Correction: New Insights on the Composition and the Structure of the Acellular Extrinsic Fiber Cementum by Raman Analysis.

[This corrects the article DOI: 10.1371/journal.pone.0167316.].

New Insights on the Composition and the Structure of the Acellular Extrinsic Fiber Cementum by Raman Analysis.

Acellular extrinsic fiber cementum is a mineralized tissue that covers the cervical half of the tooth root surface. It contains mainly extrinsic or Sharpey's fibers that run perpendicular to the root surface to anchor the tooth via the periodontal ligament. Acellular cementum is continuously and slowly produced throughout life and exhibits an alternating bright and dark pattern under light microscopy. However, although a better understanding of the structural background of acellular cementum is relevant to many fields, such as cementochronology, periodontology and tissue engineering, acellular cementum remains rarely studied and poorly understood. In this work, we studied the acellular cementum at the incremental line scale of five human mandibular canines using polarized Raman spectroscopy. We provided Raman imaging analysis and polarized acquisitions as a function of the angular orientation of the sample. The results showed that mineral crystals were always parallel to collagen fibrils, and at a larger scale, we proposed an organizational model in which we found radial collagen fibers, "orthogonal" to the cementum surface, and "non-orthogonal" fibers, which consist of branching and bending radial fibers. Concerning the alternating pattern, we observed that the dark lines corresponded to smaller, more mineralized and probably more organized bands, which is consistent with the zoological assumption that incremental lines are produced during a winter rest period of acellular cementum growth.

Cementochronology, to cut or not to cut?

One of the continuing problems in paleopathology and paleoepidemiology is an inability to accurately age adult skeletons. Accurate age estimations are critical to the proper evaluation of population health and are necessary in circumventing certain aspects of the osteological paradox. Cementochronology is most likely the only age indicator in anthropology that directly considers a continuously growing tissue and does not require either complex statistical manipulations or the use of a reference population. The major issues and recent advances linked to this technique are reviewed for its successful implementation. This review is a partial outcome of an international research program initiated in 2010 to develop and expand cementochronology. Because cementochronology is a reasonably straightforward histological protocol, it can be implemented in less than 24h for one tooth at a relatively low cost. The only aspect of cementochronology that requires extensive previous experience is the counting of increments. These unique aspects largely justify the regular implementation of cementochronology in paleoepidemiology and paleopathology in the confident exploration of "population health" issues and demographic inferences.

The impact of periodontal disease on cementochronology age estimation.

Estimating an individual's age at death is essential for post-mortem identification, paleopathology and paleodemography. With substantial development over the past 10 years in cementochronology analyses, some concerns have arisen that oral pathological conditions may artificially reduce or increase cementum apposition. The objective of this study was to observed the impact of periodontal disease on acellular cementum and on the reliability of cementochronology to test its accuracy for estimating individual age at death. The study included 41 teeth presenting different degrees of bone destruction, extracted from 18 individuals affected by untreated periodontal disease. The results demonstrated that the degree of alveolysis had only limited effects on the counting of cementum annulations in the middle (rp=0.92, p<0.01 between estimated and civil age) and the cervical (rp=0.85, p<0.01) thirds of the root, whereas in the apical third, the increments were affected considerably. This cementum reactive process compensates for bone destruction and loss of the attachment apparatus. These data suggest that cementum could continue to grow at a slower rate despite bone destruction due to periodontal disease. Cementochronology can thus be applied to teeth with a damaged periodontium by sectioning the middle third of the root.

The leprosarium of Saint-Thomas d'Aizier: The cementochronological proof of the medieval decline of Hansen disease in Europe?

This study compares the adult survivorship profiles of people interred in the Saint-Thomas d'Aizier leprosarium, estimated by cementochronology, to eight archaeological series in northern France dated from Late Antiquity to the Late Middle Ages, periods of significant visibility for Hansen's disease (leprosy). The goals are to understand the impact of leprosy on various social groups and to explore the cause of leprosy's decline by analyzing male and female fertility. Survival rates differed between medieval leprosy-free sites and the Saint-Thomas d'Aizier leprosarium, although this difference was statistically significant only for the female leprosarium sample. The selective female frailty, a consequence of social exclusion and the collapse of the quality of life, combined with the infertility of lepromatous couples, offer a multi-causal explanation to the end of the expansion and then decline of leprosy in southern and western European countries.

Cementochronology and sex: A reappraisal of sex-associated differences in survival in past French societies.

The objective of the present study is to test our general knowledge of sex-specific survival differences in past northern France societies by implementing the tooth cementum annulations method of age estimation (i.e., cementochronology) to bio-archaeological series. 1255 individual estimated ages at death covering a millennium from the 3rd c. AD to the 15th c. AD matched different patterns of sex mortality from the late Antiquity to the Late Middle Age. Female survival curves are consistently inferior to those of their male counterparts. Maternal mortality is clearly visible in survival curves between 20 and 50 years of age in individual sites and pooled samples. Variations of sex mortalities also affected sites with peculiar recruitment, such as religious communities, pathological samples, leprosaria, and migrants. Whisker plots of median ages at death variations confirmed in both sex that populations within the Early Middle Ages were better off compared to Late Antiquity and Late Medieval Ages when group inequalities prevailed. Due to its sensitivity and applicability to small samples, cementochronology should be extended to other series.

Tuberculosis and survival in past populations: A paleo-epidemiological appraisal.

Historical assessments of the last two centuries consistently placed tuberculosis as the leading cause of mortality. However, for earlier periods, we can only calculate the frequencies of archaeological bone lesions, which tell us little about the real impact of the disease on mortality. These lesions are usually observed in individuals who have developed immune resistance, which is visible as healed osteo-articular lesions. This study aimed to test the differential impacts of tuberculosis, cribra orbitalia and cribra femoris on adult survival and sex-based survival. We analyzed 28 French adult samples from the Antiquity and the Early Middle Ages. The age-at-death of 1480 individuals was estimated using cementochronology. Survival curves and median age-at-death were calculated to test new hypotheses that challenge the parasitic and deficiency theories of bone stress markers. Comparisons between carriers and non-carriers provided new information concerning the plausible causes of bone stress markers related to infections and TB. The most likely hypothesis is skeletal demineralization and osteoclastic resorption, which are usually observed close to tubercular granuloma or distant from active lesions. The bone marrow niche of Mycobacterium tuberculosis within CD271(+) BM-MSCs stem cells is the proposed explanation for the localized cortical resorption that is observed in bone stress markers.

Langerhans cell histiocytosis or tuberculosis on a medieval child (Oppidum de la Granède, Millau, France - 10th-11th centuries AD).

In 2008, a skeleton of a 1 - 2.5-year-old child radiocarbon dated from the 10th - 11th century AD was discovered on the oppidum of La Granède (Millau, France). It presents multiple cranial osteolytic lesions having punched-out or geographical map-like aspects associated with sequestrum and costal osteitis. A multi 3D digital approach (CT, µCT and virtual reconstruction) enabled us to refine the description and identify the diploic origin of the lytic process. Furthermore, precise observation of the extent of the lesions and associated reorganization of the skeletal micro-structure were possible. From these convergent pieces of evidence, the differential diagnosis led to three possibilities: Langerhans cell histiocytosis, tuberculosis, or Langerhans cell histiocytosis and tuberculosis.

Specific patterns of canine scavenging in indoor settings.

Postmortem animal mutilations due to domestic dogs in isolated domestic deaths are taphonomic modifications regularly observed by forensic pathologists. They are rarely described in the literature; however, even though they present specific patterns. Through 41 cases, 10 at the forensic institute in Lille (France) and 31 at the New York City Office of Chief Medical Examiner (USA), plus 22 cases from the literature, specific locations and patterns of postmortem scavenging lesions are proposed. These lesions are mainly distributed in three locations: the face, especially the nose and the mouth (73.1%), the neck (43.1%), and the arm (shoulder/upper limb [29.2%], hand [26.8%]). We discuss the time span between death and scavenging, the consequences on identification, and comparison with outdoor settings. Outdoor scavenging lesions are mainly located on the trunk and limbs usually sparing the head, which strongly differs from indoor distribution and imply different animal motivations.