The lack of a standardized methodology complicates accuracy assessment in computer-assisted mandibular reconstruction. Existing landmark-based methods are susceptible to operator variability, while surface-based comparisons can mask local deviations. This study validates a novel, automated protocol, the Global Positioning Layout (GPL), to quantify the 3D discrepancy between the virtual surgical plan and the postoperative outcome, by comparing its performance and reliability against Methods A and B. A retrospective cohort of 17 patients was analysed, with three operators performing all measurements on two occasions. The GPL method demonstrated complete reproducibility, with no inter- or intra-operator variability, providing a detailed, spatially-oriented assessment of deviations. In contrast, the landmark-based method showed poor reproducibility and systematic bias and was often inapplicable due to the absence of landmarks after resection. The surface-based method, while objective for its mean error metric, was operator-dependent for initial alignment and its non-directional output masked significant localized deviations. This study validates GPL as a robust and fully reproducible tool that overcomes the critical limitations of established techniques. The GPL method provides a strong foundation for a standardized protocol, essential for the reliable comparison of surgical outcomes, refinement of surgical techniques, and improvement of long-term patient outcomes.

Additive Manufacturing (AM) is no longer limited to prototyping, as it is gaining an increasingly large market share. With this expansion, there is a growing demand for the development of standardized rules to establish product specifications and verification procedures. AM offers unique opportunities in free-form shape design and multi-material processing, in contrast to traditional manufacturing processes and communication methods. Because of AM’s unique features, existing standards struggle to describe its product specifications. New regulations are therefore under development This paper reviews the state of the art in Additive Manufacturing (AM) product specification. This research examines the most up-to-date literature and standards published by the ISO, and ASME committees. A research gap has been identified in the accurate determination of design intent, which is crucial for defining product specifications. “Profile tolerance” is recognized as the most versatile specification for free-form geometries; however, new tools can be developed to control lattice structures. Additionally, the authors identified a significant gap in the assessment of dimensional and geometrical deviations in AM processes, as these are often estimated using geometrical benchmarks designed for subtractive technologies. Finally, verification remains one of the most critical aspects of AM products. Computed Tomography (CT) currently represents the only viable approach for measuring inaccessible features; however, standardized reconstruction methods are still lacking, as is a specification method tailored specifically for this measurement technique.

Geometrical Product Specification (GPS) plays a critical role in ensuring functional compliance, manufacturability, and verifiability across the product development lifecycle. Recent research has highlighted the evolutionary nature of specifications: from functional (FunSpec) to manufacturing (ManSpec), verification (VeriSpec), and contractual (ConSpec) documents; yet the allocation of clear responsibilities among stakeholders remains underdeveloped. This paper proposes the integration of the RACI (Responsible, Accountable, Consulted, Informed) matrix into the ISO GPS workflow as a structured means to clarify roles, responsibilities, and communication pathways across design, manufacturing, and quality assurance domains, therefore building upon the responsibility principle presented in ISO 8015. Starting from the specification document types presented in ISO/TS 21619 and the interaction between these document types, this study introduces a RACI-supported framework that maps stakeholder involvement to each stage of specification evolution. A possible implementation example demonstrates how the method enhances transparency, prevents overlaps or gaps in responsibilities, and supports compliance with industrial standards such as ISO 9001. The results suggest that embedding RACI within GPS workflows strengthens interdisciplinary collaboration, reduces ambiguity, and lays the foundation for responsibility-aware product specification management.

This study presents a genetic algorithm-based methodology for reconstructing the nominal profile of airfoils belonging to the NACA four- and five-digit series. By minimizing the geometric deviations between measured point clouds and parametrically generated airfoil profiles, the algorithm identifies the best-fitting nominal geometry. The approach was implemented using Rhino 8, Grasshopper, and the Galapagos plugin, and validated through extensive testing on 3D-printed samples. Across 200 test runs, the algorithm consistently identified the correct nominal geometry, demonstrating robustness despite inherent stochastic variability and computational challenges. The average number of iterations needed to converge was found to be 953 across all cases. This methodology offers a valuable tool for reverse engineering and metrological applications, providing a parametric and efficient alternative to traditional free-form surface reconstruction.

This work presents a computational framework for tolerance chain analysis based on multivariate statistical modelling accommodating both prescribed moments and correlations. The proposed method generates multivariate datasets matching either measured or proposed component characteristics, enabling realistic statistical virtual assembly. By using a transformed multi-variate Normal distribution, it is possible to represent the mean, variance, skewness, kurtosis, and covariance structure of the real parts' geometric variability. This allows tolerance propagation analysis that reflects actual manufacturing variability. Applications include predictive assembly simulations, functional tolerance optimization, and data-driven design verification in industrial contexts.

OBJECTIVES:This study aimed to investigate the effect of erythritol air-polishing on implant surface topography and bacterial colonization, and to determine the antimicrobial activity of erythritol powder. MATERIALS AND METHODS:Titanium implants, with machined/acid-etched hybrid design, were divided into three groups: erythritol air-polishing for 1 min (E1), 5 min (E5), and untreated control. Surface analysis was performed using a stylus profilometer and scanning electron microscope (SEM). To test the ability to prevent biofilm formation, four bacteria strains (Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus mutans, Streptococcus sanguinis) were separately cultured on five implants per group and colony counting was performed. The intrinsic erythritol antibacterial activity was investigated by means of minimum inhibitory concentration against the same strains. RESULTS:At SEM analysis implant surfaces appeared unaltered by air-polishing and presented increasing amount of residues depending on the treatment duration. Machined surfaces exhibited no significant differences in roughness parameters between the groups. On acid-etched surfaces, E5 presented significantly lower Ra (vs. E1 and control) and Rz (vs. control). The count of colonies was significantly lower for all bacterial strains on treated implants as compared to control, with E1 and E5 being equally capable to reduce by 1.5 log bacteria growth. Erythritol antimicrobial activity against all tested bacterial strains was confirmed. CONCLUSIONS:The proposed erythritol air-polishing protocols did not alter implant surfaces and the antimicrobial properties of erythritol are conserved by the titanium implant surfaces. CLINICAL RELEVANCE:Erythritol air-polishing could be repeatedly used in supportive peri-implant care programmes.

This work introduces the concept of variable-dependent admissible limits for tolerance stack-up analysis, where limits adapt based on geometrical and non-geometrical variables. Unlike traditional methods that assume fixed limits, the proposed approach integrates these dependencies into both variational and Monte Carlo analyses, enabling broader tolerances while maintaining functionality. A case study from the automotive sector demonstrates the methodology's effectiveness. This innovation shifts tolerance analysis from a purely geometrical to a functional domain, improving accuracy, reducing costs, and supporting compact and safe designs in industrial applications. (c) 2025 The Author(s). Published by Elsevier Ltd on behalf of CIRP. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

When pattern of fits are not designed following the boundary condition design criterion, the rejection rate due to failure in assemblability need to be considered. Since in a pattern of fits it is not possible to define an assembly equation it is not trivial to create a tolerance stack-up. The paper proposes a strategy to achieve a generalized rejection rate computation for nx patterns based on an interpolation model derived from Monte Carlo simulations. The rejection rate as function of the number of element in the pattern is simulated for different size and location tolerances. An exponential convergent function is fitted to the data and a generalize regression model is used to estimate the function parameters. Validation of the proposed methodology is provided. Moreover, future development are outlined.

PURPOSE:This study aims to compare the occlusal trueness and precision of teeth manufactured using two modern digital milling processes. MATERIALS AND METHODS:A total of 38 complete dentures (CDs) were fabricated and analyzed. CDs in Group 1 (monolithic) (n = 19) were produced using a monolithic bicolor resin disk, whereas in Group 2 (oversize) (n = 19) were fabricated using the oversize process, which involves two separate resin disks of different colors. Two investigation methods were developed to evaluate trueness and precision: cusp area analysis and cusp vertex analysis. The study included three levels of analysis: a comparison of the two measurement methods, an evaluation of the monolithic versus oversize processes, and an assessment of under- and overcontouring inaccuracies. RESULTS:Statistical analysis using the Welch two-sample t-test, the non-parametric Wilcoxon signed-rank test, and the modified signed-likelihood ratio test (SLRT) revealed a statistically significant difference (P < 2.2 × 10-16) between the two measurement methods (vertex vs. area) for both the monolithic and oversize groups, with the vertex method demonstrating greater accuracy. The analysis of over- and undercontouring inaccuracies revealed that 55% of the surface for the monolithic process exhibited overcontouring, compared to 99% for the oversize process, indicating a strong tendency toward surface roughness in the latter. CONCLUSION:The monolithic milling method exhibited significantly superior accuracy compared to the oversize process (P < .05). Additionally, the Reference Point System (RPS) metrological method proved more reliable than the best-fit method for comparing complex structures, offering more accurate estimates of both trueness and precision.

Digital workflows have revolutionized dentistry, especially when it comes to fabrication of complete dentures through Computer-Aided Design and Computer-Aided Manufacturing (CAD-CAM) procedures. Digital articulators manage to simulate mandibular movements and are emerging as alternatives to mechanical articulators like the Gerber semi-adjustable model. Despite being a promising tool, digital articulators require refinement in order to grant consistent functionality and effective occlusal balance. The aim of this research is to present a semi-automated MATLAB tool designed to compare trajectories from different articulator types—digital versus analog—used in dental practice. Validation of the MATLAB tool compared to existing data demonstrates its reliability and effectiveness. Sensitivity analyses assess the tool's robustness under various settings. Results suggest optimal input parameters and settings ensuring precision. Future developments may include integrating anatomically-based reference systems and advanced metrics for rotational analysis of condylar path elements (CPEs), thereby enhancing digital dentistry potentialities. Ultimately, the semi-automated MATLAB tool represents a significant step towards improving dental occlusal analysis, bridging the gap between analog and digital methodologies and enabling comparison among these tools.

The availability of foaming materials with properties that vary according to the heat transferred to the filament in the fused filament fabrication (FFF) process provides the opportunity to develop new design methodologies that allow the exploitation of the range of characteristics offered by these materials. In this work, an integrated CAD-CAM method to realize graded density foamed components via FFF is proposed. The method consists in the post-processing of a G-code file obtained from a CAD model according to functional requirements defined by a density map volumetric model. The method relies on the material propertyprocess parameters correlation to drive the foaming in a specific extruder configuration. The temperature effect on extrusion width and density is experimentally investigated as the primary process parameter driving the foaming behaviour of a commercially available filament. Based on the density map of the volumetric model and the experimental characterization, temperature and extrusion amount are updated in the G-code file. The method is applied to a simple buoyant 3D shape to ensure its orientation in water.

This paper focuses on the applicability of various new product development (NPD) models to small and medium-sized enterprises (SMEs) and the challenges they face, including limited resources, informal innovation systems, and difficulty obtaining external feedback. Traditional NPD models offer structure but may be too rigid for SMEs, while Agile methodologies provide flexibility but can be challenging to implement outside the software industry. Hybrid models, blending traditional and Agile approaches, offer a good compromise. Through comparative analysis, the study evaluates the strengths and weaknesses of different NPD models in the SME context. By utilizing modern technologies like additive manufacturing and artificial intelligence, the NPD process can be accelerated, aligning with Agile principles to provide faster feedback and enhance overall efficiency. In conclusion, SMEs are encouraged to consider hybrid solutions to innovate and compete effectively. Future research should address specific challenges in different industry sectors and focus on scalability.

PURPOSE:To compare condylar path elements (CPEs) in edentulous patients using fully adjustable (FA) and semiadjustable (MS) digital articulators. MATERIALS AND METHODS:A total of 10 patients with at least one edentulous arch were included. Arch relation records were digitally set in the articulators using two approaches: The MS group employed standard mean occlusal parameter values, while the FA group used individual values obtained using a digital arch motion-tracking device. Differences in CPEs, represented as Δ-values, were statistically analyzed using nonparametric Wilcoxon signed-rank test and post-hoc Tukey test. These analyses evaluated overall differences between FA and MS articulators, identified the regions with the greatest Δ-errors, and determined the percentage of movement required for statistical significance. RESULTS:CPEs differed significantly between MS and FA articulators. Significant variations were observed in individual CPEs (P < .001), with motion percentage significantly influencing Δ-values (P < .001). Notably, within the first 20% of CPE MS pathways, significant differences were found within the initial 2 mm of movement, a critical range for prosthetic rehabilitation. CONCLUSIONS:This study highlights statistically significant differences in CPEs between MS and FA digital articulators, particularly within the initial 2 mm of movement. These findings underscore the importance of precise CPE replication for occlusal design of complete dentures.

This clinical study compares condyle path elements (CPE) in edentulous patients using fully adjustable (FA) and semi-adjustable (MS) digital articulators. Ten patients with at least one edentulous jaw were included. Jaw relation records were digitally set in the articulators using two approaches: the MS group employed standard mean occlusal parameter values, while the FA group used individual values obtained using a digital jaw motion tracking device. Differences in CPEs, represented as Δ-values, were statistically analyzed using the non-parametric Wilcoxon signed-rank test and post-hoc Tukey tepPst. These analyses evaluated overall differences between FA and MS articulators, identified the regions with the greatest Δ-errors, and determined the percentage of movement required for statistical significance. CPEs differed significantly between semi- and fully adjustable articulators. Significant variations were observed in individual CPEs (P < .001), with motion percentage significantly influencing Δ-values ( P< .001). Notably, within the first 20% of CPEs MS pathways, significant differences were within the initial 2 mm of movement, a critical range for prosthetic rehabilitation. This study highlights statistically significant differences in CPEs between semiand fully adjustable digital articulators, particularly within the initial 2 mm of movement. These findings underscore the importance of precise CPEs replication for occlusal design of complete dentures.

In product design and development, achieving the desired performance requires meeting specific product requirements within defined boundaries. These requirements are encapsulated in the Product Definition Dataset, which consists of two key models: the Nominal Model and the Specification Model. The Nominal Model outlines the product’s properties, features, and relationships, while the Specification Model defines the targets, boundary conditions, requirements, allowable variation, and interrelationships essential for meeting these targets. This study focuses on the relationships between variable quantities and the limits set by geometrical product specifications. Currently, the limits defined within geometric specifications are considered static, excluding maximum and minimum material conditions. This implies that each variable is treated independently, meaning the actual state of one variable does not influence the functional limits of others. However, in actual parts and assemblies, variable quantities do affect each other, as they are not independent. In this paper, we explore the link between specifications and the variables they define through a case study, with the aim of fulfilling product requirements more effectively. By establishing these connections, it becomes possible to produce functional parts with greater allowable variation and reduced costs, while ensuring that specifications are grounded in actual performance requirements and physics. This approach aims to enhance the flexibility of product manufacturing and streamline the process of meeting both functional and cost-related objectives.

This study aims to define the assembly shift for "nx" fit patterns, considering scrap and the influence of increasing elements. The methodology includes rejection rate estimation via Monte Carlo simulation, gap distribution estimation, and assembly shift computation based on gap distribution. It also proposes a design methodology for dimensioning tolerances to meet assembly shift requirements. Results show narrower assembly shift distributions with more pattern elements, revealing an exponential relationship. A case study based on a real application demonstrates how the proposed methodology can be applied to actual industrial cases.

This study introduces a numerical methodology for computing the statistical assembly shift in patterns of fits, addressing scenarios with variable numbers of elements and scrap caused by assembly failure. Using Monte Carlo simulations, the methodology estimates rejection rates, determines gap distributions, and calculates assembly shifts while considering both intrinsic and external datum systems. The findings indicate that adding more elements to a pattern reduces assembly shifts exponentially, presenting a design opportunity to control alignment and optimize component performance. A case study involving engine block and cylinder head alignment demonstrates the methodology’s applicability to real-world mechanical design. Three approaches for tolerance stack-up are evaluated: the standard Root Sum Square (RSS) method, where assembly shift is treated as a worst-case scenario; a proposed RSS method that models the assembly shift as a Gaussian distribution with a standard deviation derived from Monte Carlo simulations; and the Monte Carlo approach, which considers the full shape of the assembly shift distribution. By comparing these approaches, the study underscores the effectiveness of the proposed methodology in capturing the statistical behavior of assembly shifts. This work contributes a robust tool for tolerance analysis, advancing the precision and accuracy of pattern fit modeling and assembly shift evaluation in mechanical design.

BACKGROUND. Assessing accuracy in CAD-CAM mandibular reconstruction poses significant challenges but is essential for ensuring reliable outcomes. Existing methods are often operator-dependent, lacking repeatability and reproducibility. PURPOSE. This study introduces the Global Positioning Layout (GPL) method, an accuracy assessment technique integrated into the reconstruction protocol based on CAD-CAM and additive printing technology. We describe the methodology and process for applying this approach in detail. METHODS. The GPL method was developed at the University of Padova, Italy. Key principles of accuracy assessment were identified and structured as Requirements, Data input, Data reference system, and Data output. The necessary 3D virtual models were defined: planned mandible, reference mandible, patient-specific implant (PSI), postoperative mandible, and postoperative PSI. A unique coordinate system (GPL-RS) was built on the reference mandible. Three Roto-Translational Matrices (RTMs) were applied to measure movements and deviations between the designed and postoperative models to assess reconstruction accuracy. RESULTS. A case study of mandibular reconstruction with a CAD-CAM titanium PSI is presented to showcase the GPL methodology. Geomagic Wrap® software is used, utilizing its Python programming tools and GEO and API libraries. CONCLUSION. The GPL method represents a significant advancement in assessing the accuracy of CAD-CAM reconstructions, providing valuable insights that can improve surgical outcomes.

This paper presents a novel metrological approach for the functional geometric characterization of lifting airfoils, utilizing an Iterative Closest Point (ICP) algorithm to assess deviations in camber, thickness, and form. Traditional geometric specification methods, such as line profile tolerances, often fail to capture the full impact of geometric deviations on airfoil performance. In response, the proposed methodology addresses this limitation by linking airfoil geometry more closely to functional requirements. The new methodology was validated using synthetic datasets and real-world data, demonstrating robustness in the absence of noise and highlighting areas for improvement in noise handling. The findings suggest that the ICP-based method is a valuable tool for airfoil manufacturing, enhancing conformity checks against design specifications. This study opens pathways for more accurate tolerance synthesis and enhanced quality control in the production of lifting airfoils.