Christine Couture

Human tooth wear in the past and the present: Tribological mechanisms, scoring systems, dental and skeletal compensations

This review of human tooth wear describes the fundamental mechanisms underlying this process. Using the tribological approach they can be systematised and this in turn aids our understanding of them. In past populations wear was ubiquitous, intense, abrasive and physiological as it was related to their food and their technologies. In these populations, it affected the proximal surfaces, and the occlusal surfaces which modified the occlusal plane profoundly. To categorise this wear many different classification systems are used, from which we can determine diet, cultural changes and the age at death of individuals. They also illustrate the evolution of certain functional dental and skeletal compensations in the masticatory apparatus such as continuous dental eruption, mesial drift of the arches and incisor lingual tipping which can then be monitored. These physiological adaptations related mainly to function and ontogenesis can also be found in present-day populations where wear is moderate, although they are much less obtrusive. Apart from certain pathological cases associated with a specific parafunction, iatrogenic tooth brushing or an eating disorder and encouraged by an acid environment, they are the result of a physiological process that should not be halted. To ensure this, it is essential to prevent lesions related to tooth wear, to detect them early and establish a reliable diagnosis. Types of tooth wear that had remained unchanged since the origin of humanity have undergone profound changes in a very short space of time. Todays tribochemical pathological model has replaced the abrasive physiological model of the past.

3D MR image analysis of the morphology of the rear foot: application to classification of bones

The purpose of this work is to characterize the three-dimensional (3D) morphology of the bones of the rear foot using MR image data. It has two sub-aims: (i) to study the variability of the various computed architectural measures caused by the subjectivity and variations in the various processing operations; (ii) to study the morphology of the bones included in the peritalar complex. Each image data set utilized in this study consists of sixty sagittal slices of the foot acquired on a 1.5 T commercial GE MR system. The description of the rear foot morphology is based mainly on the principal axes, which represent the inertia axes of the bones, and on the bone surfaces. We use the live-wire method [Falcao AX, Udupa JK, Samarasekera S, Shoba S, Hirsch BE, Lotufo RA. User-steered image segmentation paradigms: live wire and live lane. Proceedings of the Society of Photo-optical Instrumentation Engineers 1996;2710:278-288] for segmenting and forming the surfaces of the bones. In the first part of this work, we focus on the analysis of the dependence of the principal axes system on segmentation and on scan orientation. In the second part, we describe the normal morphology of the rear foot considering the four bones namely calcaneus, cuboid, navicular, and talus, and compare this to a population from the upper Pleistocene. We conclude that this non-invasive method offers a unique tool to characterize the bone morphology in live patients towards the goal of understanding the architecture and kinematics of normal and pathological joints in vivo.

Anatomical Placement of the Human Eyeball in the Orbit—Validation Using CT Scans of Living Adults and Prediction for Facial Approximation*

Abstract:  Accuracy of forensic facial approximation and superimposition techniques relies on the knowledge of anatomical correlations between soft and hard tissues. Recent studies by Stephan and collaborators (6,8,10) reviewed traditional guidelines leading to a wrong placement of the eyeball in the orbit. As those statements are based on a small cadaver sample, we propose a validation of these findings on a large database (n = 375) of living people. Computed tomography scans of known age and sex subjects were used to collect landmarks on three‐dimensional surfaces and DICOM with TIVMI. Results confirmed a more superior and lateral position of the eyeball relatively to the orbital rims. Orbital height and breadth were used to compute regression formulae and proportional placement using percentages to find the most probable position of the eyeball in the orbit. A size‐related sexual dimorphism was present but did not impact on the prediction accuracy.

Type-Constrained Robust Fitting of Quadrics with Application to the 3D Morphological Characterization of Saddle-Shaped Articular Surfaces

The scope of this paper is the guaranteed fitting of specified types of quadratic surfaces to scattered 3D point clouds. Since we chose quadrics to account for articular surfaces of various shapes in medical images, the models thus estimated usefully extract global symmetry-related intrinsic features in human joints: centers, axes, extremal curvatures. The unified type-enforcing method is based on a constrained weighted least-squares minimization of algebraic residuals which uses a robust and bias- corrected metric. Provided that at most one quadratic constraint is involved, every step produces closed-form eigenvector solutions. In this framework, guaranteeing the occurrence of 3D primitives of certain types among this eigendecomposition is not a straightforward transcription of the priorly handled 2D case. To explore possibilities, we re-exploit a mapping to a 2D space called the quadric shape map (QSM) where the influence of any constraint on shape and type can in fact be studied visually. As a result, we provide a new enforceable quadratic constraint that practically ensures types such as hyperboloids, which helps characterize saddle-like articular surfaces. Application to a database shows how this guarantee is needed to coherently extract the center and axes of the ankle joint.

Endostructural Characterisation of the Regourdou 1 Neanderthal Proximal Arm: Bilateral Asymmetry and Handedness

Cross-sectional properties of long bones are commonly used for reconstructing mechanical loading histories related to locomotion, subsistence strategies, manipulative behavior. In this respect, a significant degree of functional bilateral asymmetry of the proximal arm, likely related to unilateral activity levels, has been reported for Neanderthals.

Ancient mitochondrial DNA from the middle neolithic necropolis of Obernai extends the genetic influence of the LBK to west of the Rhine

OBJECTIVES The arrival of Neolithic farmers in Europe was the source of major cultural and genetic transitions. Neolithic settlers brought a new set of maternal lineages (mitochondrial DNA), recently well-characterized on the continental road, from the Balkans to West Germany (Rhine River). In the present study, the first mitochondrial DNA data from groups associated with this continental expansion wave located west of the Rhine River has been provided and their genetic affinities with contemporary groups have been discussed. MATERIAL AND METHODS The mitochondrial DNA analysis of 27 human remains originating from Obernai (5,000-4,400 cal. BC), a necropolis located in French Alsace Region and attributed to Grossgartach, Planig-Friedberg, and Roessen cultures was conducted. RESULTS AND DISCUSSION Among the 27 individuals studied, 15 HVR-I sequences and 17 mitochondrial haplogroups could be determined. The analysis of the Obernai gene pool clearly confirmed the genetic homogeneity of Linearbandkeramik (LBK) groups on both sides of the Rhine River. Notably, one N1a sequence found in Obernai is shared with LBK farmers from Central Europe, including one individual from the Flomborn site located approximately 200 km north-east of Obernai. On the whole, data gathered so far showed major genetic influence of the Danubian wave from Transdanubia to Atlantic French Coast, going by Alsace Region. However, the genetic influence of descendants from the Mediterranean Neolithic expansion and the significant hunter-gatherer admixture detected further west in the Paris Basin were not perceived in the Obernai necropolis. CONCLUSIONS Genetic homogeneity and continuity within LBK groups can be proposed on both sides of the Rhine River for the middle Neolithic groups. Nevertheless, mitochondrial data gathered so far for Neolithic groups from the entire extant French Territory clearly point out the complexity and the variability of Neolithic communities interactions that is worthy of further investigation.

Determination and validation of criteria to define hypercementosis in two medieval samples from France (Sains-en-Gohelle, AD 7th–17th century; Jau-Dignac-et-Loirac, AD 7th–8th century)

OBJECTIVE The main aim of this article was to develop different visual criteria allowing for an objective definition of hypercementosis (cementum hyperplasia). This preliminary study must notably show how to better understand at a later stage the significance of its frequency as well as its aetiologies, especially in past populations. MATERIALS AND METHODS we set up a study protocol (macroscopic and photographic observations) on material consisting of 2 medieval samples from France (1) Sains-en-Gohelle sample-SG (AD 7th-17th century; 407 individuals; 5756 teeth observed, 319 with hypercementosis) which was used to develop the different criteria for defining hypercementosis (2) Jau-Dignac-et-Loirac sample-JDL (AD 7th-8th century; 55 individuals; 709 teeth observed, 24 with hypercementosis) which was used to test the reproducibility of the criteria. RESULTS From our observations we formulated different inclusion criteria with which to define hypercementosis objectively (k intraobserver≥0.96; k interobserver≥0.63). We were able to distinguish moderate (1m) and marked (1M) forms of diffuse hypercementosis, focal hypercementosis in the form of small knots (2m) or large nodules (2M), or excrescences in the form of ridges (3m) or spurs (3M). Different exclusion criteria were also determined. CONCLUSION The definition that we propose in this study are based on various statistically validated inclusion and exclusion criteria. It is hoped that this will improve the significance of hypercementosis. More generally, this would also give a better understanding of the dynamics of cementum apposition.

3D morphology of the rear foot from MRI data: technical validation and clinical description

The purpose of this work is to characterize the 3D morphology of the bones of the rear foot using MR data. This work has two subaims: (1) to study the variability of the various computed architectural measures as a result of the subjectivity and variations in the various processing operations; (2) to study the morphology of the bones included in the peritalar complex. Each image data set utilized in this study consists of 60 longitudinal slices of the foot acquired on a 1.5 T commercial GE MR system. Our description of the rear foot morphology is based mainly on the principal axes, which represent the inertia axes of the bones, as well as on the bone surfaces. We use the live-wire method for segmenting and forming the surfaces of the bones. In the first part of this work, we focus on the dependence of the principal axes system on segmentation and on scan orientation. In the second part, we describe the normal morphology of the rear foot considering the four bones (calcaneus, cuboid, navicular, talus) and compare them to a population from the Upper Pleistocene. We conclude that this non-invasive method can be used in live patients to characterize the bone morphology or as a comparative method to classify population of bones. in spite of the variations involved in the various processing operations.