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Within an investigation focused on effect of casting conditions on steel quality in an industrial beam blanks mould, different nozzle geometries were tested with Computational Fluid Dynamics modelling. The innovative nature of the work consisted in feeding with only one nozzle, whereas two nozzles in the flange-tip zone are commonly used. This configuration has the advantage of a simplified mono-slide gate casting layout, but single nozzle feeding can bring about risks of too high steel velocity in the mould, harmful for shell integrity and meniscus stability.Having in mind the mentioned constraints, different geometry solutions were checked and, to assess the solutions found, suitable indices were defined, related to flow conditions able to prevent slag entrapment at the meniscus, and hot-spotting at walls, harmful for the solid shell integrity.The modelling work gave general indications on undesired flow features and guidelines to improve reference conditions, involving number of holes and holes angle, size and shape. For the caster mould and the operating conditions under concern, a solution was found satisfying the indices, and expected to fulfil the quality requests. It consisted of a nozzle with a 50 mm diameter throat, a 50 mm× 60 mm elliptical lateral port inclined 25° downwards and a 20 mm-diameter bottom hole. A water model check with such a nozzle prototype validated the model supporting the solution identified to be used on plant.KEY WORDS: beam blanks; flow field; nozzle; cracks; shell remelting; slag entrapment. ForewordIn continuous casting of beam blanks, the occurrence of longitudinal surface cracks plays a relevant role in affecting as-cast quality. Not so many studies on surface crack occurrence in beam blanks are shown in literature. Lee and others, 1) within the as-cast beam blank shape (Fig. 1) identified the web and fillet region as mostly prone to crack formation, also noticing that shell formation is somewhat retarded at the flange-center region, due to the steel stream impingement from the feeding nozzle. The conclusions were gained based on a suitably defined crack susceptibility coefficient. Furthermore, Seok and Yoon 2) investigated the effect of steel composition on longitudinal crack formation. The most relevant results were the identification of: a) a mostly sensitive crack susceptibility range of carbon contents (0.12-0.13 wt.%); b) the effect of casting speed on crack formation (a linear relationship). Then, Hibbeler et al., 3) performed a thorough 3D thermo-mechanical analysis of beam blank steel solidification without accounting for liquid metal flow. A coupled thermal-mechanical model of steel casting was applied to accurately simulate casting of steel beam blanks, validated with plant measurements. An efficient local-global numerical procedure is given to integrate a realistic elasticvisco-plastic phase-dependent constitutive model implemented into the commercial package ABAQUS, and insights are provided into the mechanisms of shell failure triggered first by a thinner she...

Subperiosteal implants (SIs) were first developed by Dahl in 1941 for oral rehabilitation in case of severe jaw atrophy. Over time, this technique was abandoned due to the high success rate of endosseous implants. The emergence of patient-specific implants and modern dentistry allowed a revisitation of this 80-year-old concept resulting in a novel “high-tech” SI implant. This study evaluates the clinical outcomes in forty patients after maxillary rehabilitation with an additively manufactured subperiosteal jaw implant (AMSJI®). The oral health impact profile-14 (OHIP-14) and numerical rating (NRS) scale were used to assess patient satisfaction and evaluate oral health. In total, fifteen men (mean age: 64.62 years, SD ± 6.75 years) and twenty-five women (mean age: 65.24 years, SD ± 6.77 years) were included, with a mean follow-up time of 917 days (SD ± 306.89 days) after AMSJI installation. Patients reported a mean OHIP-14 of 4.20 (SD ± 7.10) and a mean overall satisfaction based on the NRS of 52.25 (SD ± 4.00). Prosthetic rehabilitation was achieved in all patients. AMSJI is a valuable treatment option for patients with extreme jaw atrophy. Patients enjoy treatment benefits resulting in high patient satisfaction rates and impact on oral health.

Additively manufactured subperiosteal jaw implants (AMSJI) are patient-specific, 3D-printed, titanium implants that provide an alternative solution for patients with severe maxillary bone atrophy. The aim of this study was to evaluate the bony remodeling of the maxillary crest and supporting bone using AMSJI. Fifteen patients with a Cawood–Howell Class V or greater degree of maxillary atrophy were evaluated using (cone beam) computed tomography scans at set intervals: one month (T1) and twelve months (T2) after definitive masticatory loading of bilateral AMSJI implants in the maxilla. The postoperative images were segmented and superimposed on the preoperative images. Fixed evaluation points were determined in advance, and surface comparison was carried out to calculate and visualize the effects of AMSJITM on the surrounding bone. A total mean negative bone remodeling of 0.26 mm (SD 0.65 mm) was seen over six reference points on the crest. Minor bone loss (mean 0.088 mm resorption, SD 0.29 mm) was seen at the supporting bone at the wings and basal frame. We conclude that reconstruction of the severely atrophic maxilla with the AMSJI results in minimal effect on supporting bone. Reduced stress shielding with a biomechanically tuned subperiosteal implant does not induce radiographically significant crestal bone atrophy.

Introduction: We described our rationale and experiences with the use of cutting jigs for vertical ostectomy in cases of terminal maxillary dentition when edentulation and an additively manufactured subperiosteal jaw implant (AMSJI®) are planned. Material and Methods: Our experience covers 15 patients treated by four clinicians. We tabulated our criteria for planning and manufacturing vertical and horizontal ostectomy guides. Results: In order to guarantee accurate osteotomy, titanium guides are preferable to guides made of polymer. The most important consideration is to avoid acute angles in the buccal arms of the AMSJI®. It is up to the surgeon whether to screw-fix the ostectomy guides or to use handles to maintain their position. Discussion: Guided ostectomy has the potential to extend the use of AMSJI® to cases where teeth have yet to be removed or where the contours of the residual bone are not favorable. The use of guided ostectomy in such cases lessens the time between edentulation and implantation and improves the design of the implants.