Growth response of dental tissues to developmental stress in the domestic pig (Sus scrofa).

OBJECTIVES: To compare relative response of enamel, dentin and bone to developmental stressors between attritional and catastrophic mortality assemblages of pigs. MATERIALS AND METHODS: Heads from 70 Sus scrofa of known sex, weight and age comprising an attritional sample of 50 sick pen (SP) pigs that died prematurely versus 20 control pigs slaughtered at 6 months (Catastrophic assemblage). Hard tissue changes (alveolar bone thinning), abnormal bone formation (Harris lines) and re-modeling (auditory bullae) were recorded. Areas and volumes of coronal enamel and dentin were recorded from microCT scans with Avizo 6.3 and Geomagic Wrap. RESULTS: Attritional and catastrophic assemblages are metrically indistinguishable. Ages at death and tissue measures in the SP pigs are differentially distributed, necessitating partition into developmental outcome cohorts. SP "late death" pigs are of lesser physiological maturity than expected, free of disease, with large dental tissue dimensions, comparable to "Controls". SP "early death" pigs have 5% less dentin and enamel and chronic bone infection. Older cohorts of the SP "early deaths" mortality assemblage show progressively reduced enamel. SP pigs show dental evidence of reduced bone mass in the maxilla. DISCUSSION: Bone, dentin and enamel tissues, each, respond distinctively to developmental stressors. Bone mass evinces malnutrition not disease. Both dental tissue reduction and abnormal bone formation link to chronic infection. Paradoxically, reduced dentin mass signals lower survivorship while reduced enamel signals enhanced survivorship. Meaningful comparison of Attritional and Catastrophic assemblages necessitates recognition of developmental outcome cohorts, stratified by age at death and physiological maturity, to reveal heterogeneity of survivorship, tissue measures and lesions.

Orangutans, enamel defects, and developmental health: A comparison of Borneo and Sumatra.

Orangutans (Pongo sp.) show among the highest occurrence of three types of developmental enamel defect. Two are attributed to nutritional factors that reduce bone growth in the infant's face early in development. Their timing and prevalence indicate that Sumatra provides a better habitat than does Borneo. The third type, repetitive linear enamel hypoplasia (rLEH) is very common but its etiology is not understood. Our objective is to draw attention to this enigmatic, episodic stressor in the lives of orangutans. We are concerned that neglect of this possible marker of ill health may be contributing, through inaction, to their alarming decline in numbers. Width and depth of an LEH are considered proxies for duration and intensity of stress. The hypothesis that Bornean orangutans would exhibit relatively wider and deeper LEH was tested on 163 independent episodes of LEH from 9 Sumatran and 26 Bornean orangutans measured with a NanoFocus AG "µsurf Mobile Plus" scanner. Non-normally distributed data (depths) were converted to natural logs. No difference was found in width of LEH among the two island taxa; nor are their differences in width or depth between the sexes. After controlling for significant differences in LEH depths between incisors and canines, defects are, contrary to prediction, significantly deeper in Sumatran than Bornean animals (median = 28, 18 µm, respectively). It is concluded that repetitive LEH records an unknown but significant stressor present in both Sumatra and Borneo, with an average periodicity of 6 months (or multiples thereof) that lasts about 6-8 weeks. It is worse in Sumatra. Given this patterning, shared with apes from a wide range of ecological and temporal sources, rLEH is more likely attributable to disease than to malnutrition.

"Missing perikymata"--fact or fiction? A study on chimpanzee (Pan troglodytes verus) canines.

Recently, a lower than expected number of perikymata between repetitive furrow-type hypoplastic defects has been reported in chimpanzee canines from the Fongoli site, Senegal (Skinner and Pruetz: Am J Phys Anthropol 149 (2012) 468-482). Based on an observation in a localized enamel fracture surface of a canine of a chimpanzee from the Taï Forest (Ivory Coast), these authors inferred that a nonemergence of striae of Retzius could be the cause for the "missing perikymata" phenomenon in the Fongoli chimpanzees. To check this inference, we analyzed the structure of outer enamel in three chimpanzee canines. The teeth were studied using light-microscopic and scanning-electron microscopic techniques. Our analysis of the specimen upon which Skinner and Pruetz (Am J Phys Anthropol 149 (2012) 468-482) had made their original observation does not support their hypothesis. We demonstrate that the enamel morphology described by them is not caused by a nonemergence of striae of Retzius but can be attributed to structural variations in outer enamel that result in a differential fracture behavior. Although rejecting the presumed existence of nonemergent striae of Retzius, our study provided evidence that, in furrow-type hypoplastic defects, a pronounced tapering of Retzius increments can occur, with the striae of Retzius forming acute angles with the outer enamel surface. We suggest that in such cases the outcrop of some striae of Retzius is essentially unobservable at the enamel surface, causing too low perikymata counts. The pronounced tapering of Retzius increments in outer enamel presumably reflects a mild to moderate disturbance of the function of late secretory ameloblasts.

Variation in perikymata counts between repetitive episodes of linear enamel hypoplasia among orangutans from Sumatra and Borneo.

The goal of this study is to evaluate whether repetitive linear enamel hypoplasia (rLEH) in apes is ecologically informative. LEH, which appears as grooves of thinner enamel often caused by malnutrition and/or disease, is a permanent record of departures from developmental homeostasis in infant and juvenile apes. Orangutans were selected for the study as they are a threatened species, have a remarkably high prevalence of rLEH, and because Sumatra is deemed a better habitat for orangutans than is Borneo, facilitating an ecological comparison. Objectives are to determine: a) whether periodicity of rLEH in orangutans corresponds to monsoon-mediated cycles in precipitation or food; and b) whether patterning of rLEH supports the view that Borneo is an inferior habitat. This study compares the counts of perikymata between adjacent LEH from 9 Sumatran and 26 Bornean orangutans to estimate the periodicity of rLEH. A total of 131 nonredundant inter-LEH perikymata counts were transformed to natural log values to reveal clusters of counts in a multiplicative series. Using a value of 10 days to form one perikyma, rLEH tends to recur semiannually in both populations. However, Sumatran orangutans show significantly fewer semiannual intervals and more annually recurring episodes. Bornean orangutans show mostly semiannual intervals and are more variable in inter-LEH perikymata counts. It is concluded that: a) developmental conditions for infant orangutans in Sumatra protect them somewhat from seasonal and environmental variation; b) temporal patterning of rLEH indicates that Borneo is the poorer habitat for orangutans; and c) the study of rLEH can be ecologically informative.

Developing a pig model for crypt fenestration-induced localized hypoplastic enamel defects in humans.

Hypoplastic pits on human deciduous canine teeth are attributed to nutritionally induced thinning of the crypt wall prior to eruption, exposing ameloblasts to unspecified physical trauma through the fenestration. Traditionally known as localized hypoplasia of the primary canine (LHPC), this little-understood condition is reported in fields ranging from public health to bioarchaeology. We propose the defect be termed a 'crypt fenestration hypoplastic enamel defect' (CFED) to reflect that an analogous lesion is created postnatally on maxillary molars of pigs. Pigs are accepted as a suitable proxy for many studies in human biology. We compare fenestration defects and CFEDs between 50 Sick Pen pigs, who died naturally, and 20 Controls. Observations were made of the presence, number and size of fenestrations in molar crypts. CFEDs were counted on erupted deciduous last molars and permanent first molars. Signs of being underweight and cranio-dental infection at death were recorded. Sick pen pigs show significantly more fenestrations at death and CFEDs acquired before death. These conditions co-occur with infection and poor growth. The deep fibers of temporalis muscle lie adjacent to the crypt wall of maxillary molars. We propose that contraction of this muscle during suckling and chewing creates large compressive forces against fenestrated bony surfaces sufficient to have physiological consequences for physically unprotected ameloblasts. While we conclude that a pig model is appropriate to study fenestration-induced enamel defects, this naturalistic experiment leaves unresolved whether osteopenia in pigs, and by extension in human infants, is due to disease and/or malnutrition.

Developmental defects of the dental crown in chimpanzees from the Taï National Park, Côte D'Ivoire: coronal waisting.

We describe a developmental defect that manifests as a mild constricted "waist" in anterior teeth from seven of nine chimpanzee individuals from Taï National Park, Côte D'Ivoire. The sample consists of 21 canine teeth and one incisor, imaged in profile with a digital microscope. Twelve teeth are affected. The waist develops during tooth formation as an external, encircling depression in the contour of the outer enamel surface, more easily seen labially. It is not a thinning of enamel per se, but rather a slight decrement in dentinal crown volume, shown in microCT scans as a change in contour of the enamel-dentin junction, spanning between 3 and 6 years of age, varying among individuals, with maximum expression at about age 4.3 years. The timing and duration of coronal waisting are consistent with descriptions of the weaning process at Taï and other chimpanzee study sites. We propose that coronal waisting records variation in the individual infant chimpanzee's physiological experiences during the process of attaining independence, increased foraging efficiency, and lactational weaning.

Reconstruction of periodicity of repetitive linear enamel hypoplasia from perikymata counts on imbricational enamel among dry-adapted chimpanzees (Pan troglodytes verus) from Fongoli, Senegal.

Periodicity of repetitive linear enamel hypoplasia (rLEH) in apes from high latitudes with single wet and dry seasons annually has not been described. We reconstruct periodicity and duration of rLEH in canine teeth from three recently deceased chimpanzees from Fongoli, Senegal with a marked seven-month dry season. High-resolution dental molds were taken in the field for magnified imaging with digital microscopy. Photomontages allowed counting of perikymata between episodes of rLEH for reconstruction of periodicity and duration of physiological stress. Where rLEH spans the imbricational enamel, the number of events is consistent with years required to form canine imbricational enamel; i.e., periodicity of rLEH seems circannual. We predicted perikymata counts between rLEH events ranging from 52 to 61 based on reported "long counts" of 7-6 days. Counts ranged from 29.5 to 44, individual mean of 36.7. This discrepancy could be explained by recurrent stress with a periodicity of 7.2-8.4 months, or by long counts of 10 days per stria. Neither is supported in the literature. Since we find evidence of rLEH with circannual periodicity, we postulate the existence of non-emergent imbricational striae. Based on evidence that stress at Fongoli recurs annually, we reconstruct stress duration of 2-3 months, longer than reported for chimpanzees living in other habitats, which we attribute to heat stress and food shortage near shrinking waterholes. We conclude that canine teeth from a small mortality cohort of chimpanzees at Fongoli preserve a faithful record of dry season stress in an extreme environment.

Safe Casting and Reliable Cusp Reconstruction Assisted by Micro-Computed Tomographic Scans of Fossil Teeth.

Dental replicas are frequently utilized in paleoanthropological studies of perikymata and enamel hypoplasia. However, fossil teeth are often fragile and worn, causing two problems: (1) the risk of damage by removing enamel fragments when impression-making material is separated from the fossil tooth surface, and (2) the need to reconstruct worn portions of the crown to assess perikymata number, distribution, and hypoplasia timing. This study presents the advantages of µCT data of canines and lateral incisors for (1) detecting cracks along the enamel-dentine junction (EDJ) which could cause damage when casting, and (2) reliably and non-destructively reconstructing worn or broken cusps. Fragile teeth of Homo naledi, Miocene, and Pleistocene specimens were µCT-scanned: 2D virtual sections and 3D models allowed for inspecting crack pattern beyond the external surface and 2D virtual sections were used to digitally reconstruct cusp tips (only Homo naledi). Micro-CT scans allowed cracks running along the EDJ and communicating with radial cracks in the enamel to be identified prior to casting. Cusp reconstructions using µCT data were conducted as precisely as when using thin-sections or photographs, and with high intra- and inter-observer agreement, while preserving the original specimen and affording numerous planes of virtual section. When available, µCT data should be inspected prior to tooth casting to exclude teeth that show a pattern of cracks that could lead to damage. Virtual sections allow for accessible, reliable, and non-destructive cusp reconstructions that may be used for developmental (e.g., perikymata and enamel hypoplasia) or enamel thickness studies. Anat Rec, 302:1516-1535, 2019. © 2018 American Association for Anatomy.

Forensic scatology: preliminary experimental study of the preparation and potential for identification of captive carnivore scat.

Carnivore scats recovered from animal attack and/or scavenging contexts frequently contain forensic evidence such as human bone fragments. Forensic cases with carnivore involvement are increasingly prevalent, necessitating a methodology for the recovery and analysis of scat evidence. This study proposes a method for the safe preparation of carnivore scat, recovery of bone inclusions, and quantification and comparison of scat variables. Fourteen scats (lion, jaguar, lynx, wolf, and coyote) were prepared with sodium-acetate-formalin fixative; analytical variables included carnivore individual, species, body size, and taxonomic family. Scat variables, particularly bone fragment inclusions, were found to vary among carnivore individuals, families, species, and sizes. The methods in this study facilitate safe scat processing, the complete recovery of digested evidence, and the preliminary identification of involved animals. This research demonstrates that scat collected from forensic contexts can yield valuable information concerning both the victim and the carnivore involved.

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.

Hypothesis for the causes and periodicity of repetitive linear enamel hypoplasia in large, wild African (Pan troglodytes and Gorilla gorilla) and Asian (Pongo pygmaeus) apes.

Repetitive linear enamel hypoplasia (rLEH) is often observed in recent large-bodied apes from Africa and Asia as well as Mid- to Late Miocene sites from Spain to China. The ubiquity and periodicity of rLEH are not understood. Its potential as an ontogenetic marker of developmental stress in threatened species (as well as their ancient relatives) makes rLEH an important if enigmatic problem. We report research designed to show the periodicity of rLEH among West African Pan troglodytes (12 male, 32 female), Gorilla gorilla (10 male, 10 female), and Bornean and Sumatran Pongo pygmaeus (11 male, 9 female, 9 unknown) from collections in Europe. Two methods were employed. In the common chimpanzees and gorillas, the space between adjacent, macroscopically visible LEH grooves on teeth with two or more episodes was expressed as an absolute measure and as a ratio of complete unworn crown height. In the orangutans, the number of perikymata between episode onsets, as well as duration of rLEH, was determined from scanning electron micrographs of casts of incisors and canines. We conclude that stress in the form of LEH commences as early as 2.5 years of age in all taxa and lasts for several years, and even longer in orangutans; the stress is not chronic but episodic; the stressor has a strong tendency to occur in pulses of two occurrences each; and large apes from both land masses exhibit rLEH with an average periodicity of 6 months (or multiples thereof; Sumatran orangutans seem to show only annual stress), but this needs further research. This is supported by evidence of spacing between rLEH as well as perikymata counts. Duration of stress in orangutans averages about 6 weeks. Finally, the semiannual stressor transcends geographic and temporal boundaries, and is attributed to regular moisture cycles associated with the intertropical convergence zone modified by the monsoon. While seasonal cycles can influence both disease and nutritional stress, it is likely the combination of seasonal variation in fruiting cycles with specific stressors (malaria and/or intestinal parasites, especially hookworm) that results in this widespread phenomenon. This seasonal stress is sufficiently common and of long duration (6 weeks on average in orangutans) that we think rLEH may reflect significant stress in recent and, inferentially, fossil apes. Increasing seasonality may have impinged negatively on later Miocene apes, especially if they lacked a clear birth peak or seasonality in their reproductive cycles.

Localized hypoplasia of the primary canine in bonobos, orangutans, and gibbons.

This paper extends observations by Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363; [2001] Am. J. Phys. Anthropol. 116:199-208) of localized hypoplasia of the primary canine (LHPC) among large apes to gibbons, bonobos, and orangutans. LHPC is a roughly circular area of deficient enamel on the labial surface of primary canine teeth which, on current evidence from humans, forms several months after birth due to malnutrition-induced craniofacial osteopenia, leading to crypt fenestration that exposes the dental follicle and more deep-sited ameloblasts to minor physical traumata during normal motor infant development. Our goal was to determine the prevalence of LHPC among a variety of apes which differ in body mass and socioecology, with a view to elucidating the etiology of the defect. We examined juvenile dentitions from 122 animals from three taxa: 8 Hylobates lar, 75 Pongo pygmaeus from Borneo and Sumatra, and 39 Pan paniscus from central Africa. Reported variables include taxon, sex, arcade, side, and tooth size. Presence/absence and ordinal severity of defect expression were recorded by description, microphotography, and scanning electron microscopy. Molds were taken in high-resolution dental impression materials and cast in epoxy resin. There are clear taxonomic, but no sex, differences. Prevalence ranged from 0.0% in gibbons to 61.5% in bonobos and 85.3% in orangutans. The result for orangutans is similar to that reported by Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363), while bonobos are much more affected than were the common chimpanzees (22%) described by Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363). There are no significant antimeric differences, but the lower canine is much more affected than the upper by LHPC. We show that larger teeth are more affected by LHPC and have more severe defects. Also, we encountered several instances of patent or healing canine crypt fenestrations, occasionally in direct association with LHPC. Location of the defect indicates that LHPC may occur perinatally but more usually several months postnatally. Histological examination showing the neonatal line and LHPC is required to resolve the issue of timing. We concur with Lukacs ([1999] Am. J. Phys. Anthropol. 110:351-363) that taxonomic, anatomical, and environmental variables combine to determine the occurrence and appearance of LHPC. Nevertheless, we conclude that LHPC probably reflects deficient growth of the arcades in infant apes and humans.