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Restoring the correct masticatory function of broken teeth is the basis of dental crown prosthesis rehabilitation. However, it is a challenging task primarily due to the complex and personalized morphology of the occlusal surface. In this article, we address this problem by designing a new two-stage generative adversarial network (GAN) to reconstruct a dental crown surface in the data-driven perspective. Specifically, in the first stage, a conditional GAN (CGAN) is designed to learn the inherent relationship between the defective tooth and the target crown, which can solve the problem of the occlusal relationship restoration. In the second stage, an improved CGAN is further devised by considering an occlusal groove parsing network (GroNet) and an occlusal fingerprint constraint to enforce the generator to enrich the functional characteristics of the occlusal surface. Experimental results demonstrate that the proposed framework significantly outperforms the state-of-the-art deep learning methods in functional occlusal surface reconstruction using a real-world patient database. Moreover, the standard deviation (SD) and root mean square (RMS) between the generated occlusal surface and the target crown calculated by our method are both less than 0.161 mm. Importantly, the designed dental crown have enough anatomical morphology and higher clinical applicability.

Objective. Restoring the correct masticatory function of partially edentulous patient is a challenging task primarily due to the complex tooth morphology between individuals. Although some deep learning-based approaches have been proposed for dental restorations, most of them do not consider the influence of dental biological characteristics for the occlusal surface reconstruction. Description. In this article, we propose a novel dual discriminator adversarial learning network to address these challenges. In particular, this network architecture integrates two models: a dilated convolutional-based generative model and a dual global-local discriminative model. While the generative model adopts dilated convolution layers to generate a feature representation that preserves clear tissue structure, the dual discriminative model makes use of two discriminators to jointly distinguish whether the input is real or fake. While the global discriminator focuses on the missing teeth and adjacent teeth to assess whether it is coherent as a whole, the local discriminator aims only at the defective teeth to ensure the local consistency of the generated dental crown. Results. Experiments on 1000 real-world patient dental samples demonstrate the effectiveness of our method. For quantitative comparison, the image quality metrics are used to measure the similarity of the generated occlusal surface, and the root mean square between the generated result and the target crown calculated by our method is 0.114 mm. In qualitative analysis, the proposed approach can generate more reasonable dental biological morphology. Conclusion. The results demonstrate that our method significantly outperforms the state-of-the-art methods in occlusal surface reconstruction. Importantly, the designed occlusal surface has enough anatomical morphology of natural teeth and superior clinical application value.

Human dentin consists of a primary layer produced during tooth formation in early childhood and a second layer which first forms upon tooth eruption and continues throughout life, termed secondary dentin (SD). The effect of attrition on SD formation was considered to be confined to the area subjacent to attrition facets. However, due to a lack of three-dimensional methodologies to demonstrate the structure of the SD, this association could not be determined. Therefore, in the current study, we aimed to explore the thickening pattern of the SD in relation to the amount of occlusal and interproximal attrition. A total of 30 premolars (50–60 years of age) with varying attrition rates were evaluated using micro-computerized tomography. The results revealed thickening of the SD below the cementoenamel junction (CEJ), mostly in the mesial and distal aspects of the root (p &lt, 0.05). The pattern of thickening under the tooth cervix, rather than in proximity to attrition facets, was consistent regardless of the attrition level. The amount of SD thickening mildly correlated with occlusal attrition (r = 0.577, p &lt, 0.05) and not with interproximal attrition. The thickening of the SD below the CEJ coincided with previous finite element models, suggesting that this area is mostly subjected to stress due to occlusal loadings. Therefore, we suggest that the SD formation might serve as a compensatory mechanism aimed to strengthen tooth structure against deflection caused by mechanical loading. Our study suggests that occlusal forces may play a significant role in SD formation.

Many aspects of diet and behaviour can be gleaned from dental wear, including environmental conditions, food-fracture properties, food processing techniques, and cultural habits. Specifically, the angulation (flat vs. steep) of molar wear has been used as an indicator of food toughness and has also been implicated in the use of grinding stones and pottery in food processing. In this work, we focus on the sequential phases of the power stroke of mastication in a functional way, measuring the inclination of molar wear facets through the occlusal fingerprint analysis method. Specifically, we have calculated the angulation of wear facets in upper and lower molars of Palaeolithic humans, extant hunter-gatherers, and proto-farmers to discern differences between groups with different diets. Contrary to previous analyses, our study shows that the molars of Late Pleistocene specimens are characterized by significantly steeper angles than those of modern hunter-gatherers. The flat molar wear found in the latter group could be related to the excessive mixture of exogenous materials accidentally introduced into their foods, as indicated by ethnographic evidence. On the contrary, the steep wear angles characterizing the Palaeolithic group are probably associated with the consumption of a less abrasive diet, which could be ultimately due to food preparation techniques that incorporated less dust and grit into their diets.

Supernumerary teeth, or teeth that develop in addition to the normal number of deciduous and permanent dentition, have been widely described in human and nonhuman primates. Most studies have focused on the morphology and on the etiology of supernumerary teeth, and little is known about their occlusal relationships with adjacent and antagonistic teeth, and their effects on individuals’ masticatory efficiency. We analyzed the occlusal wear pattern of an adult male Western lowland gorilla (Gorilla gorilla gorilla) with a fully erupted extra maxillary right premolar. We used a virtual method, occlusal fingerprint analysis, to reconstruct the major mandibular occlusal pathways responsible for the creation of wear facets on the tooth crowns. This approach is based on analysis of facet parameters such as inclination, directions, and areas, all measured using high-resolution 3-D virtual models of dental crowns. The results show unusual wear patterns in the supernumerary premolar and on its antagonist contacts (lower P4 and M1) that cannot be associated with a normal masticatory behavior. Occlusal simulation and kinematic analyses reveal a high level of directional overlapping combined with the absence of common occlusal contacts. This indicates a case of malocclusion that must have caused discomfort in this gorilla when biting or chewing, and may represent the first evidence of bruxism (grinding the teeth and clenching the jaw) in wild great apes.

The use of teeth as tools for manipulating objects and simple food-processing methods was common among prehistoric and modern hunter-gatherer human populations. Paramasticatory uses of teeth frequently produce enamel chipping and distinctive types of dental wear that can readily be related to specific tool functions. In particular, the presence of unusual occlusal wear areas (named para-facets) on maxillary teeth of prehistoric, historic and modern hunter-gatherers has been associated with cultural habits involving extensive use of teeth (Fiorenza et al., 2011; Fiorenza and Kullmer, 2013). However, Sarig and Tillier (2014) believe that this wear had been caused by pathological occlusal relationships rather than by the use of teeth as tools. In this contribution, we show how occlusal contacts are created and how it is possible to distinguish between masticatory and non-masticatory wear facets by using an innovative digital approach called Occlusal Fingerprint Analysis. Statistical results from the analysis of comparative modern samples clearly demonstrate that described para-facets in Skhul and Qafzeh could not have been produced by dental occlusal anomalies such as malocclusions and crossbites. Moreover, dental pathologies in prehistoric humans were extremely rare. Only with the adoption of the modern lifestyle between 18th and 19th centuries, did the emergence of malocclusions become significantly more common. Because more than 50% of the Skhul and Qafzeh individuals analysed in our study are characterised by this distinctive type of wear, it is highly unlikely that their para-facets occurred as a result of dental pathologies.

The mastication of tough and hard foods combined with the extensive use of teeth as tools, have been considered possible antemortem causes in determining enamel microfractures of the tooth crown. This phenomenon, known as dental chipping, has been found in different fossil hominins and in several pre-historic and historic human populations who adopted different subsistence strategies. However, little is understood of the mechanism, function and the formation of dental chipping. In this study we analyze the maxillary molar wear areas associated with dental chipping (and named para-facets) of several hunter–gatherer specimens, using the Occlusal Fingerprint Analysis method. We employ three-dimensional digital models of tooth crowns created by surface scanning of dental replicas, to analyze the dip and dip directions of normal occlusal wear areas and para-facets. This allows us to reconstruct the jaw movements responsible for the creation of para-facets, and investigate whether they are produced during normal mastication or not. Vectors of the para-facets do not show any preferred direction and are distributed randomly as visualized by the occlusal compass, displaying significant differences with the major jaw movements in action during the normal chewing cycle. More importantly, no antagonist contacts in the lower teeth are associated with the para-facets of the upper teeth. This excludes the possibility that the para-facets are created during normal mastication. We therefore suggest that this unusual type of tooth wear is mainly due to attritional and abrasive contacts generated through daily task activities for foods processing and/or manufacturing of objects.

Morphometrics of the molar crown is based traditionally on diameter measurements but is nowadays more often based on 2D image analysis of crown outlines. An alternative approach involves measurements at the level of the cervical line. We compare the information content of the two options in a three-dimensional (3D) digital sample of lower and upper first molars (M(1) and M(1) ) of modern human and Neanderthal teeth. The cervical outline for each tooth was created by digitizing the cervical line and then sectioning the tooth with a best fit plane. The crown outline was projected onto this same plane. The curves were analyzed by direct extraction of diameters, diagonals, and area and also by principal component analysis either of the residuals obtained by regressing out these measurements from the radii (shape information) or directly by the radii (size and shape information). For M(1) , the crown and cervical outline radii allow us to discriminate between Neanderthals and modern humans with 90% and 95% accuracy, respectively. Fairly good discrimination between the groups (80-82.5%) was also obtained using cervical measurements. With respect to M(1) , general overlap of the two groups was obtained by both crown and cervical measurements; however, the two taxa were differentiable by crown outline residuals (90-97%). Accordingly, while crown diameters or crown radii should be used for taxonomic analysis of unworn or slightly worn M(1) s, the crown outline, after regressing out size information, could be promising for taxonomic assignment of lower M1s.

Information about food ingestion and mastication behavior during the lifespan of an individual is encoded in the dental occlusal wear pattern. To decode this information, we describe a new method called occlusal fingerprint analysis (OFA). Structural parameters of wear facets on the occlusal surface of teeth are quantified from digitized casts for the interpretation of occlusal aspects. The OFA provides an individual three-dimensional dental occlusal compass that indicates the major pathways of interaction between antagonists, revealing information about development, spatial position, and enlargement of wear facets. Humans develop a very similar overall pattern of crown contacts, although specific characteristics of wear facets reflect an individual's occlusal relationships and masticatory behavior. We hypothesize that the wear pattern is a unique character and therefore valuable for individual identification. Furthermore we suggest that OFA, when further developed, may be useful for identification of behavioral, biological, and chemical factors affecting crown morphology.

Neanderthals have been commonly depicted as top predators who met their nutritional needs by focusing entirely on meat. This information mostly derives from faunal assemblage analyses and sta- ble isotope studies: methods that tend to underestimate plant consumption and overestimate the intake of ani- mal proteins. Several studies in fact demonstrate that there is a physiological limit to the amount of animal proteins that can be consumed: exceeding these values causes protein toxicity that can be particularly danger- ous to pregnant women and newborns. Consequently, to avoid food poisoning from meat-based diets, Neander- thals must have incorporated alternative food sources in their daily diets, including plant materials as well. Yrbk Phys Anthropol 156:43-71, 2015. V C 2014 American Association

Department of Palaeoanthropology and Messel Research, Senckenberg Research Institute, D-60325 Frankfurt amMain, GermanyKEY WORDS Neanderthals; anatomically modern humans; occlusal compass; Levant;para-facetsABSTRACT Neanderthals and anatomically modernhumans (AMHs) may have lived in close proximity inthe Near East region during Middle Paleolithic times.Although functional morphological analyses suggest amarked behavioral contrast between these two humangroups, new dental micro- and macro-wear studies,together with new archaeological data, have revealedsome similarities in ecology and dietary habits. In thisstudy, we analyze the tooth wear patterns of Neander-thals and AMH from Middle Paleolithic sites of Israeland Northern Iraq, using the Occlusal Fingerprint Anal-ysis (OFA) method to virtually reconstruct the jaw move-ments responsible for the creation of the occlusal wearareas. We particularly focus on para-facets, a distinctivetype of wear which has been previously described in thedentition of historic and modern hunter-gatherers. Theanalysis reveals a similarity in para-facet frequencybetween early Near Eastern Neanderthals and AMH,and a significant difference with other Pleistocenehuman groups. The absence of antagonist occlusal con-tacts in the lower teeth and the occlusal compass analy-sis suggest that para-facet formation is not related tonormal mastication but to nonmasticatory activities.Thus, the identification of these nonmasticatory wearareas on the molars of early Near Eastern Neanderthalsand AMH may indicate analogous tooth-tool uses fordaily task activities. These may have emerged independ-ently or could be interpreted as indirect evidence of cul-tural interactions between these two groups. Am J PhysAnthropol 152:107-117, 2013.

The issue of reconstructing lost or deformed bone presents an equal challenge in the fields of paleoanthropology, bioarchaeology, forensics, and medicine. Particularly, within the disciplines of orthodontics and surgery, the main goal of reconstruction is to restore or create ex novo the proper form and function. The reconstruction of the mandibular condyle requires restoration of articulation, occlusion, and mastication from the functional side as well as the correct shape of the mandible from the esthetic point of view. Meeting all these demands is still problematic for surgeons. It is unfortunate that the collaboration between anthropologists and medical professionals is still limited. Nowadays, geometric morphometric methods (GMM) are routinely applied in shape analysis and increasingly in the reconstruction of missing data in skeletal material in paleoanthropology. Together with methods for three-dimensional (3D) digital model construction and reverse engineering, these methods could prove to be useful in surgical fields for virtual planning of operations and the production of customized biocompatible scaffolds. In this contribution, we have reconstructed the missing left condylar process of the mandible belonging to a famous Italian humanist of the 15th century, Pico della Mirandola (1463–1494) by means of 3D digital models and GMM, having first compared two methods (a simple reflection of the opposite side and the mathematical–statistical GMM approach) in a complete human mandible on which loss of the left condyle was virtually simulated. Finally, stereolithographic models of Pico’s skull were prototyped providing the physical assembly of the bony skull structures with a high fitting accuracy. Anat Rec, 292:1088–1097, 2009. V C 2009 Wiley-Liss, Inc.