Metrics details Molar Incisor Hypomineralisation (MIH) is defined as a qualitative demarcated enamel hypomineralisation defect of tooth enamel affecting at least one first permanent molar (FPM) the term Hypomineralised Second Primary Molar (HSPM) was used to describe similar defects affecting second primary molars Our observational study aimed at determining HSPM and MIH frequencies in a medieval and early-modern-age population population (Sains-en-Gohelle 7th − 17th centuries) and compare it to the current worldwide and French prevalence values there are no other studies on this subject in France but the diagnosis of these pathologies is based solely on a visual examination Our study differs from others by using objective diagnostic The use of these diagnostic methods allows differentiation between hypomineralised and taphonomic lesions there were 10 individuals with at least one first permanent molar affected by MIH amongst the 81 individuals with at least one first permanent molar present and 15 individuals with at least one second primary molar affected by HSPM among the 113 individuals with at least one second primary molar present.The presence of MIH and HSPM in ancient populations with frequencies respectively equivalent and higher than current worldwide averages renews the debate and questioning about the aetiological factors of these pathologies have been proposed as possible contributing factors despite the exploration of these various pathways current research has not yet conclusively determined the causes of this anomaly These enamel defects may cause significant functional and aesthetic damages to both primary and permanent teeth posing a real public health problem with medical consequences such as carious lesions and pain as well as economic consequences including repeated care and multiple dental appointments and in the absence of identified cause(s) to date no preventive measure for limiting the effect of the risk factors can be implemented the presence or absence of HSPM and MIH in an archaeological population will make it possible to give more or less credence to some aetiological theories Although interest in this condition is growing many questions remain unanswered regarding its underlying causes Previous studies have mainly focused on modern populations with limited data available on historical populations Understanding the frequency and distribution of hypomineralisation in these populations could provide valuable insights into the evolution of this condition over time and the possible influences of past environmental and genetic factors This study aims to fill this gap by examining the frequencies of HSPM and MIH in an archaeological population from Sains-en-Gohelle The second objective concerns comparing comparing the frequencies of MIH and HSPM in this historical population with modern prevalence rates We hypothesize that the frequencies of HSPM and MIH in the medieval and early-modern-age population will not differ from that of contemporary populations because the causes of these were timeless The visual examination allowed the identification of staining on the SPM and on the FPM these teeth were analysed using microtomography and X-ray fluorescence enabling the diagnosis of hypomineralisation Regarding HSPM, out of 256 individuals aged 2–9 years, 137 individuals with dental remains were selected. Amongst these individuals, 113 had at least one SPM. In total, 337 SPM were observed. Amongst these 337 SPM, there were more mandibular SPM than maxillary SPM (Table 1) 40 individuals had at least one SPM and at least one FPM few demarcated white opacities were present compared to demarcated yellow or brown opacities This difference may be explained by the porous nature of the enamel associated with demarcated opacities when exposed to specific environmental conditions Given that the studied specimens are buried in the soil it is likely that initially visible white spots transform into yellow or brown spots due to chemical and physical degradation and alteration processes These dynamic underscores the importance of considering taphonomic conditions in the interpretation of enamel anomalies as they can significantly impact the appearance and classification of the observed opacities The microscanning of 55 stained SPM and 28 stained FPM was carried out Photograph of one second primary molars from S1245 (7th -16th France) - Second maxillary left primary molar (65) Photographs of four first permanent molars from S191 (7th − 13th (a) Occlusal view of the maxilla with the arrow indicating hypomineralisation on 16 (b) Occlusal view of the mandible (c) Buccal view of the right maxilla with the arrow indicating hypomineralisation on 16 Of the 242 observed primary second molars (SPM) 23 were affected by hypomineralised second primary molars (HSPM) resulting in 9.5% of the observed SPM being affected Among the 236 observed permanent first molars (FPM) 12 were affected by molar-incisor hypomineralisation (MIH) meaning 5% of the observed FPM were affected Amongst the 40 individuals with at least one SPM and at least one FPM present and for MIH it was 12.3% in the population of Sains-en-Gohelle The frequency of individuals who had both MIH and HSPM was 5% the sample on which we estimated these frequencies values was small; so it will be necessary to conduct multiple frequencies studies in the future to obtain valid data The perinatal and postnatal factors include prematurity All of these putative aetiological factors existed in medieval times Perinatal factors cannot be completely ruled out but if there is a link between them and enamel hypomineralisation the frequency of the latter would have been reduced in medieval times due to infantile death and advances in the medical field now make it possible to increase the chances of survival of a child born prematurely These studies were conducted in contemporary populations and it would be interesting to compare the frequency of hypomineralisation in different social classes in archaeological populations These results suggest a genetic implication since twins will be exposed to the same environmental factors we were interested in determining if there was a familial clustering of individuals affected by MIH and/or HSPM We could assume that individuals from the same family might be buried in close proximity to each other Localization of individuals with at least one second primary molar (blue dot) and individuals with at least one second primary molar diagnosed with HSPM (red dot) on the archaeological site of Sains-en-Gohelle (France, Pas-de-Calais, 7th -17th ). Localization of individuals with at least one first permanent molar (blue dot) and individuals with at least one first permanent molar with MIH (red dot) on the archaeological site of Sains-en-Gohelle (France These two examples illustrate the potential exposure of pregnant women and young children to teratogenic agents and endocrine disruptors during medieval times which could lead to developmental disturbances and may be partly responsible for dental mineralisation disruptions resulting in enamel hypomineralisation the population studied can be considered homogeneous both genetically and spatially the frequency of caries remains consistent between the two periods studied (the so-called recent post 11th century period and the ancient pre 11th century period) and there is no clear social distinction within the burial space which suggests a coherence in living conditions and dietary habits over time This points to the possibility that similar causes were relevant both in medieval times and today while genetic predisposition cannot be ruled out that MIH may result from multiple interacting factors Consistent findings of MIH frequency in past populations would support our conclusions antibiotics) may play less of a unique role than previously thought The present study demonstrates the cross-disciplinary and complementary contribution of two fields Biological Anthropology and Dental Sciences in the analysis and understanding of the aetiological factors of MIH and HSPM This type of study also provides new significant insights into describing the health status of ancient populations The data were collected during the years 2022 and 2023 individuals for whom no dental remains recorded were excluded we refined our sample to include 137 individuals aged 2–9 years and 157 individuals aged 6–18 years (294 total) Several steps are necessary to diagnose HSPM on the SPM and MIH on the FPM of the medieval and early-modern-age collection of Sains-en-Gohelle: macroscopic and photographic examinations X-ray fluorescence spectroscopy was used to differentiate taphonomic stains Through the application of the standardized method described below Efforts were made to minimize potential sources of bias all available dental remains from the relevant age groups of the medieval and early-modern-age population of Sains-en-Gohelle were examined to ensure a representative sample all visual assessments of enamel hypomineralisation were performed by two MIH experts Photographs of teeth with (a) enamel hypoplasia (b) demarcated opacity (c) carious lesions (d) post-eruptive enamel breakdown if a difference persists at the surface of the enamel we can then possibly suggest an initial carious lesion or taphonomic discoloration This was clarified using X-ray fluorescence analysis Non-parametric statistical tests (Wilcoxon test for paired samples) were carried out using PAST (PAleontological STatistics Version 4.1778) to compare data from normal and stain enamel The datasets 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Paleontological statistics software package for education and data analysis Download references This work was supported by the Institut Français de Recherche Odontologique (IFRO) and the PRC CNRS-University of Melbourne (N°501911 GL) We gratefully acknowledge Nicolas Vanderesse (PLACAMAT UMR 5060) and Pierre-Hadrien Decaup (UMR 5199 We grateful to Laetitia Maggio (Service Régional de l’archéologie - DRAC Hauts-de-France) and Armelle Masse (Direction de l’Archéologie Département du Pas-de-Calais) for granting access to the archaeological collections This work was supported by EVODIBIO team (PACEA This study received financial support from the French government in the framework of the university of Bordeaux’s IdEx “Investments for the Future” program / GPR Human Past Centre de Compétence des Maladies Rares Orales et Dentaires Academic Center for Dentistry Amsterdam (ACTA) University of Amsterdam and Vrije Universiteit Amsterdam drafted and critically revised the manuscript; D.J.M contributed to data interpretation and critically revised the manuscript for important intellectual content All authors gave final approval and agree to be accountable for all aspects of the work 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 Download citation DOI: https://doi.org/10.1038/s41598-025-87589-1 Anyone you share the following link with will be able to read this content: a shareable link is not currently available for this article Sign up for the Nature Briefing newsletter — what matters in science Metrics details Molar Incisor Hypomineralisation (MIH) and Hypomineralised Second Primary Molars (HSPM) involve prevalent qualitative structural developmental anomalies of tooth enamel affecting the first permanent molars (and often incisors) and the second primary molars These demarcated hypomineralised lesions of enamel manifest as white-cream or yellow-brown opacities with possible post-eruptive localised loss of enamel Aetiological hypotheses have involved contemporary life factors (i.e environmental pollutant exposure or early childhood medications) in contrast to factors not limited to a specific time period (i.e hypoxia at birth or genetic predisposition) Evidence of MIH in ancient populations would reinforce aetiological factors present for many centuries By means of microtomographic and X-ray fluorescence analyses the present study provides evidence that (i) two archaeological specimens: “S407” (Sains-en-Gohelle and (ii) one individual “S323” was affected by HSPM and MIH (Sains-en-Gohelle no author has identified an HSPM case in a past population teeth showing defects indicative of MIH and HSPM 298 and 14 individuals aged from 6 to 18 years were analysed Three individuals affected by yellow-brown opacities on first permanent molars incisors or second primary molars were selected for analysis: B335 (Beauvais 7th–11th centuries) and S407 (Sains-en-Gohelle After distribution of shared high resolution images securely via the internet clinical diagnoses of the three individuals were given by nineteen MIH specialists to confirm or refute these clinical diagnoses of MIH and HSPM and discuss their implications Photographs of materials from B335 (Beauvais, France). *teeth affected by discolorations. Photographs of materials from S323 (Sains-en-Gohelle, France). *teeth affected by discolorations. Photographs of materials from S407 (Sains-en-Gohelle) A yellow demarcated opacity was present on the occlusal third of the buccal surface of tooth 26 No other discolorations were observed but some carious lesions on primary molars were present (teeth 54 84 and 85) and slight occlusal wear was observed on the primary molars Photographic images of the three specimens (Figs 1–3) were examined by 19 MIH specialists (see Methods and SI) seven MIH experts did not confirm the MIH diagnosis and one of them refuted this diagnosis Only eight experts confirmed the MIH diagnosis for S323 Scores were better correlated for S407 because 14/19 specialists gave an MIH diagnosis The Fleiss’ kappa test performed for each specimen showed a poor agreement between responses (κ < 0) concerning MIH diagnosis (SI) Images of microcomputed tomography analyses in 3D and 2D: (a,b) location of 5 analysis cubes from DEJ to surface on normal (blue cubes) and discoloured (red cubes) areas (c,d) location of profile lines from EDJ to surface through normal (AB) and discoloured (CD) areas Mineral densities of normal (blue line) and hypomineralised (red line) enamel from 99 equidistant measurements taken on line from DEJ to surface including the discoloured sample (n = 8 with the exception of S323(11)) and the control sample (n = 3) Elemental chemical analyses (see Methods) provided information on taphonomic contamination by one or several chemical elements (Mn, Fe, Cu and Pb). The discolorations on teeth 65 and 75 from S323 were characterised by an increase in Mn (respectively, P = 0.01 and 0.04; Table 2) An increase in Fe was observed in the discoloured area of tooth 46 from B335 (P = 0.01) Other teeth did not show evidence of a taphonomic contamination by these elements (P > 0.05) Pending the results of prospective studies the increase of MIH prevalence study numbers on ancient populations including well documented archaeological series will improve understanding of the MIH pathophysiology the discovery of the oldest specimens with MIH and the first archaeological specimen with HSPM in an immature individual from archaeological series dated from 7th–18th centuries indicates similar aetiological factors existing now and in the medieval period such as hypoxia during deliveries But it should be borne in mind that the aetiology of MIH may be multifactorial The repeat of observations of a significant prevalence of MIH in older populations would confirm our observations downplaying somewhat the role of uniquely modern aetiological factors (derivatives of dioxin The present study highlights the potential contribution of bio-archaeological studies on a current public health problem The individuals’ teeth were examined by means of a hand magnifying lens with artificial lighting Standardised photographs of the three specimens showing brown discolorations similar to MIH and HSPM were taken with a Nikon® (Tokyo USA) macro ring flash and a Tamron® (Saitama mandible and teeth were photographed on a black matt paper: occlusal view for bones and five views (labial The samples including nine discoloured teeth (B335(46) S323(85) and S407(26)) and three control teeth (B335(36) were imaged using high resolution microtomography at the laboratory PLACAMAT (UMS 3626) in Bordeaux France (Microtomograph X GE™ V/TOME/X S equipment exposure time 500 ms with four integrations per projection 2550 projections/360° and 0.1 mm copper filter placed on the source to reduce beam hardening artefacts The final volume was reconstructed in 16-bit The microCT images were compiled with the 7.0.1 software Avizo® (Visualization Sciences Group In order to take measurements at the same coronal height images were reconstructed according to the plane of section through two points located at the buccal cervical surface and one point on the lingual cervical surface From a selected tooth area, five cubes (≈49 × 49 × 49 µm3) were located by means of the square brush segmentation tool from the enamel surface to the DEJ (Fig. 4a and SI): cube n°3 at the midway between cubes 1 and 5; cube n°2 at the midway between cubes 1 and 3; cube n°4 at the midway between cubes 3 and 5 Normal enamel measurements from the control group (n = 3) and normal enamel of the discoloured group were determined (n = 8 with the exception of S323(11)) Discoloured enamel measurements were from discoloured enamel from the discoloured group (n = 8 with exception of 321(11)) Non-parametric statistical tests (Wilcoxon test for paired samples) were carried out using Statistica® software Package Version 7.1 (Statsoft Dell USA) to compare data from normal and discoloured enamel A Fleiss’s kappa test was performed with R software to test the inter-examiner agreement (n = 19) In Dental Perspectives on Human Evolution: State of the Art Research in Dental Paleoanthropology (eds Bailey Do parents and children perceive molar-incisor hypomineralization as an oral health problem In Advances in Human Palaeopathology (eds Pinhasi Beauvais Caserne Taupin “Antenne Universitaire” Service Régional de l’Archéologie de Picardie Rapport d’opération de fouilles archéologiques Sains-en-Gohelle (2012) 3D X-ray microscopic study of the extent of variations in enamel density in first permanent molars with idiopathic enamel hypomineralisation The Burning Issue: Historical Reflections on Municipal Waste Incineration Short Report (AHRB Research Centre for Environmental History In Juvenile Osteology 67–95 (Academic Press Le cimetière du couvent des Sœurs Grises de Beauvais de la fin du XVe au XVIIIe siècle Download references Bordeaux University) and Jean-Marc Fémolant (director of the Archeological Service of Beauvais) for access to the osteological series of the “Couvent des Soeurs Grises” We gratefully acknowledge Frédéric Santos (CNRS Bordeaux University) for his help with statistics UMR 5060) and the 19 anonymous MIH specialists are acknowledged for their contributions to the study LaScArBx is a research programme supported by the ANR (ANR-10-LABX-52) Christine Couture-Veschambre & Patrick Rouas The authors declare that they have no competing interests Download citation DOI: https://doi.org/10.1038/s41598-017-01745-w European Archives of Paediatric Dentistry (2022) European Archives of Paediatric Dentistry (2020)