Virtual reconstruction of cranial remains : the H. Heidelbergensis, Kabwe 1 fossil

Human skeletal remains and fossils are often fragmented and distorted, limiting further research. Thus, reconstruction has long been used to restore the original morphology of specimens and enable subsequent research. With advances in computing and imaging, virtual reconstruction approaches are increasingly being applied to this task. Thus, models of fragmentary remains are increasingly being reconstructed from medical images, using visualization software and geometric morphometric techniques to repair defects and restore symmetry. In this chapter we review some virtual reconstruction techniques and provide a description of CT based virtual reconstruction applied to a fossil hominin, the Kabwe 1 cranium. This specimen is dated from 150 - 250 thousand years ago and was reconstructed to enable further biomechanical research, however the approaches and tools used to make the reconstruction are directly applicable to more recent skeletal remains

Recent hominim cranial form and function

This thesis aims to assess if biting mechanics drives craniofacial morphology in recent hominins. To that end, a virtual functional morphology toolkit, that includes Finite Element Analysis (FEA) and Geometric Morphometrics (GM), is used to simulate biting, measure bite force and quantify deformations arising due to simulated biting in Homo sapiens and its proposed ancestral species, Homo heidelbergensis. Moreover, the mechanical significance of the frontal sinus and of the brow-ridge is also assessed in Kabwe 1 (a Homo heidelbergensis specimen). The frontal sinus is examined by comparing the mechanical performance in three FE models with varying sinus morphology. A similar approach is applied to the brow-ridge study. This approach relies on the assumption that FEA approximates reality. Thus, a validation study compares the deformations experienced by a real cranium under experimental loading with those experienced by an FE model under equivalent virtual loading to verify this assumption. A sensitivity analysis examines how simplifications in segmentation impact on FEA results. Lastly, the virtual reconstruction of Kabwe 1 is described.Results show that prediction of absolute strain magnitudes is not precise, but the distribution of regions of larger and smaller (i.e. pattern of) deformations experienced by the real cranium is reasonably approximated by FEA, despite discrepancies in the alveolus. Simplification of segmentation stiffens the model but has no impact on the pattern of deformations, with the exception of the alveolus. Comparison of the biting performance of Kabwe 1 and H. sapiens suggests that morphological differences between the two species are likely not driven by selection of the masticatory system. Frontal sinus morphogenesis and morphology are possibly impacted by biting mechanics in the sense that very low strains are experienced by this region. Because bone adapts to strains, the frontal sinus is possibly impacted by this mechanism. Lastly, biting mechanics has limited impact on brow-ridge morphology and does not explain fully the enormous brow-ridge of Kabwe 1. Hence, other explanations are necessary to explain this prominent feature

Testing the reliability of CT scan‐based dental wear magnitude scoring

Objectives: Digital models are now frequently used in biological anthropology (bio anthropology) research. Despite several studies validating this type of research, none has examined if the assessment of dental wear magnitude based on Computerized Tomography (CT) scans is reliable. Thus, this study aims to fill this gap and assess if dental wear magnitude scoring based on CT scans provides results consistent with scoring based on direct observation of the physical specimens. Materials and Methods: Dental wear magnitude from 412 teeth of 35 mandibles originating from the Portuguese Muge and Sado Mesolithic shell-middens was scored. The mandibles were also CT scanned and visualized using 3D Slicer. CT scan based scoring of dental wear magnitude was then undertaken. Two scoring rounds were undertaken for each observation method (totaling four scoring rounds) and an intra-observer error test was performed. The averaged results of the two observation methods were compared via boxplots with paired cases. Results: Intra-observer error was negligible and non-significant. Scoring results are comparable between the two observation methods. Notwithstanding, some differ ences were found, in which CT scan assessment generally overestimates dental wear when compared to direct observation. Discussion: Our results generally validate the use of CT scans in studies of dental wear magnitude. Notwithstanding several caveats relating to CT scanning and visualization limitations should be considered to avoid over or under-estimation of dental wear.ALG-01-0145-FEDER-29680, 57/2016/CP1361/CT0029info:eu-repo/semantics/publishedVersio

Mesolithic and chalcolithic mandibular morphology: using geometric morphometrics to reconstruct incomplete specimens and analyse morphology

Human skeletal remains are routinely used to examine cultural and biological aspects of past populations. Yet, archaeological specimens are frequently fragmented/incomplete and so excluded from analyses. This leads to decreased sample sizes and to potentially biased results. Digital methods are now frequently used to restore/estimate the original morphology of fragmented/incomplete specimens. Such methods include 3D digitisation and Geometric Morphometrics (GM). The latter is also a solidly established method now to examine morphology. In this study, we use GM-based methods to estimate the original morphology of incomplete Mesolithic and Chalcolithic mandibles originating from present Portugal and perform ensuing morphological analyses. Because mandibular morphology is known to relate to population history and diet, we hypothesised the two samples would differ. Thirty-seven specimens (12 complete and 25 incomplete) were CT-scanned and landmarked. Originally complete specimens were used as reference to estimate the location of absent anatomical landmarks in incomplete specimens. As predicted, our results show shape differences between the two samples which are likely due to the compounded effect of contrasting population histories and diets.info:eu-repo/semantics/publishedVersio

Changes in dental wear magnitude in the last ∼8000 years in southwestern Iberia

Objective: This study examines changes in dental wear magnitude in the past -8000 years, i.e., since Mesolithic until the 19th century, in southwestern Iberia. Thus, it encompasses the transition from hunting-gathering to agro-pastoralism, and then to the industrialization of food production and pre-processing. Design: Dental wear magnitude was scored in a total of 191 individuals and 1557 teeth from Mesolithic (individuals=56; teeth=643), Neolithic (individuals=35; teeth=169), Chalcolithic (individuals =35; teeth=221), Modern Age (individuals=17; teeth=209), and Late Modern Age (individuals=48; teeth=315) samples originating in southwestern Iberia (i.e., present central and southern Portugal) and according to the 8 levels ordinal scale of Smith (1984). Results: Results show a general trend for decreased wear magnitude in these two major transitions and during this timespan (although the hunting-gathering - agro-pastoralism transition had larger impact). The only meaningful differences in wear rate were found between the Late Modern Age and all remaining samples. Conclusion: Dental wear generally decreased during this timespan (although wear magnitude was less impacted by the industrialization of food production and pre-processing). Our results are consistent with studies documenting skull morphological gracilization associated with reduced masticatory demands due to the adoption of softer diets.ALG-01-0145-FEDER29680;info:eu-repo/semantics/publishedVersio

The biomechanical significance of the frontal sinus in Kabwe 1 (Homo heidelbergensis)

Paranasal sinuses are highly variable among living and fossil hominins and their function(s) are poorly understood. It has been argued they serve no particular function and are biological 'spandrels’ arising as a structural consequence of changes in associated bones and/or soft tissue structures. In contrast, others have suggested that sinuses have one or more functions, in olfaction, respiration, thermoregulation, nitric oxide production, voice resonance, reduction of skull weight, and craniofacial biomechanics. Here we assess the extent to which the very large frontal sinus of Kabwe 1 impacts on the mechanical performance of the craniofacial skeleton during biting. It may be that the browridge is large and the sinus has large trabecular struts traversing it to compensate for the effect of a large sinus on the ability of the face to resist forces arising from biting. Alternatively, the large sinus may have no impact and be sited where strains that arise from biting would be very low. If the former is true, then infilling of the sinus would be expected to increase the ability of the skeleton to resist biting loads, while removing the struts might have the opposite effect. To these ends, finite element models with hollowed and infilled variants of the original sinus were created and loaded to simulate different bites. The deformations arising due to loading were then compared among different models and bites by contrasting the strain vectors arising during identical biting tasks. It was found that the frontal bone experiences very low strains and that infilling or hollowing of the sinus has little effect on strains over the cranial surface, with small effects over the frontal bone. The material used to infill the sinus experienced very low strains. This is consistent with the idea that frontal sinus morphogenesis is influenced by the strain field experienced by this region such that it comes to lie entirely within a region of the cranium that would otherwise experience low strains. This has implications for understanding why sinuses vary among hominin fossils

Finite element analysis of the cranium : Validity, sensitivity and future directions

Finite element analysis (FEA) is increasingly applied in skeletal biomechanical research in general, and in fossil studies in particular. Underlying such studies is the principle that FEA provides results that approximate reality. This paper provides further understanding of the reliability of FEA by presenting a validation study in which the deformations experienced by a real cadaveric human cranium are compared to those of an FE model of that cranium under equivalent simulated loading. Furthermore, model sensitivity to simplifications in segmentation and material properties is also assessed. Our results show that absolute deformations are not accurately predicted, but the distribution of the regions of relatively high and low strains, and so the modes of global deformation, are reasonably approximated

Geometric morphometrics and finite elements analysis : Assessing the functional implications of differences in craniofacial form in the hominin fossil record

The study of morphological variation in the hominin fossil record has been transformed in recent years by the advent of high resolution 3D imaging combined with improved geometric morphometric (GM) toolkits. In parallel, increasing numbers of studies have applied finite elements analysis (FEA) to the study of skeletal mechanics in fossil and extant hominoid material. While FEA studies of fossils are becoming ever more popular they are constrained by the difficulties of reconstruction and by the uncertainty that inevitably attaches to the estimation of forces and material properties. Adding to these modelling difficulties it is still unclear how FEA analyses should best deal with species variation.Comparative studies of skeletal form and function can be further advanced by applying tools from the GM toolkit to the inputs and outputs of FEA studies. First they facilitate virtual reconstruction of damaged material and can be used to rapidly create 3D models of skeletal structures. Second, GM methods allow variation to be accounted for in FEA by warping models to represent mean and extreme forms of interest. Third, GM methods can be applied to compare FEA outputs - the ways in which skeletal elements deform when loaded. Model comparisons are hampered by differences in material properties, forces and size among models but how deformations from FEA are impacted by these parameters is increasingly well understood, allowing them to be taken into account in comparing FEA outputs.In this paper we review recent advances in the application of GM in relation to FEA studies of craniofacial form in hominins, providing examples from our recent work and a critical appraisal of the state of the art

Is enamel the only reliable hard tissue for sex metric estimation of burned skeletal remains in biological anthropology?

Sex diagnosis is a crucial element in the analysis of skeletal remains from forensic and archaeological contexts. Thus, researchers have developed several methods using different anatomical regions to estimate sex. Despite such variety of methods, sexing of collective cremated human skeletal remains is still challenging due to heat-induced size changes and fragmentation, along with the typical commingling of collective contexts. This study aims to examine the potential of burned tooth crowns for odontometric sex estimation. To that end, heat-induced size changes were quantified in experimentally heated teeth. Then, odontometric sex estimation was performed in a set of theoretical samples of pre and post-heated tooth crowns. Results show heated tooth crowns undergo variable but consistent and statistically significant expansion, which is due to micro-fracturing. Such heat induced size changes are of sufficient magnitude to impact odontometric sex diagnosis and sex ratios of the theoretical samples. Yet, sexing using heated/burned tooth crowns may still be useful to estimate the minimum number of females in a given sample. Further, the effect of heat-induced size changes may be calculated and removed using mu CT scanning.Portuguese Foundation for Science and TechnologyPortuguese Foundation for Science and Technology [SFRH/BPD/84268/2012, SFRH/BD/139158/2018, UID/MULTI/00070/2013, PTDC/EPH-ARQ/0798/2014, PTDC/IVC-ANT/1201/2014, POCI-01-0145-FEDER016766, PEst-OE/SADG/UI0283/2013][UID/ECI/04028/2013]info:eu-repo/semantics/publishedVersio

Nutritional and motor functional status in Parkinson’s disease: the NutriSPark protocol

Communication abstract: Proceedings of the 5th International Congress of CiiEM - Reducing inequalities in Health and Society, held at Egas Moniz’ University Campus in Monte de Caparica, Almada, from June 16th to 18th, 2021.This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.A growing body of evidence suggests that nutritional status may play an important role in the development and course of Parkinson’s disease (PD). Nutritional status is known to influence PD motor and non-motor features and is in turn influenced by disease duration and severity. A proper nutritional status assessment and intervention should be incorporated in the management and follow-up of PD patients. This study aims to characterize the impact of nutritional status in multiple domains of PD and to explore the feasibility and the effectiveness of a customized and intensive nutritional intervention compared to standard care.info:eu-repo/semantics/publishedVersio