The stiffness of a dorsal leaf AFO that minimizes walking energy cost in people with plantarflexor weakness varies between individuals. Using predictive simulations, we studied the effects of plantarflexor weakness, passive plantarflexor stiffness, body mass, and walking speed on the optimal AFO stiffness for energy cost reduction.We employed a planar, nine degrees-of-freedom musculoskeletal model, in which for validation maximal strength of the plantar flexors was reduced by 80%. Walking simulations, driven by minimizing a comprehensive cost function of which energy cost was the main contributor, were generated using a reflex-based controller. Simulations of walking without and with an AFO with stiffnesses between 0.9 and 8.7 Nm/degree were generated. After validation against experimental data of 11 people with plantarflexor weakness using the Root-mean-square error (RMSE), we systematically changed plantarflexor weakness (range 40–90% weakness), passive plantarflexor stiffness , body mass (+ 30%) and walking speed (range: 0.8–1.2 m/s) in our baseline model to evaluate their effect on the optimal AFO stiffness for energy cost minimization.Our simulations had a RMSE < 2 for all lower limb joint kinetics and kinematics except the knee and hip power for walking without AFO. When systematically varying model parameters, more severe plantarflexor weakness, lower passive plantarflexor stiffness, higher body mass and walking speed increased the optimal AFO stiffness for energy cost minimization, with the largest effects for severity of plantarflexor weakness.Our forward simulations demonstrate that in individuals with bilateral plantarflexor the necessary AFO stiffness for walking energy cost minimization is largely affected by severity of plantarflexor weakness, while variation in walking speed, passive muscle stiffness and body mass influence the optimal stiffness to a lesser extent. That gait deviations without AFO are overestimated may have exaggerated the required support of the AFO to minimize walking energy cost. Future research should focus on improving predictive simulations in order to implement personalized predictions in usual care.Trial Registration Nederlands Trial Register 5170. Registration date: May 7th 2015. http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5170The online version contains supplementary material available at 10.1186/s12984-023-01239-z. Individuals with plantarflexor weakness caused by neuromuscular disorders walk with excessive ankle dorsiflexion, persistent knee flexion and a reduced push-off during stance , 2. ThesTo improve the gait pattern and reduce walking energy cost, a dorsal leaf spring ankle–foot orthosis (AFO) can be provided , 7. In cTo maximize the AFO’s effect on walking energy cost reduction, the AFO’s bending stiffness needs to be individually optimized –19. A veWhat factors affect the individual optimal stiffness is not completely understood , 20. MusBy means of human experiments, these interactions are challenging to study, as systematic variations cannot be imposed in most cases and/or require extensive testing. Forward dynamic predictive simulations are not limited in this regard and have shown their potential by validly predicting the effects of bilateral plantarflexor muscle weakness on gait . Yet, whTo generate walking simulations, a forward simulation framework consisting of a reflex-based controller and a neuromuscular model with plantarflexor weakness and an AFO was created. First, we validated this framework against previously collected gait data of people with bilateral plantarflexor weakness walking with and without dorsal leaf spring AFO’s . Secondlhttps://hyfydy.com [We used a previously developed musculoskeletal model, consisting of seven segments , nine degrees of freedom, and nine musculotendon units on each leg modelled with the Millard Equilibrium muscle model . The folfydy.com ) model ufydy.com . Hyfydy To activate the muscles, a gait state-dependent reflex-based controller was used , which wReflex gains within each gait phase, transition thresholds between the phases and the initial joint angles were optimized by minimizing a cost function using the Covariance Matrix Adaptation Evolution Strategy (CMA-ES) , as implWalking was simulated for bouts of 10 s with a minimum walking speed of 0.3 m/s. We optimized each simulation six times with different random seeds, as the optimization algorithm is based on random alterations. The optimization was terminated when, averaged over the last 500 simulation generations, the improvement in cost function outcome was smaller than 0.001%. The best of the six optimizations was selected as outcome.To impose plantarflexor weakness, the isometric force of the Soleus and Gastrocnemius muscles was reduced, while passive muscle and tendon stiffness were adapted such that passive fibre and tendon force–length curves matched those of the unimpaired model . The AFOFor validation of the framework, we first performed simulations for a model without weakness, our model with 80% plantarflexor weakness without and with an AFO with a stiffness of 2.6 Nm/degree. The simulations were compared with the average experimental 3D gait data of 11 participants of the PROOF-AFO trial with bilateral plantarflexor weakness and manually tested maximal ankle dorsiflexion angle of at least zero . These pFor validation, the agreement between the simulations with plantarflexor weakness without and with AFO and experimental data was quantified by time-normalized cross-correlations (R) and the root mean square error (RMSE) normalised to the standard deviation (SD) for sagittal lower limb joint angles, moments and powers. An RMSE below 2 standard deviations (SD) means that on average the simulation was within the 95% confidence interval of the experimental data. Additionally, to test in which time periods within the gait cycle the simulations differed significantly from the experimental data, an independent t-test was performed over the whole gait cycle using statistical parameter mapping  .Next, we created models in which muscle pathophysiology and body mass were systematically varied. For each model, we performed simulations for walking without AFO (stiffness 0 Nm/degree) and with AFO with stiffness levels ranging from 0.9 Nm/degree, being very flexible, to 8.7 Nm/degree, being very stiff, with increments of 0.87 Nm/degree. This range coincides with the range of stiffness levels typically used in clinical practice , 37. To To systematically evaluate the effects of walking speed we simulated walking with the baseline 80% weakness model with the speed set at 0.75, 1.0 and 1.2 m/s, which represents the range of walking speeds clinically seen in these patients [For each model, the optimal stiffness for walking energy cost reduction was determined by the minimum  of a 3rd order polynomial fit across the eleven simulations, i.e. without AFO (stiffness 0) and with AFO for 10 stiffness levels Fig. . A polynrd order best polynomial fit was drawn between AFO stiffness and the maximal ankle angle, maximal ankle moment, minimal knee angle and minimal external knee moment. The stiffnesses where the fit equalized the mean normative value for maximal ankle angle (angle of 17.2 degrees), minimal knee angle (4.2 degrees) and external knee extension moment (below 0.34 Nm/kg) during stance were calculated. For maximal ankle moment the mean normative value minus 2 SD was used (1.17 Nm/kg), as no stiffness reached the mean normative value and ankle moment levelled off at high stiffness levels . With a larger reduction in plantarflexor strength, the optimal stiffness increased from 2.4 Nm/degree at 40% plantarflexor weakness to 5.2 Nm/degree at 90% weakness, coinciding with a higher reduction in energy cost (from 0.29 to 0.89 J/kg/m) , ankle moment , knee angle  and knee moment . To best normalize the ankle angle and moment, a higher AFO stiffness was needed with more severe plantarflexor weakness, higher body mass and lower levels of passive plantarflexor stiffness  was higher compared to the average stiffness resulting in a normalized maximal ankle angle   and limiIn conclusion, our forward simulations demonstrate that more severe plantarflexor weakness and faster walking speed can double the AFO stiffness aiming for minimal walking energy cost in individuals with bilateral plantarflexor. Passive muscle stiffness and body mass also noticeable influence the optimal stiffness, although to a lesser extent. These are an important step towards better matching the AFO stiffness to the individual user, although, before clinical implementation improved predictions of gait are required as currently the match with experimental data is insufficient. Future research should focus on predicting the optimal stiffness based on these characteristics using individualized models.Additional file 1: Model property settings.Additional file 2: Difference between OpenSim and HyFyDy models.Additional file 3: Simulation results without AFO.Additional file 4: SPM results of simulation without AFO and AFO of 2.6 Nm/degree.


Leishmania donovani hydrophilic acylated surface protein B1 as a potential vaccine candidate using in silico methods. For this aim, server-based predictions were performed regarding physicochemical characteristics, solubility, antigenicity, allergenicity, signal peptide, transmembrane domain, and posttranslational modifications (PTMs). Also, secondary and tertiary structures were predicted using NetSurfP-3.0 and I-TASSER, respectively. The 3D model was further subjected to refinement and validation, and promising B-cell, cytotoxic T-lymphocyte , and helper T-lymphocyte  epitopes were predicted. The protein had a molecular weight of 42.19 kDa, with high solubility (0.749), stability (instability index: 21.34), and hydrophilicity (GRAVY: -2.322). No signal peptide or transmembrane domain was predicted, and the most abundant PTMs were phosphorylation, O-glycosylation, and acetylation. Many coils and disordered regions existed in the secondary structure analysis, and the tertiary model had a good confidence score (-0.79). Next, the ProSA-web and PROCHECK tools showed adequate improvements in the refined model compared to the crude model. Only 4 shared B-cell epitopes among three web servers  were shown to be antigenic, nonallergenic, and with good water solubility. Also, five potent CTL epitopes in dogs and five in humans were predicted. Notably, two HTL epitopes were found to be potential IFN-γ inducers. In conclusion, our results demonstrated several immunogenic epitopes in this protein, which could be directed towards multiepitope vaccine design.Visceral leishmaniasis is a life-threatening infectious disease worldwide. Extensive experiments have been done to introduce potential vaccine candidates to combat leishmaniasis. The present study was done to evaluate  Leishmania (family Trypanosomatidae) are known as the causative agents, being transmitted through biting by female phlebotomine sandflies, i.e., Phlebotomus and Lutzomyia, in the Old World and New World, respectively , “F, “Fγ) inThose 9-10-mer CTL epitopes (MHC-I binders) specific to humans were predicted using the IEDB MHC-I epitope prediction tool, available, using the IEDB recommended method 2020.09 (NetMHCpan EL 4.1) . This prn = 106) than positively charged ones (n = 53). The half-life of LdHASPB1 in mammalian reticulocytes was over 30 hours, and the protein was demonstrated to be low thermotolerant , stable (instability index: 21.34), and an extremely hydrophilic molecule (GRAVY: -2.322)  in the sequence ( -2.322) .No signal peptide or transmembrane domain was detected in the LdHASPB1 protein sequence, based on the SignalP and DeepTMHMM web servers, respectively. Additionally, the DeepLoc tool revealed that the protein is probably a cell membrane component (likelihood: 0.63). N-Glycosylation and palmitoylation sites were rarely predicted in the protein sequence, whereas lysine acetylation, O-glycosylation, and phosphorylation sites were abundantly predicted in the LdHASPB1, with 11, 16, and 28 regions, respectively. The detailed properties of the PTM sites are provided in The residues were exposed in most parts of the sequence, according to the NeteSurfP-3.0 server, with frequent coil regions. Also, there observed a high probability of disordered regions throughout the protein sequence .C-scores of -0.79 (model 1), -2.84 (model 2), -2.99 (model 3), -3.88 (model 4), and -4.16 (model 5) were predicted. Pertinent to a higher C-score in model number 1 : 8.6 ± 4.5 Å) (Z-score: -1), in comparison with the crude model (Z-score: -0.77)  , it was : -0.77) . Based o: -0.77) .In this study, three different methods of prediction were used for linear B-cell epitopes using the ABCpred, BepiPred-2.0, and SVMTriP web tools, with strict thresholds. The output of each server was compared with that of two others; shared epitopes were extracted and screened. On this basis, among the 8 common linear B-cell epitopes, 4 were shown to possess good antigenicity, no allergenicity, and with good water solubility, based on the VaxiJen, AllerTOP, and PepCalc servers, respectively. These epitopes were as follows: “TQKNDGDG,” “KEDGHTQK,” “AQEKNEDGHNVGD,” and “GDGPKEGENLQ” . Also, tγ induction. Only two epitopes, including “EANHGGATGVPPKHT” and “TEANHGGATGVPPKHT,” possessed good antigenicity and positive IFN-γ induction without allergenicity . Reportedly, charged residues in a protein sequence play a significant role in protein orientation/position , and abuC-score (-0.79) was selected with a TM-score of 0.61 ± 0.14 and an estimated RMSD of 8.6 ± 4.5 Å. The 3D model was further subjected to refinement and validation. According to the ProSA-Web and PROCHECK analyses, the quality of the refined model was enhanced after refinement as compared with the crude model.Using the NetSurfP-2.0 server, surface accessibility, secondary structure, and disordered regions were predicted in the submitted protein sequence. The output showed that almost all regions of the protein were structurally disordered and surface accessible in nature. Disordered proteins are highly abundant and mostly dedicated to regulatory functions and molecular signaling. Supposedly, these regions are likely immunological targets for antibodies; hence, they seem to be important in vaccination studies . Also, eLeishmania-induced infection in susceptible hosts. During the metacyclic phase, the HASPB1 protein can be exposed to the plasma membrane surface, facilitating detection by specific antibodies [Acquired immune responses play a major role in the prevention and/or control of tibodies . On thisLeishmania parasites, helper type-1 CD4+ (Th1) and cytotoxic CD8+ T-cells (CTLs) are key regulators in controlling leishmaniasis. Moreover, the capability of IFN-γ induction is a pivotal function for Th1-type epitopes, resulting in the activation of macrophages and downstream parasite clearance mechanisms [L. donovani infection via direct and/or indirect interleukin-12 (IL-12) production and subsequent CD8+-dependent IFN-γ induction [γ and IL-4) immune responses against L. major [L. donovani [L. infantum [γ induction. Of note, predicted HTL epitopes were mostly located at positions 23-39. Potent human IFN-γ inducing HTL epitopes predicted by the IEDB server was in association with the HLA-DQA1∗05 : 01/DQB1∗03 : 01, as one of the prevalent HLA alleles, including “EANHGGATGVPPKHT” (antigenicity score: 0.9030) and “TEANHGGATGVPPKHT” (antigenicity score: 1.0112). Among human CTL epitopes, five were selected as potentially antigenic and nonallergenic ones, based on the IEDB HLA reference set covering over 97% of the population, enclosing “EANHGGATGV” (HLA-A∗68 : 02), “EPQKRADNI” (HLA-B∗51 : 01), “SAKEPQKRA” (HLA-A∗30 : 01), “APKEDGHTQ” (HLA-B∗07 : 02), and “EPQKRADNI” (HLA-B∗08 : 01). Since dogs are important reservoirs of L. donovani in the Old World countries, CTL epitope analysis for LdHASPB1 was, also, done regarding DLA, using the IEDB server. Our results suggested five high-ranked antigenic and nonallergenic epitopes regarding DLA class-I molecules, such as “KDSAKEPQKR” (DLA-8803401), “EANHGGATGV,” and “KTTEANHGGA” (DLA-8850101), as well as “KDSAKEPQKR” and “TQKNDGDGPK” (DLA-8850801). Altogether, the clinical implications of these specific B- and T-cell epitopes can be assigned to design and engineer different and novel multiepitope vaccine constructs using the predicted epitopes and those of other highly immunogenic Leishmania proteins, along with a Th1-biasing adjuvant such as the RS-09 synthetic protein (toll-like receptor 4 agonist) for enhanced immunogenicity. The major challenge in designing such vaccine candidates may be their in vivo safety and reliability, which need to be further evaluated using wet experimental methods against human or canine challenges with VL.Given the intracellular nature of chanisms . It has nduction . MoreoveL. major , L. donodonovani , and L. infantum . On thisL. donovani antigens in the context of unprecedented immunization platforms provides novel insights into the vaccination against kala-azar. In the present study, the most functional and important biophysical properties and novel B- and T-cell-binding epitopes were predicted in the LdHASPB1 protein of L. donovani using a set of immunoinformatic servers. Notably, several CTL epitopes were predicted for human HLA reference alleles and three DLA class-I alleles, which could be further allocated in vaccination studies against VL, as alone or combined with other epitopes/antigens, in the context of a multiepitope vaccine. As a final word, the information provided here, particularly the immunogenic CTL, HTL, and B-cell epitopes, can be of interest to vaccinology researchers and may give insight for designing novel vaccines against VL.Due to the importance of VL in tropical and subtropical regions and its zoonotic aspects, preventive measures such as vaccination seem to be more effective than therapeutic approaches. Next-generation vaccine design using strictly screened, highly antigenic epitopic fragments of known


The PL was associated  with the percentage of Skeletal Muscle Mass (%SMM) and cardiorespiratory fitness . Conclusions: Developing the PL for the most disadvantaged secondary school students in a PA program could be a suitable strategy to increase their PA level, reduce their adiposity, and promote better long-term health.Background: Overweight and obese adolescents are often associated with lower Physical Activity (PA) levels and low Cardiorespiratory Fitness (CRF). Recently, the concept of Physical Literacy (PL), has been suggested to be associated with higher levels of active behavior and better health in adolescents. The purpose of this study is to investigate the relationships between PL, body composition, cardiorespiratory fitness and physical activity levels in French secondary school students. Methods: The level of PL was assessed in 85 French adolescents using a French version of the Perceived Physical Literacy Instrument (F-PPLI). Cardiorespiratory fitness was measured by the “20 m adapted walk/shuttle run test”. The PA level was assessed by the Youth Risk Behavior Surveillance System questionnaire. Weight status was measured by the Body Mass Index (BMI) and the body composition data. Results: We find a significant association between the PL and the percentage Fat Mass (%FM) (r = −0.43;  In children and adolescents, overweight and obesity are identified by the International Obesity Task Force’s (IOTF) Body Mass Index (BMI) cut-offs. Overweight is defined as a BMI between the IOTF cut-offs of 25 and 30 and obesity as a BMI above the IOTF cut-off of 30 . The intOn the other hand, recent national and international epidemiological studies confirm an increasing trend in time spent in behaviors described as “obesogenic”  ,4. In FrThe interdependence of PA levels with physical fitness is important. Indeed, Hui et al.  showed tMVPA and CRF are also negatively correlated with weight status and the body composition of adolescents ,17. OverThus, adolescents with low levels of CRF and low levels of PA associated with high BMI, high %FM, and low %SMM are most at risk of developing cardiometabolic complications in adulthood. However, we can note that, independently of weight status, improving CRF in adolescents would reduce these risks ,21. It iRecently, the concept of Physical Literacy (PL) has gained increased attention and has become a key element in the issue of promoting PA . It can PL is a key component of an active lifestyle and «optimal» health. This concept was first explored in the field of education . Later, Cairney et al.  proposedTo our knowledge, we are the first study to examine the relationship between PL, body composition, PA levels, and CFR in high school students. Moreover, in France, no correlational study has been carried out on the theme of PL and health in adolescents. Therefore, we are interested in this.A high level of PL among French adolescents could, therefore, be associated with high levels of PA and a superior CRF, determinants of long-term health.The aim of this study is, therefore, to evaluate and investigate the relationships between PL, body composition, CRF, and the levels of PA in a population of French adolescents.Four 6th-grade classes  took part in this study. These four classes were chosen because they volunteered to participate in the study.The evaluations took place between February and June 2021. For each class of approximately 30 students, the assessments took place during physical education and sports classes over four specific sessions distributed over four consecutive weeks. The order of the assessments was the same for all classes: (1) 20 m shuttle run/walk test (TMNA-20), (2) Youth Risk Behavior Surveillance System, (3) Perceived Physical Literacy Instrument (PPLI), and (4) Anthropometric data and impedance measurement. The first author of the publication and the physical education and sports teachers supervised these evaluations.Parents signed a consent form agreeing to data collection for the project and all subjects gave their informed consent for inclusion before they participated in the study.The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Research Ethics Committee of the Sciences and Techniques of Physical and Sports Activities (CER STAPS) (n°2020-11-02-44).z Fisher test). The inclusion criteria for our study were the agreement of physical education, for the sports teachers to participate in the study of their class, that the teenagers are in 6th-grade classes, and that they can participate correctly in all the evaluations. Any limitations in the adolescents that made it impossible to complete the assessments were a non-inclusion criterion.A total of 84 participants were needed to reach a power of 0.8 with an effect size of 0.3 and an alpha of 0.05  years, participated in our study. In total, 72 of them were normal weight, 2 were underweight, and 11 were overweight and obese.®, 22089, Hambourg, Germany) according to the standard procedure: adolescents stood with their feet together, without shoes, and leaned against a wall with their heads, shoulders and feet aligned.The height was measured to the nearest 0.5 cm using a wall height gauge . The weighing took place in minimal clothing . The BMI was then calculated using the formula: BMI = weight (kg)/height (m)2.The weight was measured to the nearest 0.5 kg with a balance . All measurements were recorded during the same morning. No vigorous to intense PA was performed 12 h before the test. Adolescents had an empty bladder and did not consume alcohol or caffeine-based beverages at least 24 h before the test. The measurement protocol was standardized and explained to everyone. The adolescent, in a seated position, placed his right hand on the rear sensors of the bioelectrical impedance and placed the front sensors at the level of the rear foot under the ankle.The raw results (rate (kg), percentage of FM (%FM), and percentage SMM (%SMM were then provided by the “BiodyManager” (version 1) software.−1). A mathematical formula is then used: (19.66 + (2.21 ∗ VMA) + (0.05 ∗ age) + (2.08 ∗ girl (0) or boy (1)) − (0.38 ∗ BMI)).The CRF was assessed by the CRF on the adapted 20 m shuttle run/walk test (TMNA-20) . This te1 <150 min of MVPA per week; 2 between 150 and 210 min of MVPA per week; 3 ≤210 min of MVPA per week.The levels of PA of secondary school students were assessed by the French adaptation of the self-administered Youth Risk Behavior Surveillance System (YRBSS) questionnaire ,36. ThisWith these results, it is possible to calculate the minutes of MVPA per week, which is an indicator of PA levels. The level of Perceived Physical Literacy (PPL) was assessed using the test from Sum et al. : PerceivAll statistical analyses are carried out by Statistica software (version 7.1).p-value ≤ 0.05 was chosen for statistical significance.The mean, standard deviation, median, and distribution of the data are calculated for each variable: age, BMI, %FM, %SMM, maximum aerobic speed (Vmax), aerobic capacity, PPL score (points), and PA levels (MVPA per week)). The normality of each variable was tested using the Shapiro-Wilk test. Due to the non-normality distribution, the non-parametric Mann-Whitney U test is used to test the gender-dependent variations in each variable. A −1), and MVPA (min/week). Using the Pearson correlation analysis, the correlation coefficient (r) is used to determine the strength of the relationship and the significance is indicated by a p value ≤ 0.05.Simple linear regression models are used to determine the relationships between PPL (independent variable) and the different dependent variables: BMI, %FM, %SMM, aerobic capacity (mL·kg·minThe mode of association between the variables is indicated by the standardized beta coefficient (β) and its 95% confidence interval.Following on from the results of the Caldwell et al.  study, mFor each relationship between the PPL (independent variable) and a Dependent Variable (DV), a multiple linear regression is used to determine the mediation of the MVPA variable (Mediator Variable).This is a sample of 85 secondary school students in the 6th grade who took part in the study. All students carried out the assessments. The detailed characteristics can be found in p = 0.33).There was no significant difference in the age variable between girls and boys (p < 0.01), and boys have a higher %SMM than girls (p < 0.01).Girls have a higher BMI and %FM than boys (p < 0.01). Boys also had a higher MVPA per week than girls, both in (328.53 min (±152.80) vs. 232.69 min (±99.78); p = 0.01). For the PPL scores, girls did not score higher than boys (p = 0.05).The results of the fitness test show a higher maximal aerobic speed and maximal oxygen volume in boys (p < 0.01) (p < 0.01). There was no significant association between PL score and BMI ; p = 0.096). < 0.01) . The PL p ≤ 0.05). We also found significant positive associations between the PL score and the MVPA per week ; p ≤ 0.01).We found a significant positive association between the PL score and CRF with aerobic capacity as an indicator ; p < 0.01) and between the CRF and the %FM . A positive association exists between the CRF (aerobic capacity) and the %SMM . The CRF was also positively and significantly associated with the MVPA . The MVPA was negatively and significantly associated with the %FM  and positively and significantly associated with the %SMM .We observed associations between the dependent variables. There were negative associations between the CRF (aerobic capacity) and the BMI . Testing the MVPA variable as a mediator variable, we also find an inverse and significant association between the PPL and the %FM ; p = 0.05).The variable MVPA does not mediate the relationship between the PPL and the %FM. Indeed, in the simple linear regression model, PPL is inversely and significantly associated with %FM ; p ≤ 0.01). In the multiple linear regression model testing the MVPA variable as a mediating variable, the effect of PPL on the %SMM is no longer significant ; p = 0.38). This means that the effect found in the simple linear regression is due to the mediation of the MVPA variable. A similar result was found in the relationship between the PPL and the CRF. In the simple linear regression model, the PPL was positively and significantly associated with the CRF ; p ≤ 0.05). By integrating the MVPA mediator variable, we no longer find a significant relationship between the PPL and the aerobic capacity ; p = 0.49). The MVPA variable is therefore a mediator of the relationship between the PPL and the aerobic capacity.The simple linear regression model shows a positive and significant relationship between the PPL and the %SMM ; p ≤ 0.05). As a mediator, MVPA per week can partly explain the effect of this relationship, as MVPA is directly associated with the level of PPL . The linear regression model showed that there was an inverse relationship between the %FM and the PPL score . Secondary school students with a high PL score had a higher %SMM than those with a low PL score ). This relationship between the PPL and the %SMM could be explained by the effect of MVPA.In this cross-sectional study, we sought to explore the relationships between the PPL, body composition, CRF, and PA levels in French secondary school students in the 6th grade. None of these relationships had been established before in France, especially among adolescents. In accordance with our hypothesis, we found that the higher the PPL score, the higher the CRF of adolescents . Thus, for each additional point on the PPL score, aerobic capacity increases by 0.33 mL·kg·min−1. The influence of the PPL on the CRF of secondary school students is partly explained by the effect of MVPA per week (measured in minutes per week).The development of PL allows for the engagement in lifelong PA through improvements in motor skills and cognitive-emotional competencies . CRF is A Canadian study of 249 children aged 10 years showed similar results with a positive relationship between the PPL (score) and the CRF (heart rate) . This rep ≤ 0.01). Thus, for each additional point of PPL, the MVPA increases by 13.97  minutes per week. This same relationship, an increase of 3.19  minutes per day, was found in the 2020 study by Caldwell et al. in Canadian adolescents [Our results also show a positive association between the PPL scores and MVPA . For each additional point on the PPL score, the %FM decreased by 0.86%. This association is direct and not mediated by MVPA. This negative relationship between the PPL score and the %FM was also found in 249 adolescents. In this study, the assessment of PL was performed using the PLAY tools [Our results also showed relationships between the level of PPL and the body composition of adolescents. There was a negative association between the PPL and the %FM ). It is positively associated with CRF in adolescents and negatively associated with mortality in adults [In our study, PL is also positively and moderately associated with the %SMM . On the other hand, the BMI has many limitations in its interpretation and in particular the non-differentiation between FM and lean mass. BMI is only an index of body shape, so we can assume that the perception of the level of PL is more strongly impacted by the MVPA and by the %SMM and the %FM than by the BMI. In contrast to our study, a negative correlation was found between the BMI and the total PL score in Spanish children . In a syThus, the adolescents most at risk are those with a high %FM and a low %SMM with the lowest levels of PA and CRF. Adolescents with these characteristics are those with low levels of PPL. The PPL was associated with body composition data, PA levels, and CRF, and some of these associations were mediated by MVPA. Improving the PL level of at-risk secondary school students could therefore increase their PA levels and, ultimately, improve their health.Our study is the first French study to assess these parameters and to show associations between the PPL, CRF, MVPA, and body composition of secondary school students. Until now, studies looking at PL and its associations with health indicators were in North America ,28,46. TAnother strength of our study is the rigor in the choice of methodological tools used to assess the CRF and weekly reported MVPAs. The 20 m adapted Shuttle Walk/Run test (TMNA-20)  and the On the other hand, this experimentation is the starting point for a study on the longitudinal follow-up of overweight and obese adolescents. The objective of this project (CAPACITES 64) will be to develop the PL of adolescents to increase their PA levels and improve their long-term health. As PA levels are predictors of associations between PPL, body composition, and CRF in adolescents, it is important to promote increased PA levels and participation in PA.This study has some limitations: The first is that the adolescent sample was not random. This type of sample presents a possible risk of recruitment bias.On the other hand, a larger sample size would have allowed us to extend the results to the entire adolescent population. Another limitation is that we did not take into account biological parameters such as pubertal development and growth. These parameters directly influence the CRF of adolescents but do not influence the level of PPL ,49.The subjective assessment of the levels of PA may have a methodological limitation on the accuracy of the results. Indeed, unlike an accelerometer, the questionnaire does not assess the amount of MVPA in an objective way. Adolescents could, therefore, have increased or decreased their PA levels in an involuntary manner. The final limitation concerns the subjective assessment of PL. This assessment was carried out by a self-administered questionnaire. The results are therefore dependent on a PPL score. The fact that this variable is assessed in a perceived and self-reported manner may lead to variations and inaccuracies in the results as adolescents may have difficulties assessing their health behavior.This study shows that in French secondary school students, the level of PPL is positively associated with CRF, MVPA, and the %SMM and negatively associated with the %FM. These results confirm our hypothesis that a good level of PL is associated with good CRF, high levels of PA, and positive health markers. This study confirms the fact that PL is a key parameter in the promotion of PA and health among French secondary school students. The results are preliminary but encouraging, as the development of PL in these secondary school students could help them maintain an active lifestyle.


Immune rejection is the most prevalent complication, and irreversible immune rejection always causes regraft failure.(1) Background: To analyze the indications, graft survival, and graft failure-related risk factors of repeat penetrating keratoplasty (RPK) in children. (2) Methods: In this case series, children younger than 12 years who received RPK at Beijing Tongren Hospital were reviewed. The indications for RPK, postoperative complications, and graft survival were analyzed. The analysis of the potential variables associated with graft survival was performed using Cox proportional hazards regression. (3) Results: A total of 30 RPK eyes of 29 children were included in this study. The mean follow-up time was 26.98 ± 18.75 months. The most common indication for RPK was a vascularized corneal scar (86.67%). Postoperative complications occurred in 27 eyes (90%), including immune rejection (46.67%), epithelial defects (36.67%), and glaucoma (26.67%). About 60% of the regrafts remained clear one year after RPK, while the overall graft survival rate was 30% at the last visit. The most common cause of regraft failure was irreversible immune rejection (8/21). The significant risks of graft failure included an age of less than 60 months at surgery ( Pediatric keratoplasty was performed infrequently before the mid-1970s ,3. The hPrevious studies indicated that the graft survival rate of RPK was lower than that of primary penetrating keratoplasty (PPK) in children. Xie et al., reported that the graft transparency rate after PPK in children was 74.3% but decreased to 38.1% after RPK ,10,11. OThis case series study was approved by the Medical Ethics Committee of Beijing Tongren Hospital, which is affiliated with Capital Medical University, and it adhered to the tenets of the Declaration of Helsinki. The medical records of children under 12 years of age who had obtained RPK at Beijing Tongren Hospital between December 2013 and June 2019 were reviewed. The included patients were followed up for at least 12 months unless regraft failure occurred within 12 months.The following items were recorded: the patients’ demographics ; systemic abnormalities ; the indications for PPK and RPK; the interval time between PPK and RPK; the intraocular pressure, lens status, and corneal vascularization of the recipients before RPK; the associated ocular surgeries performed concurrently or subsequently to RPK; and the graft diameter of the donor, follow-up duration, graft survival time after RPK, postoperative complications, and graft clarity status after RPK at the last visit.Graft failure is defined as the irreversible loss of clarity. The graft survival time is defined as the time between the date of surgery and the date of corneal clouding onset or the date of the last visit .Routine PK techniques and postoperative medication regimens were performed, as described in a previous study . All thep < 0.05 was considered statistically significant.Statistical analyses were carried out using IBM/SPSS software version 21 . Descriptive statistics were reported. The survival of the regrafts was analyzed using the Kaplan–Meier survival method. Analysis of the potential variables associated with graft survival was performed using Cox proportional hazards regression. A total of 30 RPK eyes of 29 patients were included in the current study, and all of them were initial RPK. One patient received bilateral RPK, and the other 28 patients received unilateral RPK. The average age of the patients at the time of RPK was 59.18 ± 31.16 months. Surgery was performed in 19 eyes at the age of 60 months or less and in 11 eyes at the age of more than 60 months. Female patients accounted for 33.33%. The average time interval between PPK and RPK was 29.08 ± 23.44 months, and the average follow-up time after RPK was 26.98 ± 18.75 months.The indications for primary and repeat penetrating keratoplasty are summarized in Furthermore, nine eyes (30%) underwent concurrent procedures at the time of RPK, including extracapsular cataract extraction (four eyes), cyclocryotherapy (two eyes), iridocyclectomy/pupilloplasty (two eyes), and anterior vitrectomy (one eye). Subsequent intraocular surgeries were performed in seven eyes (26.67%), including extracapsular cataract extraction and/or intraocular lens insertion and/or anterior vitrectomy (four eyes), anterior chamber irrigation (one eye), anterior vitrectomy and retro-corneal membrane resection (one eye), and cyclocryotherapy (one eye).Postoperative complications occurred in 27 eyes (90%) after RPK . A totalAt the most recent follow-up, nine (30%) regrafts were clear. The Kaplan–Meier graft survival curve is shown in Of the 21 failed regrafts, irreversible immune rejection was the most common cause (eight eyes), followed by compound factors (six eyes), unclear factors (two eyes), epithelial disease (one eye), uncontrolled glaucoma (one eye), a graft ulcer (one eye), primary graft dysfunction (one eye), and graft endothelial dysfunction (one eye) . The detp = 0.009), corneal vascularization , and a postoperative epithelial defect   .RPK is quite often required as there is a high probability of initial graft failure in children. Previous studies have analyzed the indications, graft survival, complications, and prognostic factors affecting graft failure of RPK in adults ,11,15, bFor the children who underwent RPK in this study, the most common indication for PPK was CCO. On the one hand, CCO is the most common indication for PPK in children in developed countries, even in China ,12,16,17A previous study, which included 279 repeat keratoplasty of 219 adults from 1991 to 2017 in New Zealand, showed that the most common indication for repeat keratoplasty was endothelial decompensation (37.6%) . HoweverPrevious studies have reported that the graft survival rate of RPK in children varies from 6% to 67% ,8,22. InCorneal vessels can destroy the local immune privilege, increase the possibility of rejection, and then cause graft failure ,24. In aA previous study reported that infants (<5 years) exhibited poorer graft survival than children aged older than 5 years , which ip = 0.004), which is consistent with that in RPK adults [A postoperative epithelial defect is another risk factor for regraft failure in RPK children (K adults . As the K adults ,30. In tIn general, we presented some data on the indications, graft survival, complications, and risk factors of RPK in children. The most common indication for RPK was a vascularized corneal scar. These patients are prone to postoperative complications due to the abnormality of limbal stem cells and the local immune status. In addition, due to the poor cooperation of children, it is difficult to find, identify, and handle postoperative complications, which leads to a low graft survival rate. Immune rejection was the most common postoperative complication and the most common cause of regraft failure. The risk of graft failure was higher in children with an age of less than 60 months at surgery, preoperative corneal neovascularization, and postoperative epithelial defects. Pediatric keratoplasty is relatively rare due to the low incidence of corneal disease in children. Additionally, the high costs of keratoplasty and the lack of donors result in a smaller number of RPKs. Although the sample size of this study was small, the clinical data may be useful for guiding the decision-making regarding corneal transplantation in children, and we think this work is very important. We will involve more children in future studies to obtain more convincing results.


Vascular prostheses (grafts) are widely used for hemodialysis blood access, trauma repair, aneurism repair, and cardiovascular reconstruction. However, smaller-diameter (≤4 mm) grafts that would be valuable for many reconstructions have not been achieved to date, although hundreds of papers on small-diameter vascular grafts have been published. This perspective article presents a hypothesis that may open new research avenues for the development of small-diameter vascular grafts. A historical review of the vascular graft literature and specific types of vascular grafts is presented focusing on observations important to the hypothesis to be presented. Considerations in critically reviewing the vascular graft literature are discussed. The hypothesis that perhaps the “biocompatible biomaterials” comprising our vascular grafts—biomaterials that generate dense, nonvascularized collagenous capsules upon implantation—may not be all that biocompatible is presented. Examples of materials that heal with tissue reconstruction and vascularity, in contrast to the fibrotic encapsulation, are offered. Such prohealing materials may lead the way to a new generation of vascular grafts suitable for small-diameter reconstructions. Vascular prostheses (grafts) are widely used for hemodialysis blood access, trauma repair, aneurism repair, and cardiovascular reconstruction. General requirements for success in all these applications are similar: The graft must not thrombose, the graft must not trigger hyperplasia, the graft must not lose mechanical integrity, and the graft must meet surgeon handling requirements .Vascular grafts used in surgery today are composed primarily of expanded Teflon (ePTFE) or Dacron fabric. Newer approaches based on tissue engineering or reprocessed natural tissue are in clinical trials.Entering the term “vascular graft” (in quotation marks) in the Google Scholar website gives 48,800 hits, evidence of the interest in these devices, their impact, and the degree to which they have been studied. Yet, vascular grafts have been unable to meet certain imperative needs in medicine. There are no regulatory agency-approved small-diameter vascular grafts (≤4 mm inner diameter). There is no widely accepted definition of a small-diameter vascular graft. Many articles propose <6 mm. In this article, I use ≤4 mm. Such grafts could be used for limb blood vessel replacement, possibly saving many of the roughly 1 million limbs amputated each year worldwide. Even smaller-diameter grafts could simplify cardiac bypass procedures . Arterio-venous grafts used for dialysis access also have a high failure rate at 1 to 2 years, leading to expensive reoperations. Grafts fail primarily due to thrombosis and hyperplasia (excess cell proliferation). These factors are interrelated in that hyperplastic narrowing of vessel lumen slows blood flow and increases the probability of thrombosis. In the 70+ years since the first synthetic vascular grafts were developed, these failure modes still plague the medical community. With so many published studies, one might imagine that solutions to less-than-ideal graft performance might have been realized and introduced to the clinic, but this has not happened. This highlights the complexity of the engineering–biology–medicine problem.This article addresses the limited progress with vascular graft development. The article develops the hypothesis that the “biocompatible” biomaterials comprising synthetic grafts are, in fact, questionably biocompatible. The long-term “attack” by the body on vascular graft biomaterials diminishes performance and accelerates graft failure. To expand upon this hypothesis, when meaningful biocompatibility is achieved, we will have much improved synthetic vascular prostheses. Biocompatible, in the context of the hypothesis presented here, means recapitulating key functional elements of the anatomy of the blood vessel. The anatomy of a heathy blood vessel is illustrated schematically in Fig. We will examine here the historical roots of vascular grafts, focusing on observations important to the biocompatibility hypothesis. New developments and strategies will be presented including tissue engineering approaches. Concepts surrounding biocompatibility will be briefly addressed. Finally, this article will justify the biocompatibility hypothesis for vascular grafts.Note that there are many review articles on vascular grafts. Just a few of these are cited here, and others are cited further into this article –5. This Articles and books have been written discussing the historical roots of vascular grafts –9. This The modern synthetic vascular prosthesis is often attributed to Dr Arthur Voorhees ,11. VorhTo illustrate the enthusiasm for such synthetic vascular grafts in the days before a medical device industry embraced vascular prostheses as a commercialized product, consider this quotation from a 1958 book on surgical materials .“The Terylene, Orlon or nylon cloth is bought from a draper’s shop and cut with pinking shears to the required shape. It is then sewn with thread of similar material into a tube and sterilized by autoclaving before use.”Nylon grafts failed rapidly due to degradation—the amide backbone chemistry of nylon is identical to the amide backbone of proteins and the body had excellent mechanisms for breaking down unwanted polyamides. Dacron (Terylene) weaves and knits dominated the field in the early days of vascular prostheses. A “trellis” concept was proposed by Dr Lester Sauvage to explain healing in vascular grafts with the goal to generate a living, functioning endothelial lining ,14. SauvExpanded Teflon, an exceptionally biostable material, was the next important advance in vascular grafts. ePTFE, fabricated by a process of extrusion, heating, and stretching, was patented by W.L. Gore Inc. in 1969. Numerous studies established that in many sites, ePTFE and Dacron performed similarly with respect to long-term patency in humans ,19. TherRelevant to this article are specific, seminal studies in baboons by Dr Alex Clowes and colleagues . They dePorosity is an important element in vascular prostheses. The 30- and 60-μm designations expressed above are related to the distance between the nodes Fig. . The porPolyurethanes are mechanically strong polymers that offer numerous fabrication possibilities and have often been used in medicine. The earliest use of polyurethanes for vascular grafts may be in a 1960 study led by cardiovascular device pioneers, Tetsuzo Akutsu and Willem Kolff . They coGrafts fabricated of natural tissue are another category of vascular prostheses that have had an impact on vessel replacement and are also relevant to central themes in this article. The earliest vascular replacements were harvested, preserved blood vessels  ,9. AlthoAt this time (2022), the most widely used vascular graft materials for coronary artery repair are autogenous saphenous vein and internal mammary artery. Autologous vessels still outperform decellularized vessel grafts and are the optimal standard of care, although bovine carotid artery does perform acceptably .Tissue engineering and tissue regeneration offer the possibility of creating living vascular graft structures that might emulate the vascular structure shown in Fig. An approach for tissue engineering, referred to as in situ tissue engineering , has genThe large numbers of studies, preclinical and clinical, for tissue-based vascular conduits highlight the interest in this approach, and there is some evidence that good outcomes can be achieved. However, the field has been plagued for 30+ years by concerns with thrombosis and aneurismal failure , especially after long implantation. Also, issues of scale-up and high cost have been challenging for the field, particularly with tissue-engineered grafts. On the other hand, the basic “biocompatibility” of natural tissue and extracellular matrix proteins continues to suggest that these approaches have merit and are worth continued exploration and development.After this brief review of historical and modern literature on approaches to replace blood vessels, especially small-diameter vessels, the following issues are highlighted. Central to this summary is: “How well do approaches to emulate or replace blood vessels recapitulate elements of native, living blood vessels?” The lack of a healed endothelial layer, particularly in humans (and older or diseased humans), is the less-than-desirable outcome most frequently observed. Also, smooth muscle cells and elastin should be present within the walls of properly healed blood vessels. The mechanical compliance of the replacement blood vessel should match that of the natural vessel to prevent flow disturbances  thought The vascular graft literature is extensive. Conclusions from one study may not be relevant for another study done under different conditions. In reviewing this literature, here are some considerations. The numerous experimental protocols (variables) that populate this vascular graft literature often make it challenging to intercompare studies and to arrive at justifiable conclusions.In general, the longer the segment length, the more prone the graft is to thrombotic occlusion. In the literature, you will find segment lengths from 1 cm to segments as long as 25 cm. A consideration that is rarely addressed is: How does the segment length scale with the size of animal (mouse? human?) receiving the implant? A human cardiovascular bypass graft is typically 10 to 20 cm in length .There are no FDA-approved small-diameter (≤4 mm) grafts—such grafts fail primarily due to thrombosis. Clinically, a 3- to 4-mm graft would be valuable for peripheral limb repair and a 2- to 3-mm-diameter graft would be applied for coronary artery repair. There are numerous studies showing acceptable results with 1-mm-diameter grafts in rats. But 1-mm-diameter grafts have never been introduced for human applications. This is another example of the issues in scaling devices between experimental animals and humans.Numerous animal models have been explored with the objective of predicting vascular graft performance in humans –76. NoneIn clinical medicine, common implantation sites for vascular prostheses include upper aortic, femoropopliteal, aortoiliofemoral, and vascular access artery–venous sites in limbs. The blood flow rate and native vessel diameter in different implantation sites can be more, or less, challenging for long-term functionality of vascular prosthesis. In humans, most common vascular graft materials work acceptably in large-diameter (upper aortic) vessels.Sutures at the distal and proximal anastomoses can be continuous or interrupted. Continuous sutures require less surgeon time. However, where newer graft materials are engineered to match the compliance of the native blood vessel, continuous sutures create a flow disturbance at the anastomoses that can lead to thrombus and hyperplasia. Interrupted sutures, though time consuming for the surgeon, greatly reduce flow disturbances at the interface of native vessel and graft polymer. Dr Lester Sauvage, a pioneer vascular surgeon and mentor to the author of this article, emphasized the quality of the suturing  as being important to the success of vascular prostheses.A tremendous number of compositions and chemistries have been described in the vascular graft literature. Also, many polymer surface modifications have been explored in the literature. Regulatory agency-approved graft materials are largely confined to Dacron and ePTFE. There are special considerations for vascular graft biomaterials: long-term durability, mechanical strength (burst strength), mechanical compliance, kink resistance, and suturability. Also, vascular graft materials must meet ISO10993 qualifications.Clearly, there are also differences in the thrombogenicity of different biomaterials, although precise rules to “rank” thrombogenicity on a quantitative scale have not been defined –80. The Early studies of vascular grafts concluded that a porous surface will outperform smooth, solid tubes . Based oMost cardiovascular implants to be assessed in animal studies are implanted for about 1 month, a time period where the most active response seen in the first hours and days of implantation subsides to a long-term, low-level reaction. Sometimes, animal studies use implants for 3 or 6 months. In preclinical research, we rarely do longer studies because of costs, ethical issues, and considerations of the lifetime of the animal . Since a vascular prosthesis is presumably implanted “forever,” the long-term outcome, so difficult to measure experimentally, is relevant. Degradation and aneurism, where observed, frequently occur in the 5- to 10-year implant period.The outcomes of vascular graft implantation, particularly in animals but sometimes in humans, are often measured with histological analysis of harvested tissues and devices . Key eleBased on the background information to this point, a hypothesis is presented here that could open pathways to explore this key question:Why after 70+ years of graft development and thousands of high-quality published studies has there been no significant progress in the clinic, particularly where smaller-diameter vascular grafts are needed?Biomaterials today are qualified as biocompatible by passing relevant ISO10993 tests ,85. ManyA widely quoted definition of the word “biocompatibility” was published based on discussions at a 1986 biomaterials consensus conference held in Chester, England and, more recently, at a consensus conference in Chengdu, China ,88.“the ability of a material to perform with an appropriate host response in a specific application”This definition is accurate but does not suggest ways to measure biocompatibility or rank materials as more or less biocompatible, and it offers no insights on how to improve or enhance biocompatibility.Consider, for this discussion, the soft tissue response. For biomaterials that have passed the ISO leachables tests, when these materials are implanted in living, soft tissue, similar outcomes are noted. After about 3 weeks, the implant is surrounded by a dense, fibrous, collagenous capsule , the FBR. The capsule has low vascularity. Within and beneath the capsule, at the interface with the biomaterial, macrophages and giant cells are noted, even years after implantation. The presence of this fibrous capsule is well documented for vascular grafts . Figure The biocompatibility hypothesis proposed here questions whether this well-accepted reaction is indeed biocompatible. The body isolates, rather than integrates, the biomaterial. The body would do this to a splinter or a bullet. Scar healing and the FBR have similarities—dense collagen and low vascularity. Scar healing is generally considered to be the opposite to regenerative or reconstructive healing. Also, all “biocompatible biomaterials” (with a few exceptions to be discussed shortly) give almost identical reactions. Are all biomaterials, and a splinter, and a bullet equally biocompatible? The biocompatibility hypothesis presented here proposes that truly biocompatible biomaterials will heal into vascularized, reconstructed tissue sites, recapitulating the original tissue into which they have been implanted .For vascular grafts, this hypothesis has significant implications beyond those for many other implants. The FBR capsule is constrictive, a phenomenon also noted with breast implants. This contraction around the vascular graft tubular structure can reduce the diameter of the vessel, creating flow disturbances and lowering blood flow rate. This contraction potentially leads to increased thrombosis. Also, the capsule is rigid (nonelastic). When a pulse of blood from the arterial system hits the nonelastic vascular graft , a flow disturbance is created, which might exacerbate hyperplasic cell proliferation , a majorIn the 1980s, the writings and research of James M. Anderson alerted the biomaterials community to the significance of the macrophage in understanding the FBR ,94. Two The M1 M2 concept was clarified and well described by Mantovani and colleagues ,96. The The DAMP concept stems from earlier immunology ideas defining pathogen-associated molecular patterns (PAMPs), a mechanism to recognize microbes and launch an attack on them . DAMPs bThe biocompatibility concept proposed in this perspective article starts with the premise that all “biocompatible biomaterials” that are declared “biocompatible” by ISO standard tests are, in fact, not all that biocompatible. These ISO tests include ISO10993-5 for cytotoxicity and 10993-6 for local effects after implantation. Important to the hypothesis proposed here, 10993-6 considers an uncomplicated, thin foreign body capsule as meeting the “biocompatibility” acceptance criteria. The fact that the body tries to wall off or isolate the biomaterial, rather than integrating or healing it, is a central observation supporting this contrarian idea on biocompatibility. Relevant to this hypothesis and to this paper, perhaps the less-than-ideal performance of vascular prostheses can be attributed to the fact that the body is attacking the prosthesis, rather than integrating it into the normal biology? By “attacking,” this is to suggest that macrophages are polarized to the M1 phenotype and that DAMPs are released. Normally, macrophages perform their physiologic function and then disappear from the wound site. When long-term macrophages are present in a nonhealing wound, this would be classified as chronic inflammation  and may The hypothesis presented and the scenarios described help to explain the concerns with the long-term performance of vascular prostheses. If they are recognized by macrophages as foreign to the normal physiology, the long-term biological attack will lead to aberrant healing and/or degradation. In the case of Dacron or ePTFE large-diameter vascular grafts, blood flow rates are so high that thrombotic occlusion or low degrees of hyperplastic narrowing are not important and so they function adequately. On the other hand, the macrophage attack on natural tissue vessels, large diameter or small, can lead to structural breakdown with the potential for aneurism and rupture.Based on this hypothesis—that today’s vascular grafts are continually under attack by the body because they are not biocompatible—what prospects are there to address these issues for the development of future vascular prostheses that can function well in small-diameter sites? Strategies to develop grafts that truly heal and integrate are reviewed in the next section of this article.At first glance, it might seem we are constrained to the classic FBR for our implanted biomaterials. However, there is evidence that synthetic biomaterials and natural tissue biomaterials that heal without the FBR can be developed. Many such materials have been summarized in a review article . Three oBiomaterials where all pores are spherical, 30 to 40 μm in diameter, and interconnected were first described in the literature in 2004 . These pThis prohealing strategy using precision-controlled pore sizes of 30 to 40 μm has been applied to vascular prostheses. Healionics Corporation  has developed a vascular graft, now in clinical trials for dialysis vascular access, based on this idea. They start with a conventional, 6-mm ePTFE vascular access graft. To the outer surface of this graft, using a silicone adhesive, they adhere silicone elastomer granules prepared by grinding up 35-μm pore-size, sphere-templated silicone elastomer. Upon implantation in sheep  up to 12 weeks, they note significantly reduced fibrosis and reduced restenosis compared to ePTFE controls . This 30Another type of material that has been shown to heal in a reconstructive, regenerative manner is based on decellularized natural tissues ,108. As The third possibility to achieve nonfibrotic, reconstructive healing involves super-nonfouling surfaces. Poly(carboxybetaine methacrylate), a zwitterionic polymer, has been shown to be unusually effective in preventing protein and cell pickup, even in the presence of undiluted blood plasma . In a 3-The definition we most often use for the word “biocompatibility” was coined in 1986, in the earliest days of molecular biology . The conAfter reviewing papers on vascular reconstructive surgery from the late 1940s and early 1950s, it is clear that huge progress has been made over the past 70+ years in developing reliable vascular grafts for many procedures. Their widespread use in medicine and their good outcomes for some procedures are the “success” of the technology that I refer to in the title of this perspective article. The “failure” is our inability to create smaller-diameter prostheses with reliable, long-term outcomes. Hopefully, some of the ideas presented here and the critical assessment of our present technology will lead to new developments in vascular prostheses that will extend our successes in vascular reconstructive procedures.


In this study, glucono-delta-lactone (GDL), which is Generally Recognized as Safe (GRAS), was added to native starches to modify their physicochemical properties. The effects of GDL on the molecular weight, pasting properties, flow behavior, gel syneresis, and crystallization properties of potato, tapioca, and corn starches were investigated. GPC results showed that as the GDL concentration increased, the molecular weight of amylose increased, whereas that of amylopectin decreased. An analysis using the Rapid Visco Analyzer revealed that the addition of GDL improved the pasting properties of potato starch, with reduced peak viscosity and breakdown viscosity, and it also improved setback viscosity. On the other hand, tapioca starch degraded substantially after GDL addition, indicating a lower tendency for short-term retrogradation, as reflected in the lower setback viscosity. The effects of GDL on corn starch pasting properties were very similar to those observed for tapioca starch, but the changes were relatively subtle. In terms of flow behavior, GDL addition decreased and increased the flow index values of the potato and tapioca starch pastes, respectively. However, the effect of GDL addition on the flow index value of the corn starch paste was found to be insignificant. The results also showed that the percentage of syneresis under the influence of GDL depended on the starch botanical origin—that is, potato starch, 14–18%, tapioca starch, 10–13%, and corn starch, 17–20%—which was substantiated by crystallinity analysis. It was observed that GDL has the potential to be used for starch modification because it creates desirable functionalities with the advantage of being a green-labelled ingredient. In recent years, plant-based foods have grown in popularity, especially as a result of vegans , vegetarians , pescatarians , and flexitarians (a reduced meat diet). People are becoming increasingly concerned about the health, ethical, environmental, and sustainability issues associated with animal-derived industries . ConsumeBecause the molecular and physicochemical properties of plant-derived ingredients differ significantly from those of animal-derived ingredients, it is critical to understand the fundamental attributes of plant-derived ingredients and how they can be assembled into structures that resemble those found in animal products . Starch,Thus, the purpose of this study was to investigate the effects of glucono-delta-lactone (GDL), a weak acid which is a green-labelled ingredient with a Generally Recognized as Safe (GRAS) status, on the properties of selected native starches. GDL is an acidity regulator that controls the pH of foods and can be used as a preservative. It is also used as a curing and pickling agent, a leavening agent, and a sequestrant . Based oDespite its widespread use, research on the effects of GDL on the physicochemical properties of native starch has not yet been reported. Kim et al.  reportedHence, the objective of this study was to investigate and compare the effects of GDL on the pasting properties and molecular weight changes of potato starch, tapioca starch, and corn starch, as well as the flow behavior of the paste formed therefrom. In addition, the influence of GDL on gel syneresis and the crystallinity of the starches was studied. w/w moisture, 0.2% w/w protein, 0.41% w/w fat, 21% amylose), tapioca starch , corn starch , and food grade glucono-delta-lactone (GDL) were purchased from Euro Chemo Pharma Sdn. Bhd., Penang, Malaysia. The composition of the individual starches was analyzed in our laboratory. Potato starch (15% v/w) and it was left overnight before use. The pH values of distilled water and GDL solutions at 0.00%, 0.05%, 0.10%, and 0.50% were 6.70, 3.77, 3.55, and 3.12, respectively. These values were measured using a pH meter . A food grade GDL solution was prepared at different concentrations . The generated data were analyzed using the RVA software program . The moisture content of the starch samples was found to be 14%. For each run, starch (2.5 g) was weighed into an RVA canister, followed by the addition of different concentrations of the GDL solution  to prepare for a 10% starch suspension. The starch suspension was analyzed under continuous shear conditions. The suspension was vigorously sheared at 960 rpm, heated from 25 °C to 90 °C in 3 min 42 s, held at 90 °C for 4 min 30 s, before cooling to 50 °C in 3 min 48 s. The RVA attributes recorded were peak viscosity, peak time, trough viscosity, pasting temperature, breakdown viscosity, final viscosity, and setback viscosity. The starch pastes prepared from the RVA were subjected to pH measurement and flow analysis.The freshly pasted sample from the RVA was transferred into a beaker and blended with an equal amount of distilled water. The pH value was measured using a pH meter .−1 shear rate. According to the “Best Fit” routine, it was found that the best fit model for the data is the Herschel–Bulkley model with a standard error value below 10 and a regression coefficient (R2) value of more than 0.99. The Herschel–Bulkley equation is−1), K is the consistency coefficient (Pa sn), n is the flow behavior index (dimensionless), and σο is the yield stress (Pa). The steady-state flow analysis was conducted using a Rheometer AR-1000N and the fresh starch pastes were produced by RVA. All measurements were conducted at 50 °C and a 40 mm diameter parallel plate geometry was used. The starch paste was placed between the geometry and the Peltier plate with a 1 mm gap. The flow experiments were conducted under steady-shear conditions with 0.1 to 200 sw/v) was heated at 85 °C in a 50 mL falcon centrifuge tube for 30 min in a water bath, followed by rapid cooling in an ice-water bath. The starch gel samples prepared were stored for 24, 48, and 120 h at 4 °C. The syneresis was measured as the percentage of water released after the process of centrifugation at 3000 rpm for 15 min. The syneresis tendencies of all starch samples were determined according to the method described in Singh et al.’s study . The staThe starch gel samples stored for 48 h from  were frew), polydispersity (Mw/Mn), and intrinsic viscosity  of non-GDL- and GDL-treated starches were determined using a Malvern Viscotek Triple Detection GPC Max  Gel Chromatography (GPC) system, which consists of an inline eluent degasser, a syringe-loading sample injector equipped with a 100 uL sample loop, and a dual linear (connected in series) Viscotek A6000M Aqueous GPC/SEC column packed with hydroxy methacrylate polymer, following the method of Chong et al. [3 and 0.02% sodium azide at a flow rate of 1.0 mL/min. The column was calibrated using dextran of known molecular weight. Starch samples (0.1 g) were prepared in dimethyl sulphoxide (DMSO), shaken for an hour in a 95 °C water bath. The sample was then stirred at room temperature for 24 h. A 1.5 mL aliquot was taken, and 6 mL of absolute alcohol was added. The precipitated starch was recovered by centrifugation at 2000× g for 30 min and washed twice with ethanol by centrifugation for 15 min to remove DMSO. The precipitated starch was then redissolved in 5 mL of deionized water and stirred for 30 min in a heated water bath. The mixture was then centrifuged at 2000× g for 15 min to remove insoluble residues prior to injection. The chromatograms have been resolved into two distinct peaks, namely Fraction I which appears at the early retention time while Fraction II appears later. The Mw, Mw/Mn, and IV were analyzed and calculated using OmniSEC software Version 5.02.438 . Freeze-dried starch powder from g et al. . The mobAll experiments were conducted in triplicate. A one-way analysis of variance (ANOVA) was used to analyze the significant effects of GDL treatment on each property studied at a 95% confidence level using IBM SPSS Statistics Campus Edition V24.0. Duncan’s test was carried out to study the significant differences between mean values. w), polydispersity (Mw/Mn), and intrinsic viscosity (η) of potato, tapioca, and corn starch. GPC is used to characterize polymers and separate mixtures into discrete fractions. The starch samples were separated into two main fractions: a high molecular weight fraction that eluted at the void volume (Fraction I), and a lower molecular weight fraction that entered the gel and was eluted after (Fraction II). As a result, a comparison of molecular weight distribution can be made according to the retention time of the samples [ samples . Thus, F samples  and Abdo samples , which f samples , the prow/Mn) is a measure of the broadness of a polymer’s molecular weight distribution. The polydispersity index will be higher with a wider molecular weight distribution [The polydispersity index  starch paste to approximately pH 3. Moreover, it is important to note that GDL could be a better acidulant compared to other acid regulators because it provides a lower level of tartness. Sumitra et al. [All the starch samples pasted in the GDL solution showed a pH value below 4.6 ; this isa et al.  state th2) value of more than 0.99. From the model fitted, the yield stress, the consistency coefficient (k), and the flow behavior index (n) are calculated and summarized in n) for all the samples studied ranged from 0.352 to 0.563, indicative of a non-Newtonian shear thinning behavior. Interestingly, GDL acidification decreased and increased the flow index value of potato and tapioca starch paste, respectively. The effect of GDL on corn starch paste flow index value was found to be non-significant. This reveals that potato and tapioca starch become more and less shear thinning when being sheared, respectively, upon GDL acidification. Moreover, treatment with GDL acidification led to a lower consistency (K) value in potato and tapioca starch, and no significant changes were detected in corn starch paste (p < 0.05). This result is in line with the GPC results, where corn starch molecular properties were found to be least affected by GDL when compared to potato starch and tapioca starch.Yield stress is the stress value below which the stress will result in no observable flow situation in the material tested . The yieStarch gel syneresis happens when starch molecules interact and expel liquid from their network. X-ray diffraction analysis was carried out to analyze the effects of GDL acidification on starch gel crystalline properties . Potato In summary, the molecular weight, pasting properties, flow behavior, gel syneresis, and crystallinity of native starch were altered by the addition of GDL. These effects differed depending on the starch source and GDL concentration. Potato starch produced the most significant results overall. Corn starch was the least sensitive to the addition of GDL, followed by tapioca starch. These effects are attributed to the charged shielding effects caused by the protons released by GDL molecules. The results of the present study may contribute to the generation of new knowledge on predicting and manipulating the quality of a product wherein native starch is used together with GDL as an acidifying agent to reduce the pH of the product. As a result, this may aid in the development of plant-derived food product quality in order to broaden food product options for vegan and vegetarian consumers. Additional studies are still needed to fully evaluate the effect of GDL addition on other types of starch, and their applicability in plant-based foods.


This study aimed to evaluate the mechanical properties of zirconia fabricated using additive manufacturing technology and compare them to those of zirconia fabricated using subtractive manufacturing technology. Sixty disc-shaped specimens were fabricated for the additive (n = 30) and subtractive manufacturing groups (n = 30), and each group was divided into two subgroups according to their air-abrasion surface treatment: control (n = 15) and air-abrasion groups (n = 15). Mechanical properties including the flexural strength (FS), Vickers hardness, and surface roughness were determined, and the values were analyzed by one-way ANOVA and Tukey’s post hoc test (α = 0.05). X-ray diffraction and scanning electron microscopy were used for phase analysis and surface topography evaluation, respectively. The SMA group exhibited the highest FS (1144.97 ± 168.1 MPa), followed by the SMC (944.58 ± 141.38 MPa), AMA (905.02 ± 111.38 MPa), and AMC groups (763.55 ± 68.69 MPa). The Weibull distribution showed the highest scale value (1213.55 MPa) in the SMA group, with the highest shape value in the AMA group (11.69). A monoclinic peak was not detected in both the AMC and SMC groups, but after air abrasion, the monoclinic phase content ( Their mechanical superiority stems from the spontaneous phase transformations of tetragonal phases into monoclinic phases inside zirconia: the zirconia grain volume expands by 3 ~ 5%, which generates compressive stress and prevents crack propagation; consequently, zirconia exhibits high strength and toughness3.Zirconia-based ceramics, especially 3% yttria-tetragonal zirconia polycrystals (3Y-TZP), have become commonly adopted materials in prosthetic and implant dentistry owing to their outstanding biocompatibility, aesthetics, and mechanical properties6. Subtractive manufacturing (SM) is considered a reliable technique that enables fast and standardized production6. In addition, a recent systematic review showed that the accuracy of SM zirconia prostheses was mostly within 60 μm in regard to marginal, internal, and total gaps, which is within the clinically acceptable range (between 50 and 120 μm)7. SM technology using fully sintered blocks eliminates the need for subsequent sintering processes and prevents shrinkage, resulting in increased precision and accuracy; however, this technology exhibits several manufacturing limitations, including material waste, a short lifetime of tooling burs, surface microcracks due to the milling process, and space limitations imposed by the milling bar size and the axis of the computer numerical control (CNC) machine9. Moreover, using a presintered block is not recommended with this technology because thermal shrinkage in the subsequent sintering process may affect the marginal accuracy by approximately 20%9.Most zirconia dental prostheses are fabricated by subtractive computer-aided manufacturing (CAM) using presintered or fully sintered zirconia blocks9. Moreover, it can be used to fabricate more accurate objects with complex geometries2 and avoid the amassment of tooling stresses related to milling8. Therefore, AM is regarded as a prospective technology for the fabrication of zirconia materials in the dental field because it enables mass customization with high efficiency, repeatability, and reproducibility10.Additive manufacturing (AM) has been proposed as another method of processing zirconia prostheses to overcome the limitations of SM technology11, stereolithography apparatus (SLA) and digital light processing (DLP) technologies have been widely used for the fabrication of zirconia prostheses, using a ceramic slurry comprising photosensitive liquid resin and zirconia powder12. DLP uses digital light projection to induce the polymerization of entire layers12. The accuracy of zirconia prostheses depends on the manufacturing technique, printing parameters, sintering procedure, photopolymerizable ceramic suspension, and postprocessing process15.Among the vat photopolymerization methods of AM technology17, and the reported shear bond strength between veneering feldspathic ceramics and AM zirconia frameworks was 19.9 ± 6.9 MPa18, which is within the specified range (16 to 42 MPa)19 for all-ceramic restorations demonstrated in a previous study, and that between resin cement and AM zirconia was 8.629 ± 0.914 MPa20.A few studies have reported the mechanical properties of zirconia manufactured using AM technology, such as the flexural strength (FS) and surface hardness. The reported FS values were in the range required for SM dental zirconia (800–1200 MPa)23. Air abrasion with aluminum oxide particles can increase the surface area for bonding by forming micron-sized irregularities and promoting the micromechanical retention of the applied resin cement25. However, the effects of air abrasion on the mechanical strength of SM zirconia remain controversial24. Various processing parameters, including the particle size, blasting time, air pressure, and aging, affect the FS and adhesive strength, and alumina particle sizes of 50–250 μm, air pressures ranging from 0.2 to 0.4 MPa, and blasting times of 10–20 s have been used for air abrasion25.The low adhesive strength between zirconia and resin cement has been studied, and various mechanical and chemical methods, such as air abrasion, silanization, hydrofluoric acid treatment, and the application of 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), have been suggested to improve the adhesive strengthAlthough a number of previous studies have reported the mechanical properties of milled dental zirconia, there is a lack of information on the properties of zirconia fabricated using AM technology, which has recently been actively developed. In particular, few studies have reported the effect of air-abrasion surface treatment. Therefore, the purpose of the present study is to evaluate and compare the mechanical properties, i.e., FS, Vickers hardness, and surface roughness, of zirconia fabricated by AM and SM technologies.The first null hypothesis was that there are no significant differences among the mechanical properties of zirconia fabricated with AM and SM technologies. The second was that air-abrasion surface treatment imposed no effect on the mechanical properties of zirconia fabricated using AM and SM technologies.Information on the material used in this study is provided in Table 2O3 particles from a distance of 10 mm at a pressure of 0.2 MPa for 20 s. Each specimen, which was fixed by a zig, was treated by the air-abrasion unit moving from the left side to the right side, and to the left side according to the manufacturer’s instructions. The air-abrasion procedures were performed by one experienced researcher (L.G.Y.). Each specimen was evaluated to determine whether the entire area was air abraded based on the loss of gloss. Finally, the specimens were washed under running water for 30 s, ultrasonically washed in distilled water for 10 min, and air dried26. All specimens were visually inspected and excluded in case of macroscopic flaws and defects.In the SM group, the specimens were fabricated from presintered 3Y-TZP  by a 5-axis milling machine  and sintered in a furnace at 1500 °C for 90 min. In the AM group, zirconia slurry  was additively manufactured in the horizontal direction by using a DLP 3D printer . Then, the specimens were debinded at 500 °C for 1 h and sintered at 1500 °C for 2 h. All specimens were wet polished with 30 ~ 40 μm diamond slurry and finally wet polished with 15 ~ 20 μm diamond slurry  with the exception of two specimens that were used to obtain clear SEM images and surface roughness data. Both sides of the specimen surface were flat and parallel within 0.05 mm and thoroughly washed so that all residual traces were removed. The air-abrasion groups were air-abraded on one side with 50 μm AlThe biaxial flexural strength test was performed according to ISO 6872 using a universal testing machine  with a 1 mm/min crosshead speed until the specimen fractured. The specimens were placed on three stainless-steel balls with a diameter of 3.2 mm. In the air-abrasion group, the air-abraded surface was positioned toward the stainless-steel ball, and a test load was applied to the opposite surface. The load-at-fracture was recorded, and the FS can be calculated as follows:27.The Weibull distribution, including shape and scale factors, was calculated using maximum likelihood estimation with a statistical software program . A material with a high shape shows a steep slope in the probability plot of the FS, indicating that a fracture may occur over small parts of the test specimen. The scale is the strength value at a probability of failure of 63.2%The microhardness was determined using a digital Vickers hardness tester  by performing 3 measurements per specimen. The measurements were performed with a diamond pyramid tip with a square cross section by applying 1000 gf for 15 s.28 as follows:The phase transformation was assessed by X-ray diffraction (XRD)  for 1 specimen per group. Scanning was performed with a step size of 0.02° for 0.6 s at 40 kV and 30 mA. The diffraction angle range ranged from 20° to 40°. The ratio of the monoclinic peak intensity 29 as follows:The volumetric percentage of the monoclinic phase content 2.The surface roughness of 2 specimens from each group was measured using a 3D optical surface roughness analyzer  at 9 locations per specimen. The average roughness (Ra) and maximum roughness (Rz) were calculated. The objective magnification was 20 ×, the zoom value was 2 ×, and the measurement field was 218 × 164 μmThe surface topography was observed using a field emission scanning electron microscope  at an acceleration voltage of 15 kV. In the analysis, 1 specimen was randomly selected from each group and sputter-coated with gold–palladium for 180 s.All statistical analyses were performed using SPSS v25 . Shapiro‒Wilk and Levene's tests were performed to verify the normality and homogeneity of variance, respectively. The FS, Vickers hardness, and surface roughness values were analyzed via one-way ANOVA, and Tukey’s post hoc test was performed to detect multiple comparisons among the groups. The significance level was set to α = 0.05. All of the methodologies were reviewed by an independent statistician.The SMA group exhibited the highest FS value (1144.97 ± 168.1 MPa), followed by the SMC (944.58 ± 141.38 MPa), AMA (905.02 ± 111.38 MPa), and AMC groups (763.55 ± 68.69 MPa). In addition, the AM groups showed statistically lower FS values than those of the SM groups under the same surface treatments (p = 0.002 in the control group and p < 0.001 in the air-abrasion group), whereas the air-abrasion group showed statistically higher FS values than those of the control group with the same materials (p = 0.019 in the AM group and p < 0.001 in the SM group)  was significantly lower than that of the SMA group (1286.33 ± 25.61 HV) (p = 0.002)  was significantly lower than those of the other groups, which increased in the following order: SMA (0.50 ± 0.03 μm), AMA (0.55 ± 0.03 μm), and SMC (0.57 ± 0.08 μm) (p < 0.001). The Rz value of the AMC group (3.62 ± 0.63 μm) was significantly lower than that of the AMA group (9.37 ± 4.29 μm) (p < 0.001), but there was no significant difference between the Rz values of the SM groups. Although the Rz value of the AMC group (3.62 ± 0.63 μm) was significantly lower than that of the SMC group (5.79 ± 0.48 μm) (p = 0.024), the Rz value of the AMA group (9.37 ± 4.29 μm) was significantly higher than that of the SMA group (6.31 ± 0.94 μm) (p = 0.001) , which was similar to that in this study, attained a significantly higher FS than the AM zirconia group (320.32 ± 40.55 MPa)2, which is much lower than the corresponding FS value in this report.In the present study, the zirconia specimens fabricated by AM technology had significantly lower FS values than those of the specimens fabricated by SM technology. These results are similar to those of other previous studies reporting that the lower FS of AM groups may result from the weak areas of the boundaries between stacked layers, where residual stress is likely to cause cracks or delamination12 regarding the aging effects on Y-TZP printed by both SM and AM technologies reported that the FS values were significantly higher for the SM group (1273.3 ± 170.2 MPa) than for both the DLP (845.6 ± 183.5 MPa) and SLA group (776.7 ± 77.0 MPa). The FS value of AM zirconia was similar to that of this study, but the milled zirconia showed a higher FS. These differences in FS values might be explained by inconsistencies in the FS testing methods, zirconia manufacturing processes, polishing procedures, sintering shrinkage and chemical composition, and the raw material grain size.Moreover, a study by Zhai22. The FS values of all groups in the present study were within this range.According to ISO 6872, dental ceramics are specified to have an FS of at least 300 MPa for a single unit and 800 MPa for a four-unit prosthesis; in addition, previous studies have reported FS values of 3Y-TZP manufactured by subtractive techniques of approximately 800 to 1200 MPa30. In the control group, the m-phase was not observed, whereas in the air-abrasion group, the m-phase of the AMA group was 9% and that of the SMA group was 7% within the standard limit of ISO 13356 that the m-phase content of zirconia should be less than 20% before low-temperature degradation (LTD) and 25% after LTD. The FS of air-abraded zirconia is considered a result of the trade-off between the damage and residual compressive stress generated by particle impact31. When surface flaws induced by the air-abrasion procedure appeared to remain confined within the transformation layer, they were probably compensated for by the 4% grain volume increase during the phase transformation, creating a layer of residual compressive stresses32. Therefore, parameters related to air abrasion should be applied with caution to prevent surface weakness.Our study showed that the FS was significantly increased by approximately 18% for the AM group and 21% for the SM group when air abrasion of the zirconia surface was performed at 0.2 MPa with 50 μm alumina particles. This increase can be attributed to toughening transformation from the tetragonal to the monoclinic phases, which induced a residual compressive stress that prevented crack development, resulting in a strength increase33. Considering solely the mean flexural strength is insufficient for accurately characterizing ceramic properties, and the significant variability in the failure strength due to flaws introduced during specimen processing should be considered35. Thus, Weibull analysis related to the flaw-size distribution was employed to consider the strength variability36. Regarding materials with low Weibull shape values, fractures can occur within a large portion of the specimens, while fracture origins cluster in areas of the highest stress with high Weibull shape values27. The shape value for most dental ceramics is reported to vary between 5 and 15, and a lower Weibull shape indicates greater variability and less reliability in the strength due to flaws and defects in the material33. The 3D printing procedure, cleaning, debinding, sintering process, and porosity content can affect the Weibull shape20. In addition, aging or LTD inducing compressive stress zones through t-m transformation at the surface can increase the Weibull shape and mechanical properties37. In this study, the Weibull shapes were 11.51 ~ 11.69 for the AM group and 7.11 ~ 8.50 for the SM group. Generally, the Weibull shape of SM is higher than that of AM17, which is explained by the imperfection of the internal material of AM zirconia16. However, a few previous studies have shown controversial results5. These discrepancies related to the shape of Weibull can be caused by inconsistencies in the testing methods, including the printing angle, grain size, and polishing method. The Weibull scale indicates the strength value at a probability of failure of 63.2%27; therefore, the change in the Weibull scale can be interpreted in terms of the material strength. The shape and scale values of the air-abrasion groups were higher than those of the control groups in this study, which may indicate that the air-abrasion surface treatment forms compressive zones by increasing the m-phase, resulting in the improvement in the mechanical properties of zirconia without causing unstable flaws or substrate damage31.The Weibull statistics characterize the structural reliability of brittle dental materials40. The Vickers hardness of the AMC group tended to be lower than that of the SMC group with no significance, but that of the AMA group was significantly lower than that of the SMA group in this study; hence, it can be inferred that the manufacturing method affected the Vickers hardness. A previous study suggested that the presence of large pores on the surface of tested DLP zirconia was a reason why the Vickers hardness of AM zirconia was 5% lower than that of milled zirconia38, which agrees with our findings that there were many irregular pores in the SEM images of the AMC group. In contrast, in the air-abrasion groups, where no surface pores were observed, it was determined that the intrinsic strength of the material affects the Vickers hardness, implying that additional research is needed. The Vickers hardness of the AM group found in this study was in the range of 1248–1261 HV, which is in agreement with the hardness of zirconia manufactured by SM reported in previous studies38. In this study, there were no significant differences between the AMC and AMA groups or between the SMC and SMA groups in terms of the Vickers hardness, indicating that air abrasion did not significantly affect this property. However, a previous study reported that the Vickers hardness of SM zirconia was significantly increased from 1219.83 ± 94.11 to 1940.63 ± 458.38 HV by air abrasion with a 50 μm particle size under 4-bar pressure for 15 s from a distance of approximately 10 mm41. The differences in the results may be related to the test parameters, such as the air pressure and time. However, 4-bar (0.4 MPa) pressure was reported as the value at which air abrasion decreased the FS22.The Vickers hardness indicates a material's ability to withstand plastic deformation, material deterioration, and fatigue. It is related to the material survival rate and generally depends on the porosity and grain sizeThe surface roughness appeared to increase significantly by air abrasion in the AM group. However, the SM group showed an increase in Rz but a decrease in Ra, which means that the air-abrasion treatment decreased the average surface roughness but increased the maximum roughness of SM zirconia due to some greater pits. Further studies are needed to obtain an appropriate air-abrasion protocol for AM zirconia under strict control in terms of sample sizes and test techniques, as well as to verify various related factors, such as the zirconia particle size and porosity. The limitation of the current study is that the effects of low-temperature degradation or aging of zirconia were not considered during the experimental evaluation of zirconia fabricated via AM technology.Within the limitations of this study, the following conclusions can be drawn: the FS and Vickers hardness of zirconia fabricated by AM technology were lower than those of zirconia fabricated by SM technology but were within the clinically acceptable ranges. Air-abrasion surface treatment increased the monoclinic phase content, FS, and surface roughness of the AM group.