Volume 12 - 2024 | https://doi.org/10.3389/fchem.2024.1361930 This article is part of the Research TopicCatalytic Production of Sustainable Fuels and Derivatives via Carbon FootprintsView all 5 articles The CuMgAl-x catalysts derived from hydrotalcite precursors with different Mg/Al molar ratios were synthesized and applied to CO2 hydrogenation to methanol reaction the effects of Mg/Al molar ratio on the structure and surface properties of CuMgAl-x catalysts were investigated by XRD and in situ DRIFTS characterization methods The results showed that an appropriate Mg/Al molar ratio can enhance the Cu-MgO interaction increasing the basic sites and obtaining suitable acid sites The dispersion of active Cu on the CuMgAl-x catalysts can be improved by strong Cu-MgO interaction which enhances the adsorption capacity of CO2 and makes H2 activation easier accelerates the conversion of intermediate species CO3* and HCO3*to HCOO* and facilitates further conversion to CH3O* and CH3OH The strong interaction between Cu and MgO was conducive to the formation of Cu+ which can inhibit the desorption of CO in the reverse water gas shift reaction The CuMgAl-3 catalyst showed the highest CO2 Conversion rate (14.3%) and STY of methanol (419.3 g⋅kgcat.−1⋅h−1) at 240°C and 2.5 MPa The results obtained in this paper can provide a new idea for the design of high-performance catalysts for CO2 hydrogenation to methanol it is of great significance to develop Cu-based catalysts with high activity and excellent stability for CO2 hydrogenation to methanol The catalyst contains small Cu nanoparticles with a narrow distribution (2 nm) The remarkable activity of this copper-based catalyst is attributed to the lattice reorganization associated with the water-promoted “HT memory effect,” which is beneficial to the stability of Cu+ ions under reaction conditions it is of great significance to develop catalysts with highly dispersed Cu NPs and a more efficient active interface to promote CO2 hydrogenation to methanol a series of CuMgAl-x catalysts derived from hydrotalcite precursors with different Mg/Al molar ratios were prepared by the coprecipitation method and supported with the same amount of Cu The structure and surface properties of the CuMgAl-x catalysts are determined by XRD The effect of Cu-MgO interaction on CO2 adsorption and further conversion during CO2 hydrogenation to methanol was studied in detail The CuMgAl-x catalysts with different Mg/Al molar ratios were prepared by an improved coprecipitation method as to the literature reported (Xiao et al., 2017) and Al(NO3)3·9H2O (Mg/Al molar ratio = 1,2,3,4,5) was dissolved in 100 mL deionized water as metal salt solution A Solution B consists of 100 mL sodium carbonate solution (0.15 M) solution A was dropped into solution B under intense agitation at 65°C The pH during precipitation was monitored by a pH electrode and adjusted with an alkali solution of NaOH (1.0 M) The resulting suspension was aged at 65°C for 5 h Then the precipitate was filtered and washed with deionized water to pH 7 and dried at 100°C for 12 h The obtained solids were the hydrotalcite-structured CuMgAl catalysts precursors The precursors were ground to fine powder and calcined in static air at 500°C for 5 h (ramp rate of 2°C/min) in a muffle furnace The resulting material was extruded into a circular sheet then crushed and sieved into particles with 20–40 mesh size The synthesized catalysts are noted as CuMgAl-x where x (x = 1,2,3,4,5) was the Mg/Al atomic ratio of the catalyst The content of Cu in all CuMgAl-x catalysts was 10 wt% Using Rigaku SmartLab SE photoelectron spectrometer with Cu Kα radiation (40 kV 40 mA) to obtain the diffraction characteristics of the prepared material XRD patterns were recorded for 2 h values from 5° to 90° with a scanning rate of 10°C/min The pore structure characteristics of the synthesized materials were obtained by N2 adsorption-desorption method: the synthesized samples were treated at 300°C vacua for 4 h by Beishide 3H-2000PS2 physical adsorption instrument and then cooled to −196°C for N2 adsorption and desorption experiments and the changes of N2 adsorption and desorption with pressure were recorded The BET equation was used to calculate the specific surface area of the samples and the BJH equation was used to calculate the pore size distribution and pore volume of the samples TEM detection was carried out on the FEI Tecnai G2 F30 transmission electron microscope equipped with X-ray energy spectroscopy (EDX) with a resolution of 0.14 nm and a voltage of 210 kV and the sample was dissolved in anhydrous ethanol and ultrasounded for 20 min Then the sample was dropped onto a nickel net coated with a carbon film The surface morphology and structural characteristics of the catalyst were ob-served by Hitachi SU8010 scanning electron microscope (SEM) with an operating volt-age of 5 kV H2 temperature-programmed reduction (H2-TPR) was carried out on AutoChem1 Ⅱ 2,920 equipped with a thermal conductivity detector (TCD) to analyze the reduction characteristics of the synthesized samples the samples (about 150 mg) need to be pretreated under flowing argon for 2 h at 300°C to remove physically adsorbed water As the temperature cooled down to 50°C the samples were heated from 50°C to 600°C at a rate of 5°C/min in 10% H2 flow (balanced with Ar) The surface basic sites or acid sites of the samples was analyzed by the CO2 and NH3 temperature-programmed desorption (TPD) experiment on ChemStar TPx chemisorption analyzer 0.1 g sample was first reduced for 2 h at 300°C in a 10 vol% H2/N2 flow the sample was saturated with CO2 or NH3 (30 mL/min) for adsorption for 0.5 h and then flushed with He (40 mL/min) for 0.5 h the experiment was tested with a heating rate of 5°C/min under He flows X-ray photoelectron spectroscopy (XPS) was measured by Kratos XSAM800 spec-trometer and the elements contained in the samples were tested by Al Kα rays (12 kV The experimental binding energies were calibrated according to C1s (284.6 eV) Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to determine the element content in the catalyst where N represents the Avogadro constant (6.02 × 1023 atom mol−1) and W represents the atomic mass of copper (63.546 g/mol) In situ diffusion reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) was recorded on the Nicolet 6,700 spectrometer with an MCT detector the sample was reduced in situ at 300°C H2 (20 mL/min) for 1 h and then cooled to room temperature for CO adsorption for 30 min Then Ar scanning was performed again to remove the adsorbed CO substance for 30 min The experimental procedure of For in-situ FTIR spectroscopy of CO2 hydrogenation the catalyst was reduced in situ in H2 (20 mL/min) at 300°C for 1 h then purged with He for 30 min to remove the physically adsorbed H2 and then cooled to 40°C to collect the background spectrum He was replaced with a mixture of raw materials (CO2:H2:N2 = 24:72:4) and the process of the intermediate product changing with time was recorded and the infrared spectrum with a resolution of 4 cm−1 was obtained [CO2]in and [CO2]out represent the input and output of carbon dioxide (mol) [CH3OH]out represents the output of methanol (mol) FCO2,in represents the molar input flow of carbon dioxide (mol⋅h−1) and Wcat represents the mass of catalyst (g) MCH3OH represents the molar mass of methanol (g⋅mol−1) The variation of total specific surface area and average pore size with Mg/Al molar ratio may be related to the difference in pore structure N2 physical adsorption-desorption of CuMgAl-x catalysts: (A) N2 adsorption isotherm; (B) Pore size distribution curves It can be found that the flower-like sphere structure formed by nanosheets on CuMgAl-3 samples was more regular which was conducive to the exposure of pores the flower-shaped spheres gradually disappeared and formed a more complex pore structure These results were consistent with BET results indicating that the morphology of samples varied with the Mg/Al ratio SEM images of the CuMgAl-x catalysts: (A) CuMgAl-1 The crystallinity of the sample gradually decreases with the further decrease the Mg/Al ratio which may be caused by the decrease of stability of hydrotalcite caused by excessive Al The diffraction peak of aluminum hydroxide was only observed in the CuMgAl-1 sample which may be due to the large amount of Al3+ can not enter the CuMgAl hydrotalcite structure and precipitated in the form of Al(OH)3 XRD patterns of CuMgAl-x catalysts: (A) before calcination TEM images of the reduced CuMgAl-x catalysts (A′–E′) corresponding Cu particle size distribution Cu dispersions and Cu specific surface area of CuMgAl-x catalysts CuO species on the surface of CuMgAl-3 catalyst had better dispersion than other catalysts When the Mg/Al molar ratio increased from 1 to 3 the reduction temperature of the β peak decreased from 235°C to 224°C which may be due to the strong interaction between CuO and MgO which weaken the strength of the Cu-O bond as the Mg/Al molar ratio increased from 3 to 5 the reduction temperature of CuO increased again which was related to the accumulation of CuO CO2-TPD curves of the reduced CuMgAl-x catalysts The distribution of basic sites over CuMgAl-x catalysts The distribution of acidic sites over CuMgAl-x catalysts (B) Infrared spectra of CO adsorption on the reduced CuMgAl-x catalysts (C) The relationship between the ratio of Cu+/(Cu++Cu0) and the molar ratio of Mg/Al (D–F) XPS spectra in the region of Mg 2p (C) The relationship between STY of CH3OH and Mg/Al molar ration The catalytic performance of CuMgAl-3 catalyst over time 2.5 Mpa and 9,000 mL⋅gcat−1⋅h−1 CuMgAl-3 showed the lowest apparent activation energy of 20.1 kJ/mol the TEM characterization of the used CuMgAl-3 catalyst showed that the Cu particle size after the reaction (7.48 nm) was slightly increased compared with that before the reaction (5.57 nm) indicating that the Cu particles in CuMgAl-3 catalyst still had good dispersion after the reaction and the relationship between the two was linear which indicated that Cu+ had a greater influence on the performance of the catalyst (A) The relationship between STY of CH3OH and SCu (B) The relationship between STY of CH3OH and the ratio of Cu+/(Cu++Cu0) mainly because the activity tests of these catalysts were performed at higher GHSV the increase in the GHSV can significantly increase the methanol production capacity CuMgAl-3 has excellent catalytic performance with the advantages of low cost so it can be used as an ideal catalyst for methanol synthesis In situ FTIR spectra of CO2 hydrogenation reaction over (A) CuMgAl-1 (C) CuMgAl-5 catalysts in the test temperature range from 40°C to 320°C the HCOO* species and CH3O* group strength were lower than CuMgAl-1 and CuMgAl-3 during temperature rise and the CO strength was the highest at high-temperature indicating that excessive Mg/Al has a negative effect on the catalytic performance the diversity of basic sites on CuMgAl-x catalyst was affected by MSI The interaction between Cu and MgO was enhanced when the Mg/Al ratio increased from 1 to 3 the number of basic sites of the catalyst decreased when further increasing the Mg/Al ratio which due to the reduction of crystallinity of the hydrotalcite structure in the catalyst precursor by excess Mg the good alkalinity of the CuMgAl-3 catalyst was conducive to the adsorption of CO2 the Cu with higher dispersion and smaller particle size was obtained on the CuMgAl-3 catalyst due to the strong interaction between Cu and MgO the overflow of H allows CO3* and HCO3* to be quickly converted to HCOO* which facilitates further conversion to CH3O* and CH3OH the strong interaction between Cu and MgO was conducive to the formation of Cu+ which can inhibit the desorption of CO in RWGS reaction to a certain extent the higher methanol production efficiency of CuMgAl-3 was the result of the adsorption of CO2 by more basic sites and the inhibition effect of Cu+ on CO desorption Mechanism comparison of CuMgAl-x catalysts for CO2 hydrogenation to methanol before and after the optimization of Mg/Al ratio a series of CuMgAl-x catalysts with different Mg/Al molar ratios with hydrotalcite as the precursor were prepared and the effect of Mg/Al molar ratios on the performance of CuMgAl-x catalysts for CO2 hydrogenation to methanol was studied The Cu-MgO interaction on the CuMgAl-x catalyst can be regulated by changing the Mg/Al molar ratio and the CuMgAl-3 catalyst showed the strongest Cu-MgO interaction The strong interaction between Cu and MgO was conducive to increasing the number of basic sites and obtaining suitable acid sites The strong Cu-MgO interaction was conducive to the formation of highly dispersed Cu accelerating the conversion of intermediate species CO32- and HCO3*to HCOO* and facilitating further conversion to CH3O* and CH3OH which can inhibit the desorption of CO in RWGS reaction CuMgAl-3 catalyst showed optimal performance for CO2 hydrogenation to methanol with the CO2 conversion rate (14.3%) and STY of methanol(419.3 g⋅kgcat.−1⋅h−1) at 240°C and 2.5 MPa The original contributions presented in the study are included in the article/Supplementary Material further inquiries can be directed to the corresponding author The author(s) declare financial support was received for the research The authors acknowledge the financial support by the National Nature Science Foundation of China under Grant No The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fchem.2024.1361930/full#supplementary-material New insights on CO and CO2 hydrogenation for methanol synthesis: the key role of adsorbate-adsorbate interactions on Cu and the highly active MgO-Cu interface CrossRef Full Text | Google Scholar Cu+-ZrO2 interfacial sites with highly dispersed copper nanoparticles derived from Cu@UiO-67 hybrid for efficient CO2 hydrogenation to methanol CrossRef Full Text | Google Scholar CO2 hydrogenation to methanol over Cu/ZnO/ZrO2 catalysts: effects of ZnO morphology and oxygen vacancy CrossRef Full Text | Google Scholar CO2 hydrogenation to methanol over Cu catalysts supported on La-modified SBA-15: the crucial role of Cu-LaOx interfaces CrossRef Full Text | Google Scholar Plasma-catalytic CO2 hydrogenation to methanol over CuO-MgO/Beta catalyst with high selectivity CrossRef Full Text | Google Scholar Enhanced methanol production over 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Metrics details Molar root canal treatment (RCT) is challenging and requires training and specific skills Rotary instrumentation (RI) reduces the time needed for instrumentation but may increase the risk of certain procedural errors The aims of this study were to evaluate the quality of molar RCTs provided by undergraduate students to compare the prevalence of procedural errors following manual and RI and to assess the students’ self-perceived confidence to perform molar RCT without supervision and their preference for either manual or RI Molar RCTs performed by the final year students were evaluated radiographically according to predefined criteria (Appendix 1) and the students’ self-perceived confidence to perform molar RCT and their preference for either manual or RI were recorded and the Chi-squared test was used to detect any statistically significant differences RI resulted in more sufficient treatments compared with MI (49% vs p < 0.001) and was the preferred technique by 93.1% of students The most common procedural errors were underextension of the root canal obturation (48.4%) and improper coronal seal (35.2%) without a significant difference between the two techniques 26.4% of the participating students reported that they did not feel confident to perform molar RCT without supervision The quality of molar RCT provided by UG students was generally insufficient RI partially improved the technical quality of RCT compared with MI UG students need further endodontic training and experience before they can safely and confidently practise molar RCT The need for this study stems from multiple observations by our faculty supervising UG endodontic work that students struggled to perform molar RCT and that procedural errors were frequent The aims of this observational study were (a) to assess the quality of molar RCTs provided by UG students (b) to compare the prevalence of procedural errors associated with manual and rotary instrumentation and (c) to assess the students’ self-perceived confidence to perform molar RCT without supervision and their preference for either manual or RI All RCTs were performed under rubber dam isolation Working length was determined using apex locators and confirmed with a working length radiograph Canal instrumentation was performed either manually using the step back technique or with rotary instrumentation using the ProTaper Gold® system (Dentsply Maillefer Obturation was carried out with gutta percha and resin sealer (AH-plus Students were supervised by faculty throughout the treatments provided different supervisors were allocated to different groups of students It was not possible to assign the same supervisors for all students due to the busy clinics schedule Treatment details including the number of visits used to complete the treatment, the students’ preference for either instrumentation technique, and their self-perceived confidence to perform RCT without supervision were recorded using an online questionnaire (Appendix 2) The questionnaire was designed was piloted on 10 students and was tested for face and content validity The first 10 respondents were asked to complete the survey once again after one week to ensure the survey was reliable The first 10 RCTs were jointly evaluated by 3 assessors (AE and SM) following a discussion of the errors detected to ensure good calibration of the assessors The rest of the RCTs were evaluated independently by 2 clinicians (AE and MA) the third experienced consultant endodontist (SM) was consulted Descriptive statistics as well as the Chi-squared test were used A total of 109 students consented to participate 104 students performed molar RCTs using both techniques and 5 students only performed manual instrumentation Post-obturation radiographs of 213 RCTs were assessed (109 using MI and 104 using RI) 75.6% of treated teeth were first molars (26.8% maxillary and 48.8% mandibular) while 24.4% were second molars (10.3% maxillary and 14.1% mandibular) The overall mean number of visits required to complete the treatment was 3.7 (median: 4 RI enabled the students to complete their treatment in fewer visits compared with MI (2.9 vs Procedural errors detected in the post-obturation radiographs; (a) under-extension of obturation in the mesio-buccal root of the maxillary right first molar (b) canal transportation in the mesial root of the mandibular left first molar (c) separated instrument in the mesio-lingual root of the mandibular left first molar and (d) Defective coronal restoration in the mandibular right first molar The overall technical quality of RCTs was deemed sufficient in 39.6% of the cases There was no statistically significant difference in the quality of RCTs provided or the prevalence of procedural errors between maxillary and mandibular molars The interrater reliability was excellent (Kappa statistic: 0.83) Most students (93.1%) reported that they preferred RI over manual More than one quarter of the students (26.4%) reported that they did not feel confident to perform molar RCT without supervision Patients with procedural errors were informed of the unfortunate mishap and were either kept under observation referred to a consultant endodontist or the post-graduate endodontic clinics where the procedural errors were non-reparable referred for extraction of the involved tooth This study demonstrated that procedural errors were very common and that students generally did not feel confident to perform molar RCT on their own without being supervised Under-extended root canal obturation could be explained by multiple reasons including errors in working length determination lack of recapitulation during the step-back phase of instrumentation improper master cone selection and improper obturation technique The specific reason for this procedural error could not be identified in this observational study Over-extension of the root canal filling was observed more often in MI Lack of apical stop creation and overzealous instrumentation can be implicated for this procedural error It only evaluated the radiographic quality of molar RCTs No clinical aspect was taken into consideration Its lack of temporal factor precluded any observation of the success or failure of treatments and their association (or lack of) with the technical quality of the treatments provided Clinical supervision varied between the participating students and there was no correlation between the students’ academic performance and the technical quality of RCTs Potential confounding factors to the results include the level of academic performance of students the technical difficulty of the RCT provided and the variation in outcome assessment between the assessors No attempts to adjust for the confounding factors were made as the purpose of the study was to report on the prevalence of procedural errors rather than investigating the potential reasons for them this study demonstrates an overall poor quality of molar RCT provided by UG students combined with their lack of confidence to perform this procedure without supervision This invites the question of whether UG students should be expected to perform molar RCT at such an early stage of their careers or whether this procedure requires further training mentorship and experience that may not be ideally delivered during undergraduate training Inexperienced clinicians may benefit from a wider exposure to simple RCTs of anterior and premolar teeth before they can embark on the more technically demanding molar RCT The authors suggest that UG endodontic clinical training should emphasize on providing simple RCTs on anterior and premolar teeth and on the conservative and emergency management of molar teeth such as vital pulp therapy access cavity and coronal pulp extirpation Clinicians who wish to perform molar RCT should receive further training following graduating from the dental school The technical quality of molar RCT provided by UG students is generally insufficient RI partially improved the quality of RCT compared with MI when used by inexperienced operators (UG students) The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request Cleaning and shaping the root canal system Quality guidelines for endodontic treatment: consensus report of the European Society of Endodontology Radiographic technical quality of root canal treatment performed by dental students at the Dental Teaching Center in Jordan Quality of root canal treatment performed by undergraduate dental students at the University of Khartoum An audit of root canal treatment performed by undergraduate students Radiographic evaluation of the technical quality of undergraduate endodontic ‘competence’ cases in the Dublin Dental University Hospital: an audit Quality of root canal treatment performed by undergraduate students using nickel-titanium reciprocating versus hand instruments A 20-year follow-up study of endodontic variables and apical status in a Swedish population Factors affecting the long-term results of endodontic treatment An overview of nickel-titanium alloys used in dentistry and treatment for age-related tendinopathy Root-canal shaping with manual and rotary Ni-Ti files performed by students Efficacy of five rotary systems versus manual instrumentation during endodontic retreatment The Accuracy of Health professions Students’ self-assessments compared to objective measures of competence Investigating the influence of achievement on self-concept using an intra-class design and a comparison of the PASS and SDQ-1 self-concept tests Students’ performance in clinics and self-perceived confidence in performing endodontic procedures: a correlation study Alsoghier A, Ali K. Self-perceived preparedness of new dental graduates from a Middle Eastern university. Eur J Dent Educ. 2023. https://doi.org/10.1111/eje.12981 Technical quality of root canal treatment performed by undergraduate students using hand instrumentation: a meta-analysis Periapical status of endodontically treated teeth in relation to the technical quality of the root filling and the coronal restoration Technical standard of root canal treatment in an adult Scottish sub-population American Association of Endodotists. Glossary of Endodontic Terms. 2020, 10th edition (https://www.aae.org/specialty/clinical-resources/glossary-endodontic-terms/) Comparative study of six rotary nickel-titanium systems and hand instrumentation for root canal preparation rotary instrumentation in endodontic treatment of permanent teeth: a systematic review and meta-analysis Clinical efficacy of Sealer-based Obturation Using Calcium Silicate Sealers: a Randomized Clinical Trial Evidence-based treatment planning for the restoration of endodontically treated single teeth: importance of coronal seal Evaluation of technical quality of endodontic treatment–reliability of intraoral radiographs Risk factors for developing apical periodontitis in a general population Undergraduate curriculum guidelines for endodontology Download references A.E.: Study design and writing the manuscript M.A.: Statistical analysis and reviewed the manuscript The protocol of this study was approved by the review board committee of the Jordan University Hospital (ref 10/2022/1726) Informed consent was obtained from the participating students and their patients The authors declare no competing interests Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations Below is the link to the electronic supplementary material unless otherwise stated in a credit line to the data Download citation DOI: https://doi.org/10.1186/s12909-024-05397-z Anyone you share the following link with will be able to read this content: a shareable link is not currently available for this article Please enable JS and disable any ad blocker In stifling hot and extremely dry conditions the young racers gave it their all on the rock hard clay in bid for the top qualifying positions and early advantage for the main event tomorrow.It was a surprise start to the weekend for JD19 KTM Racing TE’s Adam Kovacs who had his little 65cc wide open here in El Molar Kovacs (in the photo by Youthstream) said he struggled with the heat a little bit and couldn’t believe he set the fastest lap time after landing hard off of a jump and breaking his bike Despite facing a few problems Kovacs set a blistering pace and took pole 1.2 seconds clear of Kay Karrsemakers.As for Karrsemakers another Dutch rider who prefers excels on the softer surfaces he was also looking super fast on the blue groove clay regardless of his roots The young Dutchman was second in qualifying ahead of Czech Republic’s Radek Vetrovsky who was the fastest in free practice.Rounding out the top five Raul Sanchez Garcia flew the flag for the hosting nation with his fourth place finish while France’s Florian Miot was fifth European Open 65cc Qualifying Practice Top Ten: 1 | Copyright 2025 FIM Europe | Terms of use - Privacy statement | Metrics details Molar-Incisor Hypomineralization (MIH) is a qualitative defect of enamel of unknown etiology affecting one or more permanent molars and may include incisors This condition is a clinical challenge and its prevalence is still uncertain given the recent increase in research we aimed to comprehensively estimate the overall prevalence of MIH and associated characteristics This systematic review is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) Heterogeneity and publication bias were computed via I2 test statistics and Egger’s significance test Random-effects meta-analysis of prevalence were processed We used the Strength of Recommendation Taxonomy [SORT] to grading the strength of evidence with one study with moderate methodological quality and the remaining of high methodological quality Subgroup analysis confirmed an influence of not using the 2003 MIH case definition (p = 0.0066) The pooled prevalence of MIH was 13.5% (95% CI 12.0–15.1 Affected incisors were seen in 36.6% (95% CI 30.0–43.7 the prevalence of hypomineralization of the second primary molars was observed in 3.6% of the MIH cases (95% CI 1.9–6.8 America was the continent with highest prevalence (15.3 I2 = 96.3%) and Asia had the lowest prevalence (10.7 however no continental differences were found Sample size and year of publication were slight contributing factors to the heterogeneity in the analysis these results were classified with a SORT A recommendation which may explain the variances between those regions both searches were conducted until mid 2017 a number of new epidemiological studies have been published other relevant information remains to be elucidated namely the prevalence of moderate/severe cases prevalence of molars and incisors affected and the prevalence of hypomineralization of the second primary molars (HSPM) conducting a new systematic review on the topic would be convenient and relevant globally and given the increase research on the prevalence of MIH we aimed to comprehensively investigate the global prevalence of MIH We aimed to answer the following PECO question: “What is the global prevalence of MIH?” The respective statements were as follows: Clinical/Epidemiologic studies in humans (P The secondary aims were the prevalence of moderate/severe MIH cases prevalence of molars and incisors affected and the prevalence of HSPM Studies were eligible for inclusion based on the following criteria: (1) Observational studies reporting the prevalence of MIH; (2) Studies with clear reporting of MIH definition; (3) Subjects with no systemic disorders; (4) Studies including both genders studies which only reported on primary molars and studies which focused on non-representative samples (e.g. those with specific dental outcomes like high caries experience Identification of studies for this systematic review was performed through detailed search strategies developed for each database (Pubmed CENTRAL [The Cochrane Central Register of Controlled Trials] SciELO [Scientific Electronic Library Online] LILACS [Latin-American scientific literature in health sciences] and TRIP [Turning Research Into Practise]) up to July 2021 Our search strategy was based on the following algorithm: "(hypomineralization OR hypomineralisation OR hypomineralized OR hypomineralized OR hypoplasia OR demarcated OR opacities OR MIH OR cheese molars) AND (survey OR questionnaire OR cross-sectional OR prevalence OR frequency OR population OR sample OR sampling) AND (molar OR molars OR incisors)" Study selection was assessed independently by two investigators (LBL and JB) who performed the assessment of titles and/or abstracts of retrieved studies inter-examiner reliability following full-text assessment was calculated via kappa statistics Any disagreements were resolved by discussion with a third author (VM) Data extraction was performed by two reviewers independently and in duplicate (LBL and JB) The agreement between the reviewers was assessed by Kappa statistics Any paper classified as potentially eligible by either reviewer was ordered as a full text and independently screened by the reviewers All disagreements were resolved through discussion with a third reviewer (VM) The following information was gathered in general description The following standard information was extracted from each eligible study: first author’s name sex-specific sample size and prevalence (if available) severity of MIH was registered whenever studies reported it We considered studies that have defined or used classifications that considered severe cases of MIH as having demarcated enamel opacities with breakdowns persistent/spontaneous hypersensitivity affecting function and strong aesthetic concerns We applied no publication year nor language restrictions. Grey literature was searched via http://www.opengrey.eu/ corresponding authors were contacted to obtain baseline data they were resolved by discussion with a third author (VM) Meta-regressions were conducted using continuous variables to appraise potential sources of heterogeneity geographic location (latitude and longitude) and year of publication The regression approach also allowed to quantify the percentage of heterogeneity that could be explained by that variable All tests were two-tailed with alpha set at 0.05 except for the homogeneity test whose significance level cutoff was 0.10 due to the low power of the χ2 test with a limited number of studies Estimates were described with 95% confidence interval (CI) Inter-examiner reliability at RoB analysis was considered very substantial (kappa score = 0.885 ranged from 6 to 9 stars (Supplementary S3) fifty-three and six articles scored 8/9 and 7/9 Only one paper was of moderate RoB (score = 6/9) The main sources of inconsistencies arose from the representativeness of the cases While all articles succeed to apply an adequate MIH case definition equal method of assessment of cases and controls and non-response rate (100.0% studies failed to provide adequate representativeness of the cases (48.7% two studies failed the definition of controls (1.8%) and 8.8% only provided information regarding MIH and not any other variables (n = 10) A first subgroup meta-analysis confirmed that estimates from studies using the EAPD 2003 classification were significantly different from studies with alternative classifications (categorized as ‘others’) (p = 0.0061) (Supplementary S4) This initial analysis comprised 133,734 participants we proceeded with the analyses using only studies reporting prevalence through the 2003 MIH case definition The overall prevalence of MIH for a total of 113,089 participants was estimated at 13.5% (95% CI 12.1–15.1, p < 0.001) (Table 2) with high heterogeneity (I2 = 98.0%) (Supplementary S5) Cumulative meta-analysis confirmed the overall estimate was not influenced by a particular study or group of studies (Supplementary S6A) We further confirmed the non-existence of influential studies through leave-one-out meta-analysis (Supplementary S6B) The prevalence of moderate to severe cases of MIH was estimated at 36.3% (95% CI 29.9–43.2, I2 = 95.2%) (Table 2, Supplementary S7). Detailed information on the definition of severity in each study was collectively presented in Table 3 estimates point to 24.3% of cases with one molar (95% CI 18.9–30.7 26.7% of cases with two molars (95% CI 23.9–29.7 18.1% of cases with three molars (95% CI 13.8–23.3 I2 = 90.0%) and 26.8% of cases with four molars (95% CI 21.1–34.7 The cases with affected incisors were estimated at 38.7% (95% CI 32.1–45.8 while cases with both molars and incisors were estimated at 42.1% (95% CI 34.9–50.0 the prevalence of HSPM cases was estimated at 3.6% (95% CI 1.9–6.8 All the latter results had high heterogeneity We further analyzed whether the prevalence results were influenced by study sample size, female/male ratio, geographic location (latitude and longitude) and year of publication (Table 4) MIH was influenced by the study sample size explaining 7.7% of the accounted heterogeneity The year of publication (estimate = − 0.09 p = 0.023) demonstrated a slight influence on the prevalence of MIH cases with one molar affected (explained 11.6% of heterogeneity) We then explored whether the prevalence between males and females would differ regarding MIH. Meta-analysis confirmed the latter result from meta-regression that MIH is not sex-related and females and males present a non-significant difference on the prevalence of MIH (0.986, 95% CI 0.940–1.035, I2 = 32.6%, p = 0.564) (Fig. 2). Forest plot of meta-analysis comparing MIH prevalence of female versus male participants We further explored the prevalence of MIH per continent (Table 5) The differences between continents (test for subgroup differences) were not significant (p = 0.1643) No publication bias was detected in the overall analysis (Table 2) except for the prevalence of cases with one molar affected (p = 0.004) we concluded the estimates obtained are classified as SORT A the results provide high level of confidence The results of the present systematic review estimated a pooled prevalence of MIH at 13.5% The moderate to severe cases of MIH were estimated at 36.3% of all cases Having three molars affected with MIH is the least probable situation and affected incisors were seen in 36.6% of the cases The prevalence of HSPM in MIH cases was estimated at 3.6% The sample size was a significant source of heterogeneity for the overall MIH prevalence and the year of publication for the prevalence of one molar affected year of publication and geographic location were not deemed influential factors in almost all the results Continents showed no different prevalence on MIH with the American continent displaying the highest prevalence and the Asian continent the lowest these results were categorized with a SORT A recommendation which means that all studies found coherent conclusions regarding the prevalence of MIH and that these results are consistent and good-quality patient-oriented evidence this is the first systematic review providing pooled estimates on molars and incisors affected with MIH and HSPM cases the present systematic review expanded the number of countries (49) confirmed the downgrading of alternative case definition of MIH to the overall pooled estimate (while the previous reviews combined classifications) and present new prevalence estimates concerning clinical characteristics of MIH (molas and incisors affected which means that both girls and boys present similar distribution of MIH lesions Africa was the continent with lowest prevalence yet in our review Asia had the lowest prevalence The American continent includes for the first time studies from the United States of America and Mexico which may explain a decrease in MIH prevalence from the two previous studies however remains as the continent (super-region) with highest prevalence by comparing the EAPD with alternative diagnostic methods as a subgroup analysis we confirmed the downgrading potential of alternative methods to the overall estimates this step methodological assortment into the analyses despite the substantial heterogeneity from the meta-analytical estimations teeth affected and HSPM were severely reduced because this sort of data is still scarce Future studies shall provide extensive information on these characteristics to confirm these results we were unable to explore hypothetical MIH-related factors (both medical sociodemographic and environmental) once again because of the lack of relevant information and this should be taken into account in future epidemiological studies readers must bear in mind that although the overall prevalence seems to be constant over the time new prevalence data has been pooled that contribute to understand the clinical characteristics of this enamel defect entity This systematic review was conducted following PRISMA a strict guideline for data reporting a comprehensive literature search and a meticulous predefined protocol we compared the EAPD case definition with other classifications than the EAPD and we confirmed substantial differences with a downgrading in prevalence when alternative methods were applied We have attempted to explore ways to mitigate heterogeneity and all studies used to compute estimates (and that employed the EAPD case definition) were of high methodological quality Another advantage of this study is that we have expanded the search for potential sources of heterogeneity with the addition of geographic measures and the further assessment into the new prevalence estimates the number of included participants has increase which is logical given the increase in studies included rather than the sources of heterogeneity considered as proven through meta-regression and given the results of the present systematic review a global partnership between all geographic representative associations shall be attained to ultimately ensure a standardization of MIH reporting and will encourage new and updated epidemiological and clinical data this suggested consensus will clarify the terminologies and guidelines towards a global alliance that will benefit all people affected by MIH these may contribute to overcoming the lack of epidemiological data and a still methodologically unsettled reporting approach the lack of a homogeneous definition may have contributed to the heterogeneity of results making it urgent to establish a consensual severity classification future studies should focus on data on these prevalence characteristics to deepen our knowledge regarding the specifics of MIH These information are of the utmost relevance for clinicians and may aid the development and implementation of future oral health programs The estimated prevalence of MIH was estimated at 13.5% Moderate to severe cases of MIH were estimated at 36.3% Affected incisors were seen in 36.6% of the cases The prevalence of hypomineralization of the second primary molars in MIH cases was estimated at 3.6% Data is provided in the materials of the paper Judgement criteria for molar incisor hypomineralisation (MIH) in epidemiologic studies: A summary of the European meeting on MIH held in Athens mechanical and chemical evaluation of molar-incisor hypomineralization-affected enamel: A systematic review Molar incisor hypomineralisation (MIH) training manual for clinical field surveys and practice Almuallem, Z. & Busuttil-Naudi, A. 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European archives of paediatric dentistry : official journal of the European Academy of Paediatric Dentistry, 11(2), 59–64. https://doi.org/10.1007/BF03262714 (2010) Epidemiologic study of idiopathic enamel hypomineralization in permanent teeth of Swedish children Download references This work is financed by national funds through the FCT—Foundation for Science and Technology Centro de Investigação Interdisciplinar Egas Moniz Egas Moniz – Cooperativa de Ensino Superior Download citation DOI: https://doi.org/10.1038/s41598-021-01541-7 Sign up for the Nature Briefing newsletter — what matters in science Best in Travel is here! Discover 2025’s destinations The 30 best countries, cities and regions to visit in 2025 Plan your trip with Elsewhere, by Lonely Planet See where a Lonely Planet Membership takes you Subscribe to our weekly newsletters to get the latest travel news, expert advice, and insider recommendations Explore the world with our detailed, insightful guidebooks Stay ahead of the curve with our guidebooks Uncover exciting new ways to explore iconic destinations Every month, we release new books into the wild Search Search Close search menu Explore Best in Travel 2024 Africa Close menu Countries Antarctica Antarctica Close menu Regions Asia Asia Close menu Countries Australia & the Pacific Australia & the Pacific Close menu Countries The Caribbean The Caribbean Close menu Countries Central America Central America Close menu Countries Europe Europe Close menu Countries Middle East Middle East Close menu Countries North America North America Close menu Countries South America South America Close menu Countries Buitrago Del Lozoya Spain © Oscar Rodriguez Gonzalez/EyeEm/Getty Images New Zealand might be off-limits to international visitors for the foreseeable future, but you can now get a taste of Middle-earth on a brand new hiking route inspired by J. 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Tolkien’s Lord of the Rings in central Spain In the Sierra Norte mountains near Madrid, the cleverly named El Camino del Anillo – the Ring Road – is a 122km-long circular walking trail that’s divided into eight sections and can be walked over the course of a week making it an attractive alternative to Spain’s other pilgrimage paths The trail meanders through mysterious landscapes of jagged peaks and ancient forests meant to evoke the fantastic scenes from Lord of the Rings books and films El Camino del Anillo starts at an interpretation centre in El Molar before heading off into the wilds passing by Buitrago del Lozoya (said to take after the Middle-earth village of Bree) Horcajuelo de la Sierra (the Elven valley of Rivendell) and the ‘White Tree of Gondor’ in Torrelaguna This rural route was established here in an attempt to bring awareness and breathe new life into this remote area with a shrinking population that could be revived through tourism El Camino del Anillo is a project that’s been five years in the making and was developed by the Laudato Si Foundation a nature conservation charity with connections to the Archbishop of Madrid but walkers of all types – believers and nonbelievers – are welcome on the trail Trekkers are allowed to hike through independently but are encouraged to contact the El Camino del Anillo foundation to secure accommodation some of which is in shelters and bunkhouses owned by the church as well as the option to complete some of the route by canoe which costs €275 for the weeklong adventure How coronavirus has impacted the power of your passportThese are the concerns travelers have about COVID-19 and air travelHere's when you can see this summer's spectacular meteor showers The poster can be seen on hundreds of billboards and billboards in almost fifty municipalities throughout Spain The Catholic Association of Propagandists has launched a new campaign this year with the slogan “Are women born or made?” The campaign starts with a question to invite reflection on a highly sensitive issue in our society and which fully compromises the dignity of women philosophical and even economic implications The campaign contrasts and underlines the dilemma put forward in 1949 by the historic feminist figure Simone de Beauvoir – “One is not born a woman: one becomes one” – to emphasise the fact that although the feelings and decisions of the individual can influence their life the nature of reality cannot be altered at the whim of the subject philosophical fashions or activist praxis claim so it seeks to put on the table the importance of giving voice to experts who can enrich the whole of the Spanish population with their formed vision while alluding to the more than worrying censorship attempts of those who seek to impose a single vision on the reality of female nature and on the occasion of the claims around 8-M the Catholic Association of Propagandists addresses the question of the nature of women from the anthropological premises that are legitimately proposed by the Magisterium of the Catholic Church always for the good of the person and society but uses the black and purple tones typical of the feminist movement and can be seen on hundreds of bus shelters and billboards in 44 municipalities throughout Spain such as Seville the municipalities throughout Spain where the campaign can be seen are: Santander Villanueva del Pardillo and Villaviciosa de Odón The Catholic Association of Propagandists (ACdP) is a group of lay faithful united in their vocation to evangelize public life the members of the ACdP have actively participated in society working to make the message of Jesus Christ and the Church present in all areas Reflection by Bishop Enrique Díaz: I will praise you Paris Marks 400th Anniversary of the Congregation of the Mission Reflection by Bishop Enrique Díaz: The Lord’s mercy is eternal Tweets by Pontifex Cement and Concrete CompositesCitation Excerpt :The retention rate of Sr2+ is high when Ca/(Si + Al) is relatively low [22] showed that the AACs with low Si/Al ratio immobilized Cs+ better than those with high Si/Al ratio It is usually true that the pore volume decreases with the increase of Si/Al ratio which means that high Si/Al ratio is beneficial to the densification of AAC ACCIONA AGUA has been awarded the contract for the operation conservation and maintenance of the urban wastewater treatment plants at Priorat (Tarragona) which come under the Catalan Water Agency (ACA) and have a capacity of over one million cubic meters per year ACCIONA will run twenty plants that provide a service to 20,500 people in the localities of: Bellmunt del Priorat The service started up on January 1st 2016 and will run for four years with a possible extension of another two years and estimated revenues of over 5 million euros in the four-year period In recent months ACCIONA Agua has intensified its presence in Catalonia through a contract for the operation conservation and maintenance of the Efficient Thermal Sludge Treatment Plant at Rubí I accept Information on data protection In compliance with Regulation (EU) 2016/679 on Data Protection and with other Data Protection regulations in force you are hereby informed that your personal data shall be processed by Acciona whose identification data are as follows: Tax ID No (NIF): A08001851; Address: Avenida de la Gran Vía de Hortaleza No.: +34 91 663 28 50; email: protecciondedatos@acciona.com Your data shall be processed in order to send you information through the subscription to our Newsletter through electronic means activities and news pertinent to our activity sectors The consent given by the data subject by indicating that they have read and accept this data protection information comprises the lawfulness of processing the subscription Request cannot be satisfied We may also process your satisfaction or preferences Data shall be stored until the elimination is requested we may give access to your data to service providers (such as technology service providers) who assist us in fulfilling this purpose may be located outside of the European Economic Area in territories that do not offer a level of data protection that is comparable to that of the European Union we transfer User data with appropriate safeguards and always ensuring the security of the same The data subject can exercise their rights of access to or rectification and/or the restriction of or objection to the processing of such data by writing the Department of Data Protection located at Avenida de la Gran Vía de Hortaleza 28033 (Madrid) or by sending the form available in the link: FORM If we consider it necessary in order to be able to identify you, we may ask you for a copy of an identity document. Furthermore, at any time the data subject may withdraw the granted consent by contacting the aforementioned address and file a claim to the Supervisory Authority (Agencia Española de Protección de Datos www.aepd.es) You can also unsubscribe from the Newsletter communication For any further information you can visit the Privacy Police on the website https://www.acciona.com/privacy-policy/ Madrid is a wine-growing region and its booming appellation of origin is proof of this It is now made up of 51 wineries and has four recognized subzones: Arganda It is also an opportunity to visit one of the jewels of Celtic sculpture in the peninsula which are just a few minutes away from the Zone A post shared by Bodega Real Cortijo Carlos III (@realcortijo) King Carlos III ordered the construction of the Bodega Real del Cortijo in 1782 which has been considered a Historic Artistic Monument since the 1980s and is only five kilometers from the Royal Site of Aranjuez It has been the supplier of wine and oil for five kings and a good list of illustrious and noble personalities And they claim to be the only winery owned by a Royal House in the world beyond the traditional tastings and pairings there is even a wine casino – games of chance animated by sommeliers – and the option of creating your own wine The Muñoz Martin Winery has been located in the historic center of Navalcarnero since 1930 They are led by a fifth generation of winemakers who have managed to combine innovation and tradition The tour of its 28 hectares of vineyards spread between this village and Villamanta includes a visit to its cave and wine tasting with a tapa The Luis Saavedra organic winery has belonged to the same family since the nineteenth century but it was not until the late twentieth century that the tests began to make a fully organic production It is located in the extreme south of the Community of Madrid and belongs to the subzone of San Martín de Valdeiglesias The wineries near Madrid continue to grow in popularity and diversity in terms of their wines They have also been able to adapt and recover the winemaking tradition of the region European Open 65cc Race OneIt may have seemed like the longest start straight in the world for most of the 65’s but it was the perfect distance for Spain’s own Raul Sanchez who was oozing adrenaline at the start of race one and took the holeshot and early race lead the freshly watered track caught the little Spaniard out which saw him drop back to sixteenth when he crashed on an uphill Holland’s little ripper Kay Karssemakers took full advantage of the gifted lead and knuckled down right away while France’s Florian Miot tried to keep up Miot could not quite match the pace of Karssemakers and ended up exerting too much energy At the half way mark Kovacs dropped the hammer on Miot and took over second where he remained for the rest of the race.Meanwhile it wasn’t over for Miot who soon had company in the form of Czech Republic’s Radek Vertovsky and Russia’s Matvey Vopilov A missed line late in the race saw Miot drop back to fourth as Vetrovsky capitalized on the error.Karssemakers took a convincing victory ahead of Kovacs European Open 65cc Race TwoSpeedy little Dutchman Kay Karssemakers sealed the deal on his European Open 65cc title mission by claiming the Fox Holeshot and controlling the final race from start to finish.While that sounds smooth sailing for the youngster who also won race one it was not that easy as the poleman Adam Kovacs was on him from gate drop Kovacs put in a good effort but as the wind picked up he fell off balance and looped out into the infield The small Hungarian managed to re-enter the track instantly but lost second position to Radek Vetrovsky.Although he was handed second he was ripping in race two and pushed Karssemakers all the way to the finish Kovacs managed to regroup and rode smart for third while Spain’s Adria Monne and Florian Miot rounded out the top five European Open 65cc OverallA double victory for Holland’s Kay Karssemakers crowned him the European Open 65cc winner ahead of yesterday’s top qualifier Hungarian Adam Kovacs and Czech Republic’s Petr Vetrovsky The first long weekend of May is full of events: folklore commemorates the uprising against the French in 1808 During these days, different events take place all over the city and this year they are extended from April 30 to May 4. Among the most picturesque is the celebration of the Mayas which usually takes place in the neighborhoods of Lavapiés Another big event that takes to the streets these days is the reenactment of the fight that liberated the city from the invaders horses and cannons will be the normality at least for a day in the capital music will be the culmination of the festival with free concerts of great Madrid bands like Carolina Durante as well as folklore groups that these days will wear the traditional goyesco costume instead of the chulapo The concerts will be held in the esplanade of Puente del Rey and admission is free until full capacity is reached Recreation of the May 2nd uprising of 1808 with the participation of more than a hundred actors carriages and cannons; includes parade and representation of the defense of the Monteleón barracks Spain lies a 1.5-hectare farm managed and owned by Filipinos manage businesses in different industries: real estate The couple invested in these sectors both in the Philippines and Spain.  Having enough staff in their businesses allows Ghie and Ramon to spend more time on their farm the couple both share farming experiences with their families back home.  The two have not only found a great way to bond over farming but tilling the land also enables them to have healthy eating habits and to maintain a healthy body by engaging in farm activities.  they always collect ‘a piece of home,’ a.k.a whenever they go on vacation to the Philippines.  It has been seven years since they started their farm in Madrid which they named after the municipality where it is located — El Molar The partners started growing crops as a hobby This pastime activity progressed into a business opportunity when they started supplying vegetables and fruits to Filipino customers and Asian grocery stores.  The climate was the biggest adjustment they had to deal with when they started farming in a country with four seasons since they were accustomed to growing crops in a tropical country the right timing is essential to the growth and quality of each crop they prepare the seedlings in a greenhouse before transplanting them to plots.  The summer season (June to August or September in Madrid) is a busy season for the farming duo because this is a time they can produce and sell most of the crops to their clientele Vegetables that they grow every summer include talong They naturally grow these crops and do not use any harmful fertilizer and pesticides They also have equipment that lightens farm operations such as a watering machine that pumps water from a nearby river and tractors for cultivating the soil They sell vegetables for one to five euros (P58 to P290) per pack and chicken eggs are also available on the farm while the flowers they grow are arranged and used as home decoration or shared with friends They also earn extra profit by offering farm equipment rental to nearby farms they collect about 5000 euros or over P200,000 per month Sharing memories with Filipino friends  The farm is regularly maintained by two permanent Filipino workers they hire fellow Filipinos who want to take a part-time job on the farm The farm also serves as a venue for celebrations with their friends where they mimic the Filipino fiestas and share dishes that remind them of home mastering the art of right timing is necessary to attain optimum harvest Accompany this with the practice of skipping chemical fertilizers and pesticides for the safety of everyone The couple envisions the farm as a public destination where anyone can hang out Read more about farming and gardening at agriculture.com.ph.