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ABSTRACT Objective Materials and Methods Results Conclusion Physical and digital casts are required for fixed dental prosthesis (FDP) fabrication. However, the effect of abutment tooth geometry on the accuracy of FDP casts obtained by digital and analog workflows remains unclear. This study evaluated the accuracy of obtaining dental casts for veneer and full crowns with digital and analog workflows.A typodont model of the maxilla with unprepared teeth and veneer and full crown preparations was digitalized with intraoral scanning (TRIOS 3; 3Shape), digital model (DM) group, and the digital files were exported to two additive manufacturing technologies, resulting in the groups digital light processing (DLP) (Hunter; FlashForge) and polyjet (PLJ) (Eden 500 V; Stratasys). In addition, plaster casts (PCs) were obtained with polyvinyl siloxane (Express XT; 3M ESPE) double impressions and type IV plaster (FujiRock; GC America) as a control group. The sample size per group (n = 6) was defined in the pilot study. The digitization of the typodont and experimental casts was performed with a laboratory scanner (inEos X5; Dentsply Sirona). The measurement deviation (trueness and precision) to the reference model was performed with reverse engineering software (Geomagic Control X 2018; 3D Systems). Two‐way ANOVA was used to assess the effect of manufacturing techniques and abutment tooth geometry on model accuracy (primary outcome). In addition, one‐way ANOVA was used to assess significant differences between manufacturing techniques for complete arches, including abutments and unprepared teeth (secondary outcome). Tukey post hoc tests were used to compare means among groups. All statistical analyses considered a significant level of p ≤ 0.05.Statistically significant interactions were observed between manufacturing technique and abutment tooth geometry, affecting both trueness (p < 0.001) and precision (p < 0.001). For trueness, DM exhibited the lowest RMS values (p < 0.001), PC and DLP showed no significant difference (p = 0.056), and PLJ had significantly higher values than other techniques (p < 0.001), while premolar and molar preparations displayed significantly lower discrepancies compared to other types (p < 0.002). For precision, DM had the lowest values (p < 0.001), with PC also showing low values (p < 0.001), and no significant differences were observed between DLP and PLJ (p = 0.986). Veneer, premolar, and molar crown preparations demonstrated significantly lower RMS compared to anterior crowns.The design of the abutment tooth significantly influenced the trueness and precision of FDP casts obtained by digital and analog workflow. For trueness, DM exhibited the highest accuracy, outperforming PC, DLP, and PLJ and achieving better results with premolar and molar preparations compared to anterior crowns and veneers. For precision, DM was most accurate, followed by PC, DLP, and PLJ, with veneer, premolar, and molar crowns consistently outperforming anterior crowns. [ABSTRACT FROM AUTHOR]

In aerospace engineering, the existence of cracks highly alters the mechanical behaviors of structural components. As a new class of key structural components, functionally graded material (FGM) rectangular plates with an interior/side crack are focused on in this study. New analytical free vibration solutions are put forward for such cracked FGM plates. First, a cracked plate is decomposed into several subplates with the necessary continuity conditions to address the physical discontinuity issue caused by the crack. The challenge then becomes deriving analytical free vibration solutions for each subplate. To accomplish this task, a symplectic superposition method (SSM) is developed to deal with FGM rectangular plates with various boundary conditions, including the complex continuity conditions. The SSM eliminates the need for a predefined solution form, and its solution procedure, including variable separation and eigen expansion, is mathematically rigorous. Afterward, the analytical solutions obtained via the SSM are integrated to serve as the final free vibration solution of the cracked FGM plate. Comprehensive results based on the obtained analytical solutions, including natural frequencies and vibration modes, are presented and validated. The solutions are further used to investigate the effects of some important parameters, such as crack length and crack location. [ABSTRACT FROM AUTHOR]

The primary aim of this in vitro study was to compare the load-bearing capacity of lithium disilicate occlusal veneers, fabricated via different manufacturing processes. Secondary objectives included assessing internal accuracy and production time-efficiency. Four fabrication methods for ultra-thin lithium disilicate occlusal veneers on extracted human molars with simulated erosive defects were compared (n = 20/group): CAM: milled lithium disilicate (IPS e.max CAD); HPR: heat-pressed lithium disilicate (IPS e.max Press) out of a milled PMMA template (Ddpmma CAST); 3DP: 3D-printed lithium disilicate (experimental lithium disilicate); PTE: heat-pressed lithium disilicate (IPS e.max Press) out of a 3D-printed template (SilaPrint cast). Internal accuracy was measured prior to thermo-mechanical aging, followed by static loading to measure the load-bearing capacity (F max). Fabrication time (time-efficiency) was also recorded. Statistical analysis was performed using the Kruskal-Wallis (KW) test. No statistically significant differences were found in median load-bearing capacities (F max) between the groups (KW p = 0.5902): CAM 1821 N, HPR 1896 N, 3DP 2003 N, PTE 1687 N. Significant differences were found in internal accuracy between the groups that employed printing processes (3DP, PTE) and all other groups in margins (p < 0.001), cusps (p < 0.0018), and fossae (p < 0.0346). The time-efficiency measurements indicated an increase in fabrication time, starting from CAM 67.2 ± 5.8 min, followed by HPR 200.8 ± 33.0 min, PTE 289.2 ± 38.7 min, and peaking with the highest duration observed for 3DP 701.6 ± 8.1 min. The fabrication method of ultra-thin lithium disilicate occlusal veneers does not significantly impact their load-bearing capacity, but affects the clinical fit and adaptation of the veneers. • All fabrication methods exhibited high load-bearing capacities, with no significant differences between the groups. • Milled or heat-pressed restorations demonstrated minimal marginal discrepancies and high internal accuracy. • 3D-printed restorations showed larger marginal gaps but superior internal accuracy in the cusp and fossa regions. • Direct milling was the most time-efficient; 3D-printing the most time-consuming, and procedures involving methacrylate-based templates were intermediate. [ABSTRACT FROM AUTHOR]

Deciding on the implementation or modification of steps in daily clinical care is a nuanced process that demands careful evaluation. This is crucial not only for selecting the most appropriate solution but also for achieving the best treatment outcome. Thus, implementing a workflow for treating cleft lip and/or palate patients with a presurgical orthodontic cleft-covering plate needs to consider objective factors, prioritized from most to least important: safety and quality level, user-friendliness, feasibility, and, finally, efficiency and cost. The goal of this workflow is to integrate CAD/CAM technologies into daily clinical routine to enhance technical and clinical efficiency, reduce the burden of cleft care, and simplify the implementation of these technologies in other facilities. To achieve this, a methodology based on intraoral scanning and additive manufacturing is employed to produce patient-specific passive palatal plates. The approach describes possible pitfalls and their resolution within the routine of a cleft centre, along with an exemplary case scenario. Comparative analysis between the digital workflow and the conventional process demonstrated the digital approach to be safer, higher in quality, more user-friendly, feasible, and cost- and time-effective than the conventional process. [ABSTRACT FROM AUTHOR]

David Nono,1– 4 Mathias Akugizibwe,5 Godfrey Bagenda,6 Isaac Okullo,3 Charles Mugisha Rwenyonyi3 1Department of Clinical Research, Central University of Nicaragua, Managua, Nicaragua; 2Department of Clinical Research, Texila American University, Georgetown, Guyana; 3Department of Dental Technology, Makerere University, Kampala, Uganda; 4Department of Research, Uganda Institute of Allied Health and Management Sciences-Mulago, Kampala, Uganda; 5Department of Research, Medical Research Council/Uganda Virus Research Institute & London School of Hygiene and Tropical Medicine, Kampala, Uganda; 6Department of Anatomy, Makerere University, Kampala, UgandaCorrespondence: David Nono, Department of Dental Technology, Makerere University, Kampala, Uganda, Tel +256773502059; +256701909347, Email nndvd45@gmail.comBackground: Globally, there is growing concern regarding mouth sores, occlusion, cost, ridge resorption, and retention, in the delivery of removable complete dentures fabrication services brought about by the aging of the population and poor oral healthcare. The therapy for edentulous patients can be realized through the use of conventional removable complete dentures, implant-supported prostheses, and computer-aided design/computer-aided manufacturing (CAD/CAM). In Uganda, the therapy for edentulous patients has predominantly been realized through the use of conventional removable complete dentures. There has been a discernible difference in the number of visits and remake rate between removable complete dentures that were made conventionally and digitally. This present study, therefore, aimed to explore dental clinicians’ and technologists’ experiences and perspectives on removable complete denture fabrication services.Methods: The study employed a qualitative design, 25 in-depth interviews were conducted with dental clinicians and technologists at Makerere University Dental Hospital. Both practicing dental technologists and clinicians were purposively selected after providing written informed consent. Interviews’ audios were transcribed verbatim, coded in NVivo 14 and data were analyzed thematically.Results: Clinical and socio-demographic assessments like age, oral hygiene, ridge level, underlying health conditions, and mental stability of the patient were done by dental clinicians before removable complete denture fabrication. Dental technologists and clinicians mentioned patients having a lot of expectations relating to being able to eat whatever they like and improving physical appearance. However, the patients also had fears and concerns about discomfort, and some worried that they would swallow the dentures.Conclusion: Prior assessments were the basis for planning for complete denture therapy. Patients’ fears and expectations can effectively be addressed in the consent process since adequate information can be shared and the patients can be psychologically prepared to receive the denture treatment.Keywords: complete denture therapy, computer-aided design, computer-aided manufacturing, dental technologists, dental clinicians

Flexible process planning (FPP) involves selecting and sequencing the requisite operations according to technological requirements, and meanwhile allocating a right machine, a right tool and a right access direction to each selected operation by a given criterion. In this article, the FPP problem is exactly and concisely formulated as linear integer programming models based on the topology of the AND/OR-network under two criteria: production cost minimisation and completion time minimisation. Distinctively, more flexible manufacturing elements and process plan evaluation criteria are considered; more complicated tool and access direction changeover identifications are linearly expressed without the big-M parameter. Compared with the latest mathematical programming models for process planning, the proposed models have lower complexity and better performance. The results from numerous comparative experiments indicate that (i) the number of decision variables of the proposed models reduces approximately by 68% and the number of constraints of the proposed models dramatically reduces by 99%; (ii) within the same running time, the proposed models can exactly solve more benchmark cases than the latest models; and (iii) the solutions obtained by the proposed models are also better than the best ones founded by some state-of-the-art meta-heuristic algorithms. [ABSTRACT FROM AUTHOR]

Abstract Objective To assess the current status of digital technology (DT) implementation in prosthodontics post-graduate (PG) programs in Saudi Arabian dental institutions. Methodology A 19-item survey was created using Google forms and the link was emailed to the 29 prosthodontics PG program directors (advanced clinical training and joint program) in Saudi Arabia. The questionnaire contained five Sect. 1) didactic training and DT usage in PG preclinical, clinical and laboratory training, 2) incorporation of DT in PG program, 3) utilization of DT and the types of cases treated by PG students during their course, 4) information on the faculties involved in prosthodontics PG education, and 5) potential challenges encountered and program directors’ satisfaction of the PG program. Descriptive statistics was used to present the frequencies and proportions, and Chi square inferential test was used to compare the participants’ response based on the type of PG programs (α = 0.05). Results Only 28 program directors responded to the survey, yielding a 95.5% response rate. Among the program directors, 24 (85.7%) and 4 (14.3%) directors supervised the advanced clinical training and joint programs, respectively. Among the DT, CAD/CAM was the most used technology (50–80%), followed by intra-oral scanning (28–96%). Digital technology implementation was largely limited by lack of resources or equipment (67%), cost (53%) and scarcity of PG teaching staff (46%). A significant difference was observed between the programs regarding the mandatory use of DT for their cases (p = 0.03). Conclusions This multi-institutional survey of program directors revealed that DT is continuously implemented in the last few years. Saudi dental institutions must prioritize implementing and utilizing DT in PG training to graduate competent prosthodontists in this fast-paced digital era. While DT is pivotal in dental education, its implementation is limited in many institutions due to resources or equipment, cost, and lack of trained faculty.

While magnesium (Mg) is a promising material for personalized temporary implants, the lack of a digital manufacturing solution for Mg implants impedes its potential progress. This study introduces a hybrid manufacturing process that integrates binder jet additive manufacturing with automated dry post-machining to enable end-to-end digital manufacturing of personalized Mg implants. Spherical cap-shaped Mg implants were additively manufactured through binder jetting. These implants were placed on graphite flakes during sintering as a potential non-reactive support material, allowing unrestricted shrinkage of 15.2 % to a relative density of 87 %. Microstructural and dimensional analysis revealed consistent interconnected porous microstructures with a shrinkage distortion within ± 0.2 mm of the original digital drawing. High-speed dry milling of the sintered samples, assessed via an orthogonal cutting test, identified the optimized cutting parameters. A three-step machining process for automated 5-axis machining, along with clamping strategies, referencing, and an adaptive plug-in, were successfully implemented. The automated dry machining on binder-jet printed Mg implants resulted in an average roughness of < 1.3 µm with no defects. In summary, this work introduces a robust digital manufacturing solution to advance the transformative landscape of Mg implants and scaffolds.

Objective: To assess the current status of digital technology (DT) implementation in prosthodontics post-graduate (PG) programs in Saudi Arabian dental institutions. Methodology: A 19-item survey was created using Google forms and the link was emailed to the 29 prosthodontics PG program directors (advanced clinical training and joint program) in Saudi Arabia. The questionnaire contained five Sect. 1) didactic training and DT usage in PG preclinical, clinical and laboratory training, 2) incorporation of DT in PG program, 3) utilization of DT and the types of cases treated by PG students during their course, 4) information on the faculties involved in prosthodontics PG education, and 5) potential challenges encountered and program directors' satisfaction of the PG program. Descriptive statistics was used to present the frequencies and proportions, and Chi square inferential test was used to compare the participants' response based on the type of PG programs (α = 0.05). Results: Only 28 program directors responded to the survey, yielding a 95.5% response rate. Among the program directors, 24 (85.7%) and 4 (14.3%) directors supervised the advanced clinical training and joint programs, respectively. Among the DT, CAD/CAM was the most used technology (50–80%), followed by intra-oral scanning (28–96%). Digital technology implementation was largely limited by lack of resources or equipment (67%), cost (53%) and scarcity of PG teaching staff (46%). A significant difference was observed between the programs regarding the mandatory use of DT for their cases (p = 0.03). Conclusions: This multi-institutional survey of program directors revealed that DT is continuously implemented in the last few years. Saudi dental institutions must prioritize implementing and utilizing DT in PG training to graduate competent prosthodontists in this fast-paced digital era. While DT is pivotal in dental education, its implementation is limited in many institutions due to resources or equipment, cost, and lack of trained faculty. [ABSTRACT FROM AUTHOR]

Purpose: To assess vertical and horizontal fit, screw removal torque, and stress analysis (considered biomechanical aspects) of full‐arch implant frameworks manufactured in Ti‐6Al‐4V through milling, and additive manufacturing Direct Metal Laser Sintering (DMLS) and Electron Beam Melting (EBM), and the effect of the thermo‐mechanical treatment Hot Isostatic Pressing (HIP) as a post‐treatment after manufacturing. Material and Methods: Maxillary full‐arch implant frameworks were made by milling, DMLS, and EBM. The biomechanical assessments were screw removal torque, strain‐gauge analyses, and vertical and horizontal marginal fits. The vertical fit was assessed by the single‐screw test and with all screws tightened. All frameworks were submitted to a standardized HIP cycle (920°C, 1000 bar pressure, 2 h), and the tests were repeated (α = 0.05). Results: At the initial time, milled frameworks presented higher screw removal torque values, and DMLS and EBM frameworks presented lower levels of strain. Using the single‐screw test, milled and DMLS frameworks presented higher vertical fit values, and with all screws tightened and horizontally, higher fit values were found for milled frameworks, followed by DMLS and EBM. After HIP, milling and EBM frameworks presented higher screw removal torque values; the lowest strain values were found for EBM. Using the single‐screw test, milled and DMLS frameworks presented higher vertical fit values, and with all screws tightened and horizontally no differences were found. Conclusions: DMLS and EBM full‐arch frameworks presented adequate values of screw removal torque, strain, and marginal fit, although the worst values of marginal fit were found for EBM frameworks. The HIP cycle enhanced the screw removal torque of milled and EBM frameworks and reduced the strain values of milled frameworks. The HIP represents a reliable post‐treatment for Ti‐6Al‐4V dental prostheses produced by milling and EBM technologies. [ABSTRACT FROM AUTHOR]

Background: File fracture during root canal treatment in endodontics is a major concern for clinicians. The strength of the file is strongly dependent on its geometry, material, and working conditions; finite element simulations are used to understand these failure mechanisms. One limitation of the models used for these simulations is the approximate geometric representation typically obtained by rotating and scaling a specific cross-section shape along the file length. Given the influence of file geometry on file strength, a more realistic representation based on the manufacturing method is needed. Methods: A computerized method was developed to generate the file geometry by simulating the flute grinding manufacturing process. This method generates the 3D geometry of the file starting from a blank and reproducing the motions of the file and grinding wheel. Results: The cross-section of the resulting geometry does not involve simple rotation and scaling but changes from the shank to the tip. The tilt angle of the grinding wheel affects the final geometry, thus altering the convexity of the cross-section. Several other parameters, such as the pitch and the radius of the grinding disc tip, impact the final geometry. Conclusions: The proposed computational method allows for the generation of endodontic file geometries that match those produced via the actual flute grinding method. This tool may help researchers and tool designers in the preparation of finite element models to assess the strength of realistic files. [ABSTRACT FROM AUTHOR]

Computer-assisted surgery is the most significant recent advancement in osseous head and neck reconstruction. Computer-aided design (CAD) software allows computerized planning of resection and reconstruction. Computer-aided manufacturing (CAM) can be used to create models, cutting guides, and patient-specific plates. Several studies have shown that these techniques are more accurate and result in decreased flap ischemia times compared with conventional techniques. CAD also facilitates the immediate placement of dental implants. The most useful application of computer-assisted surgery is delayed reconstruction, in which soft tissue contraction and the absence of a specimen as a reference make accurate estimation of the defect challenging. The drawbacks of CAD/CAM are lack of intraoperative flexibility and cost. Some centers have created in-house CAD/CAM processes using open-source software and commercially available three-dimensional printers. [ABSTRACT FROM AUTHOR]

• First-ever study on the full digital manufacturing process chain for Mg alloys. • Interaction of as-printed Mg implants with sintering support materials during sintering. • Compared cutting performance of printed and sintered Mg alloy versus wrought alloy. • Developed a three-step process for automated 5-axis machining of printed Mg implants. • Attained uniform porous structure in printed, sintered, and machined Mg implants. While magnesium (Mg) is a promising material for personalized temporary implants, the lack of a digital manufacturing solution for Mg implants impedes its potential progress. This study introduces a hybrid manufacturing process that integrates binder jet additive manufacturing with automated dry post-machining to enable end-to-end digital manufacturing of personalized Mg implants. Spherical cap-shaped Mg implants were additively manufactured through binder jetting. These implants were placed on graphite flakes during sintering as a potential non-reactive support material, allowing unrestricted shrinkage of 15.2 % to a relative density of 87 %. Microstructural and dimensional analysis revealed consistent interconnected porous microstructures with a shrinkage distortion within ± 0.2 mm of the original digital drawing. High-speed dry milling of the sintered samples, assessed via an orthogonal cutting test, identified the optimized cutting parameters. A three-step machining process for automated 5-axis machining, along with clamping strategies, referencing, and an adaptive plug-in, were successfully implemented. The automated dry machining on binder-jet printed Mg implants resulted in an average roughness of < 1.3 µm with no defects. In summary, this work introduces a robust digital manufacturing solution to advance the transformative landscape of Mg implants and scaffolds. [Display omitted] [ABSTRACT FROM AUTHOR]

Laser metal deposition is a branch of additive manufacturing that offers advantages over traditional manufacturing techniques for forming overhanging thin-walled metal parts. Previously, helical paths that were suitable for manufacturing such parts were not only limited to stacking material on a flat surface but were also fixed to the model boundaries. In order to solve these two problems to meet more complex process requirements, a non-planar helical path generation method is proposed for laser metal deposition. The method is based on the characteristics of the additive manufacturing process planning flow, which first slices the model using curved surfaces, then offsets the contours on the sliced layering, and finally generates continuous helical paths according to the contracted or expanded contours. In order to verify the feasibility of the method, hollow blades are formed on cylindrical surfaces following the planned paths. The results show that the proposed method is not only capable of assisting the laser metal deposition process to fabricate thin-walled structures on non-planar surfaces but also capable of freely adjusting the contour dimension. [ABSTRACT FROM AUTHOR]

Abstract Aim The study was performed to compare the mandibular resection guide with a directional guidance slot with the conventional guide regarding three-dimensional positional accuracy. Materials and methods Twenty-six patients with lateral segmental mandibular defects were selected, and randomly allocated into two groups. All defects were managed with preoperative virtual surgical planning. Resection in the test group was conducted using a resection guide with a directional guidance slot, while a conventional resection guide design was utilized in the control group. The linear and angular deviation of the osteotomy planes was analyzed for both groups, along with the accuracy of the insertion of the reconstruction bone block in the resected defect. Data were documented, absolute deviation was calculated, statistical analysis was performed and significance was set at the 5% level. Results The cases conducted with a directional guidance templet reported a statistically significant difference when compared to the conventional edge-cutting guide regarding the linear and angular spatial osteotomy plane position (P

Abstract Background Dynamic navigation for implant placement is becoming popular under the concept of top-down treatment. The purpose of this study is to verify the accuracy of a dynamic navigation system for implant placement. Methods Implant placement was performed on 38 patients using 50 implant fixtures. Patients in group C were treated using a conventional method, in which thermoplastic clips were fixed to the teeth, and patients in group M were treated using thermoplastic clips fixed to a mouthpiece attached to the teeth. The groups were compared to verify whether an accuracy difference existed. A treatment planning support program for dental implants was used to superimpose the postoperative computed tomography data on the preoperative implant design data to measure the entry point, apex point, and angular deviation. Results The accuracy of group C was 1.36 ± 0.51 mm for entry point, 1.30 ± 0.59 mm for apex point, and 3.20 ± 0.74° for angular deviation. The accuracy of group M was 1.06 ± 0.31 mm for the entry point, 1.02 ± 0.30 mm for the apex point, and 2.91 ± 0.97° for angular deviation. Significant differences were observed in the entry and apex points between the two groups. Conclusions The results indicate that group M exhibited better accuracy than group C, indicating that the stability of the thermoplastic clip is important for ensuring the accuracy of the dynamic navigation system. No previous studies have verified the accuracy of this system using the mouthpiece method, and additional data is required to confirm its accuracy for dental implant placement. The mouthpiece method improves the accuracy of implant placement and provides a safer implant treatment than the conventional method. Trial registration University hospital Medical Information Network Clinical Trials Registry (UMIN-CTR), Registration Number: UMIN000051949, URL: https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view_his.cgi on August 21, 2023.

Additive manufacturing has advantages over other traditional manufacturing technologies for the fabrication of complex thin-walled parts. Previous correlation path strategies, when applied to laser metal deposition processes, suffer from contour deposition transboundary and surface "scar" type overstacking. Therefore, this paper proposes a hybrid path generation method for the laser metal deposition process. First, the topological logic of the STL model of the part is restored to reduce redundant calculations at the stage of obtaining the layered contour. Then, the path points are planned on the basis of the offset contours in a helical upward trend to form a globally continuous composite path in space considering the melt channel width. Finally, vectors that adaptively fit to the model surface are generated for the path points as tool orientations and they are optimized by smoothing the rotation angles. The results of experiments conducted on a multi-axis machine equipped with a laser metal deposition module show that the path generated by the proposed method is not only capable of thin-walled structures with overhanging and curved surface features but also improves the surface imperfections of the part due to sudden changes in the angle of rotation while ensuring the boundary dimensions. [ABSTRACT FROM AUTHOR]

Background: Dynamic navigation for implant placement is becoming popular under the concept of top-down treatment. The purpose of this study is to verify the accuracy of a dynamic navigation system for implant placement. Methods: Implant placement was performed on 38 patients using 50 implant fixtures. Patients in group C were treated using a conventional method, in which thermoplastic clips were fixed to the teeth, and patients in group M were treated using thermoplastic clips fixed to a mouthpiece attached to the teeth. The groups were compared to verify whether an accuracy difference existed. A treatment planning support program for dental implants was used to superimpose the postoperative computed tomography data on the preoperative implant design data to measure the entry point, apex point, and angular deviation. Results: The accuracy of group C was 1.36 ± 0.51 mm for entry point, 1.30 ± 0.59 mm for apex point, and 3.20 ± 0.74° for angular deviation. The accuracy of group M was 1.06 ± 0.31 mm for the entry point, 1.02 ± 0.30 mm for the apex point, and 2.91 ± 0.97° for angular deviation. Significant differences were observed in the entry and apex points between the two groups. Conclusions: The results indicate that group M exhibited better accuracy than group C, indicating that the stability of the thermoplastic clip is important for ensuring the accuracy of the dynamic navigation system. No previous studies have verified the accuracy of this system using the mouthpiece method, and additional data is required to confirm its accuracy for dental implant placement. The mouthpiece method improves the accuracy of implant placement and provides a safer implant treatment than the conventional method. Trial registration: University hospital Medical Information Network Clinical Trials Registry (UMIN-CTR), Registration Number: UMIN000051949, URL: https://center6.umin.ac.jp/cgi-open-bin/ctr%5fe/ctr%5fview%5fhis.cgi on August 21, 2023. [ABSTRACT FROM AUTHOR]

Feature recognition (FR) is one of the main tasks involved in computer-aided design, computer aided process planning, and computer-aided manufacturing systems. Conventional FR methods have topology, voxel, and pixel as model input data, which are rule-based, body decomposition-based, and neural network-based, respectively. However, FR methods are mostly applied to identify geometric features and are rarely manufacturing oriented. Recognizable feature types depend on the establishment of a feature database, which can easily lead to complex FR errors or omissions. This study proposes a novel recognition method for the general machining feature of 2.5-axis, one of the basic and commonly encountered feature types in manufacture industries. A novel ray fading algorithm is proposed to calculate the feature machining direction, and the type of 2.5-axis machining features is determined by both machining direction and topology. Features with machining directions can effectively assist the intelligent process planning to reduce the clamping changes and can potentially lead to significant time reduction for part machining. [ABSTRACT FROM AUTHOR]

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Objective: It solved the problem of low accuracy and large random error when cutting fresh corn, which is easy to damage the grain. Methods: A new process of sweet and waxy corn processing production line was designed, the production line used machine vision technology to judge the attitude of corn, completed the adjustment of corn attitude through reversing equipment, designed adaptive positioning structure to cut the head and tail of corn, and then carried out layer retention processing according to the difference characteristics of ear bract adhesion after cutting results, packed after camera quality screening, and used prototype to carry out processing tests. Results: The processing efficiency of the production line was up to 1 500 spikes/h, the pass rate of retention layer was 90.2%, and the grain breakage rate was 1.81%. Conclusion: The fresh corn processing production line realizes the automation of corn feeding, sorting, cutting, peeling and other processes, realizes the reasonable retention of bracts and leaves, and protects corn grains more than traditional equipment.

Objective To analyze the application effects of rubber dam isolation technology in chairside computer-aided design (CAD)/computer-aided manufacturing (CAM) ceramic inlay repair treatment. Methods A total of 90 patients who received chairside CAD/CAM ceramic inlay repair treatment in the hospital from January 2020 to January 2022 were selected and randomly divided into experimental group and control group, with 45 cases in each group. The control group did not use rubber dams to block moisture in the treatment, but used cotton rolls to block moisture, and the experimental group used rubber dams to block moisture in the treatment. The treatment time and the occurrence of adverse reactions between the two groups were compared. Results The inlay crown restoration of the experimental group and the control group was good in crown edge, adhesion and occlusal relationship. The treatment time of the experimental group was (118. 83±19. 15)min, which was shorter than (141. 26±11. 74)min of the control group, with a significant difference (P＜0. 05). There was a case of adverse reaction reported in the control group. Conclusion The rubber dam isolation technology can effectively reduce the treatment time of CAD/CAM porcelain inlays at the chairside. (目的 研究橡皮障隔离技术在椅旁计算机辅助设计(CAD)/计算机辅助制作(CAM)瓷嵌体修复治疗中的应用效果。方法 选择2020年1月—2022年1月医院牙体牙髓科行椅旁CAD/CAM瓷嵌体修复治疗的患者60例, 随机分为研究组和对照组, 各30例。对照组按照常规流程操作, 使用常规方法进行术野隔离; 研究组在操作治疗中运用橡皮障隔离技术。比较两组总治疗时间和不良反应发生情况。结果 两组患者的嵌体冠修复体在冠边缘、密合性、咬合关系等方面均良好。研究组总治疗时间(118. 83±19. 15)min, 较对照组(141. 26±11. 74)min缩短, 差异有统计学意义(P＜0. 05); 研究组无不良反应发生, 对照组发生1(3. 33%)例不良反应。结论 橡皮障隔离技术可有效缩短椅旁 CAD/CAM 瓷嵌体修复治疗时间。)

Deciding on the implementation or modification of steps in daily clinical care is a nuanced process that demands careful evaluation. This is crucial not only for selecting the most appropriate solution but also for achieving the best treatment outcome. Thus, implementing a workflow for treating cleft lip and/or palate patients with a presurgical orthodontic cleft-covering plate needs to consider objective factors, prioritized from most to least important: safety and quality level, user-friendliness, feasibility, and, finally, efficiency and cost. The goal of this workflow is to integrate CAD/CAM technologies into daily clinical routine to enhance technical and clinical efficiency, reduce the burden of cleft care, and simplify the implementation of these technologies in other facilities. To achieve this, a methodology based on intraoral scanning and additive manufacturing is employed to produce patient-specific passive palatal plates. The approach describes possible pitfalls and their resolution within the routine of a cleft centre, along with an exemplary case scenario. Comparative analysis between the digital workflow and the conventional process demonstrated the digital approach to be safer, higher in quality, more user-friendly, feasible, and cost- and time-effective than the conventional process.

Flexible process planning involves selecting and sequencing the requisite operations, and assigning the right machine, tool and access direction to each selected operation for minimising the production cost or the completion time. It is one of the challenging combinatorial optimisation problems due to sequencing flexibility, processing flexibility and operation flexibility. A sequence learning harmony search algorithm is accordingly proposed. Distinctively, the well-designed algorithm searches for the optimal process plan by intelligently finding the proper immediate successor for each selected operation in turn rather than resorting to the common shifting and swapping operators in sequencing. The innovative algorithm does not also require extra efforts to plot the operational precedence graph or the AND/OR-network graph. The experimental results indicate that the proposed algorithm significantly outperforms other heuristics in terms of the quality of solution found and the convergence rate of the algorithm. For the large-scale complicated instances, the proposed algorithm establishes a challenging flag. [ABSTRACT FROM AUTHOR]