Spatial Distributions of Oxygen Stable Isotope Ratios in Tap Water From Mexico for Region of Origin Predictions of Unidentified Border Crossers

One of the many difficulties associated with identifying undocumented border crossers stems from an inability to narrow down the search area for the region of origin and family members to obtain family reference samples for DNA comparison. While the geography of regions of origins is wide, the biological profiles of the undocumented border crossers often show strong similarities, young and male. The isotopic composition of human bones, teeth, and hair has been demonstrated to be useful biomarkers for tracing locations and movements of individuals and for aiding in the identification of human remains. Data obtained from human remains can be compared to and aligned with various reference sources, such as soils and bedrock, archaeological remains, or cultural data. Here, the spatial deficiency in isotopic reference data for Mexico, specifically for oxygen (δ¹⁸O) isotopes in tap water, is being addressed through the collection and analysis of over 150 water samples and explored with tooth enamel isotopic values from recently identified Mexican nationals. The isoscape was developed using a Spine with Barriers interpolation method and shows sufficient detail to narrow down the regions where specific isotopic values are represented. The individuals were plotted on the developed isoscape using conditional correlations. The methodology was successful in assigning the correct regions of origin for the two individuals, which shows the tremendous potential of the developed isoscape. Nonetheless, there is more research needed to further improve upon this geolocation method, including analysis of multiple isotopes in different tissues, and the development of new isotopic methods.     

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.     

Analysis of enamel rod end patterns on tooth surface for personal identification--ameloglyphics

Ameloglyphics is the study of enamel rod end patterns on a tooth surface. Our aim was to study the in vivo analysis of enamel rod end patterns on tooth surfaces for personal identification. In this study, the maxillary left canine and 1st premolar of 30 men and 30 women were included. The cellulose acetate peel technique was used to record enamel rod endings on tooth surfaces. Photomicrographs of the acetate peel imprint were subjected to VeriFinger Standard SDK v5.0 software for obtaining enamel rod end patterns. All 120 enamel rod end patterns were subjected to visual analysis and biometric analysis. Biometric analysis revealed that the enamel rod end pattern is unique for each tooth in an individual. It shows both intra- and interindividual variation. Enamel rod end patterns were unique between the male and female subjects. Visual analysis showed that wavy branched subpattern was the predominant subpattern observed among examined teeth. Hence, ameloglyphics is a reliable technique for personal identification.     

Identification of a tooth-like foreign body in Swine sausage

A tooth-like foreign body (FB) was found inside a sausage bread. Analysis aimed to investigate whether the FB was a tooth and its origin. The FB was measured, weighed, photographed, and radiographed. Macroscopic findings were suggestive of an anterior tooth. Histological slides of undecalcified cross-sections of the FB and samples of human and swine teeth were prepared. Histological features of the FB (in light microscopy, 125× magnification) were discrepant from human tissues. Compared histological analysis displayed majority of features consistent with a hypsodont swine tooth, probably a canine. Cellularized cementum in crown region, adjacent to the enamel, and shape of the cementocytes were the main criteria excluding the possibility of human origin of the FB. Scanning electronic microscopy and energy-dispersive spectroscopy were not performed because of fewer features to be analyzed and FB size. It was concluded that the FB may have been incorporated during meat grinding of the sausage.     

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.     

Stable isotope analyses of heroin seized from the merchant vessel Pong Su

A new type of heroin HCl seized in Australia was examined by stable isotope analysis. The final origin/process classification of these samples by chromatographic signature profiles of the impurity/manufacturing by-products was previously determined to be "unknown" by two independent national laboratories. Various drug enforcement authorities speculated that the heroin might be from a new region or new illicit process due to the unusual chromatographic impurity profiles that were present. Samples from 20 different kilogram packages were examined for isotopic content to determine if the samples fit isotopic patterns of known origins or if they were unique to any known origins. Authentic specimens from Southeast Asian (N=59), Southwest Asia (N=37), South America (N=104), and Mexico (N=21) we concomitantly examined for comparison purposes. Both continuous flow elemental analysis-isotope ratio mass spectrometry and gas chromatography-isotope ratio mass spectrometry techniques were utilized. Heroin samples were also converted to morphine, without apparent isotopic fractionation, utilizing methanolic HCl for gas chromatography-isotope ratio mass spectrometry. The Pong Su samples were found to be isotopically and isotopically/alkaloidally distinct from the known origin/process classifications of Southwest Asian, Southeast Asian, South American, and Mexican.     

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.     

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.     

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.     

Forensic isoscapes based on intra-individual temporal variation of δ18O and 206Pb/207Pb in human teeth

Isotopic signatures used in the georeferencing of human remains are largely fixed by spatially distinct geologic and environmental processes. However, location-dependent temporal changes in these isotope ratios should also be considered when determining an individual’s provenance and/or trajectory. Distributions of the relevant isotopes can be impacted by predictable external factors such as climate change, delocalisation of food and water sources and changes in sources and uses of metals. Using Multi-Collector Inductively-Coupled Plasma Mass Spectrometer (MC-ICP-MS) analyses of ²⁰⁶Pb/²⁰⁷Pb in tooth enamel and dentin from a population of 21 ± 1-year-old individuals born circa 1984 and isotope ratio mass spectrometry (IRMS) of δ¹⁸O in their enamel, we examined the expected influence of some of these factors. The resulting adjustments to the geographic distribution of isotope ratios (isoscapes) found in tooth enamel and dentin may contain additional useful information for forensic identification, but the shifts in values can also impact the uncertainty and usefulness of identifications if they are not taken into account.

KEY POINTS

• Isoscapes of ²⁰⁶Pb/²⁰⁷Pb and δ¹⁸O used for geolocation are not static.
• Within a few years, the enamel and dentin of a person may exhibit measurable differences in ²⁰⁶Pb/²⁰⁷Pb even without changing locations.
• Changes in climatic patterns tied to rising temperatures are more significant than the direct effect of increasing temperature on δ¹⁸O fixed in tooth bioapatite.
• Third molar (M3) enamel mineralisation includes material incorporated from before formal amelogenesis takes place.

     

Estimation of age from a tooth by means of racemization of an amino acid, especially aspartic acid--comparison of enamel and dentin.

In a study of age estimation from teeth by means of measuring racemization of aspartic acid (Asp), a representative amino acid, the accuracy of data from enamel and dentin in the same tooth was compared. The correlation of D/L ratio of aspartic acid with actual age gave the following parameters: r = 0.928, sigma = +/- 5.2, k = 4.47 x 10(-4) yr-1 in enamel and r = 0.995, sigma = +/- 1.4, k = 5.75 x 10(-4) yr-1. The difference in ages between one estimated by the D/L ratio and the actual one was within +/- 3 years in dentin, while in enamel an error of from 2 to 11 years was observed. Reaction rate constants of the racemization in a dry postmortem state (15 degrees C) were calculated as k = 9.70 x 10(-8) yr-1 in enamel, and k = 1.33 x 10(-7) yr-1 in dentin. Compared to rates determined from teeth recently extracted from living subjects, the rate was higher in dentin than in enamel. These data reconfirmed that dentin is superior to enamel in making exact age estimations from teeth.     

Is re-creation of human identity possible using tooth prints? An experimental study to aid in identification

Enamel in teeth, as documented is the hardest substance in the entire human body. Tooth prints are the enamel rod end patterns on the tooth surface. Could this fact be a boon in utilizing it for an individual's identification in the hands of forensic experts? A study has been attempted towards the same. These tooth prints were recorded for 60 extracted tooth specimens after acid etching using a cellophane tape. Subsequently a digital image of the print was obtained which was subjected to biometric conversion using Verifinger standard SDK version 6.0 software followed by the use of Automated Fingerprint Identification System (AFIS) software for comparison of the tooth prints. In results we observed that tooth prints were composed of varied patterns and sub-patterns. A comparison was made between the tooth prints of different and the same individual and also between different classes of teeth (incisors, canines, premolars and molars). None of the patterns exhibited intra- and inter-individual similarity. Nor did any particular class of the tooth could be preferentially used over the other for an individual identification. This field demands a need for further exploration towards the use of tooth prints for establishing an individual's identity.     

Using Carbon,Oxygen, Strontium,and Lead Isotopes in Modern Human Teeth for Forensic Investigations: A Critical Overview Based on Data from Bulgaria

Isotopic data obtained from human remains can provide information about an individual's origin, migration, and diet. We evaluate the usefulness of carbon, oxygen, strontium, and lead isotopes for forensic investigations by comparing data from Bulgarian teeth with data from other regions. Geo‐referencing based on oxygen or strontium isotopes can be misleading due to overlap with other countries in Europe and other continents. Carbon and lead isotopes, in combination with oxygen and strontium isotopes, provide the most useful information for identification of local vs foreigner status. In particular, high‐precision Pb isotopes show a distinct “Bulgarian” range; however, it is possible that individuals from other countries in Eastern Europe and/or central to western Asia could have overlapping isotopic values. Additional high‐precision multi‐isotope data from modern humans from different regions in the world are required to transition from speculative to more quantitative estimation of a geographical place of origin for unidentified human remains.     

限定继承的悖理与我国《继承法》的修正

源于古罗马法的限定继承制度其实是受将遗产范围视为被继承人的财产权利义务、遗产归属于继承人所有等制度相互影响的结果。然而,近世大陆法系的不同国家或地区在规定限定继承制度的同时,又以遗产为基础构建了遗产管理制度。但就遗产管理人所履行的职责而言,遗产管理人不仅要清理被继承人的财产权利义务,而且也要将清偿被继承人债务后的剩余财产分配给继承人。如此,遗产范围对遗产管理人、继承人就有所不同,即遗产管理人所面对的遗产范围应为被继承人的财产权利义务,继承人所面对的遗产范围为被继承人的财产权利;同时,遗产并不归属继承人所有或者遗产管理人所有,清偿完遗产债务后的剩余遗产才由继承人取得所有权。进而,遗产管理制度所逻辑演绎的遗产范围和遗产归属已经与限定继承的形成基础相悖,立法再予以规定限定继承制度也就欠缺合理。     

Radiocarbon analysis of dental enamel and bone to evaluate date of birth and death: perspective from the southern hemisphere

Radiocarbon analysis was conducted on dental enamel, cortical bone and trabecular bone from four human adults from Andean Peru with known birth dates and death dates, the latter all falling within the modern bomb-curve period. Radiocarbon results were compared with known tropospheric values from the southern hemisphere. The results demonstrate that dental enamel can provide useful information regarding birth dates in consideration of known formation times of the specific teeth examined if the radiocarbon values fall within the modern bomb-curve period. Trabecular bone radiocarbon values are closer to the tropospheric values at the date of death than are values from cortical bone reflecting relative differences in the rate of bone remodeling in those tissues. Age at death also represents an important factor.     

Age at death determinations for autopsied remains based on aspartic acid racemization in tooth dentin: importance of postmortem conditions

The extent of aspartic acid racemization in human dentin can be used to assess chronological age of the individual. This novel chemical method of aging human remains has potential applications in forensic sciences. Six autopsy cases have been analyzed for D/L aspartic acid contents, and their ages at death calculated. Independent age information came from known identity, tooth maturation, or tooth wear estimations. The six cases represented a range of postmortem fates: recent demise, burial, and ground surface exposure. Five samples, four recently deceased and one a burial, showed racemization ages in close agreement with other age data. One specimen, subjected to 51 days of open air exposure, exhibited a vastly inflated racemization age. Postmortem conditions are crucial to the accuracy of racemization age at death measurements.     

Development and Assessment of Postcranial Sex Estimation Methods for a Guatemalan Population

This study tests whether postcranial sex estimation methods generated from Hispanic, and mainly Mexican samples, can be successfully applied to other increasingly common migrant populations from Central America. We use a sample of postcranial data from a modern (1980s) Guatemalan Maya sample (n = 219). Results indicate a decrease in classification accuracies for previously established univariate methods when applied to the Guatemalan study sample, specifically for males whose accuracies ranged from 30 to 84%. This bias toward inaccuracies for Guatemalan males is associated with the smaller skeletal sizes for the Guatemalan sample as compared to the samples used in the tested sex estimation methods. In contrast, the tested multivariate discriminant function classification yielded less sex bias and improved classification accuracies ranging from 82 to 89%. Our results highlight which of the tested univariate and multivariate methods reach acceptable levels for accuracy for sex estimation of cases where the region of origin may include Guatemala.     

Crack Propagation in Teeth: A Comparison of Perimortem and Postmortem Behavior of Dental Materials and Cracks*

Abstract: This study presents a new method for understanding postmortem heat-induced crack propagation patterns in teeth. The results demonstrate that patterns of postmortem heat-induced crack propagation differ from perimortem and antemortem trauma-induced crack propagation patterns. Dental material of the postmortem tooth undergoes dehydration leading to a shrinking and more brittle dentin material and a weaker dentin-enamel junction. Dentin intertubule tensile stresses are amplified by the presence of the pulp cavity, and initiates crack propagation from the internal dentin, through the dentin-enamel junction and lastly the enamel. In contrast, in vivo perimortem and antemortem trauma-induced crack propagation initiates cracking from the external surface of the enamel toward the dentin-enamel junction where the majority of the energy of the crack is dissipated, eliminating the crack’s progress into the dentin. These unique patterns of crack propagation can be used to differentiate postmortem taphonomy-induced damage from antemortem and perimortem trauma in teeth.     

Third molar development according to chronological age in populations from Spanish and Magrebian origin

Spain is frequently the entrance country into the European Union for undocumented immigrants, especially those from the Magreb (Northern Africa). Forensic age estimates for these persons are difficult because systematic studies of dental maturity are lacking. Three different populations were analyzed to determine the pattern of development of third molars as a tool for age estimation in people of different ethnic and geographic origin. Orthopantomograms from two different populations of Spanish origin (Galicia in northwestern continental Spain, and Ceuta, a Spanish province in Northern Africa) were compared to radiographs of molars from a Magrebian population (Northern Africa) resident in Ceuta. Orthopantomograms were obtained from a private dental clinic (n=344) in Galicia and from the Public Oral Health Services (n=228) in Ceuta. We looked for differences in third molar mineralization (determined with the Demirjian scale) that might serve as age indicators (older versus younger than 18 years). Differences in maturation patterns were found between sexes and populations of origin. Mineralization of tooth 38 was more advanced in males than females among subjects 18 years of age and older in all three populations. Moreover, mineralization of tooth 38 in subjects aged 18 years and older was significantly slower in the Spanish-Galicia population than in the Magrebian-Ceuta population. We found no significant differences between Magrebian and Spanish individuals from Ceuta. We conclude that differences in tooth 38 mineralization may be related more with socio-geographical than ethnic origin (ancestry), and thus constitute evidence of the relevance of socio-geographic rather than genetic factors in third molar development. We used ROC analysis to determine the accuracy of the examiner's ability to correctly estimate age as younger or older than 18 years. The results suggest that Demirjian stage for tooth 38 can be considered a good indicator of age in all three populations.     

The use of quantitative light-induced fluorescence (QLF) to identify composite restorations in forensic examinations

There has been a large increase in the number of tooth colored restorations "white fillings" placed in recent years. An increased demand from the public for more aesthetic dental restorations causes a potential problem for forensic dentists who may find the fillings difficult to identify and hence include in postmortem odontograms. This has implications for the accuracy of dental identifications, particularly in situations where limited time is available for postmortem identification, e.g., mass casualty incidents. A new method for the detection of composite restorations is presented. Quantitative Light-induced Fluorescence (QLF) is a technique currently employed to detect small changes in enamel mineral content. An experiment was conducted to determine if the technique would afford a greater degree of contrast between composite and enamel and thus enable the accuracy of composite identification in enamel. Twenty-four previously extracted human premolars were gently cleaned with pumice and wet-and-dry paper. Twelve were subsequently randomly selected and restored on their buccal surfaces with Spectrum (a composite) following manufacturer's instructions. No attempt was made to color match the teeth and all were filled with shade B3. Twelve teeth were left unrestored. QLF and normal white light images were taken of both restored and non-restored surfaces with teeth wet and then dried. Ten forensic dentists were asked on two separate occasions (one month between each attempt) to indicate whether or not they thought the surface was: a) restored or b) unrestored. Results indicate that forensic dentists detected a significantly higher proportion (p<0.005) of filled surfaces with QLF.