Article

A probable genetic origin for pitting enamel hypoplasia on the molars of Paranthropus robustus

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

We report the frequencies of linear enamel hypoplasia (LEH) and, specifically, pitting enamel hypoplasia (PEH) defects in the teeth of Paranthropus robustus, for comparison with four other South African hominin species and three extant nonhuman primate species. Unlike LEH, the lesser known PEH is characterized by multiple circular depression defects across a tooth crown and is often difficult to interpret in terms of developmental timing and etiology. Teeth in all samples were examined macro-scopically with type, position and number of defects recorded. Frequencies of teeth with LEH vary among hominin species, but the differences in PEH are considerable. That is, P. robustus has much higher rates of pitting defects, with 47% of deciduous teeth and 14% of permanent teeth affected, relative to 6.7% and 4.3%, respectively, for all other hominin teeth combined; none of the extant primate samples evidences comparable rates. The defects on P. robustus molars are unlike those in other species, with entire crowns often covered in small circular depressions. The PEH is most consistent with modern human examples of amelogenesis imperfecta. Additionally, the defects are: 1) not found on anterior teeth, 2) uniform in shape and size, and 3) similar in appearance/severity on all molars. Therefore, this form of PEH may have been a side effect of selection on another trait that shares the same coding gene(s), i.e., these defects have a genetic origin. We discuss a possible scenario that may explain how this form of PEH evolved to become so common in the Paranthropus genus.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Pits can be anything from small circular pin like defects up to vast irregular depressions (Hillson and Bond, 1997;Skinner, 1996). Additionally, some pits form rows around the circumference of a crown, or are associated with plane-form defects, whilst others are much more randomly scattered (Goodman and Rose, 1990;Hillson and Bond, 1997;Lauc et al., 2015;Towle and Irish, 2019). Each pit is created due to cessation/diminution of ameloblast activity, but it is not clear why only some ameloblasts are affected along the plane of a brown stria of Retzius during formation. ...
... Specimen numbers and species classifications are detailed in the supplementary files. Some data presented has been published in Towle and Irish (2019), with additional data added in the present study, notably localised hypoplasia prevalence's. The hominin samples are curated at The Ditsong National Museum of Natural History and the University of the Witwatersrand. ...
... This methodology is also justified by the presence of PEH and localised defects on severely worn teeth. There is variation in wear patterning between the samples studied, however overall the average wear severity is similar between species meaning wear is unlikely to have had a significant effect on overall enamel hypoplasia differences (Towle and Irish, 2019;Towle, 2019). Data are presented by tooth count rather than individual, with the number of hypoplastic teeth displayed as a percentage of the total number of observable teeth. ...
Article
Enamel hypoplasia is often split into several macroscopic categories, including pit, localised, linear and plane-form defects. All types have been considered a sign of 'non-specific stress' during dental development in archaeological, as well as palaeoanthropological and other samples. There is growing evidence suggesting many defects may not be caused by illness or malnutrition during childhood, instead relating to trauma to the developing tooth, genetic conditions or specific environmental factors, i.e., may not be associated with 'stress' to the individual. In this study all types of macroscopic enamel hypoplasia were recorded, including pitting, linear, plane and localised type defects, in two extant great ape species and three fossil hominin species. The aim is to compare the characteristics and prevalence of different types of enamel hypoplasia among species and discuss potential differences in aetiology. The results show that samples have diverse prevalence's of different kinds of defects, and pitting, linear and localised defects likely have different aetiologies. Additionally, dental characteristics (e.g., tooth morphology, developmental timing/speed and enamel structure) heavily influence the likelihood of specific types of enamel hypoplasia forming. In sum, studies that include only one type of enamel hypoplasia, or focus on one tooth type, to generate a 'stress' rating for a sample may miss relevant information when comparing groups. Instead, it may be beneficial to record different types of defects separately, for all teeth, and then consider how genetic, environmental and tooth property factors may influence sample differences.
... We found that deciduous teeth were less affected than permanent teeth. This has been reported in several other studies focusing on various mammals (Dobney and Ervynck, 1998;Lukacs, 1999;Bacon et al., 2018;Towle and Irish, 2019;McGrath et al., 2021), and several factors might explain this difference. First, in rhinocerotids, deciduous teeth develop partially (d1/D1 and d4/ D4) or totally (d2/D2 and d3/D3) in utero, which provides a relatively stable environment (Hitchins, 1978;Hillman-Smith et al., 1986;Böhmer et al., 2016). ...
... Crown fractures are also more likely to form on teeth with enamel defects or unusual wear (Soukup, 2019). The pitting enamel hypoplasia present on a large proportion of P. robustus molars (Towle and Irish, 2019) suggests they may have been more fracture prone. Thus, durophagy may have been even less frequent than the low chipping rate suggests. ...
... 8,46 Enamel hypoplasia likely influenced caries formation in P. robustus SK 55 and SK 13/14, with substantial hypoplastic pitting present; pitting is a common feature of this species. 47 Other pathologies and wear can also create an environment in which caries is more likely to form, e.g. in response to unusual occlusion patterns. 14 It is noteworthy that several fossil teeth with interproximal caries also have substantial cupped occlusal wear and enamel chipping, either above the lesion or on interproximal surfaces of adjacent teeth (SKX 5023, DNH 40 and UW 101-001). ...
Article
Full-text available
Once considered rare in fossil hominins, caries has recently been reported in several hominin species, requiring a new assessment of this condition during human evolution. Caries prevalence and location on the teeth of South African fossil hominins were observed and compared with published data from other hominin samples. Teeth were viewed macroscopically, with lesion position and severity noted and described. For all South African fossil hominin specimens studied to date, a total of 10 carious teeth (14 lesions), including 4 described for the first time here, have been observed. These carious teeth were found in a minimum of seven individuals, including five Paranthropus robustus, one early Homo, and one Homo naledi. All 14 lesions affected posterior teeth. The results suggest cariogenic biofilms and foods may have been present in the oral environment of a wide variety of hominins. Caries prevalence in studied fossil hominins is similar to those in pre-agricultural human groups, in which 1–5% of teeth are typically affected. Significance: • This study adds to the growing evidence that dental caries was present throughout the course of human evolution. Caries prevalence in the fossil species studied is similar to those in non-agricultural human groups, with 1–5% of teeth displaying cavities. • Differences in prevalence and position of dental caries can provide insight into dietary aspects of past populations. South African fossil hominins display lesions on their posterior teeth, suggesting sugary foods were consumed.
... It is the oldest hereditary disorder affecting enamel, observed in early hominins. It has been described in a Homo erectus child from Melka Kunture, Ethiopia (Garba IV) dated to circa 1.5 MY [4] and possibly as pitted AI in Paranthropus [5]. The defects in AI are classified according to their clinical appearances: Type 1: hypoplastic, Type 2: hypomaturation, Type 3: hypocalcified and Type 4: hypomature-hypoplastic enamel with taurodontism [6]. ...
Article
Full-text available
The angle and shape of lithic tool edges have long been used as a method of inferring prehistoric tool function. However, accurately measuring and characterizing edge angles of lithic tools is notoriously difficult. Studies using goniometers, calipers, or morphometrics often rely on two-dimensional representations of edges. Furthermore, there have been limited attempts to quantitatively document stone tool edges based on surface metrology, most notably edge curvature. In this study, we use microCT to capture models of the complex geometry, or ‘freeform’ surfaces, of experimental quartzite flakes from Olduvai Gorge (Tanzania) to document and mathematically calculate edge curvature using multiscalar length-scale analysis. Through this analysis, we also explore the quantification of re-entrant (overhang) features on lithic edge cross-sections. On lithic tools, especially coarse-grained rocks with complex surface topographies, such as quartzite, traditional techniques for edge angle measurement are incapable of capturing re-entrant features on edge profiles. Here we present the first archaeological study that addresses the measurement of these re-entrant features, using novel length-scale and curvature analysis methods of calculating edge angles for complex freeform surfaces. With these new methods for measuring edge angles, we can consider the impact of complex geometry, including re-entrant features, on the function of lithic tools in the past.
Article
Dental caries has been reported in a variety of primates, although it is still considered rare in wild populations. In this study, 11 catarrhine primate taxa (n = 339 individuals; 7946 teeth) were studied for the presence of caries. A differential diagnosis of lesions in interproximal regions of anterior teeth was undertaken, since they had been previously described as both carious and non-carious in origin. Each permanent tooth was examined macroscopically, with severity and position of lesions recorded. Two specimens were examined further, using micro-CT scans to assess demineralization. Differential diagnosis confirmed the cariogenic nature of interproximal cavities on anterior teeth (ICATs). Overall results show 3.3% of all teeth (i.e., anterior and posterior teeth combined) were carious (n = 262), with prevalence varying among species from 0% to >7% of teeth affected. Those with the highest prevalence of ICATs include Pan troglodytes verus (9.8% of anterior teeth), Gorilla gorilla gorilla (2.6%), Cercopithecus denti (22.4%), Presbytis femoralis (19.5%), and Cercopithecus mitis (18.3%). ICATs make up 87.9% of carious lesions on anterior teeth. These results likely reflect dietary and food processing differences among species, but also between the sexes (e.g., 9.3% of all female P. troglodytes verus teeth were carious vs. 1.8% in males). Processing cariogenic fruits and seeds with the anterior dentition (e.g., wadging) likely contributes to ICAT formation. Further research is needed in living primate populations to ascertain behavioral/dietary influences on caries occurrence. Given the presence of ICATs in frugivorous primates, their diagnosis in archaeological and paleontological specimens may shed light on diet and food processing behaviors in fossil primates.
Article
Full-text available
Childhood is an ontogenetic stage unique to the modern human life history pattern. It enables the still dependent infants to achieve an extended rapid brain growth, slow somatic maturation, while benefitting from provisioning, transitional feeding, and protection from other group members. This tipping point in the evolution of human ontogeny likely emerged from early Homo. The GAR IVE hemi-mandible (1.8 Ma, Melka Kunture, Ethiopia) represents one of the rarely preserved early Homo infants (~ 3 years at death), recovered in a richly documented Oldowan archaeological context. Yet, based on the sole external inspection of its teeth, GAR IVE was diagnosed with a rare genetic disease–amelogenesis imperfecta (AI)–altering enamel. Since it may have impacted the child’s survival, this diagnosis deserves deeper examination. Here, we reassess and refute this diagnosis and all associated interpretations, using an unprecedented multidisciplinary approach combining an in-depth analysis of GAR IVE (synchrotron imaging) and associated fauna. Some of the traits previously considered as diagnostic of AI can be better explained by normal growth or taphonomy, which calls for caution when diagnosing pathologies on fossils. We compare GAR IVE’s dental development to other fossil hominins, and discuss the implications for the emergence of childhood in early Homo .
Article
Objective To describe two maxillary deciduous bi-rooted canines, one archaeological and one modern, and examine the possible etiology of this condition. Design Two cases of bi-rooted canines were described and compared to published examples. Both specimens were radiographed and measured and compared to one-rooted samples. The archaeological specimen was scanned using CBCT to facilitate detailed examination of the deciduous teeth. The extracted modern tooth was embedded in epoxy resin and two coronal sections were cut, one through the crown and one through the roots and examined with a light microscope. Results The bi-rooted canines were larger than the control samples. They showed none of the features commonly associated with gemination. The radiographs and scans showed that the canine roots in the archaeological case diverged mesio-distally like the buccal roots in the adjacent first deciduous molar. In the clinical case, the root trunk was elongated mesio-distally and the furcation was located very close to the apex with a C-shaped root canal. Conclusions Both variants of the condition described above are rare in deciduous canines. They do not seem to be associated with fusion or gemination. However, as the teeth are relatively flattened bucco-lingually and we tentatively propose that this form results from spatial constraints during the early stages of crown development that have contributed to the development of additional roots. The megadont dimension of the recent bi-rooted deciduous canine may affect root development and the necessity of two mesio-distally located roots for anchorage in the maxilla.
Article
Objectives: Linear enamel hypoplasia (LEH) is a common skeletal marker of physiological stress (e.g., malnutrition or illness) that is studied within and across populations, without reference to familial risk. We examine LEH prevalence in a population with known genealogical relationships to determine the potential influence of genetic heritability and shared environment. Methods: LEH data of 239 individuals from a single population were recorded from the Ohio State University Menegaz-Bock collection dental casts. All individuals were of known age, sex, and genealogy. Narrow-sense heritability estimates were obtained for LEH presence and count data from all unworn, fully erupted teeth (excluding third molars) using SOLAR (v.8.1.1). Age, sex, and age-sex interaction were included as covariates. Models were re-run with a household effect variable. Results: LEH persists across generations in this study population with moderate, significant heritability estimates for presence in four teeth, and count in four teeth (three teeth were significant for both). When a household effect variable was added, no residual heritability remained for LEH count on any tooth. There was no significant household effect for three of the four teeth that had significant heritability estimates for LEH presence. Age was a significant covariate. Further analyses with birth year data revealed a secular trend toward less LEH. Conclusions: This study provides evidence for familial risk of LEH (genetic and environmental) that has consequences for the broad use of this skeletal marker of stress. These results have repercussions for archaeological assemblages, or population health studies, where genetic relatives and household groups might be heavily represented.
Article
While much is known about the rise and expansion of the Inca Empire (AD 1438–1532) throughout the Andean region of South America, the health effects of the empire in its capital region remain unclear. The present study addresses the Inca Empire's impact on health in the Cuzco region of Peru through an analysis of four conditions (dental enamel hypoplasias, cribra orbitalia, porotic hyperostosis, and periosteal lesions) in 929 pre‐Inca and Inca burials. The study results show little change in health from the Late Intermediate Period (AD 1000–1438) to the Inca Imperial Period (AD 1438–1532). When the location of the Inca burial sites was analyzed, individuals from sites closest to the center of the empire's capital showed lower frequencies in pathological conditions compared with individuals from sites in the countryside. These results suggest that individuals centered in the Inca imperial sphere benefited from their position and experienced better health. A similar finding was also seen with the previous Wari occupation of Cuzco in the Middle Horizon (AD 600–1000), as burials within the Wari imperial sphere exhibited fewer non‐specific stress indicators than those outside of it. Overall, the frequencies of pathological conditions in the Cuzco region, which ranged from 4.6% for porotic hyperostosis to 18.8% for periosteal lesions, were lower than frequencies from many coastal Peruvian sites. These differences may relate to a diverse diet provided by the Cuzco region ecosystem, as well as the absence of ecological challenges that affected coastal populations.
Article
Full-text available
Ribonucleic acid interference (RNAi) is one of modern techniques which involved in suppressing protein productions , this occurred via inserted of double stranded (ds) RNA into the cytoplasm in a cell which leads to particulate and effective degradation of complementary messenger (m RNA). It discovered fortuitously during attempts to produce flowers with elevated color intensity. The possible of this technique to recognizing the physiological and pathological processes is vet important, while its improvement as a therapeutic agent carries out much promise as targeted therapeutic agents. This review article will discuss the basic biological processes that drive RNAi, indicate present and prediction future areas research, and some of applicable limitations.
Article
Full-text available
Because of the ubiquitous adaptability of our material culture, some human populations have occupied extreme environments that intensified selection on existing genomic variation. By 32,000 years ago, people were living in Arctic Beringia, and during the Last Glacial Maximum (LGM; 28,000–18,000 y ago), they likely persisted in the Beringian refugium. Such high latitudes provide only very low levels of UV radiation, and can thereby lead to dangerously low levels of biosynthesized vitamin D. The physiological effects of vitamin D deficiency range from reduced dietary absorption of calcium to a compromised immune system and modified adipose tissue function. The ectodysplasin A receptor (EDAR) gene has a range of pleiotropic effects, including sweat gland density, incisor shoveling, and mammary gland ductal branching. The frequency of the human-specific EDAR V370A allele appears to be uniquely elevated in North and East Asian and New World populations due to a bout of positive selection likely to have occurred circa 20,000 y ago. The dental pleiotropic effects of this allele suggest an even higher occurrence among indigenous people in the Western Hemisphere before European colonization. We hypothesize that selection on EDAR V370A occurred in the Beringian refugium because it increases mammary ductal branching, and thereby may amplify the transfer of critical nutrients in vitamin D-deficient conditions to infants via mothers’ milk. This hypothesized selective context for EDAR V370A was likely intertwined with selection on the fatty acid desaturase (FADS) gene cluster because it is known to modulate lipid profiles transmitted to milk from a vitamin D-rich diet high in omega-3 fatty acids.
Article
Full-text available
This report describes a case of amelogenesis imperfecta in the dentition of a female chimpanzee. Amelogenesis imperfecta is a group of rare genetic conditions that create severe enamel defects, which, although well researched in humans, has not yet been investigated in wild non-human primates.
Article
Full-text available
Enamel defects can provide insight into the life histories of past individuals and populations, in-cluding information on a wide range of disturbances during childhood. This study investigates a particularly severe case of plane-form enamel hypoplasia from a Roman site in Gloucester, UK. Dentine protrudes above the occlusal enamel of upper central incisors, both upper canines, the lower left canine, lower right central incisor, and all four first molars. Given the morphology and location of these defects, along with the developmental tim-ing of the affected teeth, such factors as molar-incisor hypomineralization, amelogenesis imperfecta, and congen-ital syphilis can likely be ruled out. The defects resulted from a nonspecific but severe physiological disturbance during the second year of life. Severe plane-form defects of this kind, where enamel formation has completely ceased, are extremely rare in premodern populations, and this example is one of the earliest reported cases. It has been suggested that these defects generally occur only in individuals that survived a life-threatening illness, which would explain the scarcity in the archaeological record, i.e., the afflicted individual would not have lived long enough for the defects to manifest. Comparisons with clinical examples and pathogen DNA analysis may provide further insight into the etiology of these defects.
Article
Full-text available
Amelogenesis imperfecta (AI) is a heterogeneous group of genetic conditions that result in defective dental enamel formation. Amelotin (AMTN) is a secreted protein thought to act as a promoter of matrix mineralisation in the final stage of enamel development, and is strongly expressed, almost exclusively, in maturation stage ameloblasts. Amtn overexpression and Amtn knockout mouse models have defective enamel with no other associated phenotypes, highlighting AMTN as an excellent candidate gene for human AI. However, no AMTN mutations have yet been associated with human AI. Using whole exome sequencing, we identified an 8,678 bp heterozygous genomic deletion encompassing exons 3-6 of AMTN in a Costa Rican family segregating dominant hypomineralised AI. The deletion corresponds to an in-frame deletion of 92 amino acids, shortening the protein from 209 to 117 residues. Exfoliated primary teeth from an affected family member had enamel that was of a lower mineral density compared to control enamel and exhibited structural defects at least some of which appeared to be associated with organic material as evidenced using elemental analysis. This study demonstrates for the first time that AMTN mutations cause non-syndromic human AI and explores the human phenotype, comparing it with that of mice with disrupted Amtn function.
Article
Full-text available
Evolutionary constraint due to pleiotropy refers to a situation in which mutations in genes shared among traits generate trait covariance; therefore, traits that are not directly exposed to selective challenge show a correlated response. When such a correlated response is deleterious, it may constrain the trait from evolving. Here, we argue that the idea of absolute constraints draws from the perception that gene effects are inherent to alleles and thus invariant across genetic and environmental backgrounds. However, evidence from studies involving genetic effects on multiple traits, observed across different genetic backgrounds and environments, supports the notion that genes' effects on traits change. Consequently, pleiotropy also varies across backgrounds. We argue for a stronger emphasis on interaction effects when describing a trait's genetic basis and its evolutionary potential. By discussing different cases of trait individuation, we demonstrate how this approach can lead to new insights.
Article
Full-text available
This study examines the skeletal remains of a subadult from an archeological site in Austria. Radiocarbon dating and archeological attribution indicate that this individual is of pre-Columbian origin. Most of the skeleton was recovered, and only the teeth and the orbital roofs show changes. Dental defects such as the mulberry molar and a tapered, fang-like canine suggest a diagnosis of congenital syphilis. This is the first probable case of congenital syphilis from pre-Columbian Central Europe. Our findings contribute to the pre-Columbian theory, offering counterevidence to the assumption that syphilis was carried from Columbus' crew from the New to the Old World.
Article
Full-text available
Without the presence of " caries sicca, " " sabre shins, " and nodes/expansion of the long bones with superficial cavitation, differential diagnosis of venereal syphilis and tuberculosis (TB) may be difficult as various infections produce similar responses. However, congenital syphilis has distinctive features facilitating a diagnosis. A case study of remains of a juvenile European settler (probably male, 8–10 years old) (B70) buried in the 19th century and excavated in 2000 from the cemetery of the Anglican Church of St. Marys in South Australia is presented. B70 demonstrated that the two diseases might have been present in the same individual, congenital syphilis and TB. Widespread destruction of vertebral bodies and kyphosis-related rib deformations indicate advanced TB. Severe dental hypoplasia is limited to permanent incisors and first molars; there is pitting on the palate, periosteal reaction on the skull vault, and thinned clavicles. Dental signs are not limited to " screwdriver " central incisors and mulberry molars. Apical portions of the crowns of permanent upper, lower, central, and lateral incisors have multiple hypoplastic-disorganized defects; deciduous canines have severely hypoplastic crowns while possibly hypoplastic occlusal surfaces of lower deciduous second molars are largely destroyed by extensive caries. These dental abnormalities resemble teeth affected by mercurial treatment in congenital syphilitic patients as described by Hutchinson.
Article
Full-text available
During childhood, systemic physiological stresses such as illness, disease, and malnutrition can disrupt the growth of dental enamel. These disruptions are often recorded in the form of linear enamel hypoplasia (LEH). Many researchers have analyzed the frequency and timing of LEH formation in Neanderthal populations as they relate to ideas about Neanderthal living conditions, nutrition, and foraging efficiency. Previous age estimates for Neander-thal LEH were largely based upon modern human dental growth standards. However, recent studies provide a more complete picture of Neanderthal tooth formation. We use data from these studies to create enamel growth charts for four Neanderthal anterior tooth types (upper central and lateral incisors, upper and lower canines) analogous to those created for modern humans by Reid and Dean (2000). The Neanderthal charts differ from those of modern humans especially in initiation ages and in the duration of enamel formation within equivalent divisions of crown height. Based on these new charts, we estimate ages at formation for a series of Krapina Neanderthal defects. We also compare estimated ages at defect formation in the Krapina sample with estimated ages of defect formation in a sample of modern humans from Point Hope, Alaska. The median ages at defect formation across different anterior tooth types range from 2.3–2.5 (based on a seven-day perikymata periodicity) and 2.6–2.8 years (based on an eight-day perikymata periodicity), suggesting that Neanderthals experienced physiological stress earlier in life than indicated by previous estimates that were derived from modern human standards. By contrast, median ages at defect formation in the Point Hope sample are later than those of the Krapina Neanderthals, which may result from differences in crown growth geometry between Neanderthals and modern humans, differences between the two populations in the ages at which they experienced episodes of stress, or both.
Article
Full-text available
Amelogenesis imperfecta is a group of inherited diseases affecting the quality and quantity of dental enamel. To date, mutations in more than ten genes have been associated with non-syndromic amelogenesis imperfecta (AI). Among these, ENAM and LAMB3 mutations are known to be parts of the etiology of hypoplastic AI in human cases. When both alleles of LAMB3 are defective, it could cause junctional epidermolysis bullosa (JEB), while with only one mutant allele in the C-terminus of LAMB3, it could result in severe hypoplastic AI without skin fragility. We enrolled three Chinese families with hypoplastic autosomal-dominant AI. Despite the diagnosis falling into the same type, the characteristics of their enamel hypoplasia were different. Screening of ENAM and LAMB3 genes was performed by direct sequencing of genomic DNA from blood samples. Disease-causing mutations were identified and perfectly segregated with the enamel defects in three families: a 19-bp insertion mutation in the exon 7 of ENAM (c.406_407insTCAAAAAAGCCGACCACAA, p.K136Ifs*16) in Family 1, a single-base deletion mutation in the exon 5 of ENAM (c. 139delA, p. M47Cfs*11) in Family 2, and a LAMB3 nonsense mutation in the last exon (c.3466C>T, p.Q1156X) in Family 3. Our results suggest that heterozygous mutations in ENAM and LAMB3 genes can cause hypoplastic AI with markedly different phenotypes in Chinese patients. And these findings extend the mutation spectrum of both genes and can be used for mutation screening of AI in the Chinese population.
Article
Full-text available
Amelogenesis Imperfecta (AI) represents a group of developmental conditions, genomic in origin, which affect the structure and clinical appearance of enamel of all or nearly all the teeth in a more or less equal manner. AI is a serious problem that reduces oral health-related quality of life and causes some physiological problems. We presented here four case reports of AI (Hypoplastic and Hypomaturation) which we diagnosed on the basis of classical clinical and radiographic features.
Article
Full-text available
Objective: The purpose of this study was to determine and compare the prevalence and presentations of developmental defects of the enamel (DDE) in the primary and permanent dentitions of a group of healthy schoolchildren residing in Granada (Spain). Study Design: A total of 1,414 healthy schoolchildren were examined using modified DDE criteria for recording enamel defects. Results: The prevalence of DDE of any type was 40.2% in primary dentition and 52% in permanent dentition (p<0.033). Of the 31,820 primary and permanent teeth examined in the study, 699 (4.1%) primary and 1,232 (8.3%) permanent teeth had some form of DDE. Diffuse opacity was the most common type of DDE observed in primary teeth, and demarcated opacity in the permanent teeth. Enamel hypoplasia was the least prevalent defect in both dentition types. Conclusions: The study population showed a high prevalence of DDE in primary as well as in permanent dentition, reflecting the current increasing trend of this condition, which should be considered as a significant public health problem. Key words:Developmental enamel defects, enamel hypoplasia, demarcated opacity, diffuse opacity.
Article
Full-text available
Defective enamel formation can be explained as defects occurring at the stages of enamel formation. Quantitative defects in matrix formation leads to hypoplastic form of amelogenesis imperfecta. Inadequate mineralization of matrix leads to hypocalcification and hypomaturation variants. The demarcation of matrix formation and mineralization is not so distinct. This paper describes a case of a 7-year-old boy with amelogenesis imperfecta - Type IA i.e., hypoplastic pitted autosomal dominant.
Article
Full-text available
Enamelin (ENAM) plays an important role in the mineralization of the forming enamel matrix. We have performed an evolutionary analysis of mammalian ENAM to identify highly conserved residues or regions that could have important function (selective pressure), to predict mutations that could be associated with amelogenesis imperfecta in humans, and to identify possible adaptive evolution of ENAM during 200 million years ago of mammalian evolution. In order to fulfil these objectives, we obtained 36-ENAM sequences that are representative of the mammalian lineages. Our results show a remarkably high conservation pattern in the region of the 32-kDa fragment of ENAM, especially its phosphorylation, glycosylation, and proteolytic sites. In primates and rodents we also identified several sites under positive selection, which could indicate recent evolutionary changes in ENAM function. Furthermore, the analysis of the unusual signal peptide provided new insights on the possible regulation of ENAM secretion, a hypothesis that should be tested in the near future. Taken together, these findings improve our understanding of ENAM evolution and provide new information that would be useful for further investigation of ENAM function as well as for the validation of mutations leading to amelogenesis imperfecta.
Article
Full-text available
Early hominins formed large and thick-enamelled cheek-teeth within relatively short growth periods as compared with modern humans. To understand better the developmental basis of this process, we measured daily enamel increments, or cross striations, in 17 molars of Plio-Pleistocene hominins representing seven different species, including specimens attributed to early Homo. Our results show considerable variation across species, although all specimens conformed to the known pattern characterised by greater values in outer than inner enamel, and greater cuspal than cervical values. We then compared our results with the megadontia index, which represents tooth size in relation to body mass, for each species to assess the effect of daily growth rates on tooth size. Our results indicate that larger toothed (megadont) taxa display higher rates or faster forming enamel than smaller toothed hominins. By forming enamel quickly, large tooth crowns were able to develop within the constraints of shorter growth periods. Besides daily increments, many animals express long-period markings (striae of Retzius) in their enamel. We report periodicity values (number of cross striations between adjacent striae) in 14 new specimens of Australopithecus afarensis, Paranthropus aethiopicus, Paranthropus boisei, Homo habilis, Homo rudolfensis and Homo erectus, and show that long-period striae express a strong association with male and average male-female body mass. Our results for Plio-Pleistocene hominins show that the biological rhythms that give rise to long-period striae are encompassed within the range of variation known for modern humans, but show a lower mean and modal value of 7 days in australopithecines. In our sample of early Homo, mean and modal periodicity values were 8 days, and therefore similar to modern humans. These new data on daily rates of enamel formation and periodicity provide a better framework to interpret surface manifestations of internal growth markings on fossil hominin tooth crowns. Importantly, our data on early hominin cross striation variation may now contribute towards solving difficult taxonomic diagnoses where much may depend on fragmentary molar remains and enamel structure.
Article
Genetic changes causing brain size expansion in human evolution have remained elusive. Notch signaling is essential for radial glia stem cell proliferation and is a determinant of neuronal number in the mammalian cortex. We find that three paralogs of human-specific NOTCH2NL are highly expressed in radial glia. Functional analysis reveals that different alleles of NOTCH2NL have varying potencies to enhance Notch signaling by interacting directly with NOTCH receptors. Consistent with a role in Notch signaling, NOTCH2NL ectopic expression delays differentiation of neuronal progenitors, while deletion accelerates differentiation into cortical neurons. Furthermore, NOTCH2NL genes provide the breakpoints in 1q21.1 distal deletion/duplication syndrome, where duplications are associated with macrocephaly and autism and deletions with microcephaly and schizophrenia. Thus, the emergence of human-specific NOTCH2NL genes may have contributed to the rapid evolution of the larger human neocortex, accompanied by loss of genomic stability at the 1q21.1 locus and resulting recurrent neurodevelopmental disorders.
Conference Paper
Developmental defects, wear, and pathologies can give insight into the diet, behavior, and environmental stresses of past populations. There have been a number of key studies looking at particular defects and types of wear but as yet no broad scale study looking at multiple types across these species. We focus on frequencies of dental caries, chipping, hypoplasia, and occlusal attrition. All South African available hominin material was studied, with the largest samples represented by Australopithecus africanus (n= 358 teeth), Paranthropus robustus (n= 278 teeth), and Homo naledi (n= 142 teeth). Teeth were recorded macroscopically, with a 10x hand lens used to confirm defects. The most striking results are high rates of crown chipping in H. naledi, with over 40% of teeth having one or more chip. Occlusal wear as well as comparisons with Cercopithecinae specimens suggest grit being incorporated into their diet may be the cause. The high frequency of pitting enamel hypoplasia in P. robustus (permanent teeth= 14%; deciduous molars= 47%) may be explained by morphological differences or a common stress occurring at a key stage in development. Caries frequency in P. robustus is 1.8% (5/278) and 2.1% in H. naledi (3/142); there are no cases in A. africanus (0/358). Dietary differences likely explains this difference, but environmental and bacterial factors are also considered. These examples reveal among-species differences and along with occlusal wear we compare these with later hominins and extant primates to highlight potential dietary and behavioral variation.
Article
Objectives: The immature partial mandible GAR IVE from the c. 1.7 Ma old Garba IV site at Melka Kunture (Upper Awash Basin, Ethiopia), the earliest human representative from a mountain-like environment, represents one of the oldest early Homo specimens bearing a mixed dentition. Following its first description (Condemi, ), we extended the analytical and comparative record of this specimen by providing unreported details about its inner morphology, tooth maturational pattern and age at death, crown size, and tooth tissue proportions. Materials and methods: The new body of quantitative structural information and virtual imaging derives from a medical CT record performed in 2013. Results: Compared to the extant human condition and to some fossil representatives of comparable individual age, the GAR IVE mandible reveals absolutely and relatively thick cortical bone. Crown size of the permanent lateral incisor and the canine fit the estimates of H. erectus s.l., while the dm2 and the M1 more closely approach those of H. habilis-rudolfensis. Molar crown pulp volumes are lower than reported in other fossil specimens and in extant humans. The mineralization sequence of the permanent tooth elements is represented four times in our reference sample of extant immature individuals (N = 795). Conclusions: The tooth developmental pattern displayed by the immature individual from Garba IV falls within the range of variation of extant human populations and is also comparable with that of other very young early fossil hominins. Taken together, the evidence presented here for mandibular morphology and dental development suggest GAR IVE is a robust 2.5- to 3.5-year old early Homo specimen.
Article
This study examines the dental developmental defects seen in an individual recovered from the Saint Sava cemetery from Bucharest, Romania, dated to the late medieval/early modern period. The remains display extended hypoplastic alterations of the permanent dentition, including linear, pitted, and planar defects. The first permanent molars are distinctive, with multiple indentations and mottling. Given the unusual pattern of defects and the close resemblance to a series of archaeological cases recently published and assigned to congenital syphilis, a differential diagnosis is discussed, with particular reference to the effects induced not only by treponemal infection, but also by treatment with mercury and nutritional deficiency.
Article
Amelogenesis imperfecta (AI) is a collection of diseases characterized by hereditary enamel defects and is heterogeneous in genetic etiology and clinical phenotype. In this study, we recruited a nuclear AI family with a proband having unique irregular hypoplastic pits and grooves in all surfaces of the deciduous molar teeth but not in the deciduous anterior teeth. Based on the candidate gene approach, we screened the laminin subunit beta 3 (LAMB3) gene and identified a novel de novo mutation in the proband. The mutation was a frameshift mutation caused by a heterozygous 7-bp deletion in the last exon (c.3452_3458delAGAAGCG, p.Glu1151Valfs*57). This study not only expands the mutational spectrum of the LAMB3 gene causing isolated AI but also broadens the understanding of genotype-phenotype correlations.
Chapter
Developmental defects of enamel, especially enamel hypoplasias and accentuated striae, can provide biological anthropologists with a detailed, retrospective record of the physiological stress experience during childhood. These non-specific indicators of stress provide insights relevant to diverse fields in biological (and dental) anthropology. This chapter reviews the etiology, enamel growth processes, and enamel microstructures involved in defect formation, and highlights approaches that maximize the information we can glean from both macroscopic and microscopic enamel defects.
Article
Human children grow at a uniquely slow pace by comparison with other mammals. When and where did this schedule evolve? Have technological advances, farming and cities had any effect upon it? Addressing these and other key questions in palaeoanthropology and bioarchaeology, Simon Hillson examines the unique role of teeth in preserving detailed microscopic records of development throughout childhood and into adulthood. The text critically reviews theory, assumptions, methods and literature, providing the dental histology background to anthropological studies of both growth rate and growth disruption. Chapters also examine existing studies of growth rate in the context of human evolution and primate development more generally, together with implications for life history. The final chapters consider how defects in the tooth development sequence shed light on the consequences of biological and social transitions, contributing to our understanding of the evolution of modern human development and cognition.
Article
This is a seminal text uniquely dedicated to oral hard tissue pathology, presenting the growth of clinical knowledge and advancement in the field in recent years. Starting with a discussion of numerical and formative anomalies and unusual eruption, the book goes on to consider caries, erosion, resorption and toothwear, as well as tooth fractures and discolouration, and ends with a chapter on congenital syndromes with dental anomalies. Pathology of the Hard Dental Tissues is an invaluable reference for specialist practitioners and researchers as well as dental students, combining a scholarly overview of the field with clinical management protocols. Includes prevention techniques as well as treatment regimes Contains many colour clinical photographs Accompanied by a large number of references Provides helpful tables to categorise the causes and characteristics of lesions Written by a leading expert in the field.
Article
The problem of the relation of rickets to defective formation of teeth and to the occurrence of dental caries is one that has been of increasing interest to investigators in recent years, and one regarding which various and differing opinions have been expressed as a result of clinical investigations and animal experimentation. The data reported in the present study are entirely clinical and have to do with observations on the permanent teeth of children whose previous history with regard to rickets is known. A review of recent literature shows that few clinical investigations have been undertaken that deal with the relation of rickets to defects of the teeth, either defects of structural development or caries. MacKay and Rose,¹ in 1931, reported a study of the incidence of dental defects in the permanent teeth of two groups of children; the first, a group of 46 who in infancy had shown
Article
Dental pathologies and enamel defects in East Asian hominins have rarely been reported. Here, we systematically document and describe a suite of enamel defects in the Xujiayao juvenile maxilla, an East Asian hominin from the early Late Pleistocene that may represent an unknown hominin lineage. In addition, we determine the chronology of growth disruptions represented by matched linear enamel hypoplasias, evaluate the long-held hypothesis that the large brownish pit on the I1 is evidence of dental fluorosis, and assess the utility of micro-computed tomography (micro-CT techniques) in analyzing enamel defects. With the use of binocular microscopy, Scanning Electron Microscopy (SEM), and micro-CT imaging techniques, the Xujiayao teeth were found to exhibit a high number of pit-form defects seldom seen in the fossil record. By matching the timing of LEH across multiple teeth, a minimum of five developmental disruptions were identified, indicating that the Xujiayao juvenile experienced several growth disturbances during its short lifespan. Our SEM and micro-CT analysis suggests that the large pit on the I1 is an enamel hypoplasia due to its morphology and pre-eruptive enamel thinning. It is not a post-eruptive fluorotic pit and there is no evidence of chalkiness or opacity associated with dental fluorosis. The micro-CT technique made it possible to verify the presence of enamel hypoplasia and to more precisely quantify defect dimensions, especially in unerupted teeth and shallow hypoplasias that are difficult to detect by binocular microscopy or SEM. This article is protected by copyright. All rights reserved.
Article
Linear enamel hypoplasia (LEH) is a macroscopically detectable band-like dental defect, which represents localized decrease in enamel thickness caused by some form of disruption to a child's health. Such dental deformations are utilized in osteoarchaeological research as permanent markers of childhood physiological stress and have been extensively studied in numerous ancient human populations. However, currently there is no such data for medieval populations from Canterbury, UK. Here, LEH is examined in the context of age-at-death in human burials from the medieval St. Gregory's Priory and adjacent cemetery (11th–16th centuries), Canterbury, UK. The cemetery and Priory burials represented lower (n = 30) and higher status (n = 19) social groups, respectively. Linear enamel hypoplastic defects were counted on mandibular and maxillary anterior permanent teeth (n = 374). The age and sex of each skeleton were estimated using standard methods. Differences in LEH counts, age-at-death, and LEH formation ages were sought between the two social groups. Results indicate significantly greater frequencies of LEH in the Cemetery (mean = 17.6) compared to the Priory (mean = 7.9; t = −3.03, df = 46, p = 0.002). Adult age-at-death was also significantly lower in the Cemetery (mean = 39.8 years) compared to the Priory burials (mean = 44.1 years; t = 2.275, df = 47, p = 0.013). Hypoplasia formation ages differed significantly between the Priory (mean = 2.49 years) and Cemetery (mean = 3.22 years; t = 2.076; df = 47; p = 0.034) individuals. Results indicate that childhood stress may reflect adult mortality in this sample, and that the wellbeing of individuals from diverse social backgrounds can be successfully assessed using LEH analyses. Results are discussed in terms of the multifactorial etiology of LEH, as well as weaning-related LEH formation. Copyright © 2012 John Wiley & Sons, Ltd.
In the course of a long-term investigation of children with three well-defined disturbances of calcium and phosphate homeostasis - hereditary vitamin D dependency rickets, X-linked hypophosphatemia and hypoparathyroidism - we have observed distinctive distributions of enamel hypoplasia and interglobular dentin that provide a clue to the pathogenesis of these dental lesions. Each of the 25 patients with X-linked hypophosphatemia had extensive interglobular dentin in the primary and permanent teeth but no enamel hypoplasia; these patients were normocalcemic but very hypophosphatemic. Each of ten patients with vitamin D dependency rickets had severe enamel hypoplasia in the permanent teeth, and in the 7 patients whose teeth were examined histologically moderate interglobular dentin was observed in each; these patients were hypocalcemic and, because of secondary hyperparathyroidism, also hypophosphatemic. Fifteen of 21 children with hypo parathyroidism had severe enamel hypoplasia but none had interglobular dentin; these patients were hypocalcemic and hypopphosphatemic. From these observations we have formulated a unifying hypothesis that enamel hypoplasia, in disturbances of calcium and phosphate homeostasis; is caused by hypocalcemia and interglobular dentin is caused by hypophosphatemia.
Article
Dental enamel hypoplasias are deficiencies in enamel thickness resulting from physiological perturbations (stress) during the secretory phase of amelogenesis. The results of a wide variety of experimental, clinical, and epidemiological studies strongly suggest that these defects and their associated histological abnormalities (such as accentuated stria of Retzius and Wilson bands) are relatively sensitive and nonspecific indicators of stress. Because of the inability of enamel to remodel, and the regular and ring-like nature of their development, these defects can provide an indelible, chronological record of stress during tooth crown formation. For these reasons, along with the ease with which they are studied, enamel hypoplasias have been increasingly employed as indicators of nutritional and disease status in paleopathology, and their study has begun to extend into other subdisciplines of physical anthropology.
Article
The defects of enamel hypoplasia can be related to the layered structure of enamel which represents the sequence of development in tooth crowns. From such studies, it is possible to see that furrow-type enamel defects (the most common form of hypoplasia seen with the naked eye) are just the most prominent expression of a continuum which extends ever smaller, down to a microscopic disturbance to a single layer in the crown formation sequence. Furthermore, the progressive decrease in spacing between development layers which occurs down the crown sides, from occlusal to cervical, affects both the prominence and apparent width of the defects. This makes it difficult to use measurements as a means of estimating the duration of the disturbance causing a particular defect. The difficulty is even greater for the less common pitted or exposed-plane-type defects, for which the apparent width bears very little relationship with the duration of the growth disturbance. The defects of enamel hypoplasia can therefore be understood clearly only when examined under the microscope in relation to the structures which mark the development sequence of the tooth crown. Am J Phys Anthropol 104:89–103, 1997. © 1997 Wiley-Liss, Inc.
Article
The chronological distributions of enamel hypoplasias (indicators of nonspecific stress) are assessed for 111 individuals from two prehistoric populations from Dickson Mounds, Lewiston, Illinois. The earlier population (circa A.D. 950–1150) involves a transition from an indigenous gathering-hunting tradition to increasing adoption of Mississippian lifeways. The later population (circa A.D. 1150–1300) is fully Mississippian (MM). Based on the occurrence of hypoplasias on all permanent teeth except third molars, 14 halfyear periods from birth to 7.0 years are graded for evidence of hypoplasiastress. Both populations have a low frequency of hypoplasia which occur before 2 years of age and after 4 years of age. A common peak frequency of hypoplasias between 2.0 and 4.0 years is suggestive of an elevated degree of stress at weaning. The peak frequency of hypoplasias is earlier in the MM (2.5–3.0 years versus 3.0–3.5 years in the pre-Mississippian population). In addition, the rise to and decline from peak frequency occurs approximately 0.5 years earlier in the MM. The earlier and sharper rise to peak frequency suggests earlier and more severe weanling-related stress. Hypoplasias chronologies are undoubtedly influenced by age-related host resistance factors (Sarnat and Schour, 1941). Nevertheless, these data demonstrate that populations may vary in their chronological distribution of hypoplasias and that these variations may provide useful information on age-related patterns of exposure to environmental stressors.
Article
Enamel hypoplasias, deficiencies in enamel thickness resulting from disturbances during the secretory phase of enamel development, are generally believed to result from nonspecific metabolic and nutritional disruptions. However, data are scarce on the prevalence and chronological distribution of hypoplasias in populations experiencing mild to moderate malnutrition. The purpose of this article is to present baseline data on the prevalences and chronological distributions of enamel hypoplasias, by sex and for all deciduous and permanent anterior teeth, in 300 5 to 15-year-old rural Mexican children. Identification of hypoplasias was aided by comparison to a published standard (Federation Dentaire Internationale: Int. Dent. J. 32(2):159−167, 1982). The location of defects, by transverse sixths of tooth crowns, was used to construct distributions of defects by age at development. One or more hypoplasias were detected in 46.7% (95% CI= 40.9−52.5%) of children. Among the unworn and completely erupted teeth, the highest prevalence of defects was found on the permanent maxillary central incisors (44.4% with one or more hypoplasias), followed by the permanent maxillary canine (28.0%) and the remaining permanent teeth (26.2 to 22.2%) Only 6.1% of the completely erupted and unworn deciduous teeth were hypoplastic. The prevalence of enamel defects on the permanent teeth was up to tenfold greater than that found in studies of less marginal populations that used the FDI method. The prevalence of defects in transverse zones suggests a peak frequency of hypoplasias during the second and third years for the permanent teeth, corresponding to the age at weaning in this group. In the deciduous teeth, a smaller peak occurs between 30 and 40 weeks post gestation. The frequency of defects after three years of age is slightly higher in females than males, suggesting a sex difference in access to critical resources.
Article
This study presents an analysis of linear enamel hypoplasias (LEH) and plane-form defects (PFD) in the hominine dental sample from the Sima de los Huesos (SH) Middle Pleistocene site in Atapuerca (Spain). The SH sample comprises 475 teeth, 467 permanent and 8 deciduous, belonging to a minimum of 28 individuals. The method for recording PFD and LEH is discussed, as well as the definition of LEH. The prevalence of LEH and PFD in SH permanent dentition (unilateral total count) is 4.6% (13/280). Only one deciduous tooth (lower dc) showed an enamel disruption. Prevalence by individual ranges from 18.7–30%. The most likely explanation for the relatively low LEH and PFD prevalence in the SH sample suggests that the SH population exhibited a low level of developmental stress. The age at occurrence of LEH and PFD was determined by counting the number of perikymata between each lesion and the cervix of the tooth. Assuming a periodicity of nine days for the incremental lines, the majority of LEH in the SH sample occurred during the third year of life and may be related to the metabolic stress associated with weaning. Am J Phys Anthropol 123:000–000, 2004. © 2004 Wiley-Liss, Inc.
Article
The differences between Middle and Upper Palaeolithic cultures from Europe have been likened to the contrast between generalized and complex hunter–gatherers. A test of this model is undertaken by comparing the types, amount, severity and timing of episodes of enamel hypoplasia between the two periods among specimens from western Europe and the circum-Mediterranean area. The earlier sample consists of 59 dentally immature individuals with 128 primary and 154 permanent teeth while the later sample consists of 47 dentally immature individuals with 162 primary and 125 permanent teeth. It was predicted that the Upper Palaeolithic would show more variation in the attributes noted above as a consequence of increased social differentiation. While the prevalence (50% of individuals) and severity of enamel hypoplasia do not differ between the samples, the Upper Palaeolithic component is significantly more variable in the types and timing of enamel defects. Localized hypoplasia of the primary canine is absent from the Middle Palaeolithic but very common among Upper Palaeolithic children. Earlier work has linked this enamel defect to craniofacial osteopenia due to low bioavailability of vitamin A. Linear enamel hypoplasia peaks at age 3·5 years in the Middle Palaeolithic sample but is as common at age 2·0 as 5·0 years in the Upper Palaeolithic sample. The age distribution differs significantly. Peak age at stress, combining all types of enamel hypoplasia, is 3·5 years in the Middle Palaeolithic and 0·5 years in the Upper Palaeolithic. The major contrast between the Middle and Upper Palaeolithic in terms of enamel hypoplasia is the advent of stressful episodes in early infancy in the Upper Palaeolithic. This is attributed to the low bioavailability of vitamin A due to the synergistic effects of malnutrition and infection exacerbated by a net increase in population density among socially competitive family lineages.
Article
As a dental indicator of generalized physiological stress, enamel hypoplasia has been the subject of several Neandertal studies. While previous studies generally have found high frequencies of enamel hypoplasia in Neandertals, the significance of this finding varies with frequencies of enamel hypoplasia in comparative samples. The present investigation was undertaken to ascertain if the enamel hypoplasia evidence in Neandertals suggests a high level of physiological stress relative to a modern human foraging group, represented here by an archaeological sample of Inuit from Point Hope, Alaska. Unlike previous studies, this study focused specifically on linear enamel hypoplasia (LEH), emphasizing systemic over localized causes of this defect by considering LEH to be present in an individual only if LEH defects occur on two anterior teeth with overlapping crown formation periods. Moreover, this study is the first to evaluate the average growth disruption duration represented by these defects in Neandertals and a comparative foraging group. In the prevalence analysis, 7/18 Neandertal individuals (from Krapina and southern France) and 21/56 Neandertal anterior teeth were affected by LEH, or 38.9% and 37.5% respectively. These values do not differ significantly from those of the Inuit sample in which 8/21, or 38.1% of individuals, and 32/111, or 28.8% of anterior teeth were affected. For the growth disruption duration analysis, 22 defects representing separate episodes of growth disruption in Neandertals were compared with 22 defects in the Inuit group using three indicators of duration: the number of perikymata (growth increments) in the occlusal walls of LEH defects, the total number of perikymata within them, and defect width. Only one indicator, the total number of perikymata within defects, differed significantly between the Inuit and Neandertal groups (an average of 13.4 vs. 7.3 perikymata), suggesting that if there is any difference between them, the Inuit defects may actually represent longer growth disruptions than the Neandertal defects. Thus, while stress indicators other than linear enamel hypoplasia may eventually show that Neandertal populations were more stressed than those of modern foragers, the evidence from linear enamel hypoplasia does not lend support to this idea.
Article
Wild-shot great apes comprising 65 lowland gorillas, 67 orang-utans and 60 chimpanzees were studied to explore the interrelationship between tooth wear, continous eruption and periodontal disease with increasing age. Observations on stages of tooth wear for upper and lower I1, M1, M2 and M3 were used as a broad scale of the increasing time a tooth was judged to have been in functional occlusion during the lifetime of the animal. Three measurements of combined alveolar and basal bone heights were made on mandibles and maxillae of male and female orang-utans and gorillas. These measurements suggest that there was no change in alveolar bone height during the period between young adulthood and old age in either sex or taxon. Measurements of total tooth height above the alveolar crestal bone remained more or less constant in all teeth measured in all taxa through successive stages of wear. Measurements of enamel height and of the amount of root exposed above the level of the alveolar bone demonstrate that with increasing tooth wear, tooth root emerges above the alveolar bone in a compensatory manner to maintain a constant height of tooth tissue. Eventual degeneration of the functioning dentition occurred in older animals when enamel was completely lost from the occlusal surfaces of the molar teeth and from the crowns of the incisors. Combined chronic pulpo/periodontal infections were judged to underlie final vertical alveolar bone and tooth loss in these great apes (probably at about 30–40 years of age).
Article
Enamel is a complex bioceramic tissue. In its final form, enamel is a reflection of the unique molecular and cellular activities occurring during organogenesis. From the ectodermal origins of ameloblasts, their gene activity and protein expression profiles exist for the sole purpose of producing a mineralized shell, almost entirely devoid of protein, deposited over the ‘bone-like’ dentine. The interface between enamel and dentine is referred to as the dentine enamel junction and it is also unique in its biology. This review article is narrow in its scope. We restrict our review to selected advances in our understanding of the genetic, molecular and structural aspects of enamel biology. We present a model of enamel formation that relates gene expression to the assembly of an extracellular protein matrix that in turn controls the structural hierarchy and mechanical aspects of enamel and the tooth organ.
Article
The Plio-Pleistocene fossil hominin site of Drimolen is located approximately 5.5km north of the other well-known South African Plio-Pleistocene sites (Sterkfontein, Swartkrans, Kromdraai, Coopers). It was discovered by A.W. Keyser in 1992. Systematic excavations led to the recovery of a remarkable number of fossil vertebrate taxa, including hominins. Most of the specimens collected consist of isolated teeth or those in jaws. The aim of this paper is to provide a morphological description of the dental specimens. The taxonomic allocation of each specimen is also reported, either confirming or revising previous provisional attributions. The analysis confirms the occurrence of two hominin species, Paranthropus robustus and Homo sp. With over 80 fossil hominin specimens recovered so far, Drimolen is the second largest sample of P. robustus, after Swartkrans. At Drimolen, P. robustus is represented mostly by craniodental specimens (63) among which are 47 isolated teeth and the remainder are maxillary and mandibular fragments with teeth. The assemblage markedly increases the dental sample of P. robustus. Furthermore, the Drimolen sample includes tooth classes not present in the Swartkrans or Kromdraai samples. The new tooth classes include both deciduous upper lateral incisors (DNH 31) and canines (DNH 23). In the dental sample described here there are nine specimens probably attributable to Homo, although a specific attribution is not yet possible. These specimens expand the small sample of early Homo from South African sites. Basic dimensions (MD and BL) of the Drimolen dental remains are compared in a preliminary analysis with other hominin samples. This analysis delineates the Drimolen P. robustus dental sample as characterized by smaller teeth overall than the Swartkrans sample (and in some cases also smaller than the Kromdraai sample), as well as a greater size range.
Article
Enamel hypoplasia in the South African Plio-Pleistocene fossil hominid sample is examined. The Swartkrans hominids are shown to have a higher incidence of hypoplasia than the Sterkfontein hominids. Within the Swartkrans sample, individuals with hypoplasia of the first upper molar have lower-than-expected ages of death. Possible taphonomic explanations for these observations are discussed.
Article
Neonatal lines in deciduous and permanent teeth showed changes in direction of the prisms and in their widths, confirming the findings of others. Structural changes in the prisms consisted of a well-defined line crossing the prisms at the prenatal side of the neonatal line and a wider diffuse zone of reduced crystal density at the postnatal side. It is suggested that these represent disturbances in physiological activity at birth and the succeeding 3 to 4 day period.
Article
Based on studies in Northern Tanzania a new classification system of dental fluorosis is proposed. The classification system includes 10 scores designed to characterize the degree of dental fluorosis affecting buccal/lingual and occlusal surfaces. With aid of polarized and ordinary light microscopy the histologic features behind the individual scores are described. The macroscopic appearance of increasing degrees of dental fluorosis were well correlated to the degree of subsurface porosity. Above a certain level of subsurface hypomineralization various degrees of loss of surface enamel occurred, presumably as a result of posteruptively acquired injuries. Application of the new classification system to samples of children born in areas with 3.5, 6.0 and 21.0 parts/10(6) F- in the water supplies revealed that the distribution of dental fluorosis within the individual followed the same pattern irrespective of fluoride concentration in the water. While the classical Dean index was unable to distinguish between dental fluorosis in the 6.0 and the 21.0 parts/10(6) area it was possible with the new system to disclose that particularly the posterior teeth were significantly more affected in the latter area. Comparisons of degree of dental fluorosis with available measurements of enamel thickness proved that the within-tooth as well as within-dentition variations are determined by enamel thickness rather than length of exposure to body fluids. The limitations of the Dean index are discussed with special attention to its validity as a biological index in relation to current efforts to determine the minimal toxic effect of fluoride on the dental hard tissues.
Article
This paper describes the hypoplastic defects commonly seen on the surface of ancient human tooth crowns, excavated from archaeological sites, and presents a new method for estimating the ages at which these defects were initiated during life. The method is based upon examination of microscopic incremental structures on the enamel surface and it is possible also to apply it to reconstruction of the sequence and timing of dental crown development. The method of examination is non-destructive and allows full use to be made of the large numbers of complete, unworn dentitions which are found amongst archaeological remains.
Article
Patterns of dental disease among Bronze Age people of the Indus Valley Civilization are currently based on early and incomplete reports by non-specialists. This deficiency precludes accurate diachronic analysis of dental disease and its relationship with increasing agriculturalism in the Indian subcontinent. The objective of this paper is to document prevalence of dental disease at Harappa (2500–2000 B.C.), Punjab Province, Pakistan, comparatively evaluate the Harappan dental pathology profile, and use these data to assess theories regarding the dental health consequences of increasingly intensive agricultural dependence. Pathological conditions of the dentition included in the study are abscesses, ante-mortem tooth loss (AMTL), calculus, caries, hypoplasia, hypercementosis, pulp chamber exposure, and alveolar resorption. The Harappan dentition exhibits a dental pathology profile typical of a population whose subsistence base is agriculture. Dental caries at Harappa are present in 6.8% (n = 751) of the teeth and 43.6% (n = 39) of the more completely preserved dental specimens. The use of a caries correction factor is recommended to permit an estimate of caries induced AMTL in calculating the caries prevalence. All dental lesions are present at higher rates in this Harappan study sample than were reported in previous investigations, and important differences in prevalence of dental disease occur between the genders. Prevalence of dental disease increases in the greater Indus Valley as subsistence becomes more intensive and as food preparation and storage technology becomes more efficient.
Article
Clinical significance of enamel hypoplasia includes poor esthetics, tooth sensitivity, malocclusion and predisposition to dental caries. It may provide diagnostic clues as to genetic influences and systemic diseases, as well as to any trauma during the span of dental development. These systemic factors include birth trauma, infections, nutritional disorders, metabolic diseases, and exposures to chemicals such as tetracycline, lead, and fluoride. Inherited types form a relatively small component overall, including genetic abnormalities of enamel formation, or dental features of many inherited diseases or dysmorphic syndromes. Developmental enamel defects range in prevalence from 4 percent to 60 percent, depending on the criteria and the population studied. It is likely that many of these individual factors may in fact act through a central mechanism: mineral deficiency.