Stefan Schlager

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Verified

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• Dr.
• Senior Researcher at University of Freiburg

The decrease in pelvic cavity dimensions that accompanied hominin pelvic adaptations for bipedal locomotion led to an obstetrical dilemma that required further pelvic adaptations to accommodate. The timing and morphology of these adaptations is largely unknown due to the hominin fossil record preserving few complete pelves. Most hominin pelvic foss...

Purpose: The aim of the study was to assess the deviation between clinical implant axes (CIA) determined by a surgeon during preoperative planning and reconstructed tooth axes (RTA) of missing teeth which were automatically computed by a previously introduced anatomical SSM. Methods: For this purpose all available planning datasets of single-imp...

Objectives: This study evaluated the accuracy of deep neural patchworks (DNPs), a deep learning-based segmentation framework, for automated identification of 60 cephalometric landmarks (bone-, soft tissue- and tooth-landmarks) on CT scans. The aim was to determine whether DNP could be used for routine three-dimensional cephalometric analysis in di...

Background: This study evaluated the accuracy of computer-assisted surgery (CAS)-driven DCIA (deep circumflex iliac artery) flap mandibular reconstruction by traditional morphometric methods and geometric morphometric methods (GMM). Methods: Reconstruction accuracy was evaluated by measuring distances and angles between bilateral anatomical land...

Purpose Morphological variability of the skull is an important consideration for cranioplasty and implant design. Differences in morphology of the skull based on the ethnicity are known. In a previous study we could show the accuracy and benefits of virtual reconstructions based on a statistical shape model (SSM) for neurocranial defects. As the SS...

Purpose: Modern virtual implant planning is a time-consuming procedure, requiring a careful assessment of prosthetic and anatomical factors within a three-dimensional dataset. In order to facilitate the planning process and provide additional information, this study examines a statistical shape model (SSM) to compute the course of dental roots bas...

Adequate soft-tissue dimensions have been shown to be crucial for the long-term success of dental implants. To date, there is evidence that placement of dental implants should only be conducted in an area covered with attached gingiva. Modern implant planning software does not visualize soft-tissue dimensions. This study aims to calculate the cours...

A course about structuring, managing and archiving research data collected from human skeletons. We are currently conceptualising a course on creation and management of osteological research data. We would like to cover general aspects of research data management, introduce data models and their formulation and help participants to structure their...

Purpose: Creating wax-ups of missing teeth for backward-planning in implant surgery is a complex and time-consuming process. To facilitate implant-planning procedures, the automatic generation of a virtual wax-up would be useful. In this study, the reconstruction of missing teeth in partially edentulous patients was performed automatically using a...

Purpose: The known preformed osteosynthesis plates for the midface are helpful tools for a precise and fast fixation of repositioned fractures. The purpose of the current study is to analyze the precision of newly developed prototypes of preformed osteosynthesis plates for the mandible. Methods: Four newly designed preformed osteosynthesis plate...

Background Complex bilateral midface fractures necessitate a surgically challenging procedure to preserve or restore the occlusion and the sensitive eye area. In this case control study, we aim to show the potential of a statistical shape model (SSM) for measuring the quality of the midface reconstruction, compared to the estimated preoperative sit...

Purpose: The current standard in reconstructing defects of the orbital floor, by using the concept of mirroring, is time-consuming and ignores the natural asymmetry of the skull. By using a statistical shape model (SSM), the reconstruction can be automatized and improved in accuracy. The present study aims to show the possibilities of the virtual...

The ongoing COVID-19 pandemic has revealed alarming shortages of personal protective equipment for frontline healthcare professionals and the general public. Therefore, a 3D-printable mask frame was developed, and its air seal performance was evaluated and compared. Personalized masks (PM) based on individual face scans (n = 8) and a statistically...

Statement of problem: The accuracy of intraoral scanners is a prerequisite for the fabrication of dental restorations in computer-aided design and computer-aided manufacturing (CAD-CAM) dentistry. While the precision of intraoral scanners has been investigated in vitro, clinical data on the accuracy of intraoral scanning (IOS) are limited. Purpos...

Genetic and climate-driven estimates of past population dynamics are increasingly influential in broader models of hominin migration and adaptation, yet the contribution of stone artifact variability remains more contentious. Scientists are increasingly recognizing the potential of unretouched stone flakes ('flakes') in exploring existing models of...

Warfare is assumed to be one of the defining cultural characteristic of steppe nomads in Eastern Eurasia, with high levels of violence used by Classical and Chinese historiographers as markers of cultural "otherness" when describing these societies. Especially for the first centuries AD, these interpretive hampers more nuanced reconstructions of th...

Objectives Warfare is assumed to be one of the defining cultural characteristics of steppe nomads in Eastern Eurasia. For the first‐centuries CE, a period of political turmoil in Northern China and Southern Siberia, relatively few data are, however, available about the degree and variability of violence in these communities. Here, we provide new da...

Objectives Understanding thoraco‐pelvic integration in Homo sapiens and their closest living relatives (genus Pan) is of great importance within the context of human body shape evolution. However, studies assessing thoraco‐pelvic covariation across Hominoidea species are scarce, although recent research would suggest shared covariation patterns in...

The skeletal torso is a complex structure of outstanding importance in understanding human body shape evolution, but reconstruction usually entails an element of subjectivity as researchers apply their own anatomical expertise to the process. Among different fossil reconstruction methods, 3D geometric morphometric techniques have been increasingly...

Background Complex bilateral midface fractures necessitate a surgically challenging procedure to preserve or restore the occlusion and the sensitive eye area. In this case control study, we aim to show the potential of a statistical shape model (SSM) for measuring the quality of the midface reconstruction, compared to the estimated preoperative sit...

Standardisation of research data helps to increase their comprehensibility, traceability and reproducibility. It supports aggregation of large databases as the compatibility of data items can be assessed and the reliability of information scrutinised. Standardised data are a prerequisite for the analysis of large bodies of data contributed by multi...

This chapter overviews the theoretical basics of geometric morphometrics (GM) and reviews its potential for the study of hominin vertebrae and vertebral columns. We show that challenges are related to seriality and the metameric nature of the spine. Measuring a series of vertebrae is a time-consuming process because the necessary sample sizes need...

Definition of aims and scope of the workgroup. The document fulfils a requirement for the formation of workgroups set by §8.1 of the GfA statutes and was part of the application to the members‘ meeting 2019 in Göttingen. Standardisation of digital research data is increasingly recognised as an issue in biological anthropology. It is related to tra...

3D Data Acquisition for Bioarchaeology, Forensic Anthropology, and Archaeology serves as a handbook for the collection and processing of 3-D scanned data and as a tool for scholars interested in pursuing research projects with 3-D models. The book's chapters enhance the reader’s understanding of the technology by covering virtual model processing p...

3D Data Acquisition for Bioarchaeology, Forensic Anthropology, and Archaeology serves as a handbook for the collection and processing of 3-D scanned data and as a tool for scholars interested in pursuing research projects with 3-D models. The book's chapters enhance the reader’s understanding of the technology by covering virtual model processing p...

Several important algorithms for machine learning and data analysis use pairwise distances as input. On Riemannian manifolds these distances may be prohibitively costly to compute, in particular for large datasets. To tackle this problem, we propose a distance approximation which requires only a linear number of geodesic boundary value problems to...

Purpose: Mirroring and manual adaptation as the main virtual reconstruction method of midfacial defects is time demanding and ignores asymmetrical skull shapes. By using a statistical shape model (SSM), the reconstruction can be automatized and specified. The current study aims to show the ability of the SSM in the virtual reconstruction of artifi...

Introduction: There has been a shift toward surgical treatment of ZMC (zygomaticomaxillary complex) fractures with open reduction and subsequent fixation in the past decades. Anatomically preformed osteosynthesis plates, already used in the field of craniomaxillofacial surgery for the treatment of fractures of the mandible and the orbit, might be...

A fundamental impediment to the adoption of digital standards in physical anthropology is the vast diversity of this area of research. Even within osteology, many investigations require some modification of existing standards to suit their specific study designs. This might be a reason for researchers not to use database software based exclusively...

Introduction: Fractures of the mandibular condyle are reported to account for 9 %-45 % of all mandibular fractures. There has been a long lasting controversy on the superiority of different treatment options with endoscopic-assisted transoral approaches gaining increasing attention in recent years. In this article, we report the application of a n...

The archaeological record represents a window onto the complex relationship between stone artefact variance and hominin behaviour. Differences in the shapes and sizes of stone flakes—the most abundant remains of past behaviours for much of human evolutionary history—may be underpinned by variation in a range of different environmental and behaviour...

From its initial appearance at ~1.7 Ma, the Acheulean was prevalent through a vast chronological span of hominin behavioural evolution that lasted nearly 1.5 million years. The origins and production patterns of large bifacial cutting tools ('LCTs') e the marker of the Acheulean techno-complex e and the systematic changes in this behaviour through...

From its initial appearance at ~1.7 Ma, the Acheulean was prevalent through a vast chronological span of hominin behavioural evolution that lasted nearly 1.5 million years. The origins and production patterns of large bifacial cutting tools ('LCTs') e the marker of the Acheulean techno-complex e and the systematic changes in this behaviour through...

Background Botulinum toxin treatment for forehead wrinkles has been extensively studied and found to be a safe and reproducible procedure. However, the effect on the position of the eyebrows which relies on the dynamic positioning of the treated muscles has received less attention and has not been studied with 3D technology. Objectives To evaluate...

Determining maximum heating temperatures of burnt bones is a long‐standing problem in forensic science and archaeology. In this pilot study, controlled experiments were used to heat 14 fleshed and defleshed pig vertebrae (wet bones) and archaeological human vertebrae (dry bones) to temperatures of 400, 600, 800, and 1000°C. Specular component inclu...

Video tutorial showing how to build a complete human endocast in few minutes.

Many fossil specimens exhibit deformations caused by taphonomic processes. Due to these deformations, even important specimens have to be excluded from morphometric analyses, impoverishing an already poor paleontological record. Techniques to retrodeform and virtually restore damaged (i.e. deformed) specimens are available, but these methods genene...

This supplementary material provides the code and data to reproduce the results from our artificial case study using a virtually deformed Gorilla gorilla cranium. (ZIP)

The mathematical/statistical software platform R has seen an immense increase in popularity within the last decade. Its main advantages are its flexibility, a large repository of freely available extensions, its open-source nature and a thriving community. This tutorial gives an introduction into landmark/surface-mesh based statistical shape analys...

Objectives We present two new automatic tools, developed under the R environment, to reproduce the internal and external structures of bony elements. The first method, Computer‐Aided Laser Scanner Emulator (CA‐LSE), provides the reconstruction of the external portions of a 3D mesh by simulating the action of a laser scanner. The second method, Auto...

Purpose: Virtual reconstruction of large cranial defects is still a challenging task. The current reconstruction procedures depend on the surgeon's experience and skills in planning the reconstruction based on mirroring and manual adaptation. The aim of this study is to propose and evaluate a computer-based approach employing a statistical shape m...

The Ceprano calvarium was discovered in fragments on March 1994 near the town of Ceprano in southern Latium (Italy), embedded in Middle Pleistocene layers. After reconstruction, its morphological features suggests that the specimen belongs to an archaic variant of H. heidelbergensis, representing a proxy for the last common ancestor of the divergin...

The frontal bone is one of the most sexually dimorphic elements of the human skull, due to features such as the glabella, frontal eminences, and frontal inclination. While glabella is frequently evaluated in procedures to estimate sex in unknown human skeletal remains, frontal inclination has received less attention. In this study we present a stra...

In recent years, the use of CT-scans in physical anthropology yielded huge improvements of the analysis of skeletal remains. Such process made the “virtual anthropology” one of the most important approaches in the study of human evolution and bioarcheology. The virtual reproduction of inner volumes has become a frequent procedure for studying the i...

Stone tools, often the sole remnant of prehistoric hunter-gatherer behavior, are frequently used as evidence of ancient human mobility, resource use, and environmental adaptation. In North America, studies of morphological variation in projectile points have provided important insights into migration and interactions of human groups as early as 12–...

A fundamental impediment to the adoption of digital standards in physical anthropology is the vast diversity of this area of research. Even within osteology, many investigations require some modification of existing standards to suit their specific study designs. This might be a reason for researchers not to use database software based exclusively...

Operations on triangular meshes based on 'VCGLIB'. This package integrates nicely with the R-package 'rgl' to render the meshes processed by 'Rvcg'. The Visualization and Computer Graphics Library (VCG for short) is an open source portable C++ templated library for manipulation, processing and displaying with OpenGL of triangle and tetrahedral mesh...

A toolset for Geometric Morphometrics and mesh processing. This includes (among other stuff) mesh deformations based on reference points, permutation tests, detection of outliers, processing of sliding semi-landmarks and semi-automated surface landmark placement.

Background. Facial rejuvenation is an expanding field with an increasing number of treatment modalities. Several non-autologous filler materials are available for soft tissue augmentation. Calcium hydroxylapatite (CaOH) is aimed at increasing collagen neosynthesis and thereby producing long term augmentation effects. Despite a multitude of observat...

The human zygomatic structure, consisting of the zygomatic bone and the zygomatic process of the temporal bone, is an essential part of the masticatory apparatus and has been shown to reflect population history and sexual dimorphism to varying degrees. In this study, we analyzed the predictive value of the outlines vs. the complete surface shape of...

Intentional cranial deformations (ICD) were obtained by exerting external mechanical constraints on the skull vault during the first years of life to permanently modify head shape. The repercussions of ICD on the face are not well described in the midfacial region. Here we assessed the shape of the zygomatic bone in different types of ICDs. We cons...

Purpose: This study evaluates the accuracy of a statistical shape model (SSM) for virtual fracture reconstruction of the lateral midface. Materials and methods: A uniform bony defect of the right zygoma was created. A virtual reconstruction was performed by using the standard procedure of mirroring the unaffected to the affected side (Group I) a...

Background Few data are available regarding blood loss during cleft palate surgery. This study assessed the effect of using tranexamic acid in the reduction of intraoperative bleeding. Methods A double-blind, randomized clinical trial compared intraoperative bleeding and the incidence of oronasal fistulas after palatoplasties in a control group th...

Assessing drivers of stone flake variability with geometric morphometrics

A toolset for Geometric Morphometrics and mesh rocessing. This includes (among other stuff) mesh deformations based on reference points, permutation tests, detection of outliers, processing of sliding semi-landmarks and semi-automated surface landmark placement.

Operations on triangular meshes based on ’VCGLIB’. This package integrates nicely with the R-package ’rgl’ to render the meshes processed by ’Rvcg’. The Visualization and Computer Graphics Library (VCG for short) is an open source portable C++ templated library for manipulation, processing and displaying with OpenGL of triangle and tetrahedral mesh...

Variability in early Acheulean technology in East Turkana, Koobi Fora, Kenya

By accompanying human travels since prehistorical times, the house mouse dispersed widely throughout the world, and colonized many islands. The origin of the travellers determined the phylogenetic source of the insular mice, which encountered diverse ecological and environmental conditions on the various islands. Insular mice are thus an exceptiona...

Operations on triangular meshes based on 'VCGLIB'. This package integrates nicely with the R-package 'rgl' to render the meshes processed by 'Rvcg'. The Visualization and Computer Graphics Library (VCG for short) is an open source portable C++ templated library for manipulation, processing and displaying with OpenGL of triangle and tetrahedral mesh...

Calculations and Visualisations Related to Geometric Morphometrics

Images in paleoanthropology are of persuasive power, since they try to illuminate ancient life which is not otherwise visually documented. The scientific community, as well as public media and museums, aim to establish a window into the past in part through visualization of scenarios from prehistoric life and environments. The role of human ancesto...

Standardisation and digital processing of osteological data is a growing concern in physical anthropology. Coding standards (e. g. Buikstra & Ubelaker 1994, GHHP Code Book 2006, Harbeck 2014) are being developed and implemented in software applications (e. g. OsteoWare, AnthroBook). These infrastructures progressively allow for large-scale analyses...

For identifying shape changes in the human mandible associated with age, two factors were considered: shape changes associated with tooth-loss and general aging. Using CT-scans, automated landmark and surface mesh extraction of the mandible was performed on 115 individuals from Germany and China. As the Chinese individuals were only little affected...

Description Operations on triangular meshes based on VCGLIB. This package integrates nicely with the R-packagèrgl'' to render the meshes processed by Rvcg. The Visualization and Computer Graphics Library (VCG for short) is an open source portable C++ templated library for manipulation, processing and displaying with OpenGL of triangle and tetrahedr...

In this study, the shape of the outer osseous nose in a German and a Chinese sample is analyzed using a dense set of semi-landmarks. Shape differences related to population and sex as well as directional and fluctuating asymmetry were statistically evaluated and also visualized. Shape differences in the bony nose were investigated between a large s...

In Physical Anthropology, an increasing number of studies relies on large amounts of data. Standards and software tools for structured data collection are being developed. As a consequence, volumes of digital data accumulate on various systems, but pooling these sources remains complicated and time-consuming. We propose a digital standard for the r...

Operations on triangular meshes based on VCGLIB. This package integrates nicely with the R-package "rgl'' to render the meshes processed by Rvcg.

A toolset for Geometric Morphometrics and mesh processing. This includes (among other stuff) mesh deformations based on reference points, permutation tests, detection of outliers, processing of sliding semi-landmarks and semi-automated surface landmark placement.

External impact to the orbit may cause a blowout or zygomatico-maxillary fractures. Diagnosis and treatment of orbital wall fractures are based on both physical examination and computed tomography scan of the orbit. Injuries of the orbit often require a reconstruction of its orbital walls. Using computer-assisted techniques, anatomically preformed...

Rvcg provides function for operations on triangular meshes based on VCGLIB. This package integrates nicely with the R-package "rgl'' to render the meshes processed by Rvcg. Source code and compiled package are available from http://cran.r-project.org/web/packages/Rvcg/index.html and https://github.com/zarquon42b/Rvcg

In Geometric Morphometrics, most methods are applied on sparse sets of homologous landmarks, manually placed on the structures to be analysed. The drawbacks of manual landmark placement are evident: though modern digital imaging provides very accurate surface representations of biological structures, there are few landmarks that are well-defined an...

The zygomatic bone is an important element of the viscerocranium. Several muscles attach here, and its shape has a marked effect on facial appearance. As a consequence, shape variation of the zygomatic bone is crucial in forensic facial reconstruction, reconstructive surgery and evolutionary studies. We analysed the shape of the zygomatic bone in 2...

Digital impression devices are used alternatively to conventional impression techniques and materials. The aims of this study were to evaluate the precision of digital intraoral scanning under clinical conditions (iTero; Align Technologies, San Jose, Calif) and to compare it with the precision of extraoral digitization. One patient received 10 full...

Forensic cases where corpses remain unidentified, call for cranio-facial reconstructions (CFR) to provide the media with material that might trigger recognition among those that used to be acquainted with the deceased. The task of reconstructing the face from the skull is usually done by an expert based on her/his knowledge and understanding of the...

In Geometric Morphometrics, most methods are applied on sparse sets of homologous landmarks, manually placed on the structures to be analysed. The drawbacks of manual landmark placement are evident: though modern digital imaging provides very accurate surface representations of biological structures, there are few landmarks that are well-defined an...

The zygomatic bone is an important element of the viscerocranium. Several muscles attach here, and its shape has a marked effect on facial appearance. As a consequence, shape variation of the zygomatic bone is crucial in forensic facial reconstruction, reconstructive surgery and evolutionary studies. We analysed the shape of the zygomatic bone in...

Analysing the symmetry/asymmetry of biologcial structures has entered the morphometric toolbox more than a decade ago. It allows the quantification and evaluation of directional and fluctuating asymmetry. Additionally, the application of semi-landmarks makes geometric analysis of structures possible where homologous landmarks can only be placed ver...