacionadas con la edad se determinaron en una muestra de 8100 personas, de las cuales 4955 eran hombres (Edad = 31,2 ± 10 años) y 3145 eran mujeres (Edad = 32,1 ± 11,3 años). Las mediciones de la estructura corporal se realizaron utilizando un método estandarizado de análisis de bioimpedancia multicanal (BIA), usando un analizador de estructura corporal - InBody 720. La muestra total se dividió en dos submuestras, según el sexo, donde cada muestra se dividió en cinco grupos de edad diferentes. Los valores de PBF de la muestra total masculina fueron 18,2 ± 8,0% y la muestra total femenina fue 28,3 ± 9,2%. Los resultados del ANOVA de Kruskal-Wallis con Dwass-Steel-Critchlow- Fligner post-corvejón mostraron que existían diferencias estadísticamente significativas (p <,001) entre todos los grupos de edad, excepto los grupos 50 - 60 y 60 - 65 (p = 0.09). El análisis de la prevalencia de obesidad según el indicador PBF en diferentes grupos de edad, reveló la existencia de tendencias estadísticamente significativas (p < 0,001) de un aumento de la obesidad con la edad, tanto en los hombres como en las mujeres. Con base en el resultado de este estudio, se puede concluir que la mayoría de la población activa de Serbia se encuentra en el rango de valores normales de PBF, excluyendo las categorías de edad de hombres de 30 a 39,9 años y de mujeres de 60 a 65 años, como los grupos que son más propensos a los niveles de obesidad.

Bond strength of restorative materials to hydroxyapatite inserts and dimensional changes of insert-containing restorations during polymerization.

OBJECTIVE: To determine the shear bond strength (SBS) between synthetic controlled porous hydroxyapatite (HAP) inserts and restorative materials and dimensional changes of insert-containing restorations during curing. METHODS: Cylinder-shaped HAP inserts (4mm in diameter, 1.6mm thick) were cemented in dentin discs (5mm×1.6mm), cut mid-coronally from human third molars, using one of the following materials: universal microhybrid composite Filtek Z250, flowable composite Filtek Ultimate or glass-ionomer Vitrebond (all 3M ESPE). SBS of the same materials to HAP inserts was tested in a universal testing machine. Three-dimensional digital image correlation system Aramis (GOM) was used to measure strains and displacements. Data were statistically analyzed using one-way ANOVA with Tukey's post-test (α=0.05). RESULTS: SBS of restorative materials to HAP inserts ranged between 12.2±2.1MPa (Filtek Z250) and 0.7±0.4MPa (Filtek Z250 without an adhesive). The 'total-etch' approach of adhesive application significantly increased SBS of both Filtek Z250 (12.2±2.1MPa) and Filtek Ultimate flowable (9.5±2.5MPa) compared to the 'self-etch' approach (8.2±1.6MPa and 4.4±0.9MPa, respectively) (p<0.05). HAP inserts reduced polymerization shrinkage to below 0.5% as well as displacements in the central region of the restorations. Peripheral shrinkage of restorative materials was similar with and without HAP inserts as were displacements of Filtek Z250 and Vitrebond. SIGNIFICANCE: Replacing major part of dentin clinically, especially in large cavities, HAP inserts may shorten clinical working time, improve dimensional stability of the restoration by reducing central shrinkage and displacements and provide adhesive bonding to universal composites following a 'total-etch' approach.

Betapapillomaviruses in the anal canal of HIV positive and HIV negative men who have sex with men.

BACKGROUND: Betapapillomaviruses (ß-PV) are etiologically associated with epidermodysplasia verruciformis and a proportion of skin precancerous lesions and cancer, mainly in immunocompromised individuals. OBJECTIVES: The prevalence and persistence of anal ß-PV infection and ß-PV type distribution were determined in a cohort of men who have sex with men (MSM). A correlation with HIV-1 infection status and selected demographic and behavioral risk factors were additionally established. STUDY DESIGN: A total of 181 anal swabs (135 initial and 46 follow-up swabs) obtained from 135 Slovenian MSMs (17.0% HIV-1 positive) were tested for the presence of 25 different ß-PV types using Diassay RHA Kit Skin (beta) HPV assay and, if negative, with an in-house nested M(a)/H(a) PCR. RESULTS: ß-PVs were detected in 88/135 (65.2%) initial anal swabs. Infection with multiple ß-PV types was found in 26 samples; the number of ß-PVs ranged from 2 to 9. A total of 29 distinct ß-PVs were detected: HPV-36 and HPV-38 were the most prevalent, followed by HPV-23, HPV-24, and HPV-93. HIV-1 positive status, promiscuity and use of alkyl nitrites were significantly associated with a higher prevalence of anal ß-PV infection. Three partial DNA sequences suggesting putative new HPV types were identified. CONCLUSION: To the best of our knowledge, this is the first study to investigate and characterize ß-PV infections in the anal region. We showed that anal ß-PV infection is highly prevalent in the MSM population and that ß-PVs can establish persistent infection in the anal region for up to 4.8 years.

Analysis of local shrinkage patterns of self-adhering and flowable composites using 3D digital image correlation.

OBJECTIVE: To analyze local shrinkage patterns in terms of surface shrinkage strains and z-axis displacements in a novel self-adhering composite and a conventional flowable composite using three-dimensional digital image correlation. METHOD AND MATERIALS: Seven samples of each material were prepared in cylindrical Teflon molds 5 mm in diameter and 2 mm thick. The surface of the composites facing the cameras was sprayed with a fine layer of black paint. The unsprayed surface of each sample, opposite the one facing the cameras, was light cured for 40 seconds using a light-emitting diode unit. Digital images were taken immediately before and after light curing. Shrinkage was calculated as von Mises strains, and z-axis displacements were measured in microns. The data were statistically analyzed using two-way ANOVA at a = .05. RESULTS: No significant difference in strain was observed between the two materials (P > .05). Strain distribution was nonhomogenous--the outer segments showed significantly higher strains than central parts in each material (P < .05). The opposite was observed for z-axis displacements-significantly greater displacements were found in central parts compared to the outer segments (P < .05). CONCLUSION: Different shrinkage vectors across the surface of the tested flowable composites showed predominant in-plane shrinkage of the outer surface segments and out-of-plane shrinkage of the inner segments. These complex local deformation patterns in composite materials indicate zones of different types of forces exerted on the tooth-restoration interface in situ.