edjes

OBJECTIVES: This study explores the outer and inner crown of lower third and fourth premolars (P3 , P4 ) by analyzing the morphological variation among diverse modern human groups. MATERIALS AND METHODS: We studied three-dimensional models of the outer enamel surface and the enamel-dentine junction (EDJ) from μCT datasets of 77 recent humans using both an assessment of seven nonmetric traits and a standard geometric morphometric (GM) analysis. For the latter, the dental crown was represented by four landmarks (dentine horns and fossae), 20 semilandmarks along the EDJ marginal ridge, and pseudolandmarks along the crown and cervical outlines...

In 1972 and 1983, four hominin teeth were recovered from Yanhui Cave, Tongzi, southern China and assigned to later Homo erectus or archaic Homo sapiens. The teeth can be dated to approximately 172,000-240,000 years before present. Here, in addition to the standard morphological comparisons, we reevaluate the morphology of the hominin teeth using geometric morphometric analyses and micro-computed tomography (micro-CT) scans. The Tongzi teeth were primarily compared to hominins from the same chronological period (late Middle Pleistocene) and/or the same geographic area (East Asia), although a wide range of hominins were included in the comparative sample...

Morphometric assessments of the dentition have played significant roles in hypotheses relating to taxonomic diversity among extinct hominins. In this regard, emphasis has been placed on the statistical appraisal of intraspecific variation to identify morphological criteria that convey maximum discriminatory power. Three-dimensional geometric morphometric (3D GM) approaches that utilize landmarks and semi-landmarks to quantify shape variation have enjoyed increasingly popular use over the past twenty-five years in assessments of the outer enamel surface (OES) and enamel-dentine junction (EDJ) of fossil molars...

Here we analyze the unpublished hominin dental remains recovered from the late Early Pleistocene Gran Dolina-TD6.2 level of the Sierra de Atapuerca (northern Spain), as well as provide a reassessment of the whole TD6.2 hominin dental sample. Comparative descriptions of the outer enamel surface (OES) and the enamel-dentine junction (EDJ) are provided. Overall, the data presented here support the taxonomic validity of Homo antecessor, since this species presents a unique mosaic of traits. Homo antecessor displays several primitive features for the genus Homo as well as some traits exclusively shared with Early and Middle Pleistocene Eurasian hominins...

OBJECTIVE: To evaluate the practical value of nearinfrared light transillumination (NILT, DIAGNOcam) on detection of incipient proximal caries in primary molars. METHODS: In this study, 4-9-year-old children with suspicious proximal lesions in primary molars were recruited. The target teeth were examined with clinical examination, bitewing radiograph and DIAGNOcam. And the caries indexes were rated as 0 (no caries), 1 (caries reaching outer 1/2 enamel), 2 (caries reaching inner 1/2 enamel), and 3 (dentine caries)...

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...

OBJECTIVES: The aim of this study was to further evaluate the caries-arresting effectiveness of micro-invasive interventions for non-cavitated proximal caries and analyze their efficacy for caries lesions of different depths. MATERIALS AND METHODS: Randomized clinical trials (RCTs) of micro-invasive interventions for non-cavitated proximal caries were included in this study. We searched the Cochrane Library, PubMed, Embase, and Web of Science on May 25, 2017, without restrictions...

This study provides new original data, including the endostructure of most Zhoukoudian H. erectus teeth preserved to date, since the publication of Black in 1927 and Weidenreich in 1937. The new evidence ratifies the similarities of Zhoukoudian with other East Asian mid-Middle Pleistocene hominins such as Hexian and Yiyuan, and allows defining a dental pattern potentially characteristic of this population commonly referred to as classic H. erectus. Given the possible chronological overlaps of classic H. erectus with other archaic Homo, the characterization of this group becomes a key issue when deciphering the taxonomy and evolutionary scenario of the Middle Pleistocene hominins in East Asia...

We studied the spatio-temporal variation of mineral apposition rate (MAR) in postnatally formed coronal dentine of mandibular first molars from Soay sheep repeatedly injected with different fluorochromes. MAR declined along the cuspal to cervical crown axis, and from early to late formed dentine, that is, from the dentine at the enamel-dentine-junction (EDJ) to the dentine adjacent to the dentine-pulp-interface (DPI). Highest mean MARs (about 21 µm/day) were recorded in cuspal dentine formed in the period of 28-42 days after birth...

Enamel formation front (EFF) angles represent the leading edge of enamel matrix secretion at particular points in time. These angles are influenced by rates of enamel extension (the rates at which tooth crowns grow in height), rates of enamel matrix secretion and the angles that prisms make with the enamel-dentine junction. Previous research suggests, but has not yet established, that these angles reflect aspects of primate biology related to their pace of growth and development, most notably brain and body size...

Evolutionary studies of mammalian teeth have generally concentrated on the adaptive and functional significance of dental features, whereas the role of development on phenotypic generation and as a source of variation has received comparatively little attention. The present study combines an evolutionary biological framework with state-of-the-art imaging techniques to examine the developmental basis of variation of accessory cusps. Scholars have long used the position and relatedness of cusps to other crown structures as a criterion for differentiating between developmentally homologous and homoplastic features, which can be evaluated with greater accuracy at the enamel-dentine junction (EDJ)...

OBJECTIVES: The aim of this study is to compare the degree and patterning of inter- and intra-individual metameric variation in South African australopiths, early Homo and modern humans. Metameric variation likely reflects developmental and taxonomical issues, and could also be used to infer ecological and functional adaptations. However, its patterning along the early hominin postcanine dentition, particularly among South African fossil hominins, remains unexplored. MATERIALS AND METHODS: Using microfocus X-ray computed tomography (µXCT) and geometric morphometric tools, we studied the enamel-dentine junction (EDJ) morphology and we investigated the intra- and inter-individual EDJ metameric variation among eight australopiths and two early Homo specimens from South Africa, as well as 32 modern humans...

Using the distal molar of a minipig as a model, we studied changes in the microstructural characteristics of apatite crystallites during enamel maturation (16-23 months of postnatal age), and their effects upon the mechanical properties of the enamel coat. The slow rate of tooth development in a pig model enabled us to reveal essential heterochronies in particular components of the maturation process. The maturation changes began along the enamel-dentine junction (EDJ) of the trigonid, spreading subsequently to the outer layers of the enamel coat to appear at the surface zone with a 2-month delay...

This study explores the morphological differences between the enamel-dentine junction (EDJ) of maxillary and mandibular molars of Neanderthals (n = 150) and recent modern humans (n = 106), and between an earlier Neanderthal sample (consisting of Pre-Eemian and Eemian Neanderthals dating to before 115 ka) and a later Neanderthal sample (consisting of Post-Eemian Neanderthals dating to after 115 ka). The EDJ was visualised by segmenting microtomographic scans of each molar. A geometric morphometric methodology compared the positioning of the dentine horns, the shape of the marginal ridge between the dentine horns, and the shape of the cervix...

OBJECTIVES: This study presents the first detailed morphological description and comparison of a Middle Pleistocene hominin mandibular fragment (PA 831) and associated teeth from the Hexian site in Eastern China. We aim to investigate where the Hexian mandible fits within the genus Homo variability in the light of an increased and better characterized Asian fossils record. METHODS: Comparative samples include Pleistocene Homo mandibles and teeth from Africa, Asia, and Europe, as well as earlier African hominins (Australopithecus and early Homo) and Holocene recent humans...

Variations in the dental crown form are widely studied to interpret evolutionary changes in primates as well as to assess affinities among human archeological populations. Compared to external metrics of dental crown size and shape, variables including the internal structures such as enamel thickness, tissue proportions, and the three-dimensional shape of enamel-dentin junction (EDJ), have been described as powerful measurements to study taxonomy, phylogenetic relationships, dietary, and/or developmental patterns...

The appearance of the earliest members of the genus Homo in South Africa represents a key event in human evolution. Although enamel thickness and enamel dentine junction (EDJ) morphology preserve important information about hominin systematics and dietary adaptation, these features have not been sufficiently studied with regard to early Homo. We used micro-CT to compare enamel thickness and EDJ morphology among the mandibular postcanine dentitions of South African early hominins (N = 30) and extant Homo sapiens (N = 26), with special reference to early members of the genus Homo...

This study aimed to assess the enamel ultrastructure in modern otariid pinnipeds and in the extinct walrus Pelagiarctos. Teeth of the New Zealand fur seal (Arctocephalus forsteri), sea lion (Phocarctos hookeri), and fossil walrus Pelagiarctos thomasi were embedded, sectioned, etched, and analyzed via scanning electron microscopy. The enamel of NZ otariids and Pelagiarctos was prismatic and moderately thick, measuring 150-450 μm on average. It consisted of transversely oriented Hunter-Schreger bands (HSBs) from the enamel-dentine junction (EDJ) to near the outer surface, where it faded into prismless enamel less than 10 μm thick...

The Middle Pleistocene represents a period of critical importance in human evolution, marked by encephalisation and dental reduction, and increasing diversification of temporally and spatially distributed hominin lineages in Africa, Asia and Europe. New specimens, especially from areas less well represented in the fossil record, can inform the debate on morphological changes to the skeleton and teeth and the phylogenetic course of human evolution during this period. The mandible from the cave of Mala Balanica, Serbia has recently been re-dated to at least 400 ka, and its well-preserved dentition presents an excellent opportunity to characterize molar crown morphology at this time period, and re-examine claims for a lack of Neandertal affinities in the specimen...

OBJECTIVE: To determine if dentine at the enamel-dentine junction (EDJ) in man is more sensitive to hydrostatic pressure stimuli then deeper dentine. DESIGN: Cavities (1mm diam.) were cut at the tips of the buccal and lingual cusps of 8 premolars in 3 subjects (ages: 22-25 years). Both cavities were initially deepened to expose the EDJ then one (the test cavity) was deepened in steps of 0.5mm to a maximum of 2.0 mm below the EDJ. The cavities were tested at each stage, before and after etching, with 5s, hydrostatic pressure stimuli between 400 mm above, and 400 mm below atmospheric...