Age estimation with cemental incremental lines in normal and periodontally diseased teeth using phase contrast microscope: an original research

Background Age estimation is an important factor in forensic science for human identification. Teeth are considered to play a vital role as they resist decomposition at death unlike other tissues. This resistance and the gradual structural changes that take place throughout the life of an individual have made teeth useful indicators for age estimation. Dental cementum shows continuous apposition throughout the life of an individual. Tooth cemental annulation is a microscopic method for the determination of an individual’s age based on the analysis of incremental lines of cementum. Light microscopy as well as specialized microscopic methods have been employed to enhance the assessment of the cemental annulations. Periodontal disease is the most common dental problem affecting millions of people. Assessing the efficiency of the tooth cemental annulations method in periodontally diseased teeth is an important requisite. This study aims at assessing and evaluating the tooth cemental annulations in normal and periodontally diseased teeth using phase contrast microscopic method for age determination. Results A total of 60 teeth were included in the study and out of which 30 teeth were normal (sound teeth without any associated pathologies) and 30 were periodontally involved teeth respectively. Longitudinal ground sections were prepared and observed under phase contrast microscope. Measurements were made using an image analyzer software. The total width of the cementum was divided by the distance between two incremental lines. The eruption age of the tooth was then added to this to obtain the chronologic age for each individual. The results in the present study showed that tooth cemental annulations are applicable to periodontally sound teeth as well as in periodontally diseased teeth. There was no significant difference of estimated age from the actual age in both periodontally sound and periodontally diseased teeth. Normal teeth showed a reliability value of 92% and periodontally compromised teeth showed 96% respectively. There was no substantial influence of periodontal health on the estimated age. Conclusions The study concludes that the use of phase contrast microscopy in conjunction with image enhancement procedures improves the accuracy of age estimation and may serve as a reliable aid in forensic identification.

Alignment-Free Sensing Module for Absolute and Incremental Lines in Linear Positioning System Based on Tunneling-Magnetoresistance Sensors

An alignment-free sensing module for the positioning system based on tunneling magnetoresistive (TMR) sensors with an absolute-incremental-integrated scale is demonstrated. The sensors of the proposed system for both lines consist of identical layer stacks; therefore, all sensors can be fabricated in identical processes from thin film deposition to device patterning on a single substrate. Consequently, the relative position of the sensors can be predefined at the lithography stage and the alignment error between sensors caused by the manual installation is completely eliminated. Different from the existing sensing scheme for incremental lines, we proposed to utilize the magnetic tunnel junctions with a perpendicular anisotropy reference layer and an in-plane anisotropy sensing layer. The sensors are placed parallel to the scale plane with magnetization of the sensing layer in the plane, which show the capability of polarity detection for the absolute line and reveal sinusoidal output signal for the incremental line. Furthermore, due to the large signal of TMR, the working distance can be further improved compared with conventional sensors. In addition, the cost of the positioning system is expected to be lowered, since all the sensors are fabricated in the same process without extra installation. Our design may pave a new avenue for the positioning system based on a magnetic detection scheme.

Preliminary paleohistological observations of the StW 573 (‘Little Foot’) skull

Numerous aspects of early hominin biology remain debated or simply unknown. However, recent developments in high-resolution imaging techniques have opened new avenues in the field of paleoanthropology. More specifically, X-ray synchrotron-based analytical imaging techniques have the potential to provide crucial details on the ontogeny, physiology, biomechanics, and biological identity of fossil specimens. Here we present preliminary results of our X-ray synchrotron-based investigation of the skull of the 3.67-million-year-old Australopithecus specimen StW 573 (‘Little Foot’) at the I12 beamline of the Diamond Light Source (United Kingdom). Besides showing fine details of the enamel (i.e., hypoplasias) and cementum (i.e., incremental lines), as well as of the cranial bone microarchitecture (e.g., diploic channels), our synchrotron-based investigation reveals for the first time the 3D spatial organization of the Haversian systems in the mandibular symphysis of an early hominin.

Relation between Fish Habitat and the Periodicity of Incremental Lines in the Fossil Otoliths

There are few research reports on the relationship between fish habitats and the periodicity of the fishes’ incremental lines of otolith fossils. The present study examines this relationship through histological and analytical studies on otolith fossils from Nobori Formation, Pliocene, Japan. The specimens were observed and analyzed using light microscopy, polarizing microscopy, Miniscopy, Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis, electron probe X-ray microanalyzer (EPMA), Raman spectroscopy, and XRD. The otolith crystals were aragonite according to XRD and Raman analysis. The incremental lines contained C, O, and Ca, with Si as a trace element. In the layer between the incremental lines, Si was not detected. The circadian incremental lines were unclear and irregularly observed in both Lobianchia gemellarii and Diaphus gigas. Their behavioral pattern included a diurnal vertical movement. By comparison, for Cetonurus noboriensis, Ventrifossa sp., Sebastes scythropus, and Congriscus megastomus, the circadian incremental lines were evident. The habitat of the fishes that live exclusively on the continental slope is kept constant, and the circadian incremental lines are formed regularly. However, for fishes that spend the day in the deep sea and ascend to the shallow sea at night, the ecosystem, such as seawater temperature and pressure, fluctuates, and the circadian incremental lines become unclear and irregular. The period of the circadian incremental lines of otolith may vary due to differences in the ecosystems.

Life history parameters in acellular extrinsic fiber cementum microstructure

Life-history parameters such as pregnancies, skeletal trauma, and renal disease have previously been identified from hypomineralized growth layers (incremental lines) of acellular extrinsic fiber cementum (AEFC). The precise periodicity of these growth layers remains vaguely approximated, so causal life-history explanations using tooth cementum cannot yet be rigorously calculated or tested. On the other hand, we show how life history parameters in AEFC can be identified by two contrasting elemental detection methods. Based on our results we reject the possibility of accurate estimation of pregnancies and other life history parameters from cementum using scanning electron microscopy alone. Here, we propose a new methodological approach for cementum research, Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), to measure degree and distribution of mineralization of cementum growth layers. Our results show that Tof-SIMS can significantly increase our knowledge of cementum composition and is therefore a powerful new tool for life history researchers.

Enamel formation and growth in non-mammalian cynodonts

The early evolution of mammals is associated with the linked evolutionary origin of diphyodont tooth replacement, rapid juvenile growth and determinate adult growth. However, specific relationships among these characters during non-mammalian cynodont evolution require further exploration. Here, polarized light microscopy revealed incremental lines, resembling daily laminations of extant mammals, in histological sections of enamel in eight non-mammalian cynodont species. In the more basal non-probainognathian group, enamel extends extremely rapidly from cusp to cervix. By contrast, the enamel of mammaliamorphs is gradually accreted, with slow rates of crown extension, more typical of the majority of non-hypsodont crown mammals. These results are consistent with the reduction in dental replacement rate across the non-mammalian cynodont lineage, with greater rates of crown extension required in most non-probainognathians, and slower crown extension rates permitted in mammaliamorphs, which have reduced patterns of dental replacement in comparison with many non-probainognathians. The evolution of mammal-like growth patterns, with faster juvenile growth and more abruptly terminating adult growth, is linked with this reduction in dental replacement rates and may provide an additional explanation for the observed pattern in enamel growth rates. It is possible that the reduction in enamel extension rates in mammaliamorphs reflects an underlying reduction in skeletal growth rates at the time of postcanine formation, due to a more abruptly terminating pattern of adult growth in these more mammal-like, crownward species.

Accurate Age Estimations from Dental Cementum and A Childbirth Indicator - A Pilot Study

This work is a pilot study that introduces an improved method for estimation of a chronological age of a human being using the incremental lines in a dental cementum. Scanning Electron Microscopy (SEM) images of longitudinal sections of the tooth roots were subject to SEM analysis. The protocol allows accurate age estimation even if the SEM images reveal a limited number of distinct incremental lines. Micrographs were analyzed with a calibrated thickness measuring tool, such as ImageJ. The study was based on fifteen freshly extracted teeth from adult males and females of a known age. An average cementum thickness (C) and average incremental line thickness (IL) was calculated for each chosen perpendicular level of the tooth root from the SEM image. The number of the incremental lines (nIL) was calculated from the ratio of the mean C and IL, averaged across all levels. Finally, the estimated age is presented as a mean age from the data measured. The proposed protocol for age estimation represents a highly accurate (95%), repeatable and reliable tool for estimation of the chronological age of an individual, using one single SEM scan. Also, from a single case study, we report that an anomalously thick incremental line occurred at the time position which could be related to a childbirth of that female individual. The method can serve forensic purposes.