Teeth are among the primary identifiers recommended by Interpol for victim identification. However, they may fragment under thermal or physical trauma, making conventional comparison methods difficult or impossible. Micro-computed tomography (micro-CT) offers high-resolution, non-destructive imaging that could enhance digital reconstruction of dental fragments for forensic purposes. This study aimed to assess the feasibility and accuracy of digitally reassociating dental fragments acquired through micro-CT, under controlled experimental conditions. Thirty-two anterior teeth and premolars all free of severe alterations (such as cavitated caries, heavy calculus deposits, and large or metallic restorations)-extracted for therapeutic reasons were scanned intact using a micro-CT device, then mechanically fragmented, rescanned, and digitally reassociated using an iterative closest point (ICP) algorithm. Mean and root-mean-square (RMS) distances between reconstructed and reference meshes were calculated. Intra-and inter-operator agreement were evaluated using Bland-Altman analyses to assess repeatability and reproducibility. The average deviation between reconstructed and reference meshes was 0.012 mm for operator A and 0.017 mm for operator B. RMS distances averaged 0.048 mm and 0.060 mm, respectively. Agreement analyses showed minimal bias (<0.01 mm) within the 95% limits of agreement, confirming high reproducibility. Micro-CT-based digitization provides highly accurate 3D data suitable for digital reassociation of dental fragments. While this feasibility study demonstrates promising accuracy under controlled conditions, further validation on teeth fragmented by physical or thermal shock is warranted before forensic case application.

BACKGROUNG/AIM:New resins for the additive manufacturing of mouthguards for contact sports are now available on the market. However, no study has evaluated the impact performance of these resins. The aim of this in vitro study was to compare the shock absorption capacities of custom-made mouthguards produced by additive manufacturing with those of thermoformed mouthguards. MATERIALS AND METHODS:Three types of custom-made mouthguards were fabricated: 3D-printed Keyguard and Dima resin mouthguards and thermoformed triple-layer mouthguards. For each type of mouthguard, eight samples were produced. Each mouthguard was subjected to an impact performance test defined by the NF S72-427 standard for industrial mouthguards. Mean transmitted deceleration must not exceed 230 g (g = 9.81 m/s2) and no individual impact should exceed 250 g. Mechanical performance was evaluated by a series of five consecutive impacts with a drop-mass impact test on the inter-incisal area. Peak force transmission and deceleration were measured. Thickness decrease was assessed by 3D scanning. RESULTS:None of the mouthguards met the impact absorption standard. Thermoformed mouthguards exhibited major structural failure after the first impact. For 3D-printed mouthguards, average peak deceleration ranged from 255 to 278 g for Dima and 292 to 299 g for Keyguard. Corresponding transmitted forces ranged from 2753 to 3106 N (Dima) and 3192 to 3292 N (Keyguard), with no significant difference between the two 3D-printed mouthguards (p > 0.05). Mean thickness decrease at the impact site was 0.2 mm for Dima mouthguards, 0.1 mm for Keyguard mouthguards, and 0.3 mm for thermoformed mouthguards. CONCLUSION:Although none of the tested mouthguards met the NF S72-427 standard, 3D-printed custom devices demonstrated promising shock absorption performance after repeated impacts. These results highlight the potential of additive manufacturing as a cost-effective alternative to conventional thermoformed mouthguards, particularly for younger athletes requiring frequent replacements.

Finite Element (FE) analysis is widely used in dental biomechanics, but studies often suffer from insufficient reporting and lack of standardization. This study aimed to develop a consensus-based checklist PRIFED 2026 for improving the transparency, reproducibility, and clinical relevance of FE studies in dentistry. A Delphi process involving 22 international experts was conducted in two stages. Participants, experts in dental FE analysis, reviewed preliminary items derived from existing guidelines and literature. Through three online surveys, panellists rated 86 sub-items on a 9-point Likert scale. Items reaching ≥70% consensus for inclusion were retained. Three online meetings were in parallel held to resolve ambiguities and refine checklist items. The response rate was 76% in the first round, and 18 experts completed the full process. After three rounds, 71 sub-items were included in the final checklist. Notably, 27% of items failed to reach consensus in the first round, reflecting ongoing debate in FE methodology. The checklist covers study design, model construction, boundary conditions, validation, and interpretation of results. The PRIFED 2026 checklist provides a comprehensive and consensus-based framework for reporting FE studies in dentistry. It highlights essential methodological components, including model construction, boundary conditions, and validation strategies, to promote transparency and reproducibility.

The main cause of failure in bonded ceramic restorations is material fracture due to excessive stress concentration at the base of the prosthesis. The design of restorative functionally graded materials (FGM) could represent a major advance in dissipating mechanical stresses during occlusal contacts. The aim of this paper is to carry out a complete factorial design of finite element analyses to optimize a multilayer FGM introduced at the bottom of an overlay prosthesis. The number and thickness of layers vary within a spectrum compatible with ceramic shaping processes whereas Young's moduli variations are set in the range of dental tissues. For a 1.5 -mm thick prosthesis, the optimal FGM configuration appears to be a 5 layers of 0.2 mm thickness with a linear distribution of Young's modulus from 30 to 70 GPa. This configuration was implemented in a 3D model of a restored tooth with realistic geometry to validate the proof -of -concept.

BACKGROUND/AIM:3D printing processes can be used to manufacture custom-made mouthguards for sports activities. Few studies have compared the impact performance of industrial-created mouthguards with that of custom-made mouthguards manufactured by thermoforming or 3D printing. The objective of this in vitro study was to compare the shock absorption capacities of custom-made mouthguards manufactured by 3D printing with industrial mouthguards and thermoformed ethylene vinyl acetate (EVA) mouthguards. MATERIALS AND METHODS:For each type of mouthguard, eight samples were produced. 3D-printed mouthguards were manufactured using digital light processing technology. Each mouthguard was subjected to an impact performance test defined by the standard AFNOR XP S72-427, which evaluate maximum deceleration and force transmitted during impact. The thickness of each mouthguard before and after a series of five impacts was measured at the impacted inter-incisal area. RESULTS:The mean maximum decelerations during impact ranged from 129 to 189 g for industrial mouthguards, 287 to 425 g for thermoformed EVA mouthguards, and 277 to 302 g for 3D-printed mouthguards. The mean reduction in mouthguard thickness at the impact zone after five tests was 1.2 mm for industrial mouthguards, 0.6 mm for 3D-printed mouthguards, and 2.2 mm for thermoformed EVA mouthguards. CONCLUSIONS:Custom-made 3D printed mouthguards showed slightly better shock absorption ability than thermoformed mouthguards with respect to the indicator proposed in XP S72-427. They seemed to combine the practical advantages of thermoformed mouthguards in sports with better shock absorption capacity and lower cost. Furthermore, they had the least thickness variation during the test, and their shock absorption capacity was the least affected by repeated mechanical tests. Other types of 3D-printing resin materials that will become available must continue to be tested for shock absorption to provide the best protection to users at low cost.

Objective: The aim of this study was to evaluate the remineralizing properties of ion-releasing restorative materials on pH cycling-induced carious dentin. Methods: Fifty sound molars were freshly extracted. The occlusal surfaces were abraded using water-cooled sandpaper (800 grit). The residual crowns were embedded in self-cured acrylic resin with the flat dentin surface exposed. A mesio-distal trench was created using a calibrated 0.5 mm deep occlusal reduction burr, and artificial dentin caries were generated by pH cycling. Then, teeth were randomly assigned to five groups according to the ion-releasing material used. For each sample, micro-CT acquisitions were performed at various intervals. Remineralization was assessed by mean gray value (MGV) measurements after registration and segmentation of the region of interest with 3D Slicer software. One-way repeated-measures ANOVA followed by Tukey's post hoc test was used to investigate the difference in MGVs among the various groups. Results: Only Cention Forte showed significantly increased MGVs after 4 weeks compared to demineralized dentin. MGVs were higher, but not significantly, after placement of the restorative materials, including in the resin composite control group. These results can be explained by the radiopacity of the materials. Significance: Cention Forte, the material with the highest radiopacity, showed a significant increase in the MGVs of artificially carious dentin after 4 weeks. However, the study of dentin remineralization by micro-CT could be impacted by the radiopacity of the restorative materials used. The relevance of this examination for the study of dentinal remineralization should be investigated.

BACKGROUND:The stud-shaped attachment systems (AS) with different shape designs (ball, cylindrical, conical) and materials (metallic, plastic, or a combination of both) are commonly used to provide better retention and stability in implant-retained mandibular overdentures (IRMO). PURPOSE:The purpose of the present study was to evaluate and compare the retention loss and the wear (patterns, location, material loss) of three resilient unsplinted AS: a well-established ball attachment system (BAS) and two more recent cylindrical attachment systems (CAS), Locator R-Tx® and Novaloc®. MATERIALS AND METHODS:The implants, their corresponding abutments, the color-coded or position-coded retention devices (RD), the matrix metal housing were incorporated within CAD/CAM resin blocks and cyclically loaded with 19.6 N along the implant axis in a chewing machine to simulate 10,000 insertion-removal cycles (IRC). At cycle 10, 100, 1,000, 5,000, and 10,000, the retention force was measured using a universal testing machine. The wear was qualitatively examined using a binocular magnifier for both systems, and quantitatively assessed from micro-computed tomography acquisitions for CAS. Material loss exceeding 50 μm was considered significant. RESULTS:The three AS showed different retentive behavior along time. All the Locator R-Tx® RD lost more than 50 % of their retention after 10,000 IRC. The retention of the Ball System slightly varied over time, the final retention loss in Bmed and Bmax groups being lower than 25 % of the initial retention. Wear was located at the tip of their gold RD and at the equator area of their ball abutment. For Locator R-Tx®, the more retentive the plastic RD, the greater its wear and retention loss. Only Novaloc® maintained a stable retention with even a slight tendency to increase and showed a negligible wear. Implant abutments of the CAS showed no significant wear. CONCLUSION:After 10,000 IRC, corresponding to approximately 5-years clinical use, almost all RD provided retention force over 5 N, which could be sufficient to maintain satisfaction in most of the patients. The retention loss observed most prominently for the Locator R-Tx®, then for the Ball System, seemed to correlate with the wear observed on their RD. The practitioner may expect less RD maintenance with the Novaloc® stable retention overtime.

PURPOSE To evaluate and compare the initial retention force of three resilient unsplinted attachment systems for implant-retained mandibular overdentures: two cylindrical attachment systems (Locator R-Tx® and Novaloc®), and one ball attachment system (Ball System). MATERIALS and methods. For each attachment system, initial retention is measured as the average of the maximal dislodging forces during 10 insertion-removal cycles. For the Ball System, 3 activation degrees of the matrix are included whereas 4 and 6 color-coded retention devices for the Locator R-Tx® and the Novaloc®, respectively, represent the complete regular retention devices panel. For each retention device or activation degree, 8 samples are tested. RESULTS The initial retention range is similar between the Ball System (7.7 ±3.4 N - 19.9 ±4.6 N) and the Novaloc® (2.0 ±0.5 N - 18.9 ±1.4 N) and broader for the Locator R-Tx® (3.3 ±5.0 N - 60.2 ±6.0 N). In each attachment system, the initial retention of each retention device is significantly different from the others, except for the two most retentive Novaloc® ones. Retention devices were also classified according to their initial retention (low, medium, and maximum). In each retention group, the Novaloc® and the Ball System provided similar retention values lower than the Locator R-Tx®. CONCLUSION Most of the retention devices tested provided an initial retention force of over 5 N for all three attachment systems. The Locator R-Tx® had the most comprehensive range, and the Novaloc® seemed to provide the most reproducible values, unlike the Ball System due to the activation required by the operator. This article is protected by copyright. All rights reserved.

Mechanical properties of polylactic acid (PLA), which is a biopolymer obtained via 3D-printing, were compared with conventional resins for the realization of interim prosthesis. A PLA built by fused deposition modeling and traditional interim resins (Unifast®, Integrity®, Temporary CB®) were divided into 4 groups (n=10). Each group was investigated for Young modulus, flexural strength, microhardness and analysis of the fractured surface. Data were analyzed by Kruskal-Wallis and ANOVA (α=0.05). The porosity of the PLA was calculated from the crystallinity degree and density. PLA-group showed an elastic modulus and flexural strength in the same range than Integrity®-group, better than Unifast®-group and inferior to Temporary CB®-group (p<0.05). PLA-group microhardness was equivalent to Unifast®-group and inferior to Integrity® and Temporary CB® groups (p<0.05). Due to mechanical properties similar to conventional resins and the low porosity rate, this biocompatible 3D-printed polymer may be an interesting alternative to conventional polymer to build temporary prosthesis.

Attachment systems (AS) enhance retention and stability by anchoring the overdentures to implants. Since 2002, the McGill consensus statement recommends the 2-implant-retained overdentures as the standard choice for edentulous mandible (2-IRMO). Considering the large number of AS available, it remains difficult for a practitioner to make a reasoned choice. A systematic review was conducted in PubMed/Medline and carried out independently by three authors, on retention, wear, and maintenance of AS used clinically or in vitro specifically for 1- or 2-IRMO. The 45 selected studies include 14 clinical and 31 in vitro studies. The risk of bias was evaluated according to the revised Cochrane risk of bias tool for randomized trials (RoB 2). The initial retention force of the cylindrical system is higher than the ball system. The retention loss, related to the wear of the retention device, is responsible for the most common need of maintenance, requiring activation or replacement. Plastic retention devices wear out faster and more significantly than metal ones, implying a worse time behavior of cylindrical systems, but their maintenance rate is similar. Neither system appears categorically superior. Cylindrical systems provide higher initial retention than ball ones; this advantage reduces over time with wear without affecting their need for maintenance.

PURPOSE To mechanically characterize and assess the biological properties of Ti6Al4V surfaces obtained by Selective Laser Melting in order to determine whether this process is conceivable for producing of implant-supported prostheses and particularly trans-gingival components. As-built and polished surfaces were studied in comparison with components obtained by computer numerical control machining technology in order to consider whether the properties are in the same range as the conventional method currently used. MATERIALS AND METHODS Cylindrical specimens of Ti6Al4V (n = 6) were built with Selective Laser Melting for the characterization of mechanical properties according to ISO 22674 and discs (n = 12) were fabricated in the same conditions for cytotoxicity evaluation. Discs (n = 12) of Ti6Al4V were also obtained by computer numerical control machining as control. Half of the number of discs (n = 6) from each process were polished, to simulate the laboratory protocol for polishing of transmucosal components and half of the discs remained unaltered (as-built). Surface roughness measurements of disc specimens (as-built and polished) were compared with computer numerical control milling specimens (as-built and polished). Proliferation of human gingival fibroblasts on Ti6Al4V surfaces was also assessed for each condition. Viability and cell morphology were then evaluated qualitatively. Ra and Sa data were compared using Student t-test (α = 0.05) and metabolic activity data were compared using Kruskal-Wallis statistical test (α = 0.05). RESULTS Selective Laser Melting specimens showed elongation at break greater than 2 % and 0.2% yield strength better than 500MPa which complied with ISO 22674 standards. Although Selective Laser Melting samples displayed significantly increased roughness on as-built surfaces compared to computer numerically-controlled milling samples (p<0.05), no statistically significant difference was observed after mechanical polishing (p = 0.279). Regarding metabolic activity, no statistical difference was observed between groups at day 3 (p>0.05) and fibroblasts showed a viability higher than 97 % on all discs. Cell shapes on polished samples suggested moderate adhesion compared to unpolished samples. CONCLUSION With the manufacturing parameters selected in this study, Selective Laser Melting of Ti6Al4V appeared to be compatible with a prosthetic application type 4 according to ISO 22674. Surfaces obtained, followed by recommended post-processing provided components with equivalent biological properties compared to computer numerical control machining technology. This article is protected by copyright. All rights reserved.

X-linked hypophosphatemia (XLH) is characterized by rickets and osteomalacia, caused by inactivating mutations in the Phosphate-regulating endopeptidase homolog X-linked (PHEX) gene. With aging, adult patients develop paradoxical heterotopic calcifications of tendons and ligaments at their insertion sites (enthesophytes), and joint alterations. Understanding the progression of this structural damage that severely affects patients' quality of life will help to improve the management of XLH. Here, we characterized the occurrence of enthesophytes and joint alterations through a 12 month in vivo micro-CT follow-up in the Hyp mouse, a murine model of XLH (n = 5 mice per group). Similar to adult patients with XLH, Hyp mice developed calcaneal enthesophytes, hip joint alterations, erosions of the sacroiliac joints and periarticular calcifications. These lesions were already present at month 3 and gradually worsened over time. In sharp contrast, no abnormalities were observed in control mice at early time points. Histological analyses confirmed the presence of bone erosions, calcifications and expansion of mineralizing enthesis fibrocartilage in Hyp mice and their absence in controls and suggested that new bone formation is driven by altered mechanical strain. Interestingly, despite a strong deformation of the curvature, none of the Hyp mice displayed enthesophyte at the spine. Peripheral enthesophytes and joint alterations develop at the early stages of the disease and gradually worsen overtime. Overall, our findings highlight the relevance of this preclinical model to test new therapies aiming to prevent bone and joint complications in XLH.

Dentin, the main tissue of the tooth, is made of tubules surrounded by peri-tubular dentin (PTD), embedded in a matrix of inter-tubular dentin (ITD). The PTD and the ITD have different relative fractions of collagen and hydroxyapatite crystals. The ITD is typically less rigid than the PTD, which can be seen as a set of parallel hollow cylindrical reinforcements in the ITD matrix. In this paper, we extend Hashin and Rozen’s homogenization scheme to a nonuniform distribution of hollow PTD cylinders, determined from image analysis. We relate the transverse isotropic elastic coefficients of a Representative Elementary Volume (REV) of dentin to the elastic and topological properties of PTD and ITD. The model is calibrated against experimental data. Each sample tested is consistently characterized by Environmental Scanning Electron Microscopy (ESEM), nanoindentation and Resonant Ultrasound Spectroscopy (RUS), which ensures that macroscopic mechanical properties measured are correlated with microstructure observations. Despite the high variability of microstructure descriptors and mechanical properties, statistical analyses show that Hashin’s bounds converge and that the proposed model can be used for back-calculating the microscopic Poisson’s ratios of dentin constituents. Three-point bending tests conducted in the laboratory were simulated with the Finite Element Method (FEM). Elements were assigned transverse isotropic elastic parameters calculated by homogenization. The tubule orientation and the pdf of the ratio inner/outer tubule radius were determined in several zones of the beams before testing. The remainder of the micro-mechanical parameters were taken equal to those calibrated by RUS. The horizontal strains found experimentally by Digital Image Correlation (DIC) were compared to those found by FEM. The DIC and FEM horizontal strain fields showed a very good agreement in trend and order of magnitude, which verifies the calibration of the homogenization model. By contrast with previous studies of dentin, we fully calibrated a closed form mechanical model against experimental data and we explained the testing procedures. In elastic conditions, the proposed homogenization scheme gives a better account of microstructure variability than micro–macro dentin models with periodic microstructure.

The coronavirus pandemic resulted in a shortage of protective equipment. To meet the request of eye-protecting devices, an interdisciplinary consortium involving practitioners, researchers, engineers and technicians developed and manufactured thousands of inexpensive 3D-printed face shields, inside hospital setting. This action leads to the concept of "concurrent, agile, and rapid engineering".

Collagen is the major component of connective tissues, where it assembles into fibrils that exhibit various sizes and form various 3D structures depending on the observed tissue. Any disruption of this microstructure is associated with tissue malfunction and defective biomechanical properties. This study thus aims to investigate the relationship between the microstructure and the macroscopic mechanical response of typical connective tissues: skin (disordered) and cornea (highly ordered). To overcome technical issues in providing experimental multiscale data in intact tissues, we have implemented an original setup combining mechanical assays at tissue scale and Second Harmonic Generation (SHG) imaging of collagen reorganization. This multiphoton imaging modality represents an effective structural probe of the micrometer-scale collagen organization in unstained tissues. 3D SHG images were acquired in dermis from ex vivo murine skin biopsies during controlled stretching until rupture, and in ex vivo Human cornea during inflation assays. Specific image processing was implemented to quantify the reorganization of tissue microstructure and correlate it with stress/stretch relationship at macroscopic scale. In murine skin, we showed that the collagen fibers continuously aligned with stretch, generating the observed increase in mechanical stress, which challenges the usual theoretical explanation of the microstructural origin of the skin macroscopic mechanical response. Moreover, dermis from transgenic mice with defective collagen microstructure exhibited altered collagen reorganization upon traction, which could be linked to the microstructural modifications. In Human cornea, our results showed no reorganization of the collagen fibrils at sub-micrometer scale within the stromal lamellae, while the lamellae at micrometer scale reorganized in a more balanced way along 2 main perpendicular directions, in line with the deformation observed at the macroscopic scale. In conclusion, our approach provides an efficient tool to investigate the biomechanics of collagen-rich tissues in normal and pathological context and to guide tissue engineering with appropriate biomechanical responses.

(2020). Impact of machining process on the flexural strength of CAD/CAM blocks for dental restorations. Computer Methods in Biomechanics and Biomedical Engineering: Vol. 23, 45th Congress of the Société de Biomécanique, pp. S31-S32.

• Bio-fidelic finite element models of the T12-L2 thoracolumbar functional spinal units were used. • Age-specific anatomical features (growth plates and apophyseal rings) were added in the models. • Load sharing and fracture initiation biomechanics have been investigated. • Vertebral fracture initiations gets delayed in the presence of growth plates and apophyseal rings. • Age-specific anatomical features modify load sharing biomechanics in spinal components.

PURPOSE:To determine whether selective laser melting (SLM) is suitable for the fabrication of dental superstructures.MATERIALS AND METHODS:Mechanical properties of Ti-6Al-4V, manufactured with SLM or numerically controlled milling, were evaluated and compared.RESULTS AND CONCLUSION:Both groups showed a mechanical strength greater than 500 MPa and an elongation greater than 2%, as required by the International Organization for Standardization 22674 standard. However, a reduced ductility was observed for SLM samples.