Study on the Effect of Inter-Layer Cooling Time on Porosity and Melt Pool in Inconel 718 Components Processed by Laser Powder Bed Fusion

This paper investigates the effects on the material microstructure of varying the Inter-Layer Cooling Time (ILCT) during the printing process in laser powder bed fusion (L-PBF) multi-laser machines. Despite these machines allowing higher productivity rates compared to single laser machines, they are affected by lower ILCT values, which could be critical for material printability and microstructure. The ILCT values depend both on the process parameter sets and design choices for the parts and play an important role in the Design for Additive Manufacturing approach in L-PBF process. In order to identify the critical range of ILCT for this working condition, an experimental campaign is presented on the nickel-based superalloy Inconel 718, which is widely used for the printing of turbomachinery components. The effect of ILCT on the microstructure of the material is evaluated in terms of porosity and melt pool analysis on printed cylinder specimens, considering ILCT decreasing and increasing in the range of 22 to 2 s. The experimental campaign shows that an ILCT of less than 6 s introduces criticality in the material microstructure. In particular, at an ILCT value of 2 s, widespread keyhole porosity (close to 1‰) and critical and deeper melt pool (about 200 microns depth) are measured. This variation in melt pool shape indicates a change in the powder melting regime and, consequently, modifications of the printability window promoting the expansion of the keyhole region. In addition, specimens with geometry obstructing the heat flow have been studied using the critical ILCT value (2 s) to evaluate the effect of the surface-to-volume ratio. The results show an enhancement of the porosity value (about 3‰), while this effect is limited for the depth of the melt pool

XENOGENEIC DERMAL MATRIX VERSUS AUTOLOGOUS CONNECTIVE TISSUE GRAFT VERSUS NO GRAFT AT ABUTMENT CONNECTION FOR IMPROVING AESTHETICS: 6-MONTH OUTCOMES OF A RANDOMISED CONTROLLED TRIAL

OBJECTIVES. The aim of this multicentre randomised controlled trial was to evaluate the efficacy of a xenogeneic dermal matrix in widening keratinised peri-implant tissues du-ring second-stage surgery, and to compare it to both autologous connective tissue graft and a control group with no augmentation. MATERIAL AND METHODS. Patients requiring an increase in keratinised gingiva width were enrolled by four university/dental practices and randomised into three different groups for grafting procedures at the implant uncovering stage: either xenogeneic dermal matrix (Group X), autologous connective tissue graft (Group A) or no graft (control, Group C). The primary outcomes were width of keratinised tissue and facial soft tissue levels, evaluated at three different time points (T0, implant uncovering stage; T1 and T2, six weeks and six months after surgery, respectively). Secondary outcomes were: implant failure, complications, marginal bone loss, papilla index, facial soft tissue level, pink esthetic score, and aesthetic assessment by patients. RESULTS. Thirty-six patients, with one implant per patient, were enrolled at two centres (18 at each centre): 12 for control, 12 for xenogeneic dermal matrix and 12 for autologous tissue graft. Three patients dropped out and two patients from the autologous group had implant failures. No complications were recorded. After six months, the width of keratini-sed tissue increased by 0.16 ± 1.01 (P = 0.79), 1.05 ± 0.76 (P = 0.01) and 0.80 ± 1.73 mm (P = 0.28), and facial soft tissue level was-0.95 ± 0.85 (P = 0.04), 0.32 ± 0.57 (P = 0.15) and 0.35 ± 0.79 mm (P = 0.30) respectively in Groups C, X and A groups. Between-group analysis showed that, with respect to control, only facial soft tissue level (1.31 mm, P = 0.01) and width of keratinised mucosa (2.43 mm, P = 0.01) outcomes in the autologous graft group were statistically significant at T2. Mean marginal bone loss between T0-T2 was-0.4 ± 0.4mm, with no differences between groups. Pink aesthetic score showed no significant differences between groups, being 0.89 for A-C (P = 0.41), 0.88 for A–X (P = 0.63) and 0.72 for X-C (P = 0.88). Patient’s aesthetic satisfaction (Visual Analogue Scale) was 92.2 ± 8.4, 93.8 ± 7.7, 97.2 ± 3.0, for Groups C, X and A, respectively. Between the two dental centres, only facial soft tissue level at T0–T2 was significantly different, by 0.67 ± 0.62 mm (P = 0.03). CONCLUSIONS. After six months, autologous connective tissue graft yielded a significant gain in facial soft tissue levels and width of keratinised mucosa, as compared to the control group (no graft)

Histomorphometric and Clinical Analysis of Ridge Preservation Procedures in Extraction Sockets with Buccal Bone Defects (>5mm) Using an In Situ Hardening Biphasic Calcium Phosphate (HA/β-TCP) Graft and a Bioresorbable Matrix: A Human Study at 6 Months

Many biomaterials have been proposed for ridge preservation techniques to counteract fresh extraction socket resorption. The primary aim of this prospective single cohort study was to evaluate the histomorphometric outcomes of a synthetic biphasic calcium phosphate (60% HA/40% β-TCP) and a synthetic poly-lactic acid membrane, used to graft fresh extraction socket sites with a full or partial (>5mm) resorption of the buccal bone plate. Patients recruited were treated at one esthetic site with a ridge preservation procedure to receive an implant-supported prosthesis. After 6 months of healing, a bone biopsy was harvested. Outcome evaluations were: biological complications, histomorphometrical analysis, and alveolar horizontal and vertical bone loss (∆AHB, ∆AVB). Thirteen subjects were included in this study. Two cases of biological complication were recorded. All 13 patients received implant insertion. From histomorphometric analysis, a mean of 48.9 ± 11.9%, 29.0 ± 9.3%, and 22.0 ± 9.7% was recorded for soft tissues, new bone, and residual graft particles, respectively. From clinical analysis, a mean of 0.5 ± 1.0 mm (p-value < 0.05) and 0.9 ± 1.3 mm (p-value < 0.05) was recorded for alveolar horizontal and vertical bone loss, respectively. In conclusion, this prospective cohort study showed encouraging results in preserving alveolar ridge dimension. A moderate percentage of new bone and an acceptable alveolar ridge loss were achieved at a 6 month follow-up

Axiomatic Design of a Test Artifact for PBF-LM Machine Capability Monitoring

Powder Bed Fusion Laser Melting (PBF-LM) additive manufacturing technology is expected to have a remarkable impact on the industrial setting, making possible the realization of a metallic component with very complex designs to enhance product performance. However, the industrial use of the PBF-LM system needs a capability monitoring system to ensure product quality. Among the various studies developed, the investigation of methodology for the actual machine capability determination has been faced and still represents an open point. There are multiple authors and institutes proposing different investigation methods, ranging from the realization of samples (ex situ analysis) to installing monitoring devices on the machine (in situ analysis). Compared to other approaches, sample realization allows for assessing how the machine works through specimen analysis, but it is sensitive to the sample design. In this article, we first present an analysis of a well-known test artifact from an Axiomatic Design perspective. Second, based on the customer needs analysis and adjustments with respect to the use of hypothetical additive production lines, a new test artifact with an uncoupled design matrix is introduced. The proposed design has been experimentally tested and characterized using artifact made of Inconel 718 superalloy to evaluate its performance and representativeness in machine capability assessment. The results show an accurate identification of beam offset and scaling factor considering all the building platform positions. In addition, the artifact is characterized by a reduced building time (more than 90% with respect to the reference NIST artifact) and a halved inspection time (from 16 h to 8 h)

A Method to Optimize Parameters Development in L-PBF Based on Single and Multitracks Analysis: A Case Study on Inconel 718 Alloy

In the context of the use of AM, particularly in the L-PBF technique, the printability characterization of material occurs through the identification of its printability map as a function of printing process parameters. The printability map identifies the region where the powder melting is optimal and ensures a dense and defect-free material. Identifying the zones affected by physical phenomena that occur during the printing process which lead to material defects such as keyhole, lack of fusion and balling mode is also possible. Classical methods for the characterization of material and the identification of its printability map require the printing of a large number of specimens. The analysis of the specimens is currently time-consuming and costly. This paper proposed a methodology to identify optimal process parameters in L-PBF using an integrated single and multi-tracks analyses embedded in an overall algorithm with detailed metrics and specific factors. The main scope is to speed up the identification of printability window and, consequently, material characterization, reducing the number of micrographic analyses. The method is validated through an experimental campaign assessing the material microstructure in terms of porosity and melt pool evaluation. The case study on IN718 superalloy shows how the application of the proposed method allows an important reduction of micrographic analysis. The results obtained in the case study are a reduction of 25% for the complete definition of the printability map and more than 90% for identifying the zone with a high productivity rate

Long-term follow-up of single crowns supported by short, moderately rough implants-A prospective 10-year cohort study

OBJECTIVES To evaluate prospectively the clinical and radiographic outcomes after ten years of short (6 mm) implants with a moderately rough surface supporting single crowns in the posterior region. MATERIAL AND METHODS Forty 6 mm modified sandblasted large-grit acid-etched (mod-SLA), soft tissue level implants were installed in the distal segments of 35 consecutive patients. After 6 weeks of healing, abutments were tightened, and single porcelain-fused-to-metal crowns were cemented. Implant survival, marginal bone loss, and clinical crown/implant ratio were evaluated at various time intervals up to 10 years after loading. RESULTS Two out of the 40 implants were lost before loading, one implant was lost after 7 years because of peri-implantitis. One patient with two implants died and was excluded from analysis. Two patients did not come at the 10-year follow-up and were considered as drop out (2 implants). The survival rate was 91.7% (n = 36). Thirty-three implants were available for marginal bone loss evaluation. A mean marginal bone loss after 10 years of function was 0.8 ± 0.7 mm. Between 5 and 10 years, the loss was 0.2 ± 0.4 mm. No technical complications were registered during the 10-year period. The clinical crown/implant ratio increased with time from 1.6 at the delivery of the prosthesis to 2.0 after 10 years of loading with no increase between 5 and 10 years. CONCLUSION Short (6 mm) implants with a moderately rough surface supporting single crowns in the posterior region and loaded after 6-7 weeks maintained full function for at least 10 years with low marginal bone resorption

Quantification of D-mannose in plasma: Development and validation of a reliable and accurate HPLC-MS-MS method

The present paper describes the development and the validation process – in compliance with the EMA guidelines – of a method based on tandem mass spectrometry coupled to liquid chromatography for the accurate quantification of mannose in human plasma samples. The quick sample preparation procedure, simplified by the absence of any derivatization step, makes the assay suitable for routine use in a clinical chemistry laboratory. The method validation yielded satisfactory selectivity, with a good separation of mannose from its epimers (glucose and galactose), linearity over the whole concentration range of interest (0.31–40 μg/mL), reproducibility with RSD <10%, and accuracy in the range 96 – 104%. Instrumental LLOD (0.31 μg/mL) and LLOQ (1.25 μg/mL) were good enough to detect endogenous plasma mannose levels and in agreement with recent data from the literature. Sensitivity was affected by a 5-fold dilution factor, which, if necessary, can be reduced. The method robustness was proven in more than 600 injections, most of them being of plasma samples, used also to assess the reference ranges in healthy subjects (9.93 ± 3.37 µg/mL) and type 2 diabetic patients (23.47 ± 6.19 µg/mL)

The Automated External Defibrillator : Heterogeneity of Legislation, Mapping and Use across Europe. New Insights from the ENSURE Study

Introduction: The rapid use of an automated external defibrillator (AED) is crucial for increased survival after an out-of-hospital cardiac arrest (OHCA). Many factors could play a role in limiting the chance of an AED use. We aimed to verify the situation regarding AED legislation, the AED mapping system and first responders (FRs) equipped with an AED across European countries. Methods: We performed a survey across Europe entitled “European Study about AED Use by Lay Rescuers” (ENSURE), asking the national coordinators of the European Registry of Cardiac Arrest (EuReCa) program to complete it. Results: Nineteen European countries replied to the survey request for a population covering 128,297,955 inhabitants. The results revealed that every citizen can use an AED in 15 countries whereas a training certificate was required in three countries. In one country, only EMS personnel were allowed to use an AED. An AED mapping system and FRs equipped with an AED were available in only 11 countries. The AED use rate was 12–59% where AED mapping and FR systems were implemented, which was considerably higher than in other countries (0–7.9%), reflecting the difference in OHCA survival. Conclusions: Our survey highlighted a heterogeneity in AED legislation, AED mapping systems and AED use in Europe, which was reflected in different AED use and survival

The automated external defibrillator: Heterogeneity of legislation, mapping and use across europe. new insights from the ensure study

Introduction: The rapid use of an automated external defibrillator (AED) is crucial for increased survival after an out-of-hospital cardiac arrest (OHCA). Many factors could play a role in limiting the chance of an AED use. We aimed to verify the situation regarding AED legislation, the AED mapping system and first responders (FRs) equipped with an AED across European countries. Methods: We performed a survey across Europe entitled “European Study about AED Use by Lay Rescuers” (ENSURE), asking the national coordinators of the European Registry of Cardiac Arrest (EuReCa) program to complete it. Results: Nineteen European countries replied to the survey re-quest for a population covering 128,297,955 inhabitants. The results revealed that every citizen can use an AED in 15 countries whereas a training certificate was required in three countries. In one country, only EMS personnel were allowed to use an AED. An AED mapping system and FRs equipped with an AED were available in only 11 countries. The AED use rate was 12–59% where AED mapping and FR systems were implemented, which was considerably higher than in other countries (0–7.9%), reflecting the difference in OHCA survival. Conclusions: Our survey highlighted a heterogeneity in AED legislation, AED mapping systems and AED use in Europe, which was re-flected in different AED use and survival