Application of Synchrotron X-ray Fluorescence (SXRF) for the diagnosis of severe Molar-Incisor Hypomineralisation (MIH) in an Imperial Roman child from Isola Sacra (1st–3rd century AD)

Molar-incisor hypomineralization (MIH) is a pathological condition involving a qualitative alteration in the mineralization process of dental enamel. In modern populations, MIH has been linked to a wide range of potential etiological factors, including environmental stress, malnutrition, chronic and metabolic diseases. While some studies have reported possible cases of MIH in ancient populations, its wide variety of phenotypes and complex clinical features pose challenges to definitive diagnosis. This study presents a case of severe MIH identified in the mandibular dental remains of a Roman child from Isola Sacra (Portus Urbis Romae, 1st–3rd century CE) by integrating modern methods of clinical classification, elemental and histomorphometric analysis. MIH-induced lesions were detected in the second deciduous molars, manifested as a post-eruptive enamel breakdown at the occlusal surface with exposure of the dentine. Synchrotron X-ray fluorescence (SXRF) was used to investigate the distribution of calcium (Ca) and phosphorus (P) in the enamel of affected teeth and a control sample to assess the potential of MIH to alter normal mineralization patterns. Unlike the control samples, which exhibited homogeneous and high-intensity distributions consistent with previous reports, MIH affected deciduous molars showed strong inhomogeneity. Compton/Rayleigh diffusion ratio and SXRF maps, as well as the Ca/P molar ratio, showed reduced intensity in the inner cuspal enamel compared to the rest of the tissue. This suggests the presence of localized hypomineralization caused by a disruption in enamel development. Histomorphometric analysis revealed physiological stress lines in the region of reduced mineral content and enabled to circumscribe the onset of the pathology to the first months of life. Following current guidelines, this study used an integrated analytical approach, combining clinical diagnosis with advanced, high-resolution analysis. This approach enabled the correct diagnosis of the so far most ancient MIH case and allowed for an in-depth microstructural and elemental analysis of the pathology.