Potential and limitations of dental cementum
We aim to impact the archaeological, bioarchaeological and forensic science communities by increasing knowledge of (1) the potential applications of cementum investigation ; (2) specific limitations and possible pitfalls and (3) recommendations for critically evaluating and implementing strategies
Bertrand B, Mesli V, Vercauteren M, Hédouin V, Bécart A, Gosset D. Age-at-death estimation using dental cementum: best method, less bad method, or one method among others?
Age-at-death estimation is a fundamental component of creating a biological profile in bioarchaeological and forensic contexts. The most commonly employed methods to assess age at death rely on macroscopic indicators offering an optimal ratio between convenience and performance. However, a microscopic technique exhibiting a reverse ratio due to an unmatched precision reached at the cost of a histological preparation is increasingly mentioned in literature. Cementochronology based on the observation of the cyclic phenomenon expressed throughout lifetime of cementum appositions is considered by some authors to be a method with the potential for directly assessing chronological age. While conventional osseous or dental procedures have long been known to yield imprecise and biased age estimates (especially in elderly individuals), cementochronology is frequently acknowledged for its overall performance reaching less than 2.5 years error. Nonetheless, although cementum analysis has become a routine method for terrestrial mammalian species, cementochronology remains an under-used method for assessing age-at-death in human. This presentation aims to provide an overview of the current theoretical and practical aspects of cementochronology by debating the aspects that contribute to the limited use of this method and by illustrating its potential. A special attention is given to handle the complications regarding protocols and taphonomical biases and qualitative and quantitative analysis on a large standardized sample will be used to discuss the potential benefits and limitations of cementum deposits when examined for age-at-death estimation.
18th Congress, Paris, France
Bertrand B, Mesli V, Cunha E, Bécart A, Hédouin V. Root for cementochronology – An efficient method for age at death estimation
Age at death estimation is a fundamental component of creating a biological profile in bioarchaeological context. Even if physiological and structural biological background of the dental cementum deposit are still not perfectly elucidated, acellular cementum is considered to be formed continually throughout life and - unlike bone - to not undergo remodelling processes. Originally developed for nonhuman mammalian species, cementochronology based on the counting of incremental lines is considered to be a method with the potential for directly assessing chronological age. Even if most of the studies have assumed the method's superior performance for age at death in adults, we address the paradoxical disregard for cementochronology by debating the aspects that may contribute to the limited use of this method and by illustrating its potential. Cementochronology clearly suffers from a lack of standardization that slows down the adoption of this method and hinders the assessment of its precision that remains unclear as well as the impact of taphonomical processes. In order to define the boundaries of the cementum ageing technique, we applied a certified protocol on a sample of 200 healthy canines from individuals of known age, sex and postmortem interval from anthropological and anatomical collections. We scored readability and preservation of cementum tissue and measured the agreement between cementum estimates, i.e. the precision, and assessed the quality of the accordance between chronological age and estimates, i.e. the accuracy. To investigate the applicability of this method on ancient material, 200 additional canines extracted from archaeological assemblages were included. Accuracy and precision were analysed for each age group in considering postmortem intervals and taphonomical conditions. A strong global correlation was found between chronological age and estimated age [r=0.927; p=0.000]. Even if results revealed a notable difference in both precision and accuracy between individuals under and over 50 years, cementochronology's performance compared to classical osseous and dental methods justifies a more regular implementation in anthropology. This presentation aims, on a large standardized sample, to argue cementochronology's potential and limitations, and to propose a prediction model to reduce differences between estimated age and chronological age.
87th Annual Meeting, Austin, Texas
Bertrand B, Cunha E, Hédouin V. Cementochronology: too precise to be true or too precise to be accurate?
Cementochronology based on annual deposition of acellular cementum is acknowledged for its superior performance for estimating age at death but is also criticised for its suspicious effectiveness. This contrasting picture is mainly due to a lack of standardization that leads to inconsistent quantitative assessment of its efficiency and to the impact of taphonomical processes that remains unclear.
In order to determine the boundaries of the cementum ageing technique, we applied a certified protocol on a sample of 200 healthy canines from individuals of known age, sex and postmortem interval from anthropological and anatomical collections. We scored readability and preservation of cementum tissue and measured the agreement between cementum estimates, i.e. the precision, and assessed the quality of the accordance between chronological age and estimates, i.e. the accuracy. To investigate the applicability of this method on ancient material, 200 additional canines extracted from archaeological assemblages dated between the 12th century and 18th century were included.
Accuracy and precision were analysed for each age group in considering postmortem intervals and taphonomical conditions. A strong global correlation was found between chronological age and estimated age [r= 0.927; p=0.000] but results revealed an association between readability of incremental lines and chronological age [p<0.05] and a notable difference in both precision and accuracy between individuals under and over 50 years.
This presentation aims, on a large standardized sample, to discuss cementochronology’s potential and limitations, and to propose a prediction model to reduce differences between estimated age and chronological age.
86th Annual Meeting, New Orleans, Louisiana
Tooth enamel and dentin are the most studied hard tissues used to explore hominin evolution, life history, diet, health, and culture. Surprisingly, cementum (the interface between the alveolar bone and the root dentin) remains the least studied dental tissue even though its unique growth, which is continuous throughout life, has been acknowledged since the 1950’s. However, the hypothesized seasonal cementum increments have been successfully used to estimate accurate age and season at death in over 70 mammal species including human, and has opened a range of invaluable interpretative opportunities. Yet archaeological applications have been particularly limited by the lack of understanding of cementogenesis and the controversial nature of the observed increments. Following our initial meeting in 2013 on cementum studies, this symposium is the first attempt to bridge the gap between faunal and human analyses and to illustrate the growing multidisciplinary uses of cementum in anthropology. The recent implementation of synchrotron x-ray imaging technologies in fluorescence mapping and micro-tomography provides new insight into cementum microstructure. Bioarchaeology and forensic age and season at death estimations now benefit from standardized protocols, as well as a greater understanding of taphonomic alterations and how to deal with them in archaeological and forensic samples. Finally, paleoanthropology can profit from nondestructive virtual cementum analyses to explore dental sexual dimorphism and morphology in hominin remains. With the recent advances in microbiology imaging technologies, and the consequent renewed awareness of cementum growth potentials, anthropologists are finally going back to the root.
Individual poster presentations and discussion led by Daniel Antoine
Cementum ultrastructure, a comparative perspective from synchrotron x-ray scanning: fluorescence and diffraction
NAJI S, RENDU W, GOURICHON L, CAI Z and STOCK S
Mammal teeth are composed of enamel, dentin, and cementum. All three have a comparable growing pattern of cyclic incremental deposits. While dentin and enamel have been extensively studied, cementum is still largely ignored. However, cementum grows throughout life, unlike dentin and enamel which both stop once the tooth is fully formed. Cementum function is to anchor the periodontal ligaments and maximize root stability within the alveolar bone. Cementum incremental growth layers are deposited in a biannual light-dark pattern when observed in thin sections using transmitted light microscopy. This pattern has been strongly correlated to age-at- death and season at death in multiple reference samples in over 72 mammal species, including human. The nature and composition of these increments are still debated in the literature. This study investigates the structure of individual accelluar increments using x-ray fluorescence mapping and x-ray diffraction mapping with microbeams of synchrotron radiation on four samples of rein- deer, one bison, and one human. Results show that throughout the cementum, peaks in calcium, phosphorous, and zinc fluorescent intensities matched the carbonated hydroxyapatite diffracted intensity and the maximum intensity of light annual growth increments observed optically in transmitted light.
Contrary to previous conclusions, the alternating light-dark pattern observed in acellular cementum in light microscopy does not come from differences in collagen fibers orientation. These results suggest that changes in contrasts in optical light interpreted as seasonal annual growth increments are related to changes in carbonated hydroxyapatite content.
Taphonomy in cementochronology
RENDU W, STUTZ AJ, GOURICHON J, NAJI S, VUILLIEN5 M, SÁNCHEZ-HERNÁNDEZ C and PUBERT E
Cementum increment analyses have been largely applied to various archaeological contexts and topics for addressing the question of age and/or season at death of individuals, from a large range of mammal species. However, few analyses have directly tackled the question of cementum taphonomic alterations.
Various post-depositional processes such as physical weathering, microbial digestion, chemical alteration, collagen leaching and apatite recrystallization can affect and damage the cementum of archaeological teeth, even when the roots are still embedded in the alveolar bone.
These modifications can hardly be detected by the macroscopic examination of the root surface and are thus prejudicial sources of distortions and errors when analyzing cementum increments for seasonality and mortality studies.
In this study, we revised several archaeological series of different taxa (human, bison, deer, sheep) from various contexts (funeral, camp sites) and time periods (Middle Paleolithic, Neolithic, Medieval), in order to evaluate the frequency and the impact of post-mortem modifications and to propose guidelines and recommendations to tackle them.
Results evidenced a wide variation in taphonomic changes from 20% to 90% of samples affected in some collections. Nevertheless, the implementation of our protocol provides solutions to get around this issue, even in extreme cases.
Understanding taphonomic changes also helped to explain why some affected samples were rejected, artificially increasing the analysis rate of success in some publications, and how this could be avoided in the future through the implementation of our revised age and seasonal spectrum for each studied sites.
Computerized cementochronology - taking the (16)bit between the teeth
BERTRAND B, JOSÉ RAMOS MAGALHAES and Colard T
Age-at-death estimation is a fundamental requirement for biological profile assessment in forensic anthropology and bioarchaeology. Cementochronology, that involves the count of acellular cementum increments on histological micrographs, is considered as an accurate and precise method to access the chronological age. However, cementochronology clearly suffers from the profusion in methodological protocols, from intra/inter-observer discrepancies and from implementation time. The main objectives of this presentation are: (i) to address the importance of establishing quality standards for the cementochronology protocol, namely through the certification according to the ISO-9001 that ensures the reproducibility of preparations (ii) to describe the development of a time saving module on the Visilog platform, which substitute the manual counting and eliminate factors such as subjectivity and tiredness of the investigator (iii) to present the results of the performance of this semi-automated tool on known-age individuals, in order to evaluate the efficiency and to compare estimates.
The application of the software on 16-bit micro- graphs from one hundred histological slices from anatomical collections allowed us to evaluate the software accuracy and the concordance of counts with the observers. The time saving module on the Visilog platform detects and counts cementum ring structures at a speed and accuracy unmatched by other methods. The computerized estimation provides consistent results and narrows down the range of estimation. This work demonstrates that, once standardized and semi-automated, cementochronology is neither time-consuming nor subjective.
Sexual dimorphism in dental cementum microstruc- ture: potential for sexing hominin remains
ROBSON BROWN K, NEWHAM E, BAYLE P, CORFE I and GILL P
Cementum, the connective tissue that anchors mammalian teeth within the alveolar socket, grows continuously and with an annual rhythm; it is recorded by a series of circum-annual incre- ments of contrasting opacity when viewed under light microscopy, with hyper-mineralized incre- ments recording a reduction of growth rates. The aim of this project is to use high-resolution synchrotron-based radiation tomography (SRCT) to test whether the microstructure of cementum is sexually dimorphic in primates. A sample of macaque molars was taken from the cadavers of animals raised under controlled conditions and with known life histories. These individuals were raised for an unrelated project and were culled independently. The molar roots were scanned at the Swiss Light Source on the TOMCAT beamline using 40x and 20x objectives at 0.35 and 0.7Î1⁄4m voxel dimensions (respectively), at 20keV. Reconstructions employed conventional X-ray absorption based (“grid rec”) algorithms, and exploratory phase-contrast enhancement (“Paganin-style”) algorithms. Reconstructed scans were analysed using commercial soft- ware (Avizo, Fiji). Quantitative morphometric techniques were applied to assess variation in microstructure between increments (tortuosity, 3D texture, cellular voids) formed in breeding females, non-breeding females, and males. Principal Component Analysis of these 3D microstructural data demonstrates that male cementum increments are relatively homogenous and have low microstructural variance, while female increments are significantly more tortuous and varied. These characteristics may reflect hormonal cycling and the impact of pregnancy. This methodology therefore has potential as a tool for sexing fragmented remains in forensic, anthropological and archaeological contexts, as well as sexing in fossil species.
Development of Dental Cementum Increment Analysis for Age at Death Determination within the Identification Process of Unaccounted-for US Service Members
KOEL-ABT K, WILSON ND and SCHMIDT KN
The Defense POW/MIA Accounting Agency (DPAA) conducts global search, recovery, and laboratory operations to identify unaccounted for Americans from past conflicts in order to support the Department of Defenses (DoD) personnel accounting efforts. The interest in utilizing tooth cementum annulations to reliably determine the age of an individual has grown over recent years (Kagerer and Grupe 2001; Grosskopf and McGlynn 2011; Naji et al. 2014). This technique has shown promising results with a rather narrow age estimation error of 2-3 years from true chronological age. Further studies with the aim to develop a standardized method will strengthen the validity and increase the use in solving forensic cases. The present study utilizes tooth cementum analysis (TCA) in the blind to determine the age of 50 teeth of a sample of known-age active duty male and female US Service Members ranging from 18-50 years old, and representing a total number of 150 spec- imen. Each tooth had three sections of acellular cementum analyzed under a light microscope by three examiners, and new z-stacking software was utilized to enhance the images and with it the countability of cementum increments. A high interobserver agreement was found along with a variance from true chronological age of under 3 years. The effects of age, tooth number, root type, pathology, and sex were all evaluated. Our group concludes that tooth cementum annulations can be reliably applied to assist in the estimation of age at death, and will be an additional asset in identifying unaccounted-for US Service Members
The Utility of Dental Cementum Increment Analysis for Estimating Season-of-Death in Naturally Decomposed Skeletons
MECKEL LA and WESCOTT DJ
Dental cementum increment analysis (DCIA) is the microscopic examination of the alternating mineralized layers in dental cementum. These layers can be seen as either a bright incre- ment representing the growth season (spring/ summer) or an opaque increment representing the dormant season (fall/winter). Wedel (2007) used DCIA to estimate the season-of-death with 99% accuracy in a sample of human teeth extracted from living individuals. This study was designed to test and replicate the Wedel method using a modern skeletal sample of individuals (N=24) over the age of fifty, with known exact date-of-death, that have undergone natural decomposition processes. If the Wedel protocol is validated on a reference sample that decomposed in a natural environment, then this method will greatly improve the estimation of time-since-death in forensic and bioarchaeolog- ical contexts.
The results of two separate observations show that there is not a strong relationship between the optical nature of the outer band and the season- of-death as suggested by Wedel (2007). The accuracy of the method was 60 and 18 percent in the first and second observations, respectively. However, a known animal sample (n=13) and a single tooth from a 22 year old human were also tested and achieved an accuracy of 100%. Based on these results, DCIA is not recommended for use on individuals over fifty years of age and further research focusing on the effect of age on cementum growth is warranted.
Determination of Season at Death Using Dental Cementum Increment Analysis to Assist in the Identification Process of Unaccounted-for US Service Members from Past Conflicts
WILSON ND, KOEL-ABT K and SCHMIDT KN
There are few published research studies on the use of dental cementum to determine the season at death in humans. With increased development of a standardized technique it may play an important role in forensic identifications and identifying some of the 83,000 unaccounted-for US Service Members. The mission of the Defense POW/ MIA Accounting Agency’s laboratory is to search for, recover, and identify U.S. personnel missing from past military conflicts, and therefore it is imperative to develop a standardized method which accurately determines the season at death especially for ground losses (e.g. battle fields). This technique is based on cementum deposition of alternating layers of dark and light. One band of light/dark represents one year that has been divided into seasons, with the outer layer representing the season of death. The present study utilizes the analysis of tooth cementum annu- lations in the blind to determine the season at death of 50 teeth with known date of extraction of current male and female US Service Members, ranging from 18-50 years old. Three sections of each tooth were evaluated with a light microscope and polarizing lenses by three different observers in the blind. A high interobserver agreement was found along with an accurate correlation of cementum ring type and season. The relation of cementum ring and season was even present in individuals whom have lived in multiple different climates throughout their lives. It is concluded that there is an accurate correla- tion between cementum ring annulations and season in humans.
Out of the Mouths of Babes: Cementum Annulations in Human Deciduous Teeth
WEDEL VL and HERMSEN KP
Dental cementum binds teeth in their sockets via the periodontal ligament and is secreted in pairs of bands annually. Age at death in adults can be determined from the total number of cementum annulations, however, it is not yet known if total cementum annulations correlate with age at death in subadults. This study tests the hypoth- esis that the alternating light and dark bands of cementum observed in adult teeth are present in deciduous teeth. It is further hypothesized the total number of pairs of cementum bands (light and dark) correlates with age at death, or in this case age at extraction. To test these hypotheses, deciduous teeth were collected with consent from pediatric patients at Creighton University’s School of Dentistry in Nebraska.
The study sample consists of 76 teeth collected between March, 2014, and June, 2016, from fifty children aged 4 to 16 years old. The sample included incisors, canines, and molars. Each tooth was embedded, sectioned at the middle third of the root, ground, polished, and imaged. Seven teeth were excluded for inadequate root structure. Alternating dark and light cementum annulations were visible in all but one tooth. The number of pairs of bands plus the age at which the tooth erupted is significantly correlated with age of tooth extraction (p<0.01). Future work will include deciduous teeth with partially resorbed roots and a sample representative of the mixed dentition seen in children.
Cementochronology to the rescue : Osteobiography of a Middle Woodland woman with a combined skeletal dysplasia
CORMIER AA, BUIKSTRA JE, NAJI S and Colard T
Accurate age-at-death estimates are essential for inferring health, identity, diversity, and demography within archaeological skeletal samples. Unfortunately, the macroscopically visible skel- etal structures most informative for estimating age-at-death ranges may be compromised by dysplastic, endocrine, and circulatory disorders. Cementochronology or the “tooth cementum annulations (TCA)” technique provides an alternative approach for evaluating acellular cementum banding without requiring a reference sample or complex statistical calculations. Using cementochronology, we present an age-at- death estimate for a pre-Columbian, adult female (EZ 3-7-1) with a combined skeletal dysplasia, achondroplasia and Leri-Weill dyschondrosteosis. In 1980, EZ 3-7-1 was excavated from Mound 3 at the Elizabeth site (11PK512) in the Lower Illinois Valley by the Center for American Archeology Contract Archeology Program and the Northwestern University Archeological Field Schools. Preliminary age-at-death estimates were tentative. The presence of in situ fetal remains within her pelvis indicates a biologically mature individual, and occlusal dental wear correspond to that of older adults. Cementochronology has re-defined the age-at-death estimate as 31.5+- 1.48 years. These results not only assist in developing a more accurate age-at-death estimation and biological profile, but they also facilitate creating nuanced interpretations for a physically challenged, pregnant female in her Middle Woodland social context. Further, this analysis emphasizes the utility of cementochronology in estimating age-at-death of skeletal individuals with pathological conditions that compromise commonly used macroscopic methods and encourages researchers to consider this technique in paleodemography, paleoepidemiology, and forensic anthropology.
Cementochronologyand Palaeodemography: A New Method to Assess the Probable Age Distribution of Immatures
LANTERI L, SALIBA-SERRE B, BIZOT B, GAUDART J, SIGNOLI M and SCHMITT A
Standard individual age estimators have been reported to be too imprecise to reconstruct valid paleodemographic mortality profiles, due to methodological biases. Although the debate is mainly centered around adults, subadult estimated age intervals overlapping two demographic age categories remain an unresolved issue. Cementochronology is traditionally applied to adults since standard subadult estimators are considered sufficiently precise. The implementation of different aging methods is thus necessary to aggregate subadults and adults in order to reconstruct complete mortality profiles. However, this approach introduces biases of the same nature since subadults overlapping two demographic age groups are also common. The recent application of cementochronology, combined with probability density analysis, provided an initial solution by calculating precise adults individual age-at-death and mortality profiles. This study expands this approach by assessing the age-at-death distribution of 42 subadults from the cathedral Notre-Dame-du-Bourg (16th-18th centuries, France), using cementochronology and probability density analysis. The goal is to test a single age indicator on a sample of deciduous and permanent teeth to minimize the biases across age categories. Results revealed that the “0-1” age category was underestimated when compared to the “archaic mortality pattern” but consistent with histor- ical records, especially in a cathedral where non-baptized newborns were excluded. However, cementochronology slightly overestimated the “15-19” age category compared to historical records in a nonsignificant way given the small sample size of this age category. Cementochronology is thus the only method that can reconstruct paleodemographic mortality profiles by including subadults and adults individual age estimates from a single skeletal collection.
Assessing Age-Related Mortality at Petra, Jordan Using Cementochronology and Hazard Modeling
PROPST AS and PERRY M
Many infectious diseases that resulted in high mortality in the past often do not result in identifiable skeletal lesions, rendering them essentially invisible in the skeletal record. Age-at-death mortality profiles provide an important supplementary record of disease-related mortality risks that archaeological populations faced. For instance, cemeteries primarily containing individuals perishing from catastrophic events, such as natural disasters or disease epidemics, will have a different age-related mortality profile than one created through normal attrition. Previous research on a 1st century BC to 1st century AD skeletal assemblage from the ancient city of Petra discovered significantly fewer skeletal lesions related to infectious disease processes than contemporary sites from the region. Here, we use hazard modeling to calculate risk of death by age for adults in the Petra sample to identify forces resulting in its creation. Age-at- death estimates used for the hazard model come from 71 individuals that were generated using cementochronology, which not only provides more accurate age estimates, but increases our sample size due to the fragmented and commingled nature of the Petra assemblage. Our results indicate that the mortality profile from Petra resembles that of an attritional sample, indicating that the lack of disease pathologies did not result from people perishing from catastrophic events not reflected in the skeleton.
Seasonality and Neanderthal hunting strategies
GOURICHON L, RENDU W, NAJI S, HASSANI M, PUBERT E and SANCHEZ-HERNANDEZ C
Neanderthal mobility patterns have become a major topic in recent research in Paleoanthropology. In particular, the spatial organization of activities in the Neanderthal’s territory has been largely used to discuss their management of food resources and scheduling abilities and indirectly to approach their cognitive capacities. Given this background, the seasonality of hunting is obviously a key factor for identifying both the spatial and temporal organization of the subsistence economy.
Several scholars have assumed that Neanderthal subsistence economy integrated the use of communal hunting strategies and reliance on delayed consumption of food resource that was frequently exported to camp sites. However, since most of the studies focused on late Neanderthal populations, little information is available for earlier populations making difficult to discuss the development through time of such planning strategies.
Here, through the study of cementum seasonal increments of animal teeth from several sites in Southwestern France and Northern Spain attributed to the MIS4-5, we investigate the seasonal organization of the Neanderthal populations during the MIS4-5 period. Although the samples are affected by a great variety of micro-taphonomic alterations (microbial attacks, chemical diagenesis), results of the cementochronological analyses provide reliable evidence of restricted times of large game predation for a number of archaeological contexts.
84th Annual Meeting, St. Louis, Missouri
Front lines and cementum lines. An attempt to identification of soldiers from the World War I using cementochronology
BERTRAND B, COLARD T, RAMOS MAGALHAES J, PHELIPPEAU H, GERMAIN F, GÉANT-CAPARROS L, PÉLISSIER A and LANDOLT M.
Cementochronology, that involves the counting of incremental lines in tooth root cementum, is considered by most of the studies as an accurate and precise method to estimate age-at-death. Yet, despite the superior performance of this technique, the overall inaccuracy, even low, makes disputable the use of the cementochronological age as a criteria for positive identification of a body. This work aims, in a singular context, to discuss the potential of cemental annulations for a positive identification by process of elimination. We applied a protocol certified according to the ISO-9001 to twenty-one German soldiers discovered in the Kilianstollen, a perfectly preserved World War I tunnel (Carspach - Alsace, France). The combatants were part of the German Army’s 94th Reserve Infantry Regiment and were buried alive on March 18, 1918 after a French bombardment. All individual were identified with help of dog tags, pay books and a memorial tablet. Even if all names were known, a doubt subsisted for the identification of three bodies. Cementum lines counting on histological micrographs was done manually in Adobe® Photoshop and with an automated module on the Visilog® platform to eliminate factors such as subjectivity and to reduce intra/inter-observers errors. Results demonstrated that the accuracy of cementochronological age is notable and that the precision of computerized estimates narrows down the range of age estimation. Despite tight civil ages of the three young soldiers with suspicions of identity, cementochronology was able to support a positive identification through inter-individual relative assessments.
82th Annual Meeting, Knoxville, Tennessee
Cementochronology, to cut or not to cut ?
NAJI S, Colard T, BERTRAND B, D’INCAU E, BRANDT E AND BLONDIAUX J
The use of cementum annulations for estimating adult age-at-death has been recently successfully revived through careful methodological advances with several tests on reference collections indicating very high correlation (r> 0.9) between civil and observed age. Cementochronology is however still not widely implemented, often because of misunderstanding of underlying biological processes or lack of training. The question thus remains for bioarchaeologists or forensic anthropologists today, to cur or not to cut?
To answer this question, we are presenting a systematic review of the cementochronology literature from all disciplines to highlight both the reliable facts and the remaining possible biases. We will then synthesized recent results that stemmed from our new “Cementochronology Research Program” which addresses some of the major issues recently expressed in the literature such as the nature of the observed increments, the variability of intra individual cementum apposition or the influence of taphonomy and pathological conditions on acellular cementum.
Finally, we present several new practical tools to help improve the implementation of cementochronology such as full protocols, automated counting software (beta version), recording spreadsheet, and self-training databases of histological sections from our reference collections.
Even though cementochronology is somewhat expensive to set up, time consuming and destructive, it is also the only method without a scoring protocol based on reference populations and without any statistical processing, which effectively remove most known methodological biases. Since cementochronology is the most precise adult age estimator published so far, the authors strongly recommend its implementation with careful supervision and training.
Microstep by microstep across dental cementum - Microanalysis of the alternating yearly deposits
BERTRAND B, Colard T, NAJI S, MARCHANDISE P, GEANT L AND FALGAYRAC G
Although the ultrastructural nature of the dental cementum is still an open question, appositional layers are used more reliably than other morphological or histological traits of the adult skeleton to estimate individual age-at-death. Considering that the alternating dark and light rings seen under light microscope reflect cementum composition and organisation variations, the ability to follow elements into the tooth matrix may provide an objective technique to identify alternating deposits.
By means of Environmental Scanning Electron Microscopy equipped with Energy-Dispersive X-ray Spectroscopy and Raman Spectrometry, dental cementum was studied in selected modern teeth of known individuals. The organic content, mainly collagen and the major elements of the inorganic content, mainly apatite, were measured along linear paths crossing the cementum deposit to verify if the position of the peaks and their number correspond to the number and positions of the layers in light microscopy. Linescans suggest a link between chemical composition variations across the width of cementum and incremental lines. Spot analyses have been done with the aim to discuss intra-dental variation in elements concentrations and reveal for some deposits a signiﬁcant difference in calcium proportion.
A first application of this methodology to archaeological samples excavated from the Saint Amé’s Collegiate Church (A.D. 950-1797) in Douai (Northern France) is presented and discussed.
Age-at-death estimation of pathological individuals. A complementary approach using teeth cementum annulations
ROBBINS SCHUG G, BERTRAND B, COLARD T, NAJI S AND POLET C
Recently, the value of cementum annulations (TCA) for age-at-death determination was confirmed for bioarchaeological research. Use of TCA for early Holocene specimens from India demonstrated systematic biases in the morphological methods, had a demonstrable impact on the age pyramid, and significantly changed paleodemographic statistics. While TCA may provide greater accuracy and precision for age estimation of skeletally healthy specimens, it is unclear the magnitude to which specific pathologies affect the accuracy of different techniques for age determination. We hypothesized that age determination methods based on gross morphological changes in the skeleton will not accurately predict age-at-death for individuals with bone growth pathologies (achondroplasia, osteomalacia, osteogenesis imperfecta). Conversely, for adult individuals with chronic and severe rhino-maxillary infections, acellular cementum formation may be disrupted and thus morphological methods should be preferred. We compared age estimates from TCA with estimates made using standards for determination from the pelvis, fourth rib, dental attrition, and cranial stenosis. Results demonstrated that morphological techniques produce variable and inaccurate age estimates for pathological specimens in archaeology. Our results confirm the utility of cementum annulations for age estimation in bioarchaeology, particularly for pathological specimens, and suggest directions for additional research on the effects of pathology on the accuracy of various aging techniques.
Cementochronology (TCA) - Evaluation of a semi-automated counting software
Tooth cementum annulation (TCA) is amongst the most precise anthropological age determination methods to date. In most TCA studies the incremental lines in tooth cementum are counted manually by various observers. This can lead to large inter- and intraobserver errors. In order to overcome observer bias and to receive statistically significant results, Czermak et al. developed in 2006 a semi-automated counting software.
The study at hand evaluates this software by applying it to 306 images of 65 soil-exposed teeth of 65 individuals with known age from the Spital field in Basel, Switzerland (19th century). Each image was counted with the software and an average age from all images of one individual (3-10 images per individual) was calculated. This process was repeated to test the software reliability.
The semi-automated software results indicate a clear trend of age underestimation. Both counts show stable results, with an average age deviation of -7,43 years (absolute 8,98 years) for the first count and an average age deviation of -7,78 years (absolute 9,09 years) for the second count.
Compared to the standard TCA method count results of 3 observers that range from an average absolute age deviation of 3,59 years (trained observer I) to 14,54 years (untrained student observer III), the actual software cannot reproduce the good results of a trained observer. However, the first evaluation of this software gives hints on how to improve it to make it a useful tool for anthropologists, especially for untrained observers.
Testing inter-teeth variability in adult individual age-at-death estimate using cementochronology (TCA)
LANTERI L, SCHMITT A, FOTI B AND NAJI S
The study of intra-individual variability of acellular cementum apposition is a major issue in the estimation of age-at-death using cementochronology. Since the literature is scarce on the subject we extracted 51 modern teeth from 15 of known-age patients. We manually counted the acellular cementum increments on five cross-sections from the middle third root of each tooth. Age estimation was then calculated by summing the number of lines to the average age of dental eruption. Our results showed some variability between counts within tooth, especially on premolars. The intra-individual variability of cementum deposition has been highlighted by comparing age estimates obtained for each tooth of one individual which is not surprising considering problems already described in the literature on this issue. Once premolars were excluded, the variation between teeth of an individual dropped to 0 to 5 years in 73% of cases. In conclusion, the intra-individual and intra-dental variability of cementum have to continue to be studied and quantified to obtain the most accurate and reliable estimation of age-at-death and potentially predict which region of interest should be considered prior to sectioning and counting.
Functional morphology of the human dentition and its probable influence on tooth cementum thickness and incremental line count
GRUPE G, LIPPITSCH A AND MCGLYNN G
A systematical investigation of 17 premolars from the lower jaw of 13 adult human skeletons from early medieval times was performed. Focus of this study was the variability of cementum thickness and incremental line number and the relationship to their location on the cross section of the tooth root. The number of 2,280 cementum thickness measurements and 4,726 incremental line counts permitted for a statistical evaluation. Cementum thickness and line count increased significantly from the cervix to the apex of the tooth root. With regard to the quadrants of the cross section, a likewise significant increase from buccal < lingual < mesial < distal was oberserved.
These results are compatible with and can be explained by the functional demands and physical loads acting on the human dentition, in particular the chewing cycle, the occlusal and mesial drift. A phenomenon previously described as “cementum exuberation” was observed in the majority of investigated teeth and is hypothetically interpreted as areas of minimized physical loading.
We conclude that the functional morphology of the human dentition should largely be responsible for the observed variability in the tooth cementum. Therefore, choice of area on the cross section for the incremental line count should not be at random.
Impact of periodontal disease on cementochronology
BROUCKER A, COLARD A, BLONDIAUX J AND NAJI S
Estimating an individual’s age-at-death is important regarding post-mortem identification as well as paleodemography. With substantial development in the past ten years of cementochronology analyses, a certain number of questions have arisen regarding the impact of oral pathologies which may artificially reduce or increase cementum apposition. The objective of this study is to observe the impact of the periodontal disease on cementum and on the method reliability in order to improve the accuracy for determining individual age-at-death. The study concerns 41 teeth presenting different degrees of bone destruction, from 18 individuals affected by an untreated periodontal disease. No correlation between cementum thickness and civil age (p>0.05, r<0.5) throughout the root was observed. Since several other studies (Solheim 1990, Stein and Corcoran, 1994) observed a correlation between cementum thickness and civil age on healthy individual, it would seem that periodontal pathologies do have a direct influence on cementum thickness. Regarding the degree of alveolysis, periodontal disease have only limited effects on cementum annulations count in the middle third of the root (r=0,92, p=5,1.10-14 between estimated and civil age) whereas in the lower third, the number of increments is considerably increased. This hypercementosis would compensate bone destruction and loss of attachment apparatus. These data suggest that cementum could continue its growth at a lower rate despite bone destruction due to periodontal disease.
Cementochronology can be thus applied to teeth presenting a damaged periodontium, by observing the middle third of the root.
Cementochronology and Gender : a reappraisal of adult survival in past societies
MARCHANDISE M, BLONDIAUX J, COLARD T, BROUCKER A, NAJI S
Knowledge of the mortality hazards linked to status for women in past populations meets two obstacles: the first is our inability to statistically control maternal and infant mortality due to bad taphonomic preservation of fetal bones; the second is the low correlation of individual age estimates by conventional methods.
The application of cementochronology to 23 series representing a total of 1037 individuals from the antiquity to the end of the medieval period in northern France allows calculations and comparisons of survival curves by sex for adults. The study of these curves shows that male and female groups in cemeteries associated with religious institutions (monasteries and church burials) demonstrates significantly higher survival rate for all ages categories compared to more secular communities, both rural and urban. For the latter, if in the vast majority of series and pooled samples there was no statistically significant difference, a gradual decline in female survival rate of various intensities is visible between 20 and 50 years of age. After 50, the two survival curves merge or intersect. A smaller sample of 45 skeletons with tuberculosis lesions shows an equivalent decline of survival for women. The attribution to maternal mortality of these survival rates during the reproductive period illustrated by cementochronology is also discussed.
A reappraisal of ancient hypotheses on stress markers using cementochronology
BINET E, BLONDIAUX J, COLARD T, NAJI N AND PITON D
Since Walker and colleague’s paper (2009) and the publication of the History of Health in the Western Hemisphere, the causes and demo-dynamique impact of the so-called markers of stress have not been re-addressed. Nevertheless, a general consensus around diet deficiencies and infections during growth periods prevail among bio-archeologists. The issue of their impact on survival of adults with lesions described as cribra orbitalia (CO) , cribra femoris (CF) and hypoplasia (LEH), was tested on two adult French samples (Nurban = 355 and Nrural = 250; AD 250-550) whose individual age-at-death was estimated using cementochronology. No correlation was found between skeletons with and without signs of LEH, while a highly significant difference (> 10 years) was found in favor individuals unaffected by CO and CF.
When compared to a pooled sample of Tuberculosis (TB) skeletons, the survival curves of cribras samples are similar while the TB one looks significantly better. LEH has no impact on the adult median age at death and survival curve but CO and CF have a significant one (> 10 years). If the etiology of both cribras occurred during the developmental phases of life, mainly during population crisis, it is difficult to hypothesize why after recovery the healed individuals experienced such a declining life expectancy. A chronic infection or lasting deleterious life conditions associated with very low social status could be the logical explanation.
The Leprosarium of Saint Thomas d’Aizier, the cementochronological proof of the medieval decline of Hansen disease in Europe?
BLONDIAUX J, COLARD T, BROUCKER A, NIEL C AND NAJI S
By counting cementum annulations to estimate individual age-at- death, paleodemographers have an incomparable tool to reconstruct demography of past populations. Until now, osteo-archaeological collections from medieval leprosaria have never been specifically studied in a paleodemographic perspective thus keeping in the dark crucial parameters for our understanding of the demo-dynamique of leprosy in Medieval Europe.
Our hypothesis is based on the comparison of adult median age-at-death and survival curves estimated using cementochronology on a pooled sample of sites (N = 20 ; AD 450-1600, N individuals = 1550). The possible bias of dental hygiene which might affect cementum has been simultaneously analyzed.
Among all the observed series, the survival curve from the leprosarium of Saint Thomas d’Aizier is the most statistically catastrophic. Dental health does not differ from other samples of various social statuses and is thus discarded as a bias. The abnormal high mortality from all age group of the forced population of the Saint Thomas leprosarium unexplained by leprosy only, emphasizes the hypothesis of the influence of systematic isolation of contagious individuals (mainly from easily identifiable lepromatous signs) in an incarcerating environment rifed with malnutrition, abuses, promiscuity and tuberculosis, particularly at the end of the medieval period when this disease was rapidly disappearing.
Cementochronology should obviously be implemented on other similar sites in order to strengthen this hypothesis in addition to comparative isotopic analyses to better identify and estimate diet deficiencies.
19th European Meeting, Lille, France
Age-at-death estimation of pathological individuals. A complementary approach using teeth cementum annulations
BERTRAND B, COLARD T, NAJI S, POLET C.
Estimating individual age-at-death is a crucial yet still intricate step in paleopathology studies. Methods for adult age determination are mainly based on bone remodeling, maturation indicators or degenerative processes. Even though the biological variability of the indicators for each method is recognized, it is necessary to question the reliability of an approach based on morphological modifications when the individual is affected by bone growth pathologies. Our study looks at several individuals exhibiting achondroplasia, osteomalacia and osteogenesis imperfecta, using the cementum annulations technique for estimating their individual age-at-death. This dental method is a complementary approach useful to validate/ invalidate an estimated individual age based on other bone indicators without the traditional biases. Teeth are often better preserved than bones archaeologically and acellular cementum observed in the median part of the root is rarely affected by pathological or degenerative processes. The observation of cementum annulations is therefore a particularly suitable tool for the required scientific carefulness necessary to individual age estimation in paleopathology/anthropology studies.