Electrical transport and persistent photoconductivity in monolayer MoS2 phototransistors.

We study electrical transport properties in exfoliated molybdenum disulfide (MoS2) back-gated field effect transistors at low drain bias and under different illumination intensities. It is found that photoconductive and photogating effect as well as space charge limited conduction can simultaneously occur. We point out that the photoconductivity increases logarithmically with the light intensity and can persist with a decay time longer than 104 s, due to photo-charge trapping at the MoS2/SiO2 interface and in MoS2 defects. The transfer characteristics present hysteresis that is enhanced by illumination. At low drain bias, the devices feature low contact resistance of [Formula: see text] ON current as high as [Formula: see text] 105 ON-OFF ratio, mobility of ∼1 cm2 V-1 s-1 and photoresponsivity [Formula: see text].

Early bone formation around immediately loaded implants with nanostructured calcium-incorporated and machined surface: a randomized, controlled histologic and histomorphometric study in the human posterior maxilla.

OBJECTIVE: The aim of this randomized, controlled histologic/histomorphometric study was to compare the early bone formation around immediately loaded implants with nanostructured calcium-incorporated (NCI) and machined (MA) surface, placed in the human posterior maxilla. MATERIALS AND METHODS: Fifteen fully edentulous patients (six males; nine females; mean age 57.9 ± 6.7 years) were selected for this study. Each patient was installed with two temporary transmucosal implants, with different surfaces: one NCI (test) and one MA (control) implant. All temporary implants were placed in the posterior maxilla, according to a split-mouth design, to help to support an interim complete maxillary denture. After 8 weeks, all temporary transmucosal implants were retrieved for histologic/histomorphometric evaluation. The bone-to-implant contact (BIC%) and the bone density (BD%) were calculated. The Wilcoxon matched-pairs signed-rank test was used to evaluate differences (BIC%, BD%) between the surfaces. The level of significance was set at 0.05. RESULTS: Eight weeks after placement, 24 clinically stable implants (12 test, 12 control) were subjected to histologic/histomorphometric evaluation. In the MA implants, the histomorphometric evaluation revealed a mean BIC(±SD)% and BD(±SD)% of 21.2(±4.9)% and 29.8(±7.8)%, respectively. In the NCI implants, the histomorphometric analysis revealed a mean BIC(±SD)% and BD(±SD)% of 39.7(±8.7)% and 34.6(±7.2)%, respectively. A statistically significant difference was found between the two surfaces with regard to BIC% (p < 0.001), while no significant difference was found with regard to BD% (p = 0.09). CONCLUSIONS: The NCI surface seems to increase the peri-implant endosseous healing properties in the native bone of the posterior maxilla, under immediate loading conditions, when compared with the MA surface. CLINICAL RELEVANCE: Under immediate loading conditions in the human posterior maxilla, the nanostructured calcium-incorporated surface has led to better histologic and histomorphometric results than the machined surface; therefore, the clinical use of implants with nanostructured calcium-incorporated surface may be beneficial in the posterior maxilla, under immediate loading protocol.

Intraoral scanners in dentistry: a review of the current literature.

BACKGROUND: Intraoral scanners (IOS) are devices for capturing direct optical impressions in dentistry. The purpose of this narrative review on the use of IOS was to: (1) identify the advantages/disadvantages of using optical impressions compared to conventional impressions; (2) investigate if optical impressions are as accurate as conventional impressions; (3) evaluate the differences between the IOS currently available commercially; (4) determine the current clinical applications/limitations in the use of IOS. METHODS: Electronic database searches were performed using specific keywords and MeSH terms. The searches were confined to full-text articles written in English and published in peer-reviewed journals between January 2007 and June 2017. RESULTS: One hundred thirty-two studies were included in the present review; among them, 20 were previous literature reviews, 78 were in vivo clinical studies (6 randomized controlled/crossover trials, 31 controlled/comparative studies; 24 cohort studies/case series; 17 case reports) and 34 were in vitro comparative studies. CONCLUSIONS: Optical impressions reduce patient discomfort; IOS are time-efficient and simplify clinical procedures for the dentist, eliminating plaster models and allowing better communication with the dental technician and with patients; however, with IOS, it can be difficult to detect deep margin lines in prepared teeth and/or in case of bleeding, there is a learning curve, and there are purchasing and managing costs. The current IOS are sufficiently accurate for capturing impressions for fabricating a whole series of prosthetic restorations (inlays/onlays, copings and frameworks, single crowns and fixed partial dentures) on both natural teeth and implants; in addition, they can be used for smile design, and to fabricate posts and cores, removable partial prostheses and obturators. The literature to date does not support the use of IOS in long-span restorations with natural teeth or implants. Finally, IOS can be integrated in implant dentistry for guided surgery and in orthodontics for fabricating aligners and custom-made devices.

Maxillary ridge augmentation with custom-made CAD/CAM scaffolds. A 1-year prospective study on 10 patients.

Several procedures have been proposed to achieve maxillary ridge augmentation. These require bone replacement materials to be manually cut, shaped, and formed at the time of implantation, resulting in an expensive and time-consuming process. In the present study, we describe a technique for the design and fabrication of custom-made scaffolds for maxillary ridge augmentation, using three-dimensional computerized tomography (3D CT) and computer-aided design/computer-aided manufacturing (CAD/CAM). CT images of the atrophic maxillary ridge of 10 patients were acquired and modified into 3D reconstruction models. These models were transferred as stereolithographic files to a CAD program, where a virtual 3D reconstruction of the alveolar ridge was generated, producing anatomically shaped, custom-made scaffolds. CAM software generated a set of tool-paths for manufacture by a computer-numerical-control milling machine into the exact shape of the reconstruction, starting from porous hydroxyapatite blocks. The custom-made scaffolds were of satisfactory size, shape, and appearance; they matched the defect area, suited the surgeon's requirements, and were easily implanted during surgery. This helped reduce the time for surgery and contributed to the good healing of the defects.

Accuracy in static guided implant surgery: Results from a multicenter retrospective clinical study on 21 patients treated in three private practices.

PURPOSE: To evaluate the accuracy of a static computer-assisted implant surgery (s-CAIS) system across different private practices. METHODS: This retrospective clinical study was based on data retrieved from 21 patients who received 61 implants between 2018 and 2020 in 3 private practices run by surgeons with extensive experience with s-CAIS. All patients were treated using the same s-CAIS system, planning software, template manufacturing process, and surgical guides. The standard tessellation language (STL) file of the intraoral scan of the fixture taken immediately after implant placement was matched with that of the preoperative plan for comparisons of preoperative and planned implant positions with postoperative and actual implant positions. The study outcomes were linear and angular deviations between the planned and actual implant positions. RESULTS: No surgical or postsurgical complications occurred. The overlap of the two STL files resulted in a mean angular deviation of 2.94° The mean linear deviation at the implant shoulder was 0.73 mm, and that at the apex was 1.06 mm. The mean vertical deviations at the implant shoulder and the apex were 0.29 mm and 0.01 mm, respectively. CONCLUSION: All cases showed satisfactory accuracy within the limits of this study (small number of patients and retrospective design). These results might be related to the use of a standardized digital workflow by experienced operators. STATEMENT OF CLINICAL RELEVANCE: The study shows that careful control of each step, from data acquisition to final execution, is key for the accuracy of stent-guided systems.

Immediate restoration of fixed partial prostheses supported by one-piece narrow-diameter selective laser sintering implants: a 2-year prospective study in the posterior jaws of 16 patients.

PURPOSE: Selective laser sintering (SLS) is a new technique that allows implants to be produced by annealing titanium powder microparticles in a focused laser beam, according to a computer-generated model. The aim of this study was to evaluate the survival and success rate of immediately restored 1-piece narrow-diameter SLS implants, placed in the posterior jaws, after 2 years of functional loading. MATERIALS AND METHODS: At the 2-year follow-up examination, several parameters were assessed. Success criteria included absence of pain, suppuration, exudation, implant mobility; distance between the implant shoulder and the first visible bone-to-implant contact <2.0 mm; and absence of prosthetic complications. RESULTS: Thirty-seven implants were placed in the posterior jaws (14 maxilla, 23 mandible) of 16 patients (9 males, 7 females). The prosthetic restorations comprised 16 immediately restored fixed partial prostheses. No implant failure occurred, resulting in a 100% survival rate. The implant success was 94.6%, and the mean distance between the implant shoulder and the first visible bone-to-implant contact (DIB) was 0.4 ± 0.3 mm. CONCLUSIONS: This study supports the hypothesis that 1-piece narrow-diameter SLS implants can be used in fixed prosthetic rehabilitations in the posterior regions of both jaws with a predictable positive outcome.

Prospective clinical evaluation of 201 direct laser metal forming implants: results from a 1-year multicenter study.

This prospective clinical study evaluated the survival rate and the implant-crown success of 201 direct laser metal forming (DLMF) implants in different clinical applications, after short-term follow-up of functional loading. At the 1-year scheduled follow-up examination, several clinical, radiographic, and prosthetic parameters were assessed. Success criteria included absence of pain, sensitivity, suppuration, exudation; absence of implant mobility; absence of continuous peri-implant radiolucency, DIB <1.5 mm; absence of prosthetic complications at the implant-abutment interface. A total of 201 implants (106 maxilla, 95 mandible) were inserted in 62 patients (39 males, 23 females; aged between 26 and 65 years) in eight different clinical centers. The sites included anterior (n = 79) and posterior (n = 122) implants. The overall implant survival rate was 99.5%, with one implant loss (maxilla: 99.0%, 1 implant failure; mandible: 100.0%, no implant failures). The mean DIB was 0.4 ± 0.2 mm. Among the survived implants (200), five did not fulfill the success criteria, giving an implant-crown success of 97.5%. This 1-year follow-up prospective clinical study gives evidence of very high survival (99.5%) and success (97.5%) rates using DLMF implants.

Custom-made computer-aided-design/ computer-assisted-manufacturing (CAD/CAM) synthetic bone grafts for alveolar ridge augmentation: A retrospective clinical study with 3 years of follow-up.

PURPOSE: To report on the results obtained with computer-aided-design/ computer-assisted-manufacturing (CAD/CAM) custom-made synthetic hydroxyapatite/beta-tricalcium-phosphate (HA/beta-TCP) bone grafts in alveolar ridge augmentation for dental implant placement. METHODS: The procedure included: (1) cone-beam computed tomography (CBCT) of the bone defect; (2) virtual design of the custom-made onlay bone grafts; (3) milling of grafts from a pre-formed block of synthetic HA/beta-TCP; and (4) bone reconstructive surgery. Implants were placed 8 months later. The patients were followed for 3 years. The study outcomes were: (1) intra- and immediate post-operative complications; (2) 8-month vertical and horizontal bone gain; (3) implant survival; (4) implant-crown success; and (5) peri-implant marginal bone loss (MBL). RESULTS: Twenty-six patients underwent ridge augmentation with custom-made CAD/CAM HA/beta-TCP onlay grafts. Eight months later, these patients were rehabilitated with dental implants. During surgery, 25/26 (96.1%) of the grafts adapted well to the bone defect. Immediate post-operative complications were pain and swelling (2/26 patients: 7.6%), and bone graft exposure (3/26: 11.5%); one exposure led to infection, removal of the graft, and failure of the procedure. Excellent integration of the other grafts was observed 8 months after the regenerative procedure, with mean vertical and horizontal bone gains of 2.10 mm (± 0.35) and 2.96 mm (± 0.45), respectively. Twenty-five implants were placed and restored with single crowns. Three years later, all implants were in function. The 3-year implant crown success rate and peri-implant MBL were 92.0% and 0.7 mm (±0.19), respectively. CONCLUSIONS: With custom-made CAD/CAM synthetic HA/beta-TCP onlay grafts reconstruction of small vertical and/or horizontal defects of the alveolar ridge was obtained; this enabled implant placement, with high implant-crown success rate after 3 years. Further studies are needed to validate this technique. STATEMENT OF CLINICAL RELEVANCE: Custom-made CAD/CAM synthetic HA/beta-TCP onlay grafts may represent an option for regeneration of small bone defects prior to implant placement.

A Prospective Longitudinal Clinical Trial Evaluating the Preservation of the Peri-implant Hard and Soft Tissues.

This prospective longitudinal clinical trial aimed to evaluate the success of a bone-level implant with an integrated platform-switched connection by assessing peri-implant soft tissue and marginal bone level. Twenty-six patients were treated in two different centers with implants placed in healed partially edentulous ridges. Implant success rate and marginal bone level were evaluated with photographs, radiographs, and clinical measurements, with a 6-month postloading follow-up. The esthetic appearance of the photographed peri-implant soft tissue was evaluated at 6 months via the Pink Esthetic Score applied by two calibrated operators. All of the implants except for one placed in the mandible demonstrated successful osseointegration, resulting in a success rate of 97.8% at the 6-month follow-up. Compared to historical controls, no detectable differences in peri-implant marginal bone loss or esthetic outcome were seen.

Graphene-Silicon Device for Visible and Infrared Photodetection.

The fabrication of a graphene-silicon (Gr-Si) junction involves the formation of a parallel metal-insulator-semiconductor (MIS) structure, which is often disregarded but plays an important role in the optoelectronic properties of the device. In this work, the transfer of graphene onto a patterned n-type Si substrate, covered by Si3N4, produces a Gr-Si device, in which the parallel MIS consists of a Gr-Si3N4-Si structure surrounding the Gr-Si junction. The Gr-Si device exhibits rectifying behavior with a rectification ratio up to 104. The investigation of its temperature behavior is necessary to accurately estimate the Schottky barrier height (SBH) at zero bias, φb0 = 0.24 eV, the effective Richardson's constant, A* = 7 × 10-10 AK-2 cm-2, and the diode ideality factor n = 2.66 of the Gr-Si junction. The device is operated as a photodetector in both photocurrent and photovoltage mode in the visible and infrared (IR) spectral regions. A responsivity of up to 350 mA/W and an external quantum efficiency (EQE) of up to 75% are achieved in the 500-1200 nm wavelength range. Decreases in responsivity to 0.4 mA/W and EQE to 0.03% are observed above 1200 nm, which is in the IR region beyond the silicon optical band gap, in which photoexcitation is driven by graphene. Finally, a model based on two parallel and opposite diodes, one for the Gr-Si junction and the other for the Gr-Si3N4-Si MIS structure, is proposed to explain the electrical behavior of the Gr-Si device.

Tolerances in the production of six different implant scanbodies: a comparative study.

PURPOSE: To investigate and compare the production tolerances of six different commercially available implant scan bodies (SBs), with the null hypothesis that there would be no tolerances in the production or significant differences between the different SBs. MATERIALS AND METHODS: Six different implant SBs (IO 6A-B and IO 2B-B, Nobel Biocare; RC 4.1 mm 025.4915 and RN 4.8 mm 048.168, Straumann; KR 352KR1A0, BTK BIOTEC; and AANISR4013T, MegaGen) were evaluated. Five specimens of each SB type (a total of 30 samples) were screwed onto the corresponding implant analogs and underwent dimensional analysis with optical microscopy (QVI Smartscope Flash 200, Optical Gaging Products) and precision probing (R 0.25, Renishaw). The outcome variables were SB height, diameter, and angle of the flat face on the top (plane). All measurements were compared with the corresponding computer-assisted design library measurements used as a reference to assess the manufacturing tolerances. Statistical analyses were performed to compare the results obtained with the different SBs. RESULTS: Tolerances in the manufacture of the SBs were reported in height, diameter, and plane measurements, and statistically significant differences between the different types of SBs were found. Therefore, the null hypothesis was rejected. Most of the deviations and tolerances were reported in height measurements with conical connection implants. CONCLUSIONS: Tolerances in the production and statistically significant differences were found among the six commercially available SBs evaluated in this study. Additional studies with larger sample sizes and other types of SBs are needed.

A noninterventional study documenting use and success of implants with a new chemically modified titanium surface in daily dental practice.

A new chemically modified titanium surface, SLActive, has recently been developed. The results obtained in controlled clinical trials indicate that this implant can be safely used and that it offers predictable results. The goal of this noninterventional study was to verify that the success rates of implants used in daily dental practice are comparable to those reported in controlled clinical trials. This study was a prospective, noninterventional study using implants with a chemically modified surface according to the daily dental practice procedures applied by private practitioners. The choice of the implantation procedure and the loading protocol were the responsibility of the investigator and were chosen according to the patient's needs. Thirty clinical centers actively participated in this study, and 226 patients were treated, of which, 8 patients were lost to follow-up. Because of the noninterventional design of the study, the patients were not selected according to strictly defined inclusion/exclusion criteria. Thus, the study included individuals with risk factors such as smoking (24%), untreated gingivitis or periodontitis (9%), and bruxism (6%). The implants were equally distributed between mandible (46%) and maxilla (54%). A bone augmentation procedure was done in 31% of the cases. Early loading (functional loading between 48 hours and 3 months after implant insertion) was applied most frequently (48%), followed by the conventional loading protocol (3 to 6 months after implant placement, 34%). Immediate restoration and immediate loading were rare (7% and 2%, respectively). Of 276 implants inserted and documented, 5 implants failures were reported, all of which were associated with a sinus floor augmentation procedure. The survival rate was 98.2% at the 1-year follow-up visit. The results showed that implants with a chemically modified surface can be successfully restored with success rates similar to those reported in formal clinical trials under more controlled conditions.

Peri-implant Soft Tissue Management: Cairo Opinion Consensus Conference.

Peri-implant soft tissues play a role of paramount importance, not only on the esthetic appearance, but also on the maintenance and long-term stability of implants. The present report presents the conclusions from the Consensus Conference of the South European North African Middle Eastern Implantology & Modern Dentistry Association (SENAME) (4-6 November 2016, Cairo, Egypt). The conference focused on the topic of the soft tissue around dental implants, and in particular, on the influence of implant configurations on the marginal soft tissues, soft tissue alterations after immediate, early or delayed implant placement and immediate loading, the long-term outcomes of soft tissue stability around dental implants, and soft tissue augmentation around dental implants. Thirty world experts in this field were invited to take part in this two-day event; however, only 29 experts were in the final consensus voting process.

Graphene Schottky Junction on Pillar Patterned Silicon Substrate.

A graphene/silicon junction with rectifying behaviour and remarkable photo-response was fabricated by transferring a graphene monolayer on a pillar-patterned Si substrate. The device forms a 0.11 eV Schottky barrier with 2.6 ideality factor at room temperature and exhibits strongly bias- and temperature-dependent reverse current. Below room temperature, the reverse current grows exponentially with the applied voltage because the pillar-enhanced electric field lowers the Schottky barrier. Conversely, at higher temperatures, the charge carrier thermal generation is dominant and the reverse current becomes weakly bias-dependent. A quasi-saturated reverse current is similarly observed at room temperature when the charge carriers are photogenerated under light exposure. The device shows photovoltaic effect with 0.7% power conversion efficiency and achieves 88 A/W photoresponsivity when used as photodetector.

A WSe2 vertical field emission transistor.

We report the first observation of a gate-controlled field emission current from a tungsten diselenide (WSe2) monolayer, synthesized by chemical-vapour deposition on a SiO2/Si substrate. Ni contacted WSe2 monolayer back-gated transistors, under high vacuum, exhibit n-type conduction and drain-bias dependent transfer characteristics, which are attributed to oxygen/water desorption and drain induced Schottky barrier lowering, respectively. The gate-tuned n-type conduction enables field emission, i.e. the extraction of electrons by quantum tunnelling, even from the flat part of the WSe2 monolayers. Electron emission occurs under an electric field ∼100 V µm-1 and exhibits good time stability. Remarkably, the field emission current can be modulated by the back-gate voltage. The first field-emission vertical transistor based on the WSe2 monolayer is thus demonstrated and can pave the way to further optimize new WSe2 based devices for use in vacuum electronics.

Bias Tunable Photocurrent in Metal-Insulator-Semiconductor Heterostructures with Photoresponse Enhanced by Carbon Nanotubes.

Metal-insulator-semiconductor-insulator-metal (MISIM) heterostructures, with rectifying current-voltage characteristics and photosensitivity in the visible and near-infrared spectra, are fabricated and studied. It is shown that the photocurrent can be enhanced by adding a multi-walled carbon nanotube film in the contact region to achieve a responsivity higher than 100   mA   W - 1 under incandescent light of 0.1   mW   cm - 2 . The optoelectrical characteristics of the MISIM heterostructures are investigated at lower and higher biases and are explained by a band model based on two asymmetric back-to-back Schottky barriers. The forward current of the heterojunctions is due to majority-carrier injection over the lower barrier, while the reverse current exhibits two different conduction regimes corresponding to the diffusion of thermal/photo generated carriers and majority-carrier tunneling through the higher Schottky barrier. The two conduction regimes in reverse bias generate two plateaus, over which the photocurrent increases linearly with the light intensity that endows the detector with bias-controlled photocurrent.

Field Emission Characterization of MoS2 Nanoflowers.

Nanostructured materials have wide potential applicability as field emitters due to their high aspect ratio. We hydrothermally synthesized MoS2 nanoflowers on copper foil and characterized their field emission properties, by applying a tip-anode configuration in which a tungsten tip with curvature radius down to 30-100 nm has been used as the anode to measure local properties from small areas down to 1-100 µm2. We demonstrate that MoS2 nanoflowers can be competitive with other well-established field emitters. Indeed, we show that a stable field emission current can be measured with a turn-on field as low as 12 V/µm and a field enhancement factor up to 880 at 0.6 µm cathode-anode separation distance.

Prognostic relevance of SOCS3 hypermethylation in patients with glioblastoma multiforme.

Alterations in the signal transduction pathways are key mechanisms in the pathogenesis of de novo glioblastoma multiforme (GBM), which are also involved in the resistance to chemo- and radiotherapy. Here, we analyzed the methylation status and mRNA expression of suppressor of cytokine signaling (SOCS)1-2-3, 3 of the most important inhibitory molecules of the signal transduction circuitry, in 46 GBM specimens. The relationship between methylation status of SOCS1-2-3 and clinical outcome was investigated. Using methylation-specific PCR (MS-PCR) and sequencing, after bisulphite modification, we found that the promoter of SOCS1-2-3 was methylated in 24, 6.5 and 35% of GBM, respectively. Real-time analysis showed that in methylated GBM, mRNA expression for SOCS1-2-3 was reduced by 5, 3 and 7-folds, respectively, when compared with unmethylated GBM. Moreover, methylation of SOCS3 promoter significantly associated with an unfavorable clinical outcome (p < 0.0002). Our data suggest that methylation of SOCS3 may be involved in the pathogenesis of GBM and in the resistance of this neoplasm to conventional treatment.

Retrospective Analysis of Long-Term (up to 12 years) Clinical and Radiologic Performance of Anodized-Surface Implants.

To accurately assess the long-term performance of anodized-surface implants, more data monitoring is needed outside of clinical evaluations. This retrospective study evaluated long-term implant survival and bone remodeling after up to 12 years of function. Data from 195 implants placed in 60 patients over a follow-up period ranging from 0.6 to 12.1 years were included. The implant-level survival rate was 99.0%. Marginal bone loss remained low across all follow-up cohorts. The data show that anodized-surface implants are a safe, reliable option with high implant survival rates and low levels of bone loss.