Initial Block Research Articles

Comprehensive repair of the alveolar cleft using cortical and cancellous bone layers: A retrospective study

To retrospectively review the clinical effect of comprehensive treatment of alveolar cleft (CTAC) using the mandible as the bone source.Patients with alveolar clefts who met the inclusion criteria were subjected to a CTAC protocol that included the following: (1) preoperative orthodontic treatment for creating good soft-tissue conditions; (2) ‘area-like grafting’ with subperiosteal osteogenic chin bone instead of cartilaginous osteogenic iliac bone; (3) simulation of normal bone anatomy via a sandwich-like bone graft consisting of ‘cortical bone + cancellous bone + cortical bone’; and (4) strong internal fixation to ensure initial bone block stability. At 6 months postoperatively, the titanium plate was removed and cone-beam computed tomography was performed to evaluate the surgical results.A total of 54 patients underwent treatment with the CTAC protocol. The average age at the initial operation was 10.3 ± 2.1 years, and the average hospital stay was 2.8 ± 0.6 days. At 6 months postoperatively, 49 patients (90.7%) showed good clinical results. The transplanted bone block formed a ‘cortical bone + cancellous bone + cortical bone’ structure similar to that of the normal jawbone. A mature bone bridge formed, and the impacted permanent teeth continued to erupt and enter the bone graft area.CTAC is a comprehensive restorative solution for alveolar cleft repair that integrates multiple concepts, including orthodontics, embryology, anatomy, and improvements to surgical methods. The method is easy to perform, causes little surgical trauma, and shows a stable success rate, and is thus worth promoting.

Chaotic Multiple-Image Encryption Algorithm Based on Block Scrambling and Dynamic DNA Coding

In this paper, a chaotic multiple-image encryption algorithm using block scrambling and dynamic DNA coding is designed. The algorithm can achieve simultaneous encryption of many different types of images. Firstly, a new block scrambling algorithm is proposed, which is divided into two scrambling modes according to the size of the initial block. And it combines with the cyclic shift operation to achieve scrambling. Secondly, dynamic DNA coding is utilized to diffuse images, which enhances the complexity and security of the proposed multiple-image encryption algorithm. Through the analysis of key space, correlation, information entropy, histogram, differential attacks and robustness, it is verified that the algorithm is safe and effective. Experimental results show that the new multiple-image encryption algorithm is suitable for multiple color and gray images encryption. The algorithm has excellent encryption performance, and can be applied in secure communication.

Effect of Orem's self-care model on the quality of life in adolescents with diabetes type 1: A randomized clinical trial

The present study aims to determine the effect of Orem's self-care model on the quality of life in adolescents with diabetes type 1. A randomized controlled trial was conducted at Guilan University of Medical Sciences in Rasht, Iran. Adolescents diagnosed with type 1 diabetes constituted the study's participants. The research enrolled 80 diabetic patients, divided randomly into two groups: the control group and the intervention group. The study employed four blocks labeled A, B, C, and D, selecting the initial block through a lottery-based method. The intervention group received a series of eight training sessions structured by the Orem’s self-care model. In contrast, the control group received standard routine education without the structured sessions aligned with the aforementioned model. The data collection instruments used in this study comprised a demographic information questionnaire, an Orem’s health status questionnaire, and an SF-36 quality of life questionnaire. The study comprised 80 diabetic type 1 patients, with 40 assigned to the control group and 40 to the intervention group. The average age of the participants was 13.40 (SD=2.25). Notably, a substantial difference was observed in the change of scores about the physical dimension between the intervention and control groups (P=0.03). Additionally, a significant disparity in mental dimension scores was observed between the intervention and control groups (P=0.02). Our investigation demonstrated that the development and execution of an educational training program grounded in the Orem's self-care model yielded an enhancement in the quality of life among adolescent patients diagnosed with type 1 diabetes.

Overreliance on inefficient computer-mediated information retrieval is countermanded by strategy advice that promotes memory-mediated retrieval

With ubiquitous computing, problems can be solved using more strategies than ever, though many strategies feature subpar performance. Here, we explored whether and how simple advice regarding when to use which strategy can improve performance. Specifically, we presented unfamiliar alphanumeric equations (e.g., A + 5 = F) and asked whether counting up the alphabet from the left letter by the indicated number resulted in the right letter. In an initial choice block, participants could engage in one of three cognitive strategies: (a) internal counting, (b) internal retrieval of previously generated solutions, or (c) computer-mediated external retrieval of solutions. Participants belonged to one of two groups: they were either instructed to first try internal retrieval before using external retrieval, or received no specific use instructions. In a subsequent internal block with identical instructions for both groups, external retrieval was made unavailable. The ‘try internal retrieval first’ instruction in the choice block led to pronounced benefits (d = .76) in the internal block. Benefits were due to facilitated creation and retrieval of internal memory traces and possibly also due to improved strategy choice. These results showcase how simple strategy advice can greatly help users navigate cognitive environments. More generally, our results also imply that uninformed use of external tools (i.e., technology) can bear the risk of not developing and using even more superior internal processing strategies.

COVID-Attention: Efficient COVID19 Detection Using Pre-trained Deep Models Based on Vision Transformers and X-ray Images

COVID19 is becoming more and more threatening to human life since the appearance of many variants like Alpha, Omicron and Delta. These variants have dozens of mutations that can make their diagnosis more challenging. Despite the recent success of Convolutional Neural Networks (CNN) to detect COVID19 automatically using transfer learning techniques, they are not the most robust to accomplish this task since some translation, scale and hyperparameter variations can affect the accuracy. Newly, Vision Transformers (ViT) are becoming increasingly popular to handle similar tasks and to deal with the aforementioned variations. In this paper, we propose an enhanced ViT architecture for COVID19 detection referred to as COVID-Attention. The proposed ViT-based models are robust due to their capability to capture long-range dependencies within images thanks to the attention mechanism, which is the core of the transformer block. We compare the efficiency of our proposed method to top-performing CNN baselines using two different transfer learning modes. We further show in our experiments that adding a convolution block to the top of the ViT model (i.e. as an initial block) can avoid the collapse issue and enhance the ViT performance using the recent ViTC model. We finally show that ViT-based models give more explainable visualization compared to CNN models using the Grad-CAM technique in order to highlight the attention map that affects the classification decision. Our experiments have been conducted on two recent databases of X-ray images and show high performance compared to the state-of-the-art methods in three-class classifications.

Influence of the Crystallization Firing Process on Marginal and Internal Adaptation of Silicate-based Glass-ceramic Inlays Fabricated With a CAD/CAM Chairside System.

Computer-aided design/computer-aided manufacturing (CAD/CAM) systems are widely used in dental treatment. Clinicians can use chairside CAD/CAM technology, which has the advantage of being able to fabricate inlays on the same day. We aimed to evaluate the effects of crystallization firing processes, fabrication methods (one-step and two-step), and materials on marginal and internal adaptations of silicate-based glass-ceramic all-ceramic inlays fabricated with CAD/CAM chairside systems. Ten artificial mandibular left first molars were prepared with standardized ceramic class II mesial-occlusal (MO) inlay cavities. Optical impressions were obtained using CEREC Omnicam Ban. IPS e-max CAD (IE), (Ivoclar Vivadent, Schaan, Liechtenstein), Initial LiSi Block (LS) (Hongo, Bunkyoku, Tokyo, Japan), VITA Suprinity (SP), (Vita Zahnfabrick, Bad Säckingen, Germany), and Celtra Duo (CD) (Ivoclar Vivadent, Schaan, Liechtenstein) (n=10) were milled using CEREC MC XL (Bensheim, Germany). IE and SP were crystallization-fired using CEREC Speed Fire. The silicone replica technique was used for the measurement of internal (axial and pulpal walls) and marginal (cervical and occlusal edge) adaptations. The adaptations were measured using a thin layer of light-body polyvinyl siloxane impression material placed between the master tooth inlay preparation and restoration. Marginal and internal adaptations of IE, LS, SP, and CD were measured using a stereomicroscope (500×). For IE and SP, marginal and internal adaptations were measured before and after the crystallization firing process. Data analyses were conducted using one-way ANOVA and the Tukey test. For IE and SP, marginal and internal adaptations before and after the crystallization firing process were analyzed using the t-test. The significance level was set at α=0.05. One-way ANOVA revealed statistically significant differences in occlusal and cervical edge marginal adaptations among the material groups (p<0.001). The Tukey HSD test revealed a significant difference in marginal occlusal and cervical edge adaptations between LS and CD groups and IE and SP groups (p≤0.05). For IE and SP inlays, the t-test revealed a significant difference between occlusal and cervical edge adaptations before the crystallization firing process and those after the crystallization firing process, with the latter group showing a more significant discrepancy in adaptation than the former group (p≤0.05). Fabrication methods (one- and two-step) affected the marginal adaptation compatibility but not internal compatibility of MO inlays. The crystallization firing process affected the marginal adaptation of inlays using lithium silicate or lithium disilicate glass-ceramics. However, adaptation to the cavity was considered clinically acceptable for all materials.

PSIV-17 Effect of Phytase Supplementation on Growth Performance, Bone Mineralization, Metabolism, and Excretion of Calcium and Phosphorous on Fattening Pigs Fed a Diet Containing no Inorganic Phosphate

Abstract Global concern about sustainability has led many countries to establish legislation to reduce phosphorus (P) pollution. Phytase application has evolved significantly in the last years, with greater dose rates leading to a greater reduction in inorganic P supplementation and decreased feeding costs. An experiment was conducted to determine the impact of 3 supplementary levels of phytase on pig growth performance, bone mineralization, and mineral excretion (P, Ca, and N) in corn/barley/wheat/SBM based diets containing no inorganic P. Crossbred [(Landrace x Large White) Duroc] pigs [n=137; initial body weight (BWi) = 16.8 ± 4.04 kg) were housed in 24 pens containing 5 or 6 pigs/pen) for 62-day trial. After a 21-day adaptation period, each pen was assigned one of three experimental treatments according to the dietary inclusion dose of the study phytase (Quantum Blue, AB Vista): 500, 800 and 1,500 FTU/kg feed. The feeding program was based on a single diet that was pelleted and formulated according to FEDNA (2013) recommendations. The basal diet was designed with a similar composition of ingredients and nutrients (2,450 kcal/kg net energy, 15.3% crude protein, and 0.23% phytic P) except for the levels of total P and calcium. Feed consumption (per pen) and individual BW of the animals were recorded on days 0, 21, 42, and 62 of the study. On day 62 of the study, pigs were euthanized. Feces and blood samples from 2 pigs per pen were collected on days 0, 42, and 62 of the study. Data were analyzed using a mixed effects model with repeated measures. The statistical model included experimental treatment, initial BW block, study day and their interaction as fixed effects, and pen as a random effect of the fit model platform in JMP 16.0. The addition of 1,500 FTU/kg phytase tended to improve (P = 0.10) feed conversion by 4.3% relative to lower phytase inclusion levels. This production improvement is explained by the combination of greater animal growth (1.3%) and lower feed consumption (3.5%). Tendencies were observed in the net bone weight (10.41, 11.50, and 11.24 g, for 500, 800, and 1,500 FTU/kg, respectively; P = 0.05) and in bone ash content (6.26, 6.88, and 6.71 g for 500, 800, and 1,500 FTU/kg, respectively; P = 0.08), with greater values at 800 and 1,500 FTU/kg compared with 500 FTU/kg. The inclusion of 1,500 FTU/kg phytase significantly (P &amp;lt; 0.05) reduced fecal P and calcium content throughout the study compared with inclusion levels of 500 and 800 FTU/kg. The results of this study demonstrate the potential of adding 1,500 FTU/kg phytase to diets formulated without inorganic P to improve feed conversion, bone mineralization, and environmental sustainability, and could be an economically advantageous solution to reduce feed costs.

256 Evaluation Calcium and Phosphorus Ratios in the Presence of Phytase on Performance and Whole-Body Bone Mineralization in Growing Pigs

Abstract The objective of this study was to evaluate the effects of dietary calcium and phosphorus ratios in the presence of super dose phytase on grower pigs growth performance and bone mineral density. In two replicates, a total of 48 mixed sex pigs (26.7 kg BW) were allotted by BW and sex into individual pens across 3 dietary treatments (16 pigs/treatment) for 28 days. All diets contain phytase at 1,500 FTU/kg of complete feed and the three diet treatments were formulated with differing levels of Ca to achieve 0.7, 1.1 and 1.5 total Ca:total P. All diets were formulated to be isocaloric and isonitrogenous and ratios were achieved by vary limestone and sand. Pig BW and feed disappearance were recorded at the start (d 0) and end (d 28) of the study to calculate ADG, ADFI and G:F. On day 28, all pigs were euthanized to determine whole body bone, foot, rib, femur and tibia bone mineral density via dual x-ray absorptiometry. Data were analyzed with pen as the experimental unit, fixed effect of dietary treatment, sex and their interaction, and initial BW block and repartition as random effects. Differences were determined significant at P ≤ 0.05. Pig ADG was increased in the 1.1 verses 0.7 and 1.5 Ca:P diets (1.01, 0.95 and 0.95 kg/d, respectively, P = 0.046). End body weight was not different in the 0.7, 1.12 and 1.5 Ca:P treatments (53.5, 54.8 and 53.1 kg, respectively, P = 0.106). Diet Ca:P ratio did not alter ADFI or G:F. Whole body, tibia and femur bone mineral density was increased by 110% in 1.5 verses 0.7 Ca:P fed pigs, with bone mineral density being intermediated in the 1.1 Ca:P diets. Whole body (0.740, 0.752, 0.797, g/cm2, for 0.7, 1.1 and 1.5 Ca:P respectively, P = 0.033). For 0.7, 1.1 and 1.5 Ca:P femurs, bone mineral density was 0.463, 0.498 and 0.516, respectively, P = 0.034). Dietary treatment did not alter whole foot or 10th rib bone mineral densities (P &amp;gt; 0.05). Sex did not affect pig performance, but gilts had a 9% increase in bone mineral content. In conclusion, formulating dietary Ca:P in the presence of super dosing phytase at 1.1:1 total Ca:P resulted in the best ADG, but a ratio of 1.5:1 had the greatest bone mineral density.

255 Evaluation of Growth Performance and Bone Mineral Density in Grower Pigs Fed Phosphorus, Calcium, and Vitamin D Deficient Diets

Abstract The objective of this study was to evaluate the effects of phosphorus, calcium and vitamin D deficient diets on growth performance and bone mineral density (BMD) in grower pigs. In two replicates, a total of 80 mixed sex pigs (26.7 kg BW) were allotted by BW and sex into individual pens across 5 dietary treatments (16 pigs/trt) for 28 days. Diets were: 1) Positive control (PC) diet containing monocalcium phosphate and no phytase, 2) PC diet containing phytase 1,500 FTU of Optiphos 2500, 3) Diet deficient in phosphorus (no monocalcium phosphate or phytase), 4) Calcium deficient diet (as diet 2 with no limestone), and 5) Diet deficient in vitamin D as diet 2 containing no added vitamin D. All diets were formulated to 3,297 kcal/kg ME, 1.15% SID Lys and contain the same AA:Lys ratios. Total Ca was formulated to be 0.76, 0.53, 0.45, 0.20 and 0.53%, with available P at 0.32, 0.32, 0.07, 0.32 and 0.32% respectively, for Treatments 1-5. Vitamin D was formulated to be at 154 IU/kg diet for Treatment 1-4. Pig BW and feed disappearance were recorded at the start and end of the study to calculate ADG, ADFI and G: F. On day 28, serum was collected, and all pigs euthanized to determine whole body bone, foot, rib, femur, and tibia BMD via dual x-ray absorptiometry. Data were analyzed with pen as experimental unit, fixed effect of dietary treatment, sex and their interaction, and initial BW block and repartition as random effects. Diet by sex interactions not observed (P &amp;gt;0.05). Compared with either Treatment 1 and 2, P and Ca deficient diets reduced ADG (0.96, 1.01, 0.80 and 0.91 kg/d, respectively (P &amp;lt; 0.001). The ADFI did not differ across dietary treatments. Vitamin D deficient pigs did not differ from either control treatments. Feed efficiency was different between treatments 1-4 (0.51, 0.53, 0.47 and 0.50, respectively, P &amp;lt; 0.001). Whole body BMD was reduced in the P and Ca deficient diets compared with Treatment 1 and 2 (0.582, 0.678, 0.803 and 0.758 g/cm2, respectively, P &amp;lt; 0.001). Similar results for 10th rib, femur, and tibia bones (P &amp;lt; 0.001). Vitamin D deficient diets reduced whole body and tibia BMD compared with Treatment 1 by 1.5% (P &amp;lt; 0.05). Gilts had greater whole body (0.762 vs. 0.703 g/cm2) and tibia (0.448 vs. 0.408 g/cm2) BMD compared with barrows (P &amp;lt; 0.05). In conclusion, dietary phytase provided similar performance and BMD to that of non-phytase control diet. Feeding P and Ca deficient diets for 28 days reduced pig growth and bone density, with P diets having more severe reductions. Further, while there was a slight reduction in growth there were no detrimental effects on bone mineralization in pigs fed vitamin D deficient diets.

Средства реализации категории диалогичности в эпистолярном тексте второй половины XVIII века

The aim of the research is to determine the role of means of representing the textual category of dialogue in the private-business epistolary of the 18th century when characterising the communicants of correspondence, particularly Nikita Akinfievich Demidov (1724-1787), a Ural factory owner. The scientific novelty of the paper lies in examining linguistic markers of the category of dialogue peculiar to the business language of the 18th century and to N. A. Demidov as a linguistic personality. As a result of analysing the form of documents sent to higher authorities, it has been determined that the category of dialogue is represented even in the initial block of the letter – in the document requisites “sender” and “recipient”, whereas in letters sent to lower authorities, the requisite “sender” is contained within the requisite “recipient”. In the main part of the analysed documents and letters, the category of dialogue is represented by core markers: interrogative, imperative and negative constructions, references to documents initiating business communication (new speech subjects) presented in the form of indirect speech using the subjective particles де and якобы that indicate the unreliability of the information provided. In the business correspondence sent to lower authorities represented by a collective subject or a specific individual, N. A. Demidov uses both core and peripheral means of expressing the category of dialogue (parenthetical words and phrases, evaluative vocabulary) characteristic of the Russian language of the 18th century.

The Wear Behavior of Glass-Ceramic CAD/CAM Blocks against Bovine Enamel

The wear of enamel and crown restorative materials often occur by occlusion. The purpose of this study was to evaluate the wear volume between glass-ceramics used for CAD/CAM blocks (lithium disilicate: Initial LiSi block (LIS), IPS e.max CAD (IPS), zirconia-reinforced lithium silicate glass-ceramics: Celtra DUO (DUO), VITA Suprinity (VITS) and feldspar-based glass-ceramics: Vitablocs Mark II (MAK)) and bovine tooth enamel using a two-body wear test, the hardness, three-point bending strength, micro-structure and the element components of glass-ceramics. The data were analyzed using a one-way analysis of variance and Tukey’s multiple comparison test (α = 0.05). IPS and DUO with relatively large size crystal gain had significantly larger abrader wear volumes. Zirconia-reinforced lithium silicate glass-ceramics (DUO, VITS) caused significantly greater wear volume in antagonist enamel. MAK with scale-shape crystals grains produced distinct scratches after wear tests, both in the material itself and in the enamel. A strong correlation between the mechanical properties (hardness, three-point bending strength) and wear volume could not be confirmed. The type of glass-ceramic, size, and shape of the crystal grains affected the wear behavior of the glass-ceramics for CAD/CAM blocks. Therefore, dentists should consider that wear behavior varies with crystal structure, size, and shape in glass-ceramics for CAD/CAM blocks.

LBM simulation for combined thermal radiation and natural convection in 2D enclosure with multiple solid blocks

A numerical investigation of conjugate natural convection in a 2D square enclosure with multiple solid blocks, considering the impact of volumetric thermal radiation, was conducted using the lattice Boltzmann method (LBM). The effect of Planck number wall surface emissivity extinction coefficient solid-to-fluid volume fraction and the number of solid blocks on the fluid-structure and heat transfer within the enclosure were analyzed. The numerical model was validated using benchmark problems from the literature, showing good agreement. The results revealed that at and increasing wall surface emissivity significantly increased the Nusselt number, ranging from approximately 51-116% for different wall emissivity values, as compared to scenarios without surface radiation (). On the other hand, reducing χ, Pl, and β improved the heat transfer rate. The results also demonstrated that subdividing the initial block reduced the heat transfer rate depending on the number of blocks and the value of the Planck number. For instance, when 64 solid blocks were present in the cavity and the Nusselt number decreased by 59.36% compared to the case with a lower solid-to-fluid volume fraction (χ = 15%). The parametric analysis provided useful insights for engineering design in the modern construction industry, with possible applications in building block design and energy efficiency enhancements.

Translucency of Lithium-Based Silicate Glass-Ceramics Blocks for CAD/CAM Procedures: A Narrative Review.

Amid chairside CAD/CAM materials, the use of lithium-based silicate glass-ceramics (LSGC) has been steadily increasing. This review aims to report on the translucency of these materials and the variables used to measure it. An electronic search was performed within the PubMed database within the period between 2 June 2011 and 11 September 2022. English-language papers investigating the translucency of IPS e.max CAD, Celtra Duo, Suprinity PC, Initial LiSi Block, Amber Mill, N!ce, and CEREC Tessera LSGC CAD/blocks were included in the search strategy. After an initial retrieval of 160 papers, the application of exclusion criteria, and the screening of abstracts and then of full texts, 33 papers were included in the study. The retrieved materials, with different degrees of translucency (LT, HT), were IPS e.max CAD (n = 33), Suprinity PC (n = 8), and Celtra Duo (n = 1). Concerning the examined colors, the most used was A2 (n = 20), followed by A1 (n = 8) and A3 (n = 2). The translucency parameter (TP) was the most used method (n = 30) with respect to the contrast ratio (CR) (n = 11) to assess translucency. Five papers measured both. Several specimens' thicknesses (0.5-4 mm) were investigated, with 1 mm (n = 23) being the most frequently analyzed. While a general tendency could be identified, conflicting results among different papers were reported.

Optical Properties of ScnYn (Y = N, P As) Nanoparticles.

In this work, using Density Functional Theory (DFT) and Time Dependent DFT, the absorption spectrum, the optical gap, and the binding energy of scandium pnictogen family nanoparticles (NPs) are examined. The calculated structures are created from an initial cubic-like building block of the form Sc4Y4, where Y = N, P, As after elongation along one and two perpendicular directions. The existence of stable structures over a wide range of morphologies was one of the main findings of this research, and this led to the study of several exotic NPs. The absorption spectrum of all the studied structures is within the visible spectrum, while the optical gap varies between 1.62 and 3 eV. These NPs could be used in the field in photovoltaics (quantum dot sensitized solar cells) and display applications.

Determination of chemical constituent yields in e-cigarette aerosol using partial and whole pod collections, a comparative analysis.

Literature reports the chemical constituent yields of electronic nicotine delivery systems (ENDS) aerosol collected using a range of aerosol collection strategies. The number of puffs to deplete an ENDS product varies widely, but collections often consist of data from the first 50-100 puffs. However, it is not clear whether these discrete puff blocks are representative of constituent yields over the life of a pod. We aimed to assess the effect of differing aerosol collection strategies on reported yields for select chemical constituents in the aerosol of closed pod-based ENDS products. Constituents analyzed were chosen to reflect important classes of compounds from the Final Premarket Tobacco Product Application Guidance. Yields were normalized to total device mass loss (DML). Collection strategies that consisted of partial pod collection were valid for determining yields of constituents whose DML normalized yields were consistent for the duration of pod life. These included primary aerosol constituents, such as propylene glycol, glycerol, and nicotine, and whole pod yields could be determined from initial puff blocks. However, changes were observed in the yields of some metals, some carbonyl compounds, and glycidol over pod life in a chemical constituent and product dependent manner. These results suggest that collection strategies consisting of initial puff block collections require validation per chemical constituent/product and are not appropriate for chemical constituents with variable yields over pod life. Whole pod collection increased sensitivity and accuracy in determining metal, carbonyl, and glycidol yields compared to puff block-based collection methodologies for all products tested.

Surface Properties of Resin Composites and CAD/CAM Blocks After Simulated Toothbrushing.

This study aimed to evaluate the surface gloss, surface roughness, and color change of restorative materials after a three-body wear abrasion. Four resin composites with different filler particle size (Gracefil Flo [GFF, 0.7 μm], Gracefil LoFlo [GFL, 0.25 μm], Gracefil ZeroFlo [GFZ, 0.15 μm], and Gracefil Putty [GFP, 0.3 μm]), two CAD/CAM resin composite blocks with different filler particle size (Cerasmart 300 [CS3, 0.7 μm] and Cerasmart Prime [CSP, 0.3 μm], GC), and one CAD/CAM lithium disilicate glass-ceramic block (Initial LiSi Block [ILS], GC) as a control were evaluated. Twenty slab-shaped specimens were obtained from each material. Ten specimens were subjected to 80,000 toothbrushing strokes and measured for surface gloss (Gloss Unit, GU), surface roughness (Ra, μm), and color (L*, a*, and b* values) before toothbrushing and at every 20,000 strokes. Color differences (ΔL*, Δa*, Δb*, and ΔE00) before and after toothbrushing were calculated. After 80,000 strokes, abraded surfaces were observed using scanning electron microscopy. The other 10 specimens were measured for Vickers microhardness (VHN). After 80,000 toothbrushing strokes, the mean GU ranged from 60.43 to 16.12 (the highest for ILS and lowest for GFL), and the mean Ra ranged from 0.079 to 4.085 (the lowest for ILS and highest for GFL). At all measuring stages, the calculated ΔE00 values ranged from 0.31 to 0.92 for all materials. The mean VHN ranged from 632.34 to 39.08 (the highest for ILS and lowest for GFZ). The resin composite containing the largest filler particle (GFF) showed significantly lower Ra and higher VHN than other resin composites (GFL, GFZ, and GFP). The CAD/CAM resin composite block containing a smaller filler particle (CSP) retained significantly higher GU than that containing a larger filler particle (CS3). A negative correlation between GU and Ra was detected. Based on the findings, toothbrush abrasion induced a decrease in GU and an increase in Ra for all resin-based materials tested. Resin-based materials with larger filler size tended to show lower Ra, while resin-based materials with smaller filler size tended to show a smaller reduction in GU. These were more pronounced for light-cure resin composites than for resin composite blocks for CAD/CAM.

Modeling Ellipsoidal Block Impacts by an Advanced Rheological Model

In this paper, an advanced rheological model for impacts of ellipsoidal blocks on deformable ground surfaces, introducing the effects of block eccentricity and orientation at impact, is presented. This allows us to assess impact penetration and force, restitution coefficients, and block trajectories. A parametric analysis was carried out by considering different block aspect ratios, impact angles and initial block orientations at impact. The results are presented in terms of restitution coefficients, penetration and force time histories, maximum penetration depth, maximum force and rotational/total kinetic ratios. Impacts along the major block axis, versus those along minor axis, are characterized by larger penetrations (ranging from 3.3 to 50%), shorter impact durations (ca 50%) and very slightly larger vertical forces (ranging from 0.3 to 60%) according to the model parameter used. In contrast, the impact angle is shown to strongly affect maximum penetration and force values, and markedly increase rotation at impact. Analogously, normal restitution coefficient is severely dependent on impact angle, with a variation of more than two orders of magnitude. A mathematical expression for computing the energetic restitution coefficient from the normal and tangential apparent restitution coefficients and the ratio between the rotation and total kinetic energy is proposed. This overcomes the drawback of classical restitution coefficients greater than one when a change in block rotation occurs allowing us to bracket the coefficient of restitutions values to support and improve classical rock fall simulations also highlighting their intrinsic limitations. Finally, the effects of block geometry and initial angular velocity on rockfall simulations were analyzed by implementing the approach in the HyStone simulation code. The simulated frequencies of the maximum height during each ballistic trajectory follow an exponential distribution, whereas those for normal and tangential apparent restitution coefficients follow normal distributions.

Electrohydraulic Crimping of Tubes within Rings

Crimping processes are commonly used in industry to join two tubular parts together. In the case of positive clearance crimping, one of the two parts must be plastically deformed to fill the initial clearance and block elastic deformations in the second one. The strength of the assembly will then depends on the residual contact pressure established at the interface. Quasi-static processes are the most commonly used to perform these operations, but over the past two decades, there has been a growing interest in the use of dynamic crimping by magnetic pulse. Processes that generate high-strain rate allow to reduce the springback, which is of great interest for crimping. However, its use is limited if the part to be deformed is made of a poor electrical conductor material or if its dimensions are too small. This paper presents an alternative for dynamically crimping tubes within rings using electrohydraulic process. An experimental equipment has been designed to guide and amplify pressure waves to the area to be deformed. Two amplifiers called acoustic and mechanical pulse shapers (APS and MPS) have been tested and allow to reach hoop strain rate at about 1000 and 100 s−1 respectively. An analytical model was also built allowing to define the stored energy and the inter-electrodes distance to maximize the pressure. Results of push-out tests are also presented and demonstrate the ability of the electrohydraulic crimping process coupled with the MPS to crimp small 316L tubes into rings made of the same material, but achieving crimping successfully with the APS still require further work.

Evaluation of fracture behavior in short fiber–reinforced direct and indirect overlay restorations

ObjectivesThe aim was to assess how incorporating a short-fiber composite (SFC) core would affect the fracture behavior of direct and indirect overlays. Furthermore, to examine the relationship between the thickness ratio of SFC core to particulate-filled composite (PFC) veneering and the fracture-behavior of bilayered-structured restorations.Materials and methodsA total of 120 molars were used to create MOD cavities, with palatal cusps removed. Four different groups of direct overlays were then made (n = 15/group), all of which featured a SFC core (everX Flow) with varying thicknesses (0, 1, 4, and 5 mm), as well as a surface layer of PFC (G-aenial Posterior), with the overall thickness of the bilayered-structured restoration set at 5 mm. Additionally, four groups of CAD/CAM restorations were created (Cerasmart 270 and Initial LiSi Block), with or without 2 mm of SFC core reinforcement. Following the fabrication of these restorations, cyclic fatigue aging was carried out for a total of 500,000 cycles, with an applied maximum load (Fmax) of 150 N. Subsequently, each restoration underwent quasi-static loading until fracture. The fracture mode was subsequently evaluated using optical microscopy and SEM.ResultsThere were no statistically significant differences (p > 0.05) observed in the fracture resistance of indirect overlays reinforced with a 2-mm SFC core compared to those made solely from restorative materials. Direct overlays constructed using plain SFC or with a 4-mm layer thickness of SFC core exhibited significantly higher fracture resistance values (2674 ± 465 and 2537 ± 561 N) (p < 0.05) when compared to all other groups tested, according to the statistical analysis ANOVA.ConclusionsThe most effective method for restoring large MOD cavities was found to be direct restoration using SFC either alone or as a bulk core in combination with PFC composite.Clinical relevanceThe use of SFC as bulk reinforcing base will significantly improve the loading performance of directly layered restorations.

Optical and Mechanical Properties of New Ceramic CAD/CAM Materials.

The purpose of this study was to compare the optical and mechanical properties of newer ceramic CAD/CAM materials to more established materials on the market. The following ceramic materials were tested: lithium disilicate/lithium-aluminum silicate (Tessera, Dentsply/Sirona), lithium disilicate (Initial LiSi Block, GC), IPS e.max CAD, Ivoclar Vivadent), and 4Y polycrystalline stabilized zirconia (IPS e.max ZirCAD MT, Ivoclar Vivadent; Katana STML, Kuraray; YZ ST, VITA). Optical properties (translucency, opalescence) were determined using a dental spectrophotometer on 0.5-, 1.0-, 1.5-, or 2.0-mm specimens. Mechanical properties (flexural strength, flexural modulus, flexural fatigue strength, Weibull modulus, and characteristic strength) were determined with beams undergoing 3-point bend testing. The data were analyzed with multiple analyses of variance and Tukey's post hoc tests (α=0.05). Significant differences were found between groups based on type of ceramic or property (p<0.05). In general, the lithium disilicate based-ceramic materials had greater optical properties and lower mechanical properties than the zirconia-based ceramic materials.