Effect of Implantoplasty on Fatigue Performance and Surface Roughness of Narrow Diameter Dental Implants

Implantoplasty (IP) is used in dental implants with peri-implantitis and aims to remove threads and polish rough surfaces in order to prevent bacterial colonization. As a result of this procedure, implant strength might be compromised. We tested 20 tapered screw-shaped Ti6Al4V dental implants with a simulated bone loss of 50%. Ten implants underwent IP and 10 served as controls. Surface topography (Sa, Sz, Ssk and Sdr) was analyzed with a confocal optical microscope. Subsequently, cyclic loads were applied with a servo-hydraulic mechanical testing machine (5x106 cycles at 15 Hz, between the maximal compression force - 529N in the IP group and 735N in the control group - and 10% of that force). We recorded the number of cycles until failure and the type of failure. Implant failure was analyzed by visual inspection and scanning electron microscopy. Implantoplasty reduced the median Sa from 1.76 (IQR=0.11) to 0.49 (IQR=0.16). The fatigue limits of the control and implantoplasty groups were 551 N and 529 N, respectively. The scanning electron micrographs showed fatigue striations indicating fatigue failure. The infinite life range of the dental implants evaluated was largely above the threshold of usual chewing forces. Implantoplasty seems to render a fairly smooth surface and has a limited impact upon fatigue resistance.

Stress-strain state of damaged reinforced concrete bended elements at operational load level

Each structure is exposed to different influences during operation. As a result, there are various defects and damages of these elements that affect their safe operation. The article presents the results of experimental studies of reinforced concrete beams with damages to stretched reinforcement made with and without initial load application. As the damages were accepted one or five Ø5.6 mm holes. In one case, the damage was made until the beam destruction (up to the 8.4 mm opening) Control samples of both series were destroyed due to crushing of the compressed zone of concrete. Samples that were damaged without initial loading collapsed due to rupture of the stretched reinforcement. The same type of failure was identified for damages at the operational load level.

Experimental Study of the Impact of Glass Beads on Adhesive Joint Strength and Its Failure Mechanism

The use of modern structural adhesives provides a lightweight, practical, and high strength joining methodology, which is increasingly being adopted in the automotive and aeronautical sectors, among many others. However, the strict mechanical performance standards that must be met in these applications require a constant search for ways of improving the adhesives’ behavior, which has led to the growing use of reinforcements as a way of improving the capabilities of bonded joints. The aim of this work was, thus, to analyze how the addition of inorganic fillers to the adhesive layer affects a joint’s strength and its failure mechanism. To this end, single lap joint specimens with mild steel and high strength steel substrates were tested, at quasi-static speeds, and with different amounts of glass microspheres reinforcing two different structural adhesives. The experimental results indicated that the addition of glass particles reduced the joint performance for both substrates under study. Furthermore, the failure pattern was found to evolve from adhesive failure to a cohesive type of failure as the amount of glass particles present in the adhesive was increased.

Analysis of Changes in the Tensile Bond Strenght of Soft Relining Material with Acrylic Denture Material

Abrasions and pressure ulcers on the oral mucosa are most often caused by excessive pressure or incorrect fitting of the denture. The use of soft relining materials can eliminate pain sensations and improve patient comfort. The main functional feature of soft elastomeric materials is the ability to discharge loads from the tissues of the mucosa. (1) Background: The aim of the work was a comparative laboratory study of ten materials used for the soft lining of acrylic dentures. (2) Methods: There were materials based on acrylates (Vertex Soft, Villacryl Soft, Flexacryl Soft) and silicones (Sofreliner Tough Medium, Sofreliner Tough Medium, Ufi Gel SC, GC Reline Soft, Elite Soft Relining, Molloplast). Laboratory tests include the analysis of the tensile bond strength between the relining material and the acrylic plate of the prosthesis. The tests were conducted taking into account 90-day term aging in the distilled water environment based on the methodology presented in the European Standard ISO 10139-2. (3) Results: After three months of observation, the highest strength of the joint was characterized by Flexacryl Soft acrylic, for which the average value was 2.5 MPa. The lowest average value of 0.89 MPa was recorded for the GC Reline Soft silicone material. Over time, an increase in the value of the strength of the combination of acrylic materials and a decrease in these values in the case of silicone materials was observed. (4) Conclusion: Each of the tested silicone materials showed all three types of damage, from adhesive to mixed to cohesive. All acrylic-based materials showed an adhesive type of failure. Time did not affect the type of destruction.

Analisis Kegagalan Pada Komponen Poros Pompa Industri

Pumps are very important industrial equipment in the petroleum industry. The component that often fails is the pump shaft. Therefore, it is necessary to conduct a failure analysis of this component to determine the mode/type of failure and how it occurred. This study used Scanning Electron Microscope (SEM), metallographic test, chemical composition test, and Brinell hardness test with the standard UNSS42000 material. Fatigue test to determine the fatigue limit of the shaft with a rotary bending fatigue test. The failure model that occurred was fatigue failure characterized by initial cracks, crack growth, ratchet marks, sudden fracture areas. Based on the comparison between the test results of chemical composition and mechanical properties of the material, the drive shaft pump material was suitable for the UNS S42000 material.

Shear strength model and prediction of failure mode for multi-spiral column

The damage of reinforced concrete columns due to shear is often serious, so this type of failure should be avoided from the design. In this paper, a model derived based on the discrete computational method is proposed to calculate the shear strength of column carried by multi-spiral transverse reinforcement, accounting for the effect of compression depth. Furthermore, based on this model, a method is proposed to predict the failure mode of multi-spiral columns. The test database of multi-spiral columns from previous studies is used to validate both the shear strength and failure mode predictions. The proposed model with a crack angle of 40 degrees gives the best estimation of the shear strength of multi-spiral columns, and the proposed method predicts well the failure mode of these columns. To avoid shear failure, the ratio of the minimum shear strength calculated from the proposed model with a crack angle of 40 degrees to the shear force based on the moment-curvature analysis is suggested to be larger than 1.2.

Micro Push-Out Bond Strength of Resin Composite to Dentin in Primary Dentition Using Three Universal Adhesives with Different pH: An In Vitro Study

To evaluate the bond strength of different universal adhesives on deciduous tooth dentineand their relationship with the composition and potential of hydrogen (pH). Methods: An in vitromicro push-out test on 150 samples (n = 50) per group per adhesive, namely, Adhese Universal(ADH; Ivoclar Vivadent), Futurabond U (FUT; Voco GmbH) (Test), and Scotchbond Universal withpre-conditioning (SCO; 3M) (Control), to record bond strength (BS) and type of adhesive failure.Results: The results of the different adhesives (megapascals (MPa)) varied, showing no statisticalsignificance. The corresponding averages are in MPa: ADH, 13.66 2.81; FUT, 14.48 2.88; SCO,14.98 3.96. Additionally, the frequency of type of failure was as follows: mixed (60.7%), adhesive(27.3%), and cohesive (12%). Conclusions: SCO, with a pH of 2.7, showed greater resistance tofracture, while FUT, with a pH of 2.3 and no pre-conditioning, approached the same values, being aone-step adhesive. No relationship was found between failure and type of adhesive.

Dynamic Analysis of Mechanical Systems Using Image Processing

Thanks to the fact that nowadays substantial progress has been made in new ways of analyzing our environment using image processing techniques, it is imperative to highlight the importance of applying this methodology to mechanisms, which are our object of study and these elements are present in various sectors, such as industrial, automotive, academic, etc. In the previously mentioned sectors, the mechanisms are a fundamental element for the correct operation of the devices that each sector has. Therefore, knowing the dynamic behavior of the mechanisms is an essential task, since, if any type of failure occurs, it could cause damage to an entire process. The article proposes to develop a methodology that allows the analysis of dynamic variables in different types of mechanisms, through the use of image processing techniques specifically the detection, filtering and tracking of objects, using filters such as the Gaussian filter and background subtraction in order to improve the quality of the information to be analyzed. The results obtained through the application of the proposed methodology were compared with a simulation of a CAD/CAM/CAE software, in this case Siemens NX 12®, these results were satisfactory under certain criteria that will be exposed in the analysis section, thanks to this it can be affirmed that the proposed methodology is acceptable at the time of knowing the dynamic variables in mechanisms

DOP46 Sustainability rate of immunomodulators monotherapy in patients with Crohn’s Diseases: A population-based analysis from the epi-IIRN cohort

Background Immunomodulators (IMM), including thiopurines and methotrexate (MTX), have been long used to maintain remission in Crohn’s disease (CD), both associated with remission, but also with toxicity and therapeutic failure. We aim to compare the sustainability of thiopurines and MTX commenced as monotherapy in patients with CD, and to explore predictors of sustainability. Methods This study was performed on data from four Health Maintenance Organizations (HMOs), covering 98% of the Israeli population. We included all biologic-naïve CD patients diagnosed after 2005 and treated with IMM monotherapy for at least three months. Sustainability was defined as continues IMM treatment without switching therapy, adding biologics or requiring surgery. In addition, at most one short steroid course was allowed. Cox regression model was used to explore estimated predictors to sustainability. To compare sustainability rate between thiopurines and MTX we used propensity score (PS) matching, and thereafter Cox regression model. Results A total of 4,891 (1,551 [32%] pediatric-onset and 3,340 [68%] adults) IMM-treated patients were included with 37,825 person-years of follow up, of whom 4,339 (89%) were treated with thiopurines and 552 (11%) with MTX. The median time from CD diagnosis to initiation of IMM was 6.1 months (IQR 1.7–19.7), and the median course duration was 11.9 months (6.1–25.3). Sustainability rate was recorded in 92% of patients after 6 months from initiation of IMM and 81%, 69% and 65% at one, three and five years, thereafter. The most common type of failure was escalation to biologics (67%), while 17% required repeated steroid courses and 15% underwent surgery. Sustainability was associated with earlier initiation of IMM during the disease course (HR 0.98 [95%CI 0.97–0.985]) and lack of steroids at initiation of IMM (HR 0.7 [95%CI 0.6–0.8]). A PS adjusted analysis that included 337 thiopurnes-treated patients individually matched with 337 MTX-treated patients, showed sustainability was significantly better with thiopurines (HR 0.7 [95%CI 0.5–0.8]). Conclusion Two thirds of biologic-naïve CD patients treated with IMM monotherapy sustain this treatment after five years, especially when initiated early during the disease course. Sustainability was more likely in those treated with thiopurines compared with MTX.

Risk Analysis of DP Incidents During Drilling Operations

This paper aims to present a method to determine the type of dynamic positioning (DP) incidents that have a more significant risk during drilling operations in the period 2007-2015, according to the element or the type of failure that causes the DP system to fail. Two different classifications are made: 1) according to the element that produces the incident (which has been the traditional classification in the industry) and 2) according to the type of error that arises, the latter being an alternative classification proposed in this paper. The predictable financial losses for each level of severity are used to define the resulting consequences for each case. A risk analysis is performed with the data obtained, showing the potentially more dangerous incidents, either because of their higher number of occurrences or because their consequences are remarkable. According to the classification proposed, the main causes with the higher risk results were power and environmental, according to the traditional classification, and fault/failure. Thus, the power segment’s combination of failures is the riskiest cause during the DP drilling operations.