Analysis of artificial radiocarbon in different skeletal and dental tissue types to evaluate date of death

Radiocarbon dating, with special reference to the modern bomb-curve, can provide useful information to elucidate the date of death of skeletonized human remains. Interpretation can be enhanced with analysis of different types of tissues within a single skeleton because of the known variability of formation times and remodeling rates. Analysis of radiocarbon content of teeth, especially the enamel in tooth crowns, provides information about the date of formation in the childhood years and in consideration of the known timing of tooth formation can be used to estimate the birth date after 1950 ad. Radiocarbon analysis of modern cortical and trabecular bone samples from the same skeleton may allow proper placement on the pre-1963 or post-1963 sides of the bomb-curve as most trabecular bone generally undergoes more rapid remodeling than does most cortical bone. Pre-1963 bone formation would produce higher radiocarbon values for most trabecular bone than for most cortical bone. This relationship is reversed for formation after 1963. Radiocarbon analysis was conducted in this study on dental, cortical, and trabecular bone samples from two adult individuals of known birth (1925 and 1926) and death dates (1995 and 1959). As expected, the dental results correspond to prebomb-curve values reflecting conditions during the childhoods of the individuals. The radiocarbon content of most bone samples reflected the higher modern bomb-curve values. Within the bone sample analyses, the values of the trabecular bone were higher than those of cortical bone and supported the known placement on the pre-1963 side of the bomb-curve.     

Radiocarbon Analysis of Human Remains: A Review of Forensic Applications

Radiocarbon analysis of organic materials, with the comparison of values with those of the post‐1950 modern bomb curve, has proven useful in forensic science to help evaluate the antiquity of evidence. Applications are particularly helpful in the study of human remains, especially with those displaying advanced decomposition of soft tissues. Radiocarbon analysis can reveal if the remains relate to the modern, post‐1950 era and if so, also provide information needed to evaluate the death and birth date. Sample selection and interpretation of results must be guided by knowledge of the formation and remodeling of different human tissues, as well as contextual information and the approximate age at death of the individual represented. Dental enamel does not remodel and thus captures dietary radiocarbon values at the time of juvenile formation. Most other human tissues do remodel but at differing rates and therefore collectively offer key information relative to the estimation of the death date.     

Fragment analysis in forensic anthropology

Anthropological analysis of fragmentary evidence can be challenging but diverse methods allow substantial information to be gleaned. Scanning electron microscopy/energy dispersive X-ray spectroscopy enables determination if bone and/or tooth tissue is present. Protein radioimmunoassay or DNA analysis can establish the species present. Histological analysis can assist in species determination and reveal information about thermal changes. Radiocarbon analysis with special reference to the modern bomb-curve can clarify the postmortem interval. Anthropologists should also be aware that DNA analysis not only can enable positive identification but assist in the evaluation of sex and age at death.     

Personal identification of cold case remains through combined contribution from anthropological, mtDNA, and bomb-pulse dating analyses

In 1968, a child's cranium was recovered from the banks of a northern Canadian river and held in a trust until the "cold case" was reopened in 2005. The cranium underwent reanalysis at the Centre for Forensic Research, Simon Fraser University, using recently developed anthropological analysis, "bomb-pulse" radiocarbon analysis, and forensic DNA techniques. Craniometrics, skeletal ossification, and dental formation indicated an age-at-death of 4.4 ± 1 year. Radiocarbon analysis of enamel from two teeth indicated a year of birth between 1958 and 1962. Forensic DNA analysis indicated the child was a male, and the obtained mitochondrial profile matched a living maternal relative to the presumed missing child. These multidisciplinary analyses resulted in a legal identification 41 years after the discovery of the remains, highlighting the enormous potential of combining radiocarbon analysis with anthropological and mtDNA analyses in producing confident personal identifications for forensic cold cases dating to within the last 60 years.     

Analysis of 14C and 13C in teeth provides precise birth dating and clues to geographical origin

The identification of human bodies in situations when there are no clues as to the person's identity from circumstantial data, poses a difficult problem to the investigators. The determination of age and sex of the body can be crucial in order to limit the search to individuals that are a possible match. We analyzed the proportion of bomb pulse derived carbon-14 ((14)C) incorporated in the enamel of teeth from individuals from different geographical locations. The 'bomb pulse' refers to a significant increase in (14)C levels in the atmosphere caused by above ground test detonations of nuclear weapons during the cold war (1955-1963). By comparing (14)C levels in enamel with (14)C atmospheric levels systematically recorded over time, high precision birth dating of modern biological material is possible. Above ground nuclear bomb testing was largely restricted to a couple of locations in the northern hemisphere, producing differences in atmospheric (14)C levels at various geographical regions, particularly in the early phase. Therefore, we examined the precision of (14)C birth dating of enamel as a function of time of formation and geographical location. We also investigated the use of the stable isotope (13)C as an indicator of geographical origin of an individual. Dental enamel was isolated from 95 teeth extracted from 84 individuals to study the precision of the (14)C method along the bomb spike. For teeth formed before 1955 (N=17), all but one tooth showed negative Δ(14)C values. Analysis of enamel from teeth formed during the rising part of the bomb-spike (1955-1963, N=12) and after the peak (>1963, N=66) resulted in an average absolute date of birth estimation error of 1.9±1.4 and 1.3±1.0 years, respectively. Geographical location of an individual had no adverse effect on the precision of year of birth estimation using radiocarbon dating. In 46 teeth, measurement of (13)C was also performed. Scandinavian teeth showed a substantially greater depression in average δ(13)C (-14.8) than teeth from subjects raised in Japan (-13.5), Middle East and North Africa (-12.7) and South America (-10.9). In summary, isotopic analysis of carbon in enamel from a single tooth can give a good estimate of the year of birth of an individual and also provide information about the geographical origin of the individual. This strategy can assist police and forensic authorities when attempting to solve unidentified homicide cases and may facilitate the identification work associated with mass disasters.     

Radiocarbon dating as tool to assist in triaging cases of unidentified human remains in Victoria,Australia: A case series

In cases where human remains are unidentified because there is no initial identification hypothesis, limited contextual information, and/or poor preservation, radiocarbon (¹⁴C) dating may be a useful tool to further assist with identification. Through measuring the amount of ¹⁴C remaining in organic material, such as bone, teeth, nail, or hair, radiocarbon dating may provide an estimated year of birth and year of death for a deceased person. This information, may assist in, establishing whether a case of unidentified human remains (UHR) is actually of medicolegal significance and therefore, requires forensic investigation and identification. This case series highlights the application of ¹⁴C dating to seven of the 132 UHR cases in Victoria, Australia. Cortical bone was sampled from each case and the level of ¹⁴C was measured to provide an estimated year of death. Four of the seven cases analyzed contained the levels of ¹⁴C consistent with an archeological timeframe, one contained a level of ¹⁴C consistent with a modern (i.e., of medicolegal significance) timeframe, and the results for the remaining two samples were inconclusive. Applying this technique not only reduced the number of UHR cases in Victoria but also has investigative, cultural, and practical implications for medicolegal casework in general.     

The application of amino acid racemization in the acid soluble fraction of enamel to the estimation of the age of human teeth

Estimation of age-at-death for skeletonised forensic remains is one of the most significant problems in forensic anthropology. The majority of existing morphological and histological techniques are highly inaccurate, and show a bias towards underestimating the age of older individuals. One technique which has been successful in forensic age estimation is amino acid racemization in dentine. However, this method cannot be used on remains where the post-mortem interval is greater than 20 years. An alternative approach is to measure amino acid racemization in dental enamel, which is believed to be more resistant to change post-mortem. The extent of amino acid racemization in the acid soluble fraction of the enamel proteins was determined for modern known age teeth. A strong correlation was observed between the age of the tooth and the extent of racemization. No systematic bias in the direction of age estimation errors was detected. For the majority of teeth analyzed, the presence of dental caries did not affect the results obtained. In a minority of cases, carious teeth showed a higher level of racemization than would be expected given the age of the individual. These results indicate that amino acid racemization in enamel has the potential to be used in age estimation of skeletal remains.     

Evaluation of seven methods of estimating age at death from mature human skeletal remains.

Different approaches to the estimation of age at death in mature human skeletal remains were evaluated utilizing samples from 19 recent French autopsy individuals of known age at death. Methods of estimating age at death from single-rooted teeth, the sternal ends of the fourth ribs, the symphyseal face of the pubis and femoral cortical remodeling were evaluated by two independent observers (three observers for the teeth). Comparison included ages estimated from three more comprehensive approaches utilizing data from the application of two or more of the individual methods. The results indicate that the comprehensive approaches are superior to the individual ones and the success of the latter reflects not only the morphological expression of the aging process, but also the technique complexity and the experience of the investigator. Of the individual techniques, the "Lamendin" dental technique was most effective for individuals of ages greater than 25 years.     

X‐ray Scattering Evaluation of Ultrastructural Changes in Human Dental Tissues with Thermal Treatment

Micro‐ and ultrastructural analysis of burned skeletal remains is crucial for obtaining a reliable estimation of cremation temperature. Earlier studies mainly focused on heat‐induced changes in bone tissue, while this study extends this research to human dental tissues using a novel quantitative analytical approach. Twelve tooth sections were burned at 400–900°C (30‐min exposure, increments of 100°C). Subsequent combined small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) experiments were performed at the Diamond Light Source synchrotron facility, where 28 scattering patterns were collected within each tooth section. In comparison with the control sample, an increase in mean crystal thickness was found in burned dentine (2.8‐fold) and enamel (1.4‐fold), however at a smaller rate than reported earlier for bone tissue (5–10.7‐fold). The results provide a structural reference for traditional X‐ray scattering methods and emphasize the need to investigate bone and dental tissues separately to obtain a reliable estimation of cremation temperature.     

Dietary health does affect histological age assessment: an evaluation of the Stout and Paine (1992) age estimation equation using secondary osteons from the rib

An age at death estimation equation that uses rib histological variables presented by Stout and Paine was used to evaluate a skeletal population of individuals with a known age at death and cause of death from either malnutrition or the niacin deficiency disease pellagra. The sample was comprised of 26 autopsied black South Africans. Histological analysis of mounted thin sections involved the microscopic measurement of cortical area and a count of the number of intact and fragmentary secondary osteons for the entire cross-section of the rib. Rib osteon population density values were then calculated for each case. It was found that this equation under-aged individuals on average by 29.2 years. Overall, secondary osteon size and Haversian canals tended to be larger than expected, while cortical bone area was less when compared with a control population. The implications of these findings are critical given that many of the skeletal remains examined by forensic anthropologists come from marginalized backgrounds, including malnutrition. This research suggests that measurements based on healthy cases may not be useful in an analysis of individuals with poor diet and health. It is argued that new standards for histological age assessment methods need to be created that account for variation in the health status of individuals examined by forensic anthropologists.     

Individualization and enamel histology: a case report in forensic anthropology.

The cranium of a native Indian child about six years old was found in 1979 near Taseko River, British Columbia, Canada. While the remains matched the report of a child missing for eight years in terms of race, age at death, locale, and elapsed time since death, the cranium and dentition were basically unidentifiable because of the claimed lack of medical or dental history. There was no dental work, and the parents were unknown or dead. We report the presence, in the dental enamel of the primary and secondary dentition, of stress markers, termed striae of Retzius, whose locations correspond well with anecdotal reports and recently discovered medical records which describe the timing of specific episodes of stress. The enhanced probability of personal identification from dental histological stress markers is evaluated.     

Strontium and geolocation, the pathway to identification for deceased undocumented mexican border-crossers: a preliminary report

Much of the difficulty associated with identifying and repatriating deceased undocumented border-crossers stems from an inability to narrow down the search area to more probable options. Analysis of the isotopic variation in the tooth enamel of modern Mexican populations is currently underway at the University of California Santa Cruz. Using Thermo Ionization Mass Spectrometry, the pilot research analyzed strontium isotopes located in the donated permanent teeth of Mexican-born individuals of known origin from four states. The preliminary results reveal the formation of three distinctly significant regions in the data set. Using the technology outlined here, a map documenting the isotopic variation in modern Mexican tooth enamel is being complied to use for cross comparison with deceased border crossers of unknown origin.     

牙髓细胞DNA含量与死后经过时间的相关性

目的探讨死后不同环境温度下离体牙的牙髓细胞平均DNA含量变化与死后时间(PM I)的相关性。方法采用细胞图像分析系统(PIPS-2020),测定离体即刻至15d牙齿在低温环境(10~15℃)和高温(30~35℃)环境下牙髓细胞DNA含量变化值,并对其数据进行统计学分析。结果在不同的环境温度下,牙髓细胞DNA降解的速度有所不同,温度的升高有加速牙髓细胞DNA降解的趋势,且DNA降解存在一个平台期。低温组牙髓细胞平均DNA含量与PM I之间的相关系数r=0.953,相关指数R2=0.917;高温组的相关系数r=0.991,相关指数R2=0.971。结论牙髓细胞平均DNA含量与PM I之间具有高度相关性,测定牙髓细胞的DNA变化情况对推断3d(高温环境)或6d(低温环境)后的PM I有参考价值。     

Age estimation in small children: reference values based on counts of deciduous teeth in Finns

The eruption of teeth in the mouth is suitable for age estimations during the period when teeth are actively emerging, in the deciduous dentition phase approximately from the age of 6 months to 2.5 years. Estimations of age can be performed simply by counting the number of teeth in the mouth. Reliability of the estimates depends on the reference data available and each population group should preferably have its own standards. In the present study timing of eruption of successive deciduous teeth was studied longitudinally in 129 Finns. The dates of clinical eruption of deciduous teeth were recorded by mothers and checked by dentists. In 40 of the 129 children emergence ages of at the most the four last teeth were based only on semiannual registrations performed by dentists. The main purpose was to provide normal timetables of tooth eruption in small children in forms that are practical in estimations of dental age. No sexual dimorphism existed in the timing of clinical eruption of successive deciduous teeth. The mean age corresponding to the presence of one tooth in the mouth was 7.1 months (S.D.=1.78) and that corresponding to tooth count 19 was 27.8 months (S.D.=3.99). If the chronological age is known, the presented distributions and means with variations make it possible to estimate the degree of advancement or delay in a child’s dental development. If the age of the child is not known, the mean and median ages can be used for estimations of chronological age. However, estimations of age should not be based only on tooth counts because of marked variation also within this homogeneous group.     

Dental CT imaging as a screening tool for dental profiling: advantages and limitations

The use of dental processing software for computed tomography (CT) data (Dentascan) is described on postmortem (pm) CT data for the purpose of pm identification. The software allows reconstructing reformatted images comparable to conventional panoramic dental radiographs by defining a curved reconstruction line along the teeth on oblique images. Three corpses that have been scanned within the virtopsy project were used to test the software for the purpose of dental identification. In every case, dental panoramic images could be reconstructed and compared to antemortem radiographs. The images showed the basic component of teeth (enamel, dentin, and pulp), the anatomic structure of the alveolar bone, missing or unerupted teeth as well as restorations of the teeth that could be used for identification. When streak artifacts due to metal-containing dental work reduced image quality, it was still necessary to perform pm conventional radiographs for comparison of the detailed shape of the restoration. Dental identification or a dental profiling seems to become possible in a noninvasive manner using the Dentascan software.     

Age estimation through histological study of trabecular volume and cortical bone width of the iliac crest

There have been many methods proposed to estimate the age of human bones in forensic medicine or in forensic anthropology, including those that assess histological structures. In this study, age was evaluated through the histomorphometric study of trabecular volume and cortical width of the right iliac crest. A total of 25 samples A total of 66 samples (42 male and 24 female) were obtained from necropsies of judicial cases, with ages ranging from 13 to 58years, who had died a sudden or violent death. The samples were obtained using Bordier's trocar for bone biopsy, in a period not exceeding 24h after death. The samples were examined without decalcification, with 96° alcohol dehydration, embedding in methyl methacrylate, and sectioned with a microtome Reichert (3μm). The sections were fixed on microscope slides and stained using toluidine blue, Goldner trichrome and hematoxylin-eosin methods. The samples were studied under a Leica DM LB microscope and the images were digitally captured. The digital images were processed using an image analysis program and data were analyzed using the SPSS statistical package. The results demonstrated that the combination of the trabecular volume and cortical width acted as predictors of the age in subjects which did not suffer from any deterioration of bone and/or mineral metabolism.     

Age estimation in small children: reference values based on counts of deciduous teeth in Finns

The eruption of teeth in the mouth is suitable for age estimations during the period when teeth are actively emerging, in the deciduous dentition phase approximately from the age of 6 months to 2.5 years. Estimations of age can be performed simply by counting the number of teeth in the mouth. Reliability of the estimates depends on the reference data available and each population group should preferably have its own standards. In the present study timing of eruption of successive deciduous teeth was studied longitudinally in 129 Finns. The dates of clinical eruption of deciduous teeth were recorded by mothers and checked by dentists. In 40 of the 129 children emergence ages of at the most the four last teeth were based only on semiannual registrations performed by dentists. The main purpose was to provide normal timetables of tooth eruption in small children in forms that are practical in estimations of dental age. No sexual dimorphism existed in the timing of clinical eruption of successive deciduous teeth. The mean age corresponding to the presence of one tooth in the mouth was 7.1 months (S.D.=1.78) and that corresponding to tooth count 19 was 27.8 months (S.D.=3.99). If the chronological age is known, the presented distributions and means with variations make it possible to estimate the degree of advancement or delay in a child's dental development. If the age of the child is not known, the mean and median ages can be used for estimations of chronological age. However, estimations of age should not be based only on tooth counts because of marked variation also within this homogeneous group.     

The core technique in the determination of age at death of skeletons.

This study proposed an histological method of estimating age at death in skeletons that uses a 0.4-cm-diameter core of cortical bone. Age-estimating regression equations were generated from data obtained from the analysis of bone cores taken from femurs, tibiae, humeri, and ulnas of cadavers. When the regression equations generated in this study were applied to eight forensic science cases, accurate ages at death were estimated.     

Color change in dental tissue as a sign of thermal damage

The appearance of hard human tissue after thermal damage permits certain conclusions to be drawn with regard to fire parameters. In addition to morphological destruction, the change in color of dental tissues like enamel, dentine, and cement is also important. We studied teeth extracted from 330 human males and females under well-defined time and temperature conditions. Using the DIN and RAL color indexes, the color phenomenon was evaluated on the basis of the amount of glowing obtained when the teeth were heated. It is easiest to determine the color change in cement, as no calculus or hindering plaques are on the root surface. In addition to this, destruction of the tooth root takes place only during extreme combustion conditions. Determining the dentine color is more difficult and is possible only after the enamel splits. Also, the different dentine thicknesses hinders the observation of color. When the enamel was tested, it was found that the differences in color caused by high temperatures are unimportant. Moreover, the enamel burst into small particles. The effect we observed regarding the anthracite lustre using low temperatures was typical, and the best results were obtained in dental roots with eight color scales. All three dental hard tissues have in common that the variations in color appear regularly and successively according to ascending temperature or duration of time: natural dental color, black, brown, blue, grey, white, and pink. In these processes, the temperature and combustion time are inversely proportional to the velocity of color change. The literature is discussed that deals with temperature- and time-dependent color phenomena of dental hard tissues destroyed as a result of thermal damage.     

A new approach to amino acid racemization in enamel: testing of a less destructive sampling methodology

Aspartic acid racemization has been found to be an accurate measure of age at death for recent forensic material. This paper examines the practicality of using acid etching of the tooth surface to extract amino acids from the enamel for racemization analysis. By serial etching of the tooth and contamination of the teeth with bovine serum albumin prior to etching, the ability of etching to remove contamination was assessed. The destructiveness of the method was visualized and quantified using micro-computed tomography (micro-CT). By bleaching the teeth and by deeper etching it was possible to obtain more consistent values. While etching had little effect on the enamel at the macroscale, it did have an impact at the microscale. The quantities of enamel removed varied depending upon the tooth morphology, but were not large. Acid etching of enamel thus appears to be a promising new method for extracting proteins for amino acid racemization age estimation noninvasively.