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1.
Biomed Res Int ; 2022: 4695193, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35229002

RESUMO

OBJECTIVE: To analyze the width and height ratios of maxillary anterior teeth at different crown levels through photographs, 3D, and plaster dental model techniques in a subset of the Pakistani population. Material and Methods. This clinical study consisted of 230 participants. The maxillary impression, standardized photographs, and models were constructed for crown width and height analysis. The SPSS version 25 was used for statistical analysis. Descriptive statistics were carried out for mean, standard deviation, and percentage calculation of teeth width and height, gender, and age of participants. Paired t-test analysis was carried out to compare the dependent variables (teeth size, width, and height ratios) with independent variables (techniques applied, side disparity). A p value of ≤ 0.05 was considered statistically significant. RESULTS: The mean width and height of maxillary anterior teeth obtained through photographs, 3D, and plater models were statistically different. The 3D dental model analysis showed reliable and accurate results. The mean width and height ratio of teeth were different on both sides of the arch. There was a significant difference (p = 0.001) in crown width-height ratios at different crown levels. CONCLUSION: The width and height ratios in the studied population were different at various crown levels. The dimensions of teeth varied from the incisal to the cervical part of the crown. Hence, rather than relying on a single, fixed ratio of 78% to 80% suggested by researchers for anterior teeth, the clinician should adopt different crown width-height ratios to restore teeth with the optimum esthetic outcome.


Assuntos
Dente Canino/anatomia & histologia , Estética Dentária , Face/anatomia & histologia , Incisivo/anatomia & histologia , Coroa do Dente/anatomia & histologia , Adulto , Estatura , Estética , Feminino , Humanos , Masculino , Odontometria , Fotografia Dentária , Fatores Sexuais
2.
PLoS One ; 16(11): e0259293, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34739497

RESUMO

BACKGROUND: The permanent tooth formation process may be disrupted in preterm infants with potential discrepancies in size and subsequent occlusal disturbances. OBJECTIVE: To systematically analyse and quantitively synthesize the available evidence regarding the impact of preterm birth on permanent tooth crown dimensions. SEARCH METHODS: Unrestricted searches in 6 databases and manual searching of the reference lists in relevant studies were performed up to March 2021 (Medline via PubMed, CENTRAL, Cochrane Database of Systematic Reviews, Scopus, Web of Science, ProQuest Dissertations and Theses Global). SELECTION CRITERIA: Observational studies investigating permanent tooth crown dimensions in preterm and control full-term born individuals. DATA COLLECTION AND ANALYSIS: Following study retrieval and selection, relevant data were extracted, and the Newcastle-Ottawa scale was used to assess the selection, comparability, and outcome domains. Exploratory synthesis and meta-regression were carried out using the random effects model. RESULTS: Three studies were located from the initially retrieved records and the assessments with the Newcastle-Ottawa scale identified issues regarding the selection and comparability domains. Overall, the mesiodistal and the buccolingual dimensions of the permanent teeth in both dental arches tended to be smaller in children born prematurely than full term children. Subgroup analyses showed statistically significant differences for the extremely preterm to control group comparisons for the incisors and the first molars. Meta-regression showed a modificatory effect of gestational age and racial background but not of birth weight and gender on tooth size. The quality of available evidence was rated at best as moderate. CONCLUSIONS: Premature birth could potentially be associated with reduced tooth-crown dimensions in some permanent teeth especially in children born extremely preterm. Although the results from these observational studies should be approached with caution until more information becomes available, the possible clinical implications in terms of diagnosis and treatment planning should be considered. REGISTRATION: PROSPERO (CRD42020182243).


Assuntos
Nascimento Prematuro/fisiopatologia , Coroa do Dente/anatomia & histologia , Coroa do Dente/crescimento & desenvolvimento , Adolescente , Criança , Pré-Escolar , Dentição Permanente , Feminino , Idade Gestacional , Humanos , Incisivo , Recém-Nascido Prematuro/metabolismo , Recém-Nascido Prematuro/fisiologia , Masculino , Dente Molar , Odontogênese/fisiologia , Dente/anatomia & histologia , Dente Decíduo
3.
Am J Phys Anthropol ; 176(2): 262-282, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34190335

RESUMO

OBJECTIVES: Size-corrected tooth crown measurements were used to estimate phenetic affinities among Homo naledi (~335-236 ka) and 11 other Plio-Pleistocene and recent species. To assess further their efficacy, and identify dental evolutionary trends, the data were then quantitatively coded for phylogenetic analyses. Results from both methods contribute additional characterization of H. naledi relative to other hominins. MATERIALS AND METHODS: After division by their geometric mean, scaled mesiodistal and buccolingual dimensions were used in tooth size apportionment analysis to compare H. naledi with Australopithecus africanus, A. afarensis, Paranthropus robustus, P. boisei, H. habilis, H. ergaster, H. erectus, H. heidelbergensis, H. neanderthalensis, H. sapiens, and Pan troglodytes. These data produce equivalently scaled samples unaffected by interspecific size differences. The data were then gap-weighted for Bayesian inference. RESULTS: Congruence in interspecific relationships is evident between methods, and with many inferred from earlier systematic studies. However, the present results place H. naledi as a sister taxon to H. habilis, based on a symplesiomorphic pattern of relative tooth size. In the preferred Bayesian phylogram, H. naledi is nested within a clade comprising all Homo species, but it shares some characteristics with australopiths and, particularly, early Homo. DISCUSSION: Phylogenetic analyses of relative tooth size yield information about evolutionary dental trends not previously reported in H. naledi and the other hominins. Moreover, with an appropriate model these data recovered plausible evolutionary relationships. Together, the findings support recent study suggesting H. naledi originated long before the geological date of the Dinaledi Chamber, from which the specimens under study were recovered.


Assuntos
Hominidae/anatomia & histologia , Hominidae/classificação , Dente/anatomia & histologia , Animais , Antropologia Física , Teorema de Bayes , Evolução Biológica , Fósseis , Humanos , Filogenia , Coroa do Dente/anatomia & histologia
4.
Sci Rep ; 11(1): 5143, 2021 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-33664401

RESUMO

Morphological variations in human teeth have long been recognized and, in particular, the spatial and temporal distribution of two patterns of dental features in Asia, i.e., Sinodonty and Sundadonty, have contributed to our understanding of the human migration history. However, the molecular mechanisms underlying such dental variations have not yet been completely elucidated. Recent studies have clarified that a nonsynonymous variant in the ectodysplasin A receptor gene (EDAR 370V/A; rs3827760) contributes to crown traits related to Sinodonty. In this study, we examined the association between the EDAR polymorphism and tooth root traits by using computed tomography images and identified that the effects of the EDAR variant on the number and shape of roots differed depending on the tooth type. In addition, to better understand tooth root morphogenesis, a computational analysis for patterns of tooth roots was performed, assuming a reaction-diffusion system. The computational study suggested that the complicated effects of the EDAR polymorphism could be explained when it is considered that EDAR modifies the syntheses of multiple related molecules working in the reaction-diffusion dynamics. In this study, we shed light on the molecular mechanisms of tooth root morphogenesis, which are less understood in comparison to those of tooth crown morphogenesis.


Assuntos
Receptor Edar/genética , Odontogênese/genética , Raiz Dentária/anatomia & histologia , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Polimorfismo Genético , Coroa do Dente/anatomia & histologia , Coroa do Dente/metabolismo , Raiz Dentária/metabolismo , Adulto Jovem
5.
Leg Med (Tokyo) ; 48: 101801, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33268276

RESUMO

In forensic anthropology, correct identification of human deciduous teeth is of paramount importance for age-at-death estimation and relies on detailed anatomical descriptions. Yet literature is scarce on indications: details on the morphology of molar tooth germs of fetuses and newborns, developing from multiple mineralized centers that will eventually coalesce, are scant. This paper presents new anatomical elements for practitioners to identify human molar tooth germs at early developmental stages. 126 deciduous molars from 22 modern skeletons of fetuses and newborns (with a known age-at-death ranging between 0 days and 2 months and 21 days postnatal), without reported or observed dental pathological signs, were selected from the Collezione Antropologica LABANOF (CAL) documented skeletal collection. Gross anatomical descriptions of the morphology and configuration of the centers were provided, considering the number of mineralized centers, the shape and the outline of the occlusal plane at different stages. Three different developmental stages were observed in the maxillary first and second molar and the mandibular first molar, whereas in the mandibular second molar four stages were observed. For each stage, we provide additional detailed morphological descriptions, sketches outlining the shape of the tooth germ, and a picture of the tooth; also, indications for siding the teeth are presented. This information can be used by forensic anthropologists and odontologists for a proper identification when tooth germs are not found in anatomical connection within the dental sockets. Further analyses that encompass more age groups on a larger sample would allow to map the entire crown development of deciduous molars.


Assuntos
Determinação da Idade pelos Dentes/métodos , Antropologia Forense/métodos , Dente Molar/anatomia & histologia , Germe de Dente/anatomia & histologia , Dente Decíduo/anatomia & histologia , Humanos , Recém-Nascido , Mandíbula , Maxila , Dente Molar/embriologia , Coroa do Dente/anatomia & histologia , Coroa do Dente/embriologia , Coroa do Dente/crescimento & desenvolvimento , Germe de Dente/embriologia , Dente Decíduo/embriologia
6.
Aust Endod J ; 47(2): 298-306, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33314382

RESUMO

This study aimed to determine the prevalence of four-rooted teeth and the corresponding crown, root and canal morphology in maxillary molars. Cone-beam computed tomographic images for 1200 patients were examined, and 1799 maxillary first molar (MFM) and 2123 maxillary second molar (MSM) teeth were evaluated. Statistical analyses were performed at a 5% significance level. Only three MFMs (0.17%) and 30 maxillary MSMs (1.41%) were four-rooted. The most common four-root type was the double palatal root. A higher proportion of four-rooted teeth were observed in men (P < 0.05), and a high percentage of root fusion was seen in these teeth. The palatal half of the crown was wider in teeth with double palatal roots. Although rarely encountered, the diagnosis and proper treatment of these teeth are very important for endodontic success.


Assuntos
Dente Molar , Coroa do Dente , Raiz Dentária , Tomografia Computadorizada de Feixe Cônico , Humanos , Maxila/diagnóstico por imagem , Dente Molar/diagnóstico por imagem , Coroa do Dente/anatomia & histologia , Raiz Dentária/diagnóstico por imagem
7.
Am J Phys Anthropol ; 174(2): 315-326, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33253429

RESUMO

OBJECTIVES: We aimed to investigate molar enamel development in fossil orangutans from Guangxi and shed light on the evolution of Asian great apes. MATERIALS AND METHODS: We collected 32 fossil orangutan molars, most of which were from Guangxi apothecaries and the Guangxi Daxin Heidong cave, and prepared histological sections of each molar. We then characterized aspects of dental development, including long period line periodicity, number of Retzius lines and lateral enamel formation time, cuspal enamel thickness, and enamel formation time. RESULTS: The long period line periodicity in fossil orangutans ranged from 9 to 10 days (mean, 9.09 days). The molar lateral enamel formation time ranged from 1.48 to 3.17 years (540-1,152 days). Cuspal enamel thickness in fossil orangutan molars ranged from 949 to 2,535 µm, and cuspal enamel formation time ranged from 0.64 to 1.87 years. Molar enamel formation time of fossil orangutans ranged from 2.47 to 4.67 years. DISCUSSION: Long-period line periodicity of fossil orangutans from Guangxi was within the variation range of extant orangutans, and the average long period line periodicity (9.09 days) of fossil orangutans from Guangxi in this study was lower than the values for extant orangutans (9.5 days) and fossil orangutans (10.9 days) from Sumatra and Vietnam. Orangutan enamel thickness may have gradually decreased from the Middle Pleistocene to Holocene. Crown formation time of fossil orangutans was slightly longer than that of extant orangutans, and the M1 emergence age of fossil orangutans from Guangxi was about 4-6 years. These findings might indicate the regional difference or evolutionary changes in orangutans since Pleistocene. Dental development of the Guangxi fossil orangutans were more similar to that of Asian Miocene apes, suggesting the closer evolutionary relationship of orangutans to Miocene Asian fossil apes.


Assuntos
Dente Molar , Pongo , Coroa do Dente , Animais , Antropologia Física , China , Esmalte Dentário/anatomia & histologia , Esmalte Dentário/crescimento & desenvolvimento , Fósseis , Hominidae/anatomia & histologia , Hominidae/crescimento & desenvolvimento , Humanos , Dente Molar/anatomia & histologia , Dente Molar/crescimento & desenvolvimento , Pongo/anatomia & histologia , Pongo/crescimento & desenvolvimento , Coroa do Dente/anatomia & histologia , Coroa do Dente/crescimento & desenvolvimento
8.
Am J Phys Anthropol ; 175(1): 106-127, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33247477

RESUMO

OBJECTIVES: Dimorphism in the dentition has been observed in human populations worldwide. However, research has largely focused on traditional linear crown measurements. As imaging systems, such as micro-computed tomography (micro-CT), become increasingly more accessible, new dental measurements such as dental tissue size and proportions can be obtained. This research investigates the variation of dental tissues and proportions by sex in archaeological samples. MATERIALS AND METHODS: Upper and lower first incisor to second premolar tooth rows were obtained from 30 individuals (n = 300), from 3 archaeological samples. The teeth were micro-CT scanned and surface area and volumetric measurements were obtained from the surface meshes extracted. Dental wear was also recorded and differences between sexes determined. RESULTS: Enamel and crown measurements were found to be larger in females. Conversely, dentine and root measurements were larger in males. DISCUSSION: The findings support the potential use of dental tissues to estimate sex of individuals from archaeological samples, while also indicating that individuals aged using current dental aging methods may be underaged or overaged due to sex differences in enamel thickness.


Assuntos
Caracteres Sexuais , Dente/anatomia & histologia , Microtomografia por Raio-X , Adulto , Idoso , Arqueologia , Esmalte Dentário/anatomia & histologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Coroa do Dente/anatomia & histologia , Desgaste dos Dentes/patologia , Adulto Jovem
9.
Sci Rep ; 10(1): 22378, 2020 12 24.
Artigo em Inglês | MEDLINE | ID: mdl-33361774

RESUMO

Triconodontidae are considered the first carnivorous crown mammals. A virtual reconstruction of the masticatory cycle in the Late Jurassic Priacodon showed that triconodontid dental function is characterized by precise cutting on elongated crests. The combination of traits linked to both carnivorous diets (e.g. fore-aft cutting edges) and insectivorous diets (transverse crests and lobes) suggests a varied faunivorous diet appropriate to the small body size of most triconodontids. Total length of molar shear decreased with wear, suggesting a dietary shift during ontogeny. Embrasure occlusion is confirmed for P. fruitaensis as indicated by premolar positioning, facet orientation, and collision areas. Embrasure occlusion is considered a general feature of all Eutriconodonta, whereas the previously assumed Morganucodon-like pattern is limited to few early mammaliaforms. Unlike modern carnivores, significant roll of around 10° of the active hemimandible occurred during the power stroke. Roll was likely passive in Triconodontidae in contrast to active roll described for extant therians. The triconodontid molar series was highly uniform and adapted to a precise fit, with self-sharpening lower molar cusps. Whereas the uniformity ensured good cutting capabilities, it likely put the dentition under greater constraints, conserving the highly stereotyped nature of triconodontid molars for 60-85 Ma.


Assuntos
Evolução Biológica , Comportamento Alimentar , Fósseis , Mamíferos , Coroa do Dente/anatomia & histologia , Animais , Mamíferos/anatomia & histologia , Mamíferos/classificação , Dente Molar
10.
Beijing Da Xue Xue Bao Yi Xue Ban ; 52(6): 1130-1134, 2020 Dec 18.
Artigo em Chinês | MEDLINE | ID: mdl-33331326

RESUMO

OBJECTIVE: To analyze the esthetic proportions of maxillary anterior teeth in term of the apparent widths proportion of the adjacent teeth and width/height ratio of the clinical crown in 120 Chinese adults. METHODS: Maxillary gypsum casts were obtained from the dental laboratories of stomatological hospitals in North China, Southeast China, and Southwest China, according to the inclusion criteria and exclusion criteria. Standardized digital photographs of each cast were recorded. The apparent widths and actual widths and heights of the central incisors, lateral incisors and canines were determined by ImageJ software for the calculation of apparent widths proportion of the adjacent teeth and width/height ratio of the clinical crown. The ideal apparent widths proportion (Golden proportion and Preston proportion) and width/height ratio (0.80) were tested. The gender, arch side, and regional differences were investigated. RESULTS: The apparent widths proportion of the lateral/central incisor was 0.724±0.047, of the canine/lateral incisor was 0.814±0.092. The width/height ratio of the central incisor was 0.848±0.072, of the lateral incisor was 0.834±0.094, of the canine was 0.883±0.098. The esthetic proportions were different from the predicted ideal ratio (P < 0.001). The apparent widths proportion of lateral/central incisor was significantly larger in the right side than that in the left side (0.730± 0.044 vs. 0.718±0.050), and was significantly smaller in North China than that in Southwest China (0.711±0.051 vs. 0.731±0.044). The width/height ratio of the central incisor was significantly larger in the female than that in the male (0.855±0.074 vs. 0.835±0.068), and in the right side than that in the left side (0.855±0.073 vs. 0.842±0.072). The width/height ratio of the lateral incisor was significantly larger in the female than that in the male (0.843±0.097 vs. 0.817±0.084). CONCLUSION: The apparent widths proportion of adjacent teeth and the width/height ratio of the clinical crown in Chinese adults are different from the foreigner's. The esthetic proportion parameters have significant population specificity, and the measurements cannot be generalized as well as it should be applied with caution.


Assuntos
Dente Canino , Coroa do Dente , Adulto , China , Estética , Estética Dentária , Feminino , Humanos , Masculino , Maxila/anatomia & histologia , Odontometria , Coroa do Dente/anatomia & histologia
11.
Sci Rep ; 10(1): 16229, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-33004827

RESUMO

The purpose was to predict the crown-to-implant ratio variation in the edentulous posterior mandibles rehabilitated with short dental implants. Hence, vertical and horizontal dimensions of dentulous posterior mandibles in a sample of 18- to 25-year-olds were measured, and correlations of these dimensions with sex and site were investigated. Mandibular computed tomography scans from 100 subjects were considered. Vertical and horizontal bone and tooth measurements were taken at the sites of the second premolar (PM), and the mesial and distal roots of the first and second molars (M1m, M1d, M2m and M2d, respectively). A hypothetical crown-to-implant ratio (C/I R) was calculated assuming the insertion of short and extra short implants (5, 6 or 7 mm), at 1.5 mm from the inferior alveolar canal, maintaining the position of the existing occlusal plane. All vertical bone dimensions decreased from the PM to the M2d. Width measurements increased from the mesial (PM) to the distal sites (M1m, M1d, M2m and M2d). Males had significantly greater vertical and horizontal measurements than females at all sites. The mean C/I R was higher than 2 for all sizes of implant. The C/I R was lower for the second molar than for the second premolar, while it was similar for the first molar and the second premolar. Males had a higher C/I R than females. Computed tomography can be used to study the anatomical features of alveolar bone, and to predict some clinical aspects of prosthetic rehabilitation with implants, such as the crown-to-implant ratio in conditions of serious bone atrophy.


Assuntos
Processo Alveolar/diagnóstico por imagem , Implantes Dentários , Mandíbula/diagnóstico por imagem , Coroa do Dente/diagnóstico por imagem , Adolescente , Adulto , Processo Alveolar/anatomia & histologia , Humanos , Arcada Edêntula/diagnóstico por imagem , Arcada Edêntula/patologia , Masculino , Mandíbula/anatomia & histologia , Radiografia Dentária , Estudos Retrospectivos , Tomografia Computadorizada por Raios X , Coroa do Dente/anatomia & histologia , Adulto Jovem
12.
J Hum Evol ; 147: 102864, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32927399

RESUMO

Recent studies have demonstrated that the outline shapes of deciduous upper and lower second molars and the deciduous upper first molar are useful for diagnosing hominin taxa-especially Homo neanderthalensis and Homo sapiens. Building on these studies, we use geometric morphometric methods to assess the taxonomic significance of the crown outline of the lower first deciduous molar (dm1). We test whether the crown shape of the dm1 distinguishes H. neanderthalensis from H. sapiens and explore whether dm1 crown shape can be used to accurately assign individuals to taxa. Our fossil sample includes 3 early H. sapiens, 7 Upper Paleolithic H. sapiens, and 13 H. neanderthalensis individuals. Our recent human sample includes 103 individuals from Africa, Australia, Europe, South America, and South Asia. Our results indicate that H. neanderthalensis dm1s cluster fairly tightly and separate well from those of Upper Paleolithic H. sapiens. However, we also found that the range of shapes in the recent human sample completely overlaps the ranges of all fossil samples. Consequently, results of the quadratic discriminant analysis based on the first 8 principal components (PCs) representing more than 90% of the variation were mixed. Lower dm1s were correctly classified in 87.3% of the individuals; the combined H. sapiens sample had greater success (90.2%) in assigning individuals than did the H. neanderthalensis sample (61.5%). When the analysis was run removing the highly variable recent human sample, accuracy increased to 84.6% for H. neanderthalensis, and 57.1% of Upper Paleolithic H. sapiens were classified correctly by using the first 4 PCs (70.3%). We conclude that caution is warranted when assigning isolated dm1 crowns to taxa; while an assignment to H. neanderthalensis has a high probability of being correct, assignment to Upper Paleolithic H. sapiens is less certain.


Assuntos
Dente Molar/anatomia & histologia , Homem de Neandertal/classificação , Coroa do Dente/anatomia & histologia , Dente Decíduo/anatomia & histologia , Animais , Fósseis , Humanos , Homem de Neandertal/anatomia & histologia
13.
J Hum Evol ; 145: 102838, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32659499

RESUMO

A diversity of pliopithecoids is known from Miocene localities in Europe, but until recently, this group was relatively poorly represented in China. However, new discoveries have shown that Chinese pliopithecoids were taxonomically diverse and geographically widespread. The earliest pliopithecoids in China (and Eurasia) are Dionysopithecus and Platodontopithecus from the Early Miocene of Sihong, Jiangsu (∼19-18 Ma). During the Middle Miocene (∼15-12 Ma), several species of pliopithecoids are recorded at localities in Gansu Province (Laogou), Inner Mongolia (Damiao), Xinjiang Uygur Autonomous Region (Tieersihabahe), and Ningxia Hui Autonomous Region (Tongxin). Finally, a late-surviving anapithecine crouzeliid, Laccopithecus robustus, is known from the Late Miocene (∼7 Ma) of Shihuiba in Yunnan, which postdates the extinction of pliopithecoids in Europe (during MN 10). Paleontological investigations at a late Early Miocene locality near Fanchang in Anhui Province have yielded a large sample of isolated teeth (more than one hundred) of a previously unknown species of pliopithecoid. The associated micromammals indicate an age contemporaneous with the Shanwang Formation in Shandong Province (MN 3-4, ∼18-17 Ma). All of the permanent teeth are represented except for I2. With its unique suite of dental features, the Fanchang pliopithecoid can be attributed to a new species and genus. Shared derived features of the lower molars confirm that the Fanchang pliopithecoid has its closest affinities with European crouzeliids, but a number of primitive traits indicate that it is a stem member of the clade. The evidence points to China as an important center for the early diversification of pliopithecoids. Contrary to previous zoogeographic scenarios, the occurrence of an early crouzeliid in China implies that the Pliopithecidae and Crouzeliidae may have diverged from a stem pliopithecoid in Asia during the Early Miocene before their arrival in Europe.


Assuntos
Catarrinos/anatomia & histologia , Catarrinos/classificação , Fósseis/anatomia & histologia , Dente Molar/anatomia & histologia , Coroa do Dente/anatomia & histologia , Animais , China , Feminino , Sedimentos Geológicos/análise , Masculino
14.
Sci Rep ; 10(1): 10103, 2020 06 22.
Artigo em Inglês | MEDLINE | ID: mdl-32572141

RESUMO

Tooth or material wear in a dentition is a common finding that requires timely diagnosis for management and prevention of further loss or associated esthetic or functional impairment. Various qualitative and quantitative methods have been suggested to measure tooth or material wear, but they present with limitations, such as imprecision, subjectivity, or high complexity. Here we developed and assessed an efficient 3D superimposition method to accurately measure occlusal tooth wear on 3D digital dental models. For this purpose, teeth on plaster casts were manually grinded on their occlusal surfaces to simulate various degrees of tooth wear. The casts were scanned using a surface scanner. Grinded tooth crowns (T1) were segmented and compared to the original crowns (T0) using five 3D surface superimposition techniques and a gold standard technique (GS). GS measurements were obtained by using intact adjacent structures as superimposition references. The technique of choice (complete crown with 30% estimated overlap of meshes) showed the best reproducibility (maximum difference < 0.050 mm3) and excellent agreement with the GS technique (median difference: 0.032 mm3). The suggested 3D superimposition method offers a highly efficient and accurate tool for tooth wear assessment, which could be applicable to clinical conditions.


Assuntos
Imageamento Tridimensional/métodos , Coroa do Dente/anatomia & histologia , Desgaste dos Dentes/diagnóstico por imagem , Oclusão Dentária , Humanos , Dente Molar , Reprodutibilidade dos Testes , Dente/anatomia & histologia , Dente/diagnóstico por imagem , Coroa do Dente/diagnóstico por imagem
15.
J Hum Evol ; 145: 102816, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32580080

RESUMO

The Carabelli trait is a dental feature that forms along the lingual margin of the protocone of deciduous and permanent maxillary molars. It is variably expressed, ranging from a small pit or furrow to a large cusp, and its development seems to be associated with crown size and molar cusp spatial configuration. The degree of expression of the Carabelli trait differs systematically between hominin taxa, and for this reason, it has been used extensively in the reconstruction of their phylogeny. However, the functional implications of having a large Carabelli trait remain unclear. In this study, we analyze the macrowear pattern of maxillary molars of early and late hominins using the occlusal fingerprint analysis method, an approach based on digital models of teeth that helps in reconstructing occlusal dynamics occurring during mastication. Tooth crowns with a small Carabelli cusp generally exhibit larger wear contact areas that extended cervically, while two additional new occlusal contact areas are common in teeth characterized by a large Carabelli cusp. These wear areas are created at the beginning of the chewing cycle, when occluding with the slopes of the lingual groove of the lower molars, between the metaconid and entoconid cusps. Advancing tooth wear leads to a slight enlargement of Carabelli occlusal contacts increasing their functional area. A steep inclination could be mechanically important in food reduction and in balancing the functional load distribution during mastication contacts. Steep wear areas are particularly developed in primates that process foods characterized by tough and fibrous textural properties. Future biomechanical and microwear texture analyses could provide additional information on the mechanical adaptation of this dental trait.


Assuntos
Hominidae/anatomia & histologia , Dente Molar/anatomia & histologia , Anormalidades Dentárias , Coroa do Dente/anatomia & histologia , Desgaste dos Dentes , Animais , Dieta , Mastigação/fisiologia , Maxila/anatomia & histologia , Paleodontologia , Filogenia
16.
PLoS One ; 15(6): e0233281, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32511250

RESUMO

Dental enamel thickness, topography, growth and development vary among hominins. In Homo, the thickness of dental enamel in most Pleistocene hominins display variations from thick to hyper-thick, while Neanderthals exhibit proportionally thinner enamel. The origin of the thin trait remains unclear. In this context, the Middle Pleistocene human dental assemblage from Atapuerca-Sima de los Huesos (SH) provides a unique opportunity to trace the evolution of enamel thickness in European hominins. In this study, we aim to test the hypothesis if the SH molar sample approximates the Neanderthal condition for enamel thickness and/or distribution. This study includes 626 molars, both original and comparative data. We analysed the molar inner structural organization of the original collections (n = 124), belonging to SH(n = 72) and modern humans from Spanish origin (n = 52). We compared the SH estimates to those of extinct and extant populations of the genus Homo from African, Asian and European origin (estimates extracted from literature n = 502). The comparative sample included maxillary and mandibular molars belonging to H. erectus, East and North African Homo, European Middle Pleistocene Homo, Neanderthals, and fossil and extant H. sapiens. We used high-resolution images to investigate the endostructural configuration of SH molars (tissue proportions, enamel thickness and distribution). The SH molars exhibit on average thick absolute and relative enamel in 2D and 3D estimates, both in the complete crown and the lateral enamel. This primitive condition is shared with the majority of extinct and extant hominin sample, except for Neanderthals and some isolated specimens. On the contrary, the SH molar enamel distribution maps reveal a distribution pattern similar to the Neanderthal signal (with thicker enamel on the lingual cusps and more peripherally distributed), compared to H. antecessor and modern humans. Due to the phylogenetic position of the SH population, the thick condition in molars could represent the persistence of the plesiomorphic condition in this group. Still, more data is needed on other Early and Middle Pleistocene populations to fully understand the evolutionary meaning of this trait.


Assuntos
Fósseis/anatomia & histologia , Hominidae/anatomia & histologia , Dente Molar/anatomia & histologia , Animais , Evolução Biológica , Esmalte Dentário/anatomia & histologia , Esmalte Dentário/metabolismo , Humanos , Dente Molar/metabolismo , Homem de Neandertal , Filogenia , Espanha , Dente , Coroa do Dente/anatomia & histologia , Coroa do Dente/metabolismo
17.
J Hum Evol ; 145: 102820, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32593871

RESUMO

Increasing evidence for both taxonomic diversity and early stone manufacture during the Pliocene highlights the importance of the hominin fossil record from this epoch in eastern Africa. Here, we describe dental remains from Lomekwi (West Turkana, Kenya), which date from between 3.2 and 3.5 Ma. The sample was collected between 1982 and 2009 and includes five gnathic specimens and a total of 67 teeth (mostly isolated permanent postcanine teeth). Standard linear dimensions indicate that, although the Lomekwi teeth are relatively small, there is broad overlap in size with contemporary Australopithecus afarensis and Australopithecus deyiremeda specimens at most tooth positions. However, some dental characters differentiate this sample from these species, including a relatively large P4 and M3 compared with the M1, a high incidence of well-developed protostylids, and specific accessory molar cuspules. Owing to a lack of well-preserved tooth crowns (and the complete absence of mandibular teeth) in the holotype and paratype of Kenyanthropus platyops, and limited comparable gnathic morphology in the new specimens, it cannot be determined whether these Lomekwi specimens should be attributed to this species. Attribution of these specimens is further complicated by a lack of certainty about position along the tooth row of many of the molar specimens. More comprehensive shape analyses of the external and internal morphology of these specimens, and additional fossil finds, would facilitate the taxonomic attribution of specimens in this taxonomically diverse period of human evolution.


Assuntos
Fósseis/anatomia & histologia , Hominidae/anatomia & histologia , Mandíbula/anatomia & histologia , Dente Molar/anatomia & histologia , Coroa do Dente/anatomia & histologia , Animais , Evolução Biológica , Hominidae/classificação , Quênia , Comportamento de Utilização de Ferramentas
18.
Ortodoncia ; 84(167): 10-18, jun. 2020. ilus, tab
Artigo em Espanhol | LILACS | ID: biblio-1147543

RESUMO

Introducción: El posicionamiento preciso de los brackets de ortodoncia en las diferentes situaciones clínicas es esencial. Para ello, se utiliza la tabla de McLaughlin-Bennett, realizada sobre una población anglosajona. Dada la gran variabilidad que puede existir en los diferentes grupos poblacionales, para estandarizar las medidas en la colocación de los brackets, sería necesario emprender un análisis de la población local y determinar cuáles serán las alturas de las coronas clínicas de todas las piezas dentarias para nuestra población. Materiales y método: Se estudiaron 200 modelos de estudio de individuos argentinos, caucásicos, de ambos sexos, con dentición permanente completa hasta el segundo molar inclusive, entre 13 y 25 años, que no recibieron tratamiento ortodóncico previo. Resultados: Las diferencias estadísticas existentes, con respecto a lo propuesto por McLaughlin y Bennett, en el maxilar superior fueron: altamente significativas (p = 0,0001) en el incisivo central, incisivo lateral y segundo molar; significativas en el canino (p = 0,0128) y en el primer molar (p = 0,018) y no significativas en el primer premolar (p = 0,239) y segundo premolar (p = 0,1741). En el maxilar inferior: altamente significativas (p = 0,0001) en el segundo molar y no significativas en el resto de las piezas dentarias. Conclusión: Los valores que se obtuvieron con el estudio, dada la variabilidad regional de la muestra, no coinciden con los valores que arroja la tabla de McLaughlin-Bennett, de origen anglosajón. Se sugiere la creación de una tabla acorde con las medidas de los pacientes locales(AU)


Accurate positioning of dental braces in different clinical situations is essential. To that end, it is used the chart developed by McLaughlin and Bennett, which was made in the Anglo-Saxon population. Due to the considerable variability among different population groups, an analysis of the local population would be necessary to be carried out in order to standardize the measurements for the positioning of braces and to determine the clinical crown height of teeth in our population. Two hundred Caucasian, Argentine male and female study models, aged between 13 and 25 with full permanent dentition, fully erupted second molars with no previous orthodontic treatment were studied. Existing statistical differences with regard to the guidelines proposed by McLaughlin and Bennett in the maxilla were: highly significant (p = 0.0001) for second molars, central and lateral incisors; significant for canines (p = 0.0128) and first molars (p = 0.018); and non-significant for first premolars (p = 0.239) and second premolars (p = 0.1741). In the mandible the differences were: highly significant (p = 0.0001) for second molars and non-significant for the other teeth. The values that were obtained in the study, given the regional variability of the sample, do not correspond to the values that are shown in the chart by McLaughlin and Bennett, of Anglo Saxon origin. It is suggested the creation of a new chart in line with the measurements of local patients(AU)


Assuntos
Ortodontia/métodos , Análise de Variância , Colagem Dentária , Braquetes Ortodônticos , Coroa do Dente/anatomia & histologia , Modelos Dentários , Odontometria
19.
Am J Phys Anthropol ; 172(3): 347-375, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32237144

RESUMO

OBJECTIVES: Crown and root traits, like those in the Arizona State University Dental Anthropology System (ASUDAS), are seemingly useful as genetic proxies. However, recent studies report mixed results concerning their heritability, and ability to assess variation to the level of genomic data. The aim is to test further if such traits can approximate genetic relatedness, among continental and global samples. MATERIALS AND METHODS: First, for 12 African populations, Mantel correlations were calculated between mean measure of divergence (MMD) distances from up to 36 ASUDAS traits, and FST distances from >350,000 single nucleotide polymorphisms (SNPs) among matched dental and genetic samples. Second, among 32 global samples, MMD and FST distances were again compared. Correlations were also calculated between them and inter-sample geographic distances to further evaluate correspondence. RESULTS: A close ASUDAS/SNP association, based on MMD and F ST correlations, is evident, with r m -values between .72 globally and .84 in Africa. The same is true concerning their association with geographic distances, from .68 for a 36-trait African MMD to .77 for F ST globally; one exception is F ST and African geographic distances, r m = 0.49. Partial MMD/F ST correlations controlling for geographic distances are strong for Africa (.78) and moderate globally (.4). DISCUSSION: Relative to prior studies, MMD/F ST correlations imply greater dental and genetic correspondence; for studies allowing direct comparison, the present correlations are markedly stronger. The implication is that ASUDAS traits are reliable proxies for genetic data-a positive conclusion, meaning they can be used with or instead of genomic markers when the latter are unavailable.


Assuntos
Genoma/genética , Polimorfismo de Nucleotídeo Único/genética , Coroa do Dente/anatomia & histologia , Raiz Dentária/anatomia & histologia , Antropologia Física , Genética Populacional , Genômica , Humanos , /estatística & dados numéricos
20.
Am J Phys Anthropol ; 172(3): 447-461, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32073646

RESUMO

OBJECTIVES: This study generates a series of narrow-sense heritability estimates for crown morphology of the deciduous and permanent dentition with two overarching aims. The first is to test the hypothesis that deciduous teeth provide a more faithful reflection of genetic information than their permanent successors. The second is to use quantitative genetic methods to evaluate assumptions underlying common data collection and analysis practices in biodistance research. MATERIALS AND METHODS: Dental morphology data were collected from longitudinal dental casts representing Australian twins and families using Arizona State Dental Anthropology System standards. Polygenic models and estimates of narrow-sense heritability were generated using SOLAR v.8.1.1. Each model considered age, sex, and age/sex interaction as covariates. RESULTS: Heritability estimates significantly differed from zero for the majority of morphological crown characters. Most estimates fell within the 0.4-0.8 range typically observed for crown morphology. Mean heritability was stable across the dental complex, but for paired homologues, permanent traits often yielded higher estimates than their deciduous counterparts. Results indicate directional asymmetry in environmental influence for crown morphology and inform biodistance "best practices" related to data collection and treatment. CONCLUSIONS: Overall, results for this sample support the use of crown morphology as a proxy for genetic variation in evolutionary research. This includes the deciduous dentition, which justifies the expansion of efforts to incorporate subadults into reconstructions of past microevolutionary processes. Results do not indicate that deciduous phenotypes more closely approximate underlying genotype, at least for deciduous/permanent homologues.


Assuntos
Dentição Permanente , Característica Quantitativa Herdável , Coroa do Dente/anatomia & histologia , Dente Decíduo/anatomia & histologia , Gêmeos/genética , Adolescente , Adulto , Austrália , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Adulto Jovem
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