Biomineralization stimulated peri-titanium implants prepared by selective laser melting

AbstractTitanium implants prepared by selective laser melting (SLM), a method of additive manufacturing, were subjected to implantation in beagle dogs for two and four weeks. Argon ion beam-polished cross sections of the implants after in vivo tests were characterized by scanning electron microscope (SEM) to evaluate the bone–implant interface and the early peri-implant biomineralization with sufficiently improved resolution. Two bone mineralization mechanisms were disclosed. As early as two weeks after implantation, a layer of new bone was found to form directly on the implant surface and bone in-growth was also observed. Osseointegration was found to establish partly at the tip of the implants. After healing for four weeks it was found that osseointegration was established around the entire tip of the implants, whereas only partly at the third thread region of the implants. The experimental evidences observed reveal that an inherent highly porous surface of the titanium implants generated by selective laser melting is favorable for new bone apposition

The migration of neighboring and antagonist teeth three months after implant placement in healed single tooth-missing sites

Objectives: To quantify the neighboring and antagonist teeth migration of a single posterior tooth-missing site within 3 months using digital scanning and measuring techniques. Materials and methods: Intraoral scans (IOS) were made in 40 patients presenting a single posterior tooth-missing gap and receiving implant therapy. IOS were obtained at the day of and three months after implant surgery rendering a digital baseline model (BM) and a digital follow-up model (FM). Digital models were superimposed using the implant scan body as reference. Antagonist models were processed by the best fit alignment. Dimensional change between anatomical landmarks on neighboring teeth and that of featuring points on antagonistic teeth were measured using a three-dimensional analysis software. The Mann-Whitney U test was applied to compare the tooth-moving distance between the mesial and distal neighboring teeth. The Kruskal-Wallis one-way ANOVA was used to test the difference in dimensional change in tooth-missing site among age subgroups. Results: The mean dimensional change in the tooth-missing site was -37.62 ± 106.36 μm (median: -28.33 μm, Q25 -72.65/Q75 38.97) mesial-distally and -67.91 ± 42.37 μm (median: -61.50 μm, Q25 -88.25/Q75 -36.75) occlusal-gingivally. Eighteen out of 40 mesial neighboring teeth and 24 out of 40 distal neighboring teeth showed migration towards the implants. When patients were grouped according to age, the mesial-distal reduction in the tooth-missing site was significantly larger in patients younger than 30 years compared with those older than 50 years (p < .05). Conclusions: The dimensions of posterior tooth-missing sites decreased over an observation period of 3 months. Keywords: dental implants; digital; three-dimensional; tooth migration; tooth movement

Time efficiency and quality of outcomes in a model-free digital workflow using digital impression immediately after implant placement: A double-blind self-controlled clinical trial

OBJECTIVE To assess the clinical and laboratory time efficiency and quality of outcomes for posterior single implant crowns by means of a model-free digital workflow using digital impressions immediately after implant placement. METHODS Forty patients missing a single posterior tooth received implant therapy. For within-subject comparison, digital impressions were taken immediately after implant placement and conventional impressions after implant healing. Two monolithic zirconia crowns were fabricated using a laboratory-based CAD-CAM system. One crown was produced from the immediate digital impression and a model-free digital workflow (test group), and the second crown was produced from the conventional impression and a hybrid workflow (control group). Clinical and laboratory time was recorded. Quality of outcomes was evaluated double-blinded. A paired-sample t test was applied for statistical analysis. RESULTS The total mean chairside time (impression and delivery) was 23.2 min (95%CI 22.2, 24.3) in the test group and 25.7 min (95%CI 24.4, 26.9) in the control group (p = 0.013). Significantly less laboratory time was needed in the model-free digital workflow (13.6 min, 95%CI 11.5, 15.6) as compared to the model-based hybrid workflow (29.9 min, 95%CI 25.7, 34.2) (p < 0.05). At crown delivery, 4/40 (test) and 12/40 (control) had no need of chairside adjustments, and 6/40 (test) and 5/40 (control) implant crowns were in need of additional laboratory interventions. CONCLUSION The fabrication of posterior single implant crowns using digital impressions taken immediately after implant placement and a model-free, laboratory-based digital workflow was more time efficient and resulted in similar quality of outcomes as a hybrid workflow using conventional impressions

Effect of Fe2O3–ZrO2 Catalyst Morphology on Sulfamethazine Degradation in the Fenton-Like Reaction

Fe2O3–ZrO2 catalysts with different morphologies (nanoplates (HZNPs), nanorods (HZNRs), nanocubes (HZNCs), and nanotubes (HZNTs)) were prepared by a hydrothermal method to investigate the effect of the morphology on the catalytic performance in the Fenton-like reaction for sulfamethazine (SMT) degradation. The Fe2O3–ZrO2 catalysts were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) analysis. The H2O2 adsorption and the Fe2+ density sites on the Fe2O3–ZrO2 catalysts had a close relationship with the morphologies and exhibited an important effect on the ·OH formation in the Fenton-like reaction. Free ·OH radicals were the main oxidative species in the reaction, and the normalized ·OH concentration per surface area of the catalysts was 4.52, 2.24, 2.20, and 0.37 μmol/m2 for HZNPs, HZNRs, HZNCs, and HZNTs, respectively. The Fe2O3–ZrO2 catalysts with different morphologies showed good catalytic performance, and the order of SMT degradation was HZNPs &gt; HZNRs &gt; HZNCs &gt; HZNTs. Total SMT removal was achieved in the Fenton-like reaction over HZNPs at pH 3.0 and 45 °C after 240 min

Experimental and numerical study of crack damage under variable amplitude thermal fatigue for compacted graphite iron EN-GJV-450

Fatigue crack under variable amplitude thermal cycles is a common failure in combustion chamber components, proposing great challenges during the temperature reproduction of actual working condition. In this paper, this complicated thermal cycle was realized with pulsed laser experimentally, causing two kinds of damage such as the low cycle thermal fatigue (LCF) and high cycle thermal fatigue (HCF). A numerical model was developed to simulate the temperature, stress and strain under variable amplitude thermal cycles. The results showed that, there was good agreement between the measured temperature curve and the simulated results with different crack parameters. The observed crack depth at different cycles was consistent with the predicted ones. Furthermore, the mechanism of crack evolution under variable amplitude thermal fatigue was discussed. The calculated thermal-structural interaction depth of LCF thermal cycle was found to be larger than the HCF thermal cycle. The effect of LCF thermal loadings was associated with the initiation of major cracks, while the failure related to the superimposed HCF action was the acceleration of crack growth with a surface wedging process. This paper provides comprehensive experimental and numerical insights into the thermal damage process under variable amplitude thermal loading, showing a significant engineering value for failure analysis and design optimization of combustion chamber components

The accuracy of dynamic computer assisted implant surgery in fully edentulous jaws: A retrospective case series

OBJECTIVES To evaluate the accuracy of implant placement using a dynamic navigation system in fully edentulous jaws and to analyze the influence of implant distribution on implant position accuracy. MATERIALS AND METHODS Edentulous patients who received implant placement using a dynamic navigation system were included. Four to six mini screws were placed in the edentulous jaw under local anesthesia as fiducial markers. Then patients received CBCT scans. Virtual implant positions were designed in the planning software based on CBCT data. Under local anesthesia, implants were inserted under the guidance of the dynamic navigation system. CBCTs were taken following implant placement. The deviation between the actual and planned implant positions was measured by comparing the pre- and postsurgery CBCT. RESULTS A total of 13 edentulous patients with 13 edentulous maxillae and 7 edentulous mandibles were included, and 108 implants were placed. The average linear deviations at the implant entry point and apex were 1.08 ± 0.52 mm and 1.15 ± 0.60 mm, respectively. The average angular deviation was 2.85 ± 1.20°. No significant difference was detected in linear and angular deviations between the maxillary and mandibular implants, neither between the anterior and posterior implants. CONCLUSIONS The dynamic navigation system provides high accuracy for implant placement in fully edentulous jaws, while the distribution of the implants showed little impact on implant position accuracy

A double-blind randomized within-subject study to evaluate clinical applicability of four digital workflows for the fabrication of posterior single implant crown

OBJECTIVE To compare efficiency and clinical efficacy of posterior single implant crowns (PSIC) fabricated using four digital workflows. MATERIALS AND METHODS Twenty-two patients with one missing first molar were included. Each patient received four screw-retained implant crowns fabricated through four different workflows including a fully digital workflow with immediate digital impression (Group i-IOS), a fully digital workflow with digital impression after implant osseointegration (Group d-IOS), a model-based hybrid workflow using immediate analogue impression (Group i-AI), and a model-based hybrid workflow with conventional analogue impression after implant osseointegration (Group d-AI). The crown delivery sequence was randomized and blinded. The efficiency for each workflow and clinical outcome of each crown were recorded. RESULTS The average clinical working time in fully digital workflows (i-IOS 46.90 min, d-IOS 45.66 min) was significantly lower than that in the hybrid workflows (i-AI 54.59 min, d-AI 55.96 min; p < .001). Significantly more laboratory time was spent in hybrid workflows (i-AI 839.60 min, d-AI 811.73 min) as compared to fully digital workflows (i-IOS 606.25 min, d-IOS 607.83 min, p < .01). No significant differences in the chairside time at delivery were found. More crowns in Group i-AI (15%) needed additional laboratory interventions than in the other groups (p = .029). CONCLUSION Digital impression and model-free fully digital workflow improved prosthetic efficiency in the fabrication of PSIC. With the limitation that the results were only applicable to the implant system used and the digital technologies applied, findings suggested that workflows integrating immediate impression with implant surgery procedure was clinically applicable for restoration of PSIC

Collective evolution of surface microcrack for compacted graphite iron under thermal fatigue with variable amplitude

With the growing demand of good performance and high reliability of the heated components, the cracking failure caused by the complex thermal loading of variable amplitude has become a crucial problem. The collective evolution of surface microcrack for compacted graphite iron under thermal fatigue with variable amplitude is studied in this paper, which is induced by pulsed laser. The thermal microcrack is analyzed with statistic method and fractal method systematically. The result shows that, the secondary microcrack is the primary crack pattern, and the number of main microcrack is the least. As the test goes on, the fractal dimension increases following the Hill's function. Furthermore, the effect of maximum temperature T-max and superimposed number N-HCP on the crack evolution is investigated. T-max in the heating stage mainly affects the number of main microcrack. With the increase of plastic strain amplitude, the fractal dimension increases exponentially, and gradually tends to be the critical fractal dimension D-o of 1.395. The superimposed number N-HCP in the high-cycle stage mainly affects the number of secondary microcrack. The fractal dimension increases exponentially with the increase of N-HCP, and tends to be the critical fractal dimension D-o of 1.404. The analysis of the collective behavior of surface microcrack is helpful for evaluating the damage degree and predicting the lifetime, which can be applied to other materials working under thermal loading of variable amplitude

modellingstudytocomparetheflowandheattransfercharacteristicsoflowpowerhydrogennitrogenandargonarcheatedthrusters

A modelling study is performed to compare the plasma flow and heat transfer characteristics of low-power arc-heated thrusters (arcjets) for three different propellants: hydrogen, nitrogen and argon. The all-speed SIMPLE algorithm is employed to solve the governing equations, which take into account the effects of compressibility, Lorentz force and Joule heating, as well as the temperature- and pressure-dependence of the gas properties. The temperature, velocity and Mach number distributions calculated within the thruster nozzle obtained with different propellant gases are compared for the same thruster structure, dimensions, inlet-gas stagnant pressure and arc currents. The temperature distributions in the solid region of the anode-nozzle wall are also given. It is found that the flow and energy conversion processes in the thruster nozzle show many similar features for all three propellants. For example, the propellant is heated mainly in the near-cathode and constrictor region, with the highest plasma temperature appearing near the cathode tip; the flow transition from the subsonic to supersonic regime occurs within the constrictor region; the highest axial velocity appears inside the nozzle; and most of the input propellant flows towards the thruster exit through the cooler gas region near the anode-nozzle wall. However, since the properties of hydrogen, nitrogen and argon, especially their molecular weights, specific enthalpies and thermal conductivities, are different, there are appreciable differences in arcjet performance. For example, compared to the other two propellants, the hydrogen arcjet thruster shows a higher plasma temperature in the arc region, and higher axial velocity but lower temperature at the thruster exit. Correspondingly, the hydrogen arcjet thruster has the highest specific impulse and arc voltage for the same inlet stagnant pressure and arc current. The predictions of the modelling are compared favourably with available experimental results

Transcriptome Sequencing Analysis of Root in Soybean Responding to Mn Poisoning

Manganese (Mn) is among one of the essential trace elements for normal plant development; however, excessive Mn can cause plant growth and development to be hindered. Nevertheless, the regulatory mechanisms of plant root response to Mn poisoning remain unclear. In the present study, results revealed that the root growth was inhibited when exposed to Mn poisoning. Physiological results showed that the antioxidase enzyme activities (peroxidase, superoxide dismutase, ascorbate peroxidase, and catalase) and the proline, malondialdehyde, and soluble sugar contents increased significantly under Mn toxicity stress (100 μM Mn), whereas the soluble protein and four hormones’ (indolebutyric acid, abscisic acid, indoleacetic acid, and gibberellic acid 3) contents decreased significantly. In addition, the Mn, Fe, Na, Al, and Se contents in the roots increased significantly, whereas those of Mg, Zn, and K decreased significantly. Furthermore, RNA sequencing (RNA-seq) analysis was used to test the differentially expressed genes (DEGs) of soybean root under Mn poisoning. The results found 45,274 genes in soybean root and 1430 DEGs under Mn concentrations of 5 (normal) and 100 (toxicity) μM. Among these DEGs, 572 were upregulated and 858 were downregulated, indicating that soybean roots may initiate complex molecular regulatory mechanisms on Mn poisoning stress. The results of quantitative RT-PCR indicated that many DEGs were upregulated or downregulated markedly in the roots, suggesting that the regulation of DEGs may be complex. Therefore, the regulatory mechanism of soybean root on Mn toxicity stress is complicated. Present results lay the foundation for further study on the molecular regulation mechanism of function genes involved in regulating Mn tolerance traits in soybean roots