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The penecontemporaneous Middle Pleistocene sites of Fontana Ranuccio (Latium) and Visogliano (Friuli-Venezia Giulia), set c. 450 km apart in central and northeastern Italy, respectively, have yielded some among the oldest human fossil remains testifying to a peopling phase of the Italian Peninsula broadly during the glacial MIS 12, a stage associated with one among the harshest climatic conditions in the Northern hemisphere during the entire Quaternary period. Together with the large samples from Atapuerca Sima de los Huesos, Spain, and Caune de l'Arago at Tautavel, France, the remains from Fontana Ranuccio and Visogliano are among the few mid-Middle Pleistocene dental assemblages from Western Europe available for investigating the presence of an early Neanderthal signature in their inner structure. We applied two- three-dimensional techniques of virtual imaging and geometric morphometrics to the high-resolution X-ray microtomography record of the dental remains from these two Italian sites and compared the results to the evidence from a selected number of Pleistocene and extant human specimens/samples from Europe and North Africa. Depending on their preservation quality and on the degree of occlusal wear, we comparatively assessed: (i) the crown enamel and radicular dentine thickness topographic variation of a uniquely represented lower incisor; (ii) the lateral crown tissue proportions of premolars and molars; (iii) the enamel-dentine junction, and (iv) the pulp cavity morphology of all available specimens. Our analyses reveal in both samples a Neanderthal-like inner structural signal, for some aspects also resembling the condition shown by the contemporary assemblage from Atapuerca SH, and clearly distinct from the recent human figures. This study provides additional evidence indicating that an overall Neanderthal morphological dental template was preconfigured in Western Europe at least 430 to 450 ka ago.

Dental enamel thickness, topography, growth and development vary among hominins. In Homo, the thickness of dental enamel in most Pleistocene hominins display variations from thick to hyper-thick, while Neanderthals exhibit proportionally thinner enamel. The origin of the thin trait remains unclear. In this context, the Middle Pleistocene human dental assemblage from Atapuerca-Sima de los Huesos (SH) provides a unique opportunity to trace the evolution of enamel thickness in European hominins. In this study, we aim to test the hypothesis if the SH molar sample approximates the Neanderthal condition for enamel thickness and/or distribution. This study includes 626 molars, both original and comparative data. We analysed the molar inner structural organization of the original collections (n = 124), belonging to SH(n = 72) and modern humans from Spanish origin (n = 52). We compared the SH estimates to those of extinct and extant populations of the genus Homo from African, Asian and European origin (estimates extracted from literature n = 502). The comparative sample included maxillary and mandibular molars belonging to H. erectus, East and North African Homo, European Middle Pleistocene Homo, Neanderthals, and fossil and extant H. sapiens. We used high-resolution images to investigate the endostructural configuration of SH molars (tissue proportions, enamel thickness and distribution). The SH molars exhibit on average thick absolute and relative enamel in 2D and 3D estimates, both in the complete crown and the lateral enamel. This primitive condition is shared with the majority of extinct and extant hominin sample, except for Neanderthals and some isolated specimens. On the contrary, the SH molar enamel distribution maps reveal a distribution pattern similar to the Neanderthal signal (with thicker enamel on the lingual cusps and more peripherally distributed), compared to H. antecessor and modern humans. Due to the phylogenetic position of the SH population, the thick condition in molars could represent the persistence of the plesiomorphic condition in this group. Still, more data is needed on other Early and Middle Pleistocene populations to fully understand the evolutionary meaning of this trait.

Early arrivals in Europe Anatomically modern humans are thought to have arrived in Europe 44,000–42,000 years ago. Physical evidence for early humans is scarce, and these dates are based largely on studies of stone tool assemblages. Two papers published this week use the latest radiocarbon dating and morphological analysis techniques to reassess museum hominid samples. Higham et al . examine a human maxilla from the Aurignacian site at Kent's Cavern in the United Kingdom, discovered in 1927 and previously dated at around 35,000 years old, and arrive at an age of 44,200–41,500 years. The dental morphology of the jawbone indicates that its attribution as early human, rather than Neanderthal, is reliable. Benazzi et al . reanalyse two teeth from the Uluzzian site Grotta del Cavallo in southern Italy and conclude that they are definitively modern, not Neanderthal, and date to 45,000–43,000 years old. A further conclusion from this work is that the Uluzzian culture of southern Europe — always found stratigraphically below the Aurignacian signature culture of the modern humans — may represent the earliest modern humans in Europe rather than the last Neanderthals. The appearance of anatomically modern humans in Europe and the nature of the transition from the Middle to Upper Palaeolithic are matters of intense debate. Most researchers accept that before the arrival of anatomically modern humans, Neanderthals had adopted several ‘transitional’ technocomplexes. Two of these, the Uluzzian of southern Europe and the Châtelperronian of western Europe, are key to current interpretations regarding the timing of arrival of anatomically modern humans in the region and their potential interaction with Neanderthal populations. They are also central to current debates regarding the cognitive abilities of Neanderthals and the reasons behind their extinction 1 , 2 , 3 , 4 , 5 , 6 . However, the actual fossil evidence associated with these assemblages is scant and fragmentary 7 , 8 , 9 , 10 , and recent work has questioned the attribution of the Châtelperronian to Neanderthals on the basis of taphonomic mixing and lithic analysis 11 , 12 . Here we reanalyse the deciduous molars from the Grotta del Cavallo (southern Italy), associated with the Uluzzian and originally classified as Neanderthal 13 , 14 . Using two independent morphometric methods based on microtomographic data, we show that the Cavallo specimens can be attributed to anatomically modern humans. The secure context of the teeth provides crucial evidence that the makers of the Uluzzian technocomplex were therefore not Neanderthals. In addition, new chronometric data for the Uluzzian layers of Grotta del Cavallo obtained from associated shell beads and included within a Bayesian age model show that the teeth must date to ∼45,000–43,000 calendar years before present. The Cavallo human remains are therefore the oldest known European anatomically modern humans, confirming a rapid dispersal of modern humans across the continent before the Aurignacian and the disappearance of Neanderthals.

Characterizing dental development in fossil hominins is important for distinguishing between them and for establishing where and when the slow overall growth and development of modern humans appeared. Dental development of australopiths and early Homo was faster than modern humans. The Atapuerca fossils (Spain) fill a barely known gap in human evolution, spanning ~1.2 to ~0.4 million years (Ma), during which H. sapiens and Neandertal dental growth characteristics may have developed. We report here perikymata counts, perikymata distributions and periodicities of all teeth belonging to the TE9 level of Sima del Elefante, level TD6.2 of Gran Dolina ( H. antecessor ) and Sima de los Huesos. We found some components of dental growth in the Atapuerca fossils resembled more recent H. sapiens . Mosaic evolution of perikymata counts and distribution generate three distinct clusters: H. antecessor , Sima de los Huesos and H. sapiens .

Teeth have been studied for decades and continue to reveal information relevant to human evolution. Studies have shown that many traits of the outer enamel surface evolve neutrally and can be used to infer human population structure. However, many of these traits are unavailable in archaeological and fossil individuals due to processes of wear and taphonomy. Enamel–dentine junction (EDJ) morphology, the shape of the junction between the enamel and the dentine within a tooth, captures important information about tooth development and vertebrate evolution and is informative because it is subject to less wear and thus preserves more anatomy in worn or damaged specimens, particularly in mammals with relatively thick enamel like hominids. This study looks at the molar EDJ across a large sample of human populations. We assessed EDJ morphological variation in a sample of late Holocene modern humans (n = 161) from archaeological populations using μ-CT biomedical imaging and geometric morphometric analyses. Global variation in human EDJ morphology was compared to the statistical expectations of neutral evolution and “Out of Africa” dispersal modeling of trait evolution. Significant correlations between phenetic variation and neutral genetic variation indicate that EDJ morphology has evolved neutrally in humans. While EDJ morphology reflects population history, its global distribution does not follow expectations of the Out of Africa dispersal model. This study increases our knowledge of human dental variation and contributes to our understanding of dental development more broadly, with important applications to the investigation of population history and human genetic structure.

Scholars have debated the taxonomic identity of isolated primate teeth from the Asian Pleistocene for over a century, which is complicated by morphological and metric convergence between orangutan (Pongo) and hominin (Homo) molariform teeth. Like Homo erectus, Pongo once showed considerable dental variation and a wide distribution throughout mainland and insular Asia. In order to clarify the utility of isolated dental remains to document the presence of hominins during Asian prehistory, we examined enamel thickness, enamel-dentine junction shape, and crown development in 33 molars from G. H. R. von Koenigswald's Chinese Apothecary collection (11 Sinanthropus officinalis [= Homo erectus], 21 \"Hemanthropus peii,\" and 1 \"Hemanthropus peii\" or Pongo) and 7 molars from Sangiran dome (either Homo erectus or Pongo). All fossil teeth were imaged with non-destructive conventional and/or synchrotron micro-computed tomography. These were compared to H. erectus teeth from Zhoukoudian, Sangiran and Trinil, and a large comparative sample of fossil Pongo, recent Pongo, and recent human teeth. We find that Homo and Pongo molars overlap substantially in relative enamel thickness; molar enamel-dentine junction shape is more distinctive, with Pongo showing relatively shorter dentine horns and wider crowns than Homo. Long-period line periodicity values are significantly greater in Pongo than in H. erectus, leading to longer crown formation times in the former. Most of the sample originally assigned to S. officinalis and H. erectus shows greater affinity to Pongo than to the hominin comparative sample. Moreover, enamel thickness, enamel-dentine junction shape, and a long-period line periodicity value in the \"Hemanthropus peii\" sample are indistinguishable from fossil Pongo. These results underscore the need for additional recovery and study of associated dentitions prior to erecting new taxa from isolated teeth.

Third permanent molars (M3s) are the last tooth to form but have not been used to estimate age at dental maturation in early fossil hominins because direct histological evidence for the timing of their growth has been lacking. We investigated an isolated maxillary M3 (SK 835) from the 1.5 to 1.8-million-year-old (Mya) site of Swartkrans, South Africa, attributed to Paranthropus robustus . Tissue proportions of this specimen were assessed using 3D X-ray micro-tomography. Thin ground sections were used to image daily growth increments in enamel and dentine. Transmitted light microscopy and synchrotron X-ray fluorescence imaging revealed fluctuations in Ca concentration that coincide with daily growth increments. We used regional daily secretion rates and Sr marker-lines to reconstruct tooth growth along the enamel/dentine and then cementum/dentine boundaries. Cumulative growth curves for increasing enamel thickness and tooth height and age-of-attainment estimates for fractional stages of tooth formation differed from those in modern humans. These now provide additional means for assessing late maturation in early hominins. M3 formation took ≥ 7 years in SK 835 and completion of the roots would have occurred between 11 and 14 years of age. Estimated age at dental maturation in this fossil hominin compares well with what is known for living great apes.

The form of two hard tissues of the mammalian tooth, dentine and enamel, is the result of a combination of the phylogenetic inheritance of dental traits and the adaptive selection of these traits during evolution. Recent decades have been significant in unveiling developmental processes controlling tooth morphogenesis, dental variation and the origination of dental novelties. The enamel-dentine junction constitutes a precursor for the morphology of the outer enamel surface through growth of the enamel cap which may go along with the addition of original features. The relative contribution of these two tooth components to morphological variation and their respective response to natural selection is a major issue in paleoanthropology. This study will determine how much enamel morphology relies on the form of the enamel-dentine junction. The outer occlusal enamel surface and the enamel-dentine junction surface of 76 primate second upper molars are represented by polygonal meshes and investigated using tridimensional topometrical analysis. Quantitative criteria (elevation, inclination, orientation, curvature and occlusal patch count) are introduced to show that the enamel-dentine junction significantly constrains the topographical properties of the outer enamel surface. Our results show a significant correlation for elevation, orientation, inclination, curvature and occlusal complexity between the outer enamel surface and the enamel dentine junction for all studied primate taxa with the exception of four modern humans for curvature (p<0.05). Moreover, we show that, for all selected topometrical parameters apart from occlusal patch count, the recorded correlations significantly decrease along with enamel thickening in our sample. While preserving tooth integrity by providing resistance to wear and fractures, the variation of enamel thickness may modify the curvature present at the occlusal enamel surface in relation to enamel-dentine junction, potentially modifying dental functionalities such as blunt versus sharp dental tools. In terms of natural selection, there is a balance between increasing tooth resistance and maintaining efficient dental tools. In this sense the enamel cap acts as a functional buffer for the molar occlusal pattern. In primates, results suggest a primary emergence of dental novelties on the enamel-dentine junction and a secondary transposition of these novelties with no or minor modifications of dental functionalities by the enamel cap. Whereas enamel crenations have been reported by previous studies, our analysis do not support the presence of enamel tubercles without dentine relief nuclei. As is, the enamel cap is, at most, a secondary source of morphological novelty.

ABSTRACT Objective: This descriptive observational study aimed to determine clinically relevant and applicable data of enamel thickness (ETH), considering the mesio-distal differences of anterior and posterior permanent teeth and their relationships. Material and Methods: The sample consisted of right-sided standardized radiographs of 34 individuals (21 females and 13 males), aged between 13 and 24 (average 16) years, with all permanent teeth intact and without crowding. Four periapical and four interproximal radiographs were obtained and digitized. ETH measurements (mesial to distal contact points at the dentin-enamel junction) were performed after correction for radiographic image magnification. The Students’ t-test was applied to the differences between paired means, with the Pearson correlation to evaluate the correlation between them. Results: The mesial and distal ETH increased from the anterior to the posterior teeth. Incisor ETH ranged between 0.60 and 0.84 mm. Canines, premolars, and molars were more than 1.0 mm thick, and molar enamel reached values between 1.26 and 1.44 mm. Conclusion: Distal ETH was significantly greater than the mesial ETH, and progressively thicker from the anterior to posterior teeth. Interproximal reduction (IPR) of the lower central and upper lateral incisors should be avoided, reduced, or performed on their distal surfaces. There is a positive and significant correlation between ETH and the mesial and distal surfaces of the teeth. Periapical radiographs and evaluation of the remaining ETH are necessary in cases of retreatment. The location and number of tooth size discrepancies should be considered in treatment planning and appropriately compensated with IPR. RESUMO Objetivo: Este estudo observacional descritivo teve como objetivo determinar dados clinicamente relevantes e aplicáveis da espessura do esmalte (EES), considerando as diferenças mésiodistais dos dentes anteriores e posteriores e suas relações. Material e Métodos: A amostra consistiu em radiografias periapicais padronizadas do lado direito de 34 indivíduos, 21 do sexo feminino e 13 do sexo masculino, com idade entre 13 e 24 anos (média = 16 anos), com todos os dentes permanentes íntegros e sem apinhamento. Quatro radiografias periapicais e quatro radiografias interproximais foram tiradas e digitalizadas. As medidas de EES (dos pontos de contato mesial e distal até a junção dentina-esmalte) foram realizadas após correção para adequar a ampliação da imagem radiográfica. Para as diferenças entre as médias pareadas, foi aplicado o teste t de Student com correlação de Pearson, para avaliar a correlação entre elas. Resultados: A EES mesial e distal aumenta dos dentes anteriores para os posteriores. A EES dos incisivos variou entre 0,6 e 0,84 mm. Caninos, pré-molares e molares apresentaram EES superior a 1,0 mm e a EES dos molares atingiu valores entre 1,26 e 1,44 mm. Conclusão: As EES distais são significativamente maiores que as mesiais e progressivamente mais espessas dos dentes anteriores para posteriores. A redução interproximal do esmalte (RIP) dos incisivos centrais inferiores e laterais superiores deve ser evitada, minimizada ou realizada em suas superfícies distais. Radiografias periapicais e avaliação da EES remanescente são necessárias nos casos de retratamento. A localização e o número de discrepâncias no tamanho dos dentes devem ser determinados e considerados no planejamento do tratamento, para que sejam adequadamente compensados durante o tratamento com RIP.

Background Establishing accurate, reliable, and convenient methods for enamel segmentation and analysis is crucial for effectively planning endodontic, orthodontic, and restorative treatments, as well as exploring the evolutionary patterns of mammals. However, no mature, non-destructive method currently exists in clinical dentistry to quickly, accurately, and comprehensively assess the integrity and thickness of enamel chair-side. This study aims to develop a deep learning work, 2.5D Attention U-Net, trained on small sample datasets, for the automatical, efficient, and accurate segmentation of enamel across all teeth in clinical settings. Methods We propose a fully automated computer-aided enamel segmentation model based on an instance segmentation network, 2.5D Attention U-Net. After data annotation and augmentation, the model is trained using manually annotated segmented enamel data, and its performance is evaluated using the Dice similarity coefficient metrics. A satisfactory image segmentation model is applied to generate a 3D enamel model for each tooth and to calculate the thickness value of individual enclosed 3D enamel meshes using a normal ray-tracing directional method. Results The model achieves the Dice score on the enamel segmentation task of 96.6%. This study provides an intuitive visualization of irregular enamel morphology and a quantitative analysis of three-dimensional enamel thickness variations. The results indicate that enamel is thickest at the incisal edges of anterior teeth and the cusps of posterior teeth, thinning towards the roots. For posterior teeth, the enamel is thinnest at the central fossae area, with mandibular molars having thicker enamel in the central fossae compared to maxillary molars. The average enamel thickness of maxillary incisors, canines, and premolars is greater than that of mandibular incisors, while the opposite is true for molars. Although there are individual variations in enamel thickness, the average enamel thickness graduallly increases from the incisors to the molars among all teeth within the same quadrant. Conclusions This study introduces an automatic, efficient, and accurate 2.5D Attention U-Net system to enhance precise and efficient chair-side diagnosis and treatment of enamel-related diseases in clinical settings, marking a significant advancement in automated diagnostics for enamel-related conditions.