Morphological assessment of modern human upper and lower first molars (original) (raw)
Related papers
A geometric morphometric approach to the study of variation of shovel-shaped incisors
American Journal of Physical Anthropology
Objectives: The scoring and analysis of dental non-metric traits are predominantly 57 accomplished by using the Arizona State University Dental Anthropology System 58 (ASUDAS), a standard protocol based on strict definitions and three-dimensional dental 59 plaques. However, visual scoring, even when controlled by strict definitions of features, 60 visual reference and the experience of the observer, includes an unavoidable part of 61 subjectivity. In this methodological contribution, we propose a new quantitative geometric 62 morphometric approach to quickly and efficiently assess the variation of shoveling in modern 63 human maxillary central incisors (UI1). 64 Materials and Methods: We analyzed 87 modern human UI1s by means of virtual imaging 65 and the ASU-UI1 dental plaque grades using geometric morphometrics by placing 66 semilandmarks on the labial crown aspect. The modern human sample was composed of 67 individuals from Europe, Africa and Asia and included representatives of all seven grades 68 defined by the ASUDAS method. 69 Results: Our results highlighted some limitations in the use of the current UI1 ASUDAS 70 plaque, indicating that it did not necessarily represent an objective gradient of expression of a 71 non-metric tooth feature. Rating of shoveling tended to be more prone to intra-and inter-72 observer bias for the highest grades. In addition, our analyses suggest that the observers were 73 strongly influenced by the depth of the lingual crown aspect when assessing the shoveling. 74 Discussion: In this context, our results provide a reliable and reproducible framework 75 reinforced by statistical results supporting the fact that open scale numerical measurements 76 can complement the ASUDAS method. 77
In archaeology and anthropology, teeth are often the most valuable sources of information owing to their durability, and studies in dental morphology play an important role in not only reconstructing the craniofacial evolution of hominin species, but also in finding links and variances between modern populations from different geographical locations. More so, dietary patterns, environmental adaptations and lifestyles of these individuals can be better understood from dentition. Therefore, there is no doubting the great scope of dental anthropology and its contribution to our understanding of the human past. The current research took a multidisciplinary approach to the study of premolars to gauge into changes in dentition over a period of 3.5 million years. Techniques such as μCT and geometric morphometrics were used to analyse the premolars of two groups. The first comprised Anatomically Modern Humans (AMH) and included Roman, Anglo-Saxon and Modern Human premolars (2012-2014 CE). The second group comprised μCT 3D models of mandibles of 9 hominin species. After reconstructing the μCT images across a number of stages, 3D models of premolars were analysed. Both, computational and linear measurements indicated that there was no significant difference between sexes and age-groups of the Anglo-Saxon and Roman populations. A negative odontometric trend was observed, especially in the first premolars, where Roman premolar crowns were evidently larger than the other two groups. In contrast, a positive odontometric trend was identified in the buccal and lingual crown lengths of lower second premolars where mean scores of modern samples were greater than that of the Anglo-Saxon populations. A significant difference was also seen in the CEJ measurements of lower first premolars between groups. The second group of samples were analysed using exploratory methods. Here, 3D models of hominin mandibles were acquired from various online resources. The crown was sliced at the cemento-enamel junction and then linear measurements were taken. Crown measurements of Roman, Anglo-Saxon and modern human premolars was included when analysing hominin samples as part of the Homo sapiens group. Results suggested that there was a trending significance between the crown measurements of pre-Homo and Homo species. The premolars of pre-Homo species showed greater asymmetry in tooth outlines as well as larger premolars with wider mesio-distal surface. Later Homo species showed more symmetrical outlines with smaller bucco-lingual lengths and mesio-distal widths. H. neanderthalensis showed extreme asymmetry of crown outlines for second lower premolars. An overall negative odontometric trend in the size and shape of premolar crowns was observed between pre-Homo and Homo species. Such a trend was associated with adaptational changes, genetic influences and dietary patterns that have been adopted by hominins over the course of evolution. Future directions were suggested to continue in this line of research as these methods prove to be extremely useful in understanding the evolution of dentition.
International Orthodontics, 2013
Introduction: The aim of this study was to identify an arch form, comprising dentition and alveolus, representative of the Caucasian population, and to compare it with the shape of the main archwires on the market. Materials and methods: The study sample comprised 35 pairs of dental casts, taken from the arches of 35 Southern Europeans with ideal natural occlusion. After the dental casts were scanned, the reference points of the dental arches (FA points) and alveolar bone (WALA ridges) were identified with 3D software. Cartesian coordinates and intercanine and intermolar diameters were calculated for each patient, and curves representing the upper and lower dentition, as well as those showing the shape of the lower supporting bone, were traced and compared with those pertaining to different types of commonly used orthodontic archwires. Results: Ideal shapes of the mandibular alveolus and of the upper and lower archwires were calculated and compared with those actually on the market. Statistical analysis showed significant differences between the two, particularly at the upper and lower molars and canines. Likewise, there were significant differences between the shapes of the available archwires and the WALA ridge, except for the intercanine width.
American Journal of Physical Anthropology, 2018
Objectives: This study aims to explore the affinities of the Sima de los Huesos (SH) population in relation to Homo neanderthalensis, Arago, and early and contemporary Homo sapiens. By characterizing SH intra-population variation, we test current models to explain the Neanderthal origins. Materials and Methods: Three-dimensional reconstructions of dentine surfaces of lower first and second molars were produced by micro-computed tomography. Landmarks and sliding semiland-marks were subjected to generalized Procrustes analysis and principal components analysis. Results: SH is often similar in shape to Neanderthals, and both groups are generally discernible from Homo sapiens. For example, the crown height of SH and Neanderthals is lower than for modern humans. Differences in the presence of a mid-trigonid crest are also observed, with contemporary Homo sapiens usually lacking this feature. Although SH and Neanderthals show strong affinities, they can be discriminated based on certain traits. SH individuals are characterized by a lower intra-population variability, and show a derived dental reduction in lower second molars compared to Neanderthals. SH also differs in morphological features from specimens that are often classified as Homo heidelbergensis, such as a lower crown height and less pronounced mid-trigonid crest in the Arago fossils. Discussion: Our results are compatible with the idea that multiple evolutionary lineages or populations coexisted in Europe during the Middle Pleistocene, with the SH paradigm phylogenetically closer to Homo neanderthalensis. Further research could support the possibility of SH as a separate taxon. Alternatively, SH could be a subspecies of Neanderthals, with the variability of this clade being remarkably higher than previously thought. K E Y W O R D S dental anthropology, European Pleistocene, hominin taxonomy, Neanderthal origins 1 | I N TR ODU C TI ON Teeth are a reliable and important source of information for paleoan-thropological studies because of their abundance and excellent preservation in the fossil record (e.g., Butler, 1963; Larsen and Kelley, 1991). The presence of a phylogenetic signal in their morphology constitutes the basis for the widely accepted use of dental features in researching the evolutionary and taxonomic relationships among 276 |
RESULTS OF THE USE OF 3D SCANNING IN DENTAL ANTHROPOLOGY STUDIES OF THE MODERN POPULATION
Leybova N.A., Chirkova A.K. Results of the use of 3D scanning in dental anthropology studies of the modern population // Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLVIII-2/W3-2023, 151–156, 2023
The article describes results of using a medical intraoral scanner Medit i500 to obtain odontological information in a course of the survey of the modern population in the western regions of the Republic of Tuva within the framework of the complex ethnographic and anthropological expedition of TuvSU-CPI under the leadership of E.V. Aiyzhi. The experience of using this scanner occurred to be very successful. From a technical point of view, the scanner demonstrated high efficiency and productivity due to the high scanning speed. The use of an intraoral scanner opens up wide methodological possibilities in conducting dental anthropology studies: first, the use of digital images for further analysis instead of wax prints, makes it possible to expand the research program by including a number of features of both the lingual and vestibular surfaces of the crowns, and the occlusive one. Secondly, the researcher has the opportunity to accurately fix the sequence and degree of teething of the permanent change, which is very important for determining the correspondence of the "dental" and passport age in children, which ultimately makes it possible to assess the processes of growth and development in the population. Thirdly, it allows us to study in more detail the morphology of the teeth, more accurately assess the severity score of the dental anthropology feature. In addition, thanks to the use of the scanner, we were able to carry out an important methodological study on the analysis of interobserver agreement in the assessment of some dental traits.
The Uniqueness of the Human Anterior Dentition: A Geometric Morphometric Analysis
Journal of Forensic Sciences, 2007
The analysis of bitemarks has a significant bearing on forensic odontology and has attracted an increasingly sophisticated array of techniques in its evaluation. Two postulates underlie all bitemark analyses: firstly, that the characteristics of the anterior teeth involved in the bite are unique, and secondly, that this uniqueness is accurately recorded in the material bitten. Here, we investigate the question of the uniqueness of the anterior dentition. To do this, we use geometric morphometric techniques based on landmark and semilandmark data. The incisor and canine occlusal surfaces of 50 randomly selected orthodontic casts of young individuals (17-20 years) of both sexes form the material for this study. We analyzed the sizes of these teeth by means of landmark and semilandmark analysis to calculate Procrustes distances between tooth outlines. In order to analyze shape variation among individuals, we carried out principal components analyses on the partial warp scores. These are derived from Partial Procrustes coordinates aligned by means of thin-plate spline decomposition based on the bending energy matrix. The results indicate that there is no sexual dimorphism in the shape of the upper or lower arches. Plots of centroid size and first relative warps show less superposition among individuals than in shape analysis. This means that, when the size and shape are considered together, the difference between arches increases. Procrustes superimposition between the two individuals located most closely (0.0444) and the two most separated (0.1567) along the first axis of relative warp analyses show that individuals are not only differentiated by the relative position of their teeth but also by their arch shape. In conclusion, it appears that the incisal surfaces of the anterior dentition are in fact unique.