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1.
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
2.
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 , Grupo com Ancestrais do Continente Asiático , China , Estética , Estética Dentária , Feminino , Humanos , Masculino , Maxila/anatomia & histologia , Odontometria , Coroa do Dente/anatomia & histologia
3.
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
4.
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
5.
BMC Oral Health ; 20(1): 59, 2020 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-32075626

RESUMO

BACKGROUND: In this study, we conducted a quantitative analysis of the clinical parameters of crown and gingival morphology (CGM) of the maxillary anterior teeth (MAT). We also analyzed the correlation of these parameters with periodontal biotype (PB), with a view to providing objective standards for PB diagnosis. METHODS: The three-dimensional (3D) maxillary digital models of 56 individuals were obtained using an intra-oral scanner. The following parameters were measured with the SpaceClaim software: gingival angle (GA), papilla width (PW), papilla height (PH), crown length (CL), crown width (CW), crown width/crown length ratio (CW/CL), bucco-lingual width of the crown (BLW), contact surface width (CSW), and contact surface height/crown length ratio (CS/CL). The PB were determined based on the transparency of the periodontal probe through the gingival sulcus. Independent factors influencing PB were analyzed by logistic regression, and the optimal cutoff values for the independent influencing factors were analyzed using receiver operating characteristic curves (ROC curves). RESULTS: There was no significant difference in the parameters of CGM of the MAT at the left and right sides. The thick biotype accounted for 69.6%, and the parameters of GA, PW, PH, CW, CW/CL and CS/CL were significantly correlated with PB (P ≤ 0.2). GA (odds ratio (OR) = 1.206) and PW (OR = 5.048) were identified as independent predictive factors of PB, with areas under the ROC curve (AUC) of 0.807 and 0.881, respectively, and optimal cutoff values of 95.95° and 10.01 mm, respectively. CONCLUSION: The CGMs of the MAT at the left and right side are symmetrical. The thin biotype accounts for a small proportion, and GA and PW are independent influencing factors of PB. GA of 95.95° and PW of 10.01 mm are the optimal cutoff values for categorization of individuals as thick biotype. This indicates that when the GA and PW of the right maxillary central incisor are G ≥ 95.95° and ≥ 10.01 mm, respectively, there is a higher probability that these individuals will be categorized as thick biotype.


Assuntos
Coroas , Gengiva/anatomia & histologia , Incisivo/anatomia & histologia , Humanos , Maxila/anatomia & histologia , Periodontia/instrumentação , Coroa do Dente/anatomia & histologia
6.
Int J Legal Med ; 134(1): 381-392, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31720771

RESUMO

Age estimation has a great importance due to legal requirements. The aim of our study was to determine the applicability of two different methods in age estimation; one of them based on the calculation of the visibility of the root pulp of mandibular third molar teeth and the other based on the calculation of the tooth coronal index (TCI) in the mandibular first and second molar teeth in the 9059 digital orthopantomogram of people aged between 15 and 40 in Bursa. In the first method in which the visibility of the fully mineralized root pulp of the mandibular third molar teeth was evaluated in 4 stages; the stages 0, 1, 2, and 3 were observed regardless of sex at the earliest 17.2; 19.1; 20.1, and 25.1 years, respectively. In the second method in which TCI was regressed on chronological age using measuring crown and coronal pulp cavity heights, the most accurate age estimation model based on simple linear regression for all cases without any sex difference was found to be with right first molar tooth (SEE ±7304 years) and the most accurate age model based on multiple regression model was found to be with bilateral first molar teeth (SEE ±7413 years). In conclusion, we believe that the root pulp visibility of the third molar teeth can be applied safely for stages 1, 2, and 3 at 16, 17, and 21 years of ages, respectively. A correlation was also found between TCI and age, and our findings have shown that both methods are available for forensic purposes.


Assuntos
Determinação da Idade pelos Dentes/métodos , Polpa Dentária/diagnóstico por imagem , Dente Molar/diagnóstico por imagem , Dente Molar/crescimento & desenvolvimento , Coroa do Dente/diagnóstico por imagem , Raiz Dentária/diagnóstico por imagem , Adolescente , Adulto , Polpa Dentária/crescimento & desenvolvimento , Feminino , Odontologia Legal , Medicina Legal , Humanos , Masculino , Mandíbula/diagnóstico por imagem , Radiografia Dentária Digital , Radiografia Panorâmica , Análise de Regressão , Caracteres Sexuais , Coroa do Dente/anatomia & histologia , Raiz Dentária/crescimento & desenvolvimento , Adulto Jovem
7.
Homo ; 70(1): 3-14, 2019 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-31475293

RESUMO

Deciduous teeth are occasionally well represented in archaeological skeletal samples, yet their potential value in reconstructing biological adaptations of prehistoric populations is often overlooked. Independent investigations of the metric dimensions of deciduous dental remains from the Chalcolithic site of Nevasa (Deccan Plateau, western India) yield a unique opportunity to compare odontometric methods and gain insight regarding dental variation in prehistoric India. Mesiodistal (MD) and buccolingual (BL) dimensions of deciduous teeth were measured by two researchers. Intra- and inter-observer precision in dental measurements are evaluated statistically using multiple methods of comparison. Mean MD and BL dental dimensions (mm) and crown areas (MD × BL; mm2) are reported for Nevasa and compared with mean crown dimensions for Inamgaon. Tooth crown size for Nevasa is evaluated using maxillary, mandibular and total crown areas. The apportionment of tooth mass to incisor and molar tooth classes permits assessment of inter-group variation. No significant differences in mean crown dimensions (MD, BL) or mean crown areas were found between Nevasa (493.6 mm2) and Inamgaon (504.6 mm2). While the apportionment of crown area to incisor and molar tooth classes differed, in overall size (total crown area) both sites are intermediate when compared with prehistoric and living groups from South, Southeast and East Asia. The well documented trend in reduction of permanent tooth size is paralleled by reduction in deciduous tooth size in South Asian prehistory.


Assuntos
Grupo com Ancestrais do Continente Europeu/estatística & dados numéricos , Coroa do Dente/anatomia & histologia , Dente Decíduo/anatomia & histologia , Humanos , Índia , Odontometria , Paleodontologia
8.
Am J Orthod Dentofacial Orthop ; 156(1): 44-52, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31256835

RESUMO

INTRODUCTION: The objective of this study was to investigate the location, orientation and root development of maxillary lateral incisors in patients with palatally impacted central incisors. Comparison was made between the lateral incisor on the affected side and that on the normally erupted side. METHODS: Cone-beam computed tomographic images from 20 patients (10 boys, 10 girls, mean age (9.01 ± 1.52 years old) with unilateral palatally impacted maxillary central incisors were imported into Dolphin imaging software 11.8 for 3-dimensional reconstruction and reorientation. Software measurement tools were used to measure the root length, crown distance, angle to palatal plane, distance to midline, and angle to midsagittal plane of the maxillary lateral incisors on both the impacted and unaffected sides. RESULTS: The Wilcoxon signed rank test indicated that lateral incisors on the impacted side were more proclined, at a mean angle difference of 29.47° in the sagittal plane (P < 0.001). The mean length of the roots of the lateral incisors was 1.21 mm shorter (P < 0.05) on the affected side compared with the normal side, and the lateral incisor crowns on the impacted side were located at an average of 4.57 mm closer to the palatal plane than on the normally erupted side (P < 0.001). The angle of long axis of the lateral incisors on the affected side had a greater angulation to the midsagittal plane compared with the unaffected side, with a mean difference of 30.27° (P < 0.001). CONCLUSIONS: Maxillary lateral incisors adjacent to palatally impacted maxillary central incisors side had abnormal root development and demonstrated angulation and position change compared with those adjacent to normally erupted central incisors.


Assuntos
Tomografia Computadorizada de Feixe Cônico/métodos , Incisivo/anormalidades , Incisivo/anatomia & histologia , Maxila/anatomia & histologia , Palato/anatomia & histologia , Dente Impactado/diagnóstico por imagem , Criança , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Imageamento Tridimensional , Incisivo/diagnóstico por imagem , Masculino , Maxila/diagnóstico por imagem , Palato/diagnóstico por imagem , Estudos Retrospectivos , Coroa do Dente/anatomia & histologia , Erupção Dentária , Raiz Dentária/anormalidades , Raiz Dentária/anatomia & histologia , Raiz Dentária/diagnóstico por imagem
9.
Am J Orthod Dentofacial Orthop ; 156(1): 94-103, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31256848

RESUMO

INTRODUCTION: Self-ligating appliances are purposed to expand the arches, but evidence on stability of the result is lacking. We measured the width of maxillary and mandibular arches and torque changes after treatment with the use of passive self-ligating appliances and assessed stability at the 2-year follow-up. METHODS: Maxillary and mandibular 3-dimensional (3D) models from 32 subjects (mean initial age 14.9 ± 0.9 years), consecutively treated with the use of self-ligating appliances, were obtained before, immediately after, and 2 years after treatment. Dental arches were examined with the use of 3D software to evaluate differences in transverse arch dimensions and torque values. RESULTS: An incremental increase of arch widths was recorded, especially regarding maxillary and mandibular premolars. The increase in the transverse diameters was associated with a significant positive torque gain. No significant changes in arch perimeter and depth were recorded. In the retention period, slight significant changes in transverse diameters were recorded, and a transverse diameter constriction detected. Torque values remained almost unchanged in the follow-up period. CONCLUSIONS: Transverse arch dimensions, along with torque values, increased significantly after treatment with the use of a passive self-ligating appliance. In the 2 years following treatment, a tendency to transverse diameter restriction, especially for the maxillary and mandibular premolars, was observed.


Assuntos
Arco Dental/anatomia & histologia , Má Oclusão/terapia , Aparelhos Ortodônticos , Técnica de Expansão Palatina , Técnicas de Movimentação Dentária/métodos , Torque , Adolescente , Adulto , Análise de Variância , Dente Pré-Molar , Desenho Assistido por Computador , Técnica de Fundição Odontológica , Modelos Dentários , Feminino , Seguimentos , Humanos , Imageamento Tridimensional/métodos , Masculino , Má Oclusão/patologia , Mandíbula , Maxila , Níquel , Desenho de Aparelho Ortodôntico , Técnica de Expansão Palatina/instrumentação , Software , Titânio , Coroa do Dente/anatomia & histologia , Técnicas de Movimentação Dentária/instrumentação , Resultado do Tratamento , Adulto Jovem
10.
Int Orthod ; 17(3): 529-537, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31279755

RESUMO

PURPOSE: To use 3-dimensional cone beam computed tomography (CBCT) images obtained on patients before treatment with dental malocclusion to calculate the heritability estimates of full-tooth angulation and inclination. A heritability estimate is a number between zero and one indicating the percentage of genetic factors involved in determining the phenotypic variation observed. METHOD: CBCT images of 111 patients (51 sibships) were analysed measuring both tooth angulation and inclination using the Anatomage Invivo5 software for central incisor to second molar. The long axis of each tooth was defined and traced as the cusp tip of the most mesiobuccal cusp to 6mm coronal to the apex of the mesiobuccal root. SPSS statistical software was used to analyse the data and calculate the heritability estimates for each tooth type in the maxilla and in the mandible regardless of the side. RESULTS: Teeth inclination showed higher heritability estimates than tooth angulation. Furthermore, maxillary teeth showed higher heritability estimates than mandibular teeth and anterior teeth showed higher heritability than posterior teeth. CONCLUSION: Genetic effect was more evident on tooth inclination than tooth angulation, on anterior teeth more than posterior teeth, and on maxillary teeth more than mandibular teeth.


Assuntos
Má Oclusão/patologia , Dente Molar/anatomia & histologia , Característica Quantitativa Herdável , Irmãos , Adolescente , Criança , Tomografia Computadorizada de Feixe Cônico/métodos , Feminino , Humanos , Imageamento Tridimensional/métodos , Masculino , Má Oclusão/diagnóstico por imagem , Mandíbula , Maxila , Ortodontia , Software , Coroa do Dente/anatomia & histologia , Raiz Dentária
11.
J Hum Evol ; 133: 198-213, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31358180

RESUMO

In apes, the mandibular third premolar (P3) is adapted for a role in honing the large upper canine. The role of honing was lost early in hominin evolution, releasing the tooth from this functional constraint and allowing it to respond to subsequent changes in masticatory demands. This led to substantial morphological changes, and as such the P3 has featured prominently in systematic analyses of the hominin clade. The application of microtomography has also demonstrated that examination of the enamel-dentine junction (EDJ) increases the taxonomic value of variations in crown morphology. Here we use geometric morphometric techniques to analyze the shape of the P3 EDJ in a broad sample of fossil hominins, modern humans, and extant apes (n = 111). We test the utility of P3 EDJ shape for distinguishing among hominoids, address the affinities of a number of hominin specimens of uncertain taxonomic attribution, and characterize the changes in P3 EDJ morphology across our sample, with particular reference to features relating to canine honing and premolar 'molarization'. We find that the morphology of the P3 EDJ is useful in taxonomic identification of individual specimens, with a classification accuracy of up to 88%. The P3 EDJ of canine-honing apes displays a tall protoconid, little metaconid development, and an asymmetrical crown shape. Plio-Pleistocene hominin taxa display derived masticatory adaptations at the EDJ, such as the molarized premolars of Australopithecus africanus and Paranthropus, which have well-developed marginal ridges, an enlarged talonid, and a large metaconid. Modern humans and Neanderthals display a tall dentine body and reduced metaconid development, a morphology shared with premolars from Mauer and the Cave of Hearths. Homo naledi displays a P3 EDJ morphology that is unique among our sample; it is quite unlike Middle Pleistocene and recent Homo samples and most closely resembles Australopithecus, Paranthropus and early Homo specimens.


Assuntos
Dente Pré-Molar/anatomia & histologia , Dentina/anatomia & histologia , Hominidae/anatomia & histologia , Coroa do Dente/anatomia & histologia , Animais , Fósseis/anatomia & histologia , Mandíbula , Especificidade da Espécie
12.
J Forensic Odontostomatol ; 37(1): 2-19, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-31187738

RESUMO

OBJECTIVE: The aim of this study was to determine whether the tooth crown sexual dimorphism pattern reported in previous small studies can be generalized for a broader range of populations. LITERATURE REVIEW: A systematic literature review was performed by two independent examiners. The following databases were searched from October 2015 to July 2016: PubMed, Scopus, Lilacs, ScienceDirect, Medline, and Cochrane Reviews. No language restrictions were applied to the search. SELECTION CRITERIA: The inclusion criteria comprised original studies investigating mesiodistal permanent teeth that reported the sample population and standard deviation. All right-sided teeth, except the third molars, were measured and separated by sex in the included studies. Thirty-one studies were included in the quantitative data synthesis and meta-analysis. Studies of non-human teeth, skeletal remains, or an overly specific study population were excluded. MAIN RESULTS: Thirty-one trials, involving 6481 participants, provided data for the meta-analysis of teeth. Sexual dimorphism in mesiodistal crowns was found in all teeth across a range of populations, principally in lower canines (5.73%) and maxillary canines (4.72%), followed by the lower second molars (3.54%) and upper second molars(3.20%), and finally in the lower first molars(3.14%) and upper first molars(2.64%). CONCLUSIONS: A small degree of sexual dimorphism exists in all human teeth. Second molars and canines show the greatest sexual dimorphism. Additionally, smaller racial differences are present in mesiodistal crowns among groups living in different geographic areas; however, it is not possible to establish a single value applicable for all populations.


Assuntos
Caracteres Sexuais , Coroa do Dente/anatomia & histologia , Humanos , Odontometria
13.
Am J Phys Anthropol ; 169(4): 646-663, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31099892

RESUMO

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. RESULTS: Certain discrete traits showed significantly different regional frequencies and sexual dimorphism. The GM analyses of both P3 s and P4 s showed extensive overlap in shape variation of the various populations (classification accuracy 15-69%). The first principal components explained about 40% of shape variance with a correlation between 0.59 and 0.87 of the features of P3 s and P4 s. Shape covariation between P3 s and P4 s expressed concordance of high and narrow or low and broad crowns. CONCLUSIONS: Due to marked intragroup and intergroup variation in GM analyses of lower premolars, discrete traits such as the number of lingual cusps and mesiolingual groove expression provide better geographic separation of modern human populations. The greater variability of the lingual region suggests a dominance of functional constraints over geographic provenience or sex. Additional information about functionally relevant aspects of the crown surface and odontogenetic data are needed to unravel the factors underlying dental morphology in modern humans.


Assuntos
Dente Pré-Molar/anatomia & histologia , Imageamento Tridimensional/métodos , Coroa do Dente/anatomia & histologia , Adolescente , Adulto , Antropologia Física , Dente Pré-Molar/diagnóstico por imagem , Criança , Pré-Escolar , Esmalte Dentário/anatomia & histologia , Esmalte Dentário/diagnóstico por imagem , Dentina/anatomia & histologia , Dentina/diagnóstico por imagem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Análise Multivariada , Odontometria , Coroa do Dente/diagnóstico por imagem , Microtomografia por Raio-X , Adulto Jovem
14.
Methods Mol Biol ; 1922: 341-356, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30838589

RESUMO

Third molar development and eruption are two related areas of major interest in dental research into the etiology of "wisdom tooth" impaction. Third molars are not only an excellent model for studying dental development but also of fundamental clinical importance because they are very frequently impacted. Because the third molar is located in the distal-most region of the oral cavity, clinical access is relatively challenging. With the increasingly widespread use of cone-beam computed tomography (CBCT) in dentistry, studies and measurements of the third molar and its eruption area have become considerably easier to do. Here we present a novel CBCT-based measurement methodology we developed for our recent investigations that we hope will also be useful for the broader dental research community.


Assuntos
Tomografia Computadorizada de Feixe Cônico/métodos , Imageamento Tridimensional/métodos , Dente Serotino/anatomia & histologia , Coroa do Dente/anatomia & histologia , Humanos , Mandíbula/anatomia & histologia , Mandíbula/crescimento & desenvolvimento , Mandíbula/ultraestrutura , Maxila/anatomia & histologia , Maxila/crescimento & desenvolvimento , Maxila/ultraestrutura , Dente Serotino/crescimento & desenvolvimento , Dente Serotino/ultraestrutura , Coroa do Dente/crescimento & desenvolvimento , Coroa do Dente/ultraestrutura
15.
Am J Orthod Dentofacial Orthop ; 155(3): 339-346, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30826036

RESUMO

INTRODUCTION: The goal of this study was to compare the size and morphologic symmetry of the maxillary teeth in subjects with and without unilateral palatally displaced canines (PDCs). METHODS: Plaster casts of 38 subjects (mean age 14.75 ± 0.95 y) with unilateral PDCs were selected (study group [SG]) and compared with casts from an age- and sex-matched control group (CG). Then dental casts of both groups were scanned into 3-dimensional (3D) models. Tooth sizes (mesiodistal [MD] and buccolingual [BL] widths and volumes) for SG and CG were measured. Afterward, 3D deviation analysis was carried out with the use of Geomagic Control X software. All of the data were normally distributed according to parametric tests. RESULTS: All of the maxillary tooth diameters were smaller in SG than in CG. Statistically significant differences (P ≤ 0.001) were obtained when comparing the widths and volumes of the PDC quadrant and the unaffected quadrant of the same patient. Morphologic tooth symmetry by surface-to-surface matching for SG (PDC side vs non-PDC side) and CG (right vs left quadrant) demonstrated significant (P ≤ 0.001) but small differences, except for the lateral upper incisors (71.27%). CONCLUSIONS: Unlike control subjects, PDC patients showed high mismatching of lateral incisor crowns of ∼30%.


Assuntos
Dente Canino/anatomia & histologia , Imageamento Tridimensional , Coroa do Dente/anatomia & histologia , Erupção Ectópica de Dente/diagnóstico por imagem , Adolescente , Estudos de Casos e Controles , Modelos Dentários , Feminino , Humanos , Incisivo , Masculino
16.
Sci Adv ; 5(1): eaau0930, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30746445

RESUMO

Several human dental traits typical of modern humans appear to be associated with the prolonged period of development that is a key human attribute. Understanding when, and in which early hominins, these dental traits first appeared is thus of strong interest. Using x-ray multiresolution synchrotron phase-contrast microtomography, we quantify dental growth and development in an archaic Homo juvenile from the Xujiayao site in northern China dating to 161,000-224,000 years or 104,000-125,000 years before present. Despite the archaic morphology of Xujiayao hominins, most aspects of dental development of this juvenile fall within modern human ranges (e.g., prolonged crown formation time and delayed first molar eruption). For its estimated age-at-death (6.5 years), its state of dental development is comparable to that of equivalently aged modern children. These findings suggest that several facets of modern human dental growth and development evolved in East Asia before the appearance of fully modern human morphology.


Assuntos
Esmalte Dentário/crescimento & desenvolvimento , Fósseis , Hominidae/anatomia & histologia , Dente Molar/crescimento & desenvolvimento , Coroa do Dente/crescimento & desenvolvimento , Envelhecimento , Animais , China , Esmalte Dentário/anatomia & histologia , Gengiva/crescimento & desenvolvimento , Dente Molar/anatomia & histologia , Coroa do Dente/anatomia & histologia , Raiz Dentária/crescimento & desenvolvimento , Microtomografia por Raio-X/métodos
17.
Am J Phys Anthropol ; 168(3): 606-631, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30747449

RESUMO

OBJECTIVES: This article presents estimates of narrow-sense heritability and bivariate genetic correlation for 14 tooth crown morphological variants scored on permanent premolars, first molars, and second molars. The objective is to inform data collection and analytical practices in dental biodistance and to provide insights on the development of molar crowns as integrated structures. MATERIALS AND METHODS: African American dental casts from the Menegaz-Bock collection were recorded for the Arizona State University Dental Anthropology System. Estimates of narrow-sense heritability and genetic correlation were generated using SOLAR v.8.1.1, which included assessment of age, sex, and birth year as covariates. Both continuous scale and dichotomized estimates are provided. RESULTS: Heritability estimates were nonsignificant for the majority of variables; however, for variables yielding significant estimates, values were moderate to high in magnitude and comparable to previous studies. Comparing left and right-side heritability estimates suggests directional asymmetry in the expression of environmental variance, something not seen in anterior tooth traits. Genetic correlations were moderate among antimeres and metameres and low for different traits scored on the same tooth crown. Although several negative correlations were noted, few reached statistical significance. Results affirm some of the current data cleaning and analytical practices in dental biodistance, but others are called into question. These include the pooling of males and females and combining left and right-side data into a single dataset. CONCLUSIONS: In comparison to anterior tooth crown traits, postcanine heritabilities were more often non-significant; however, those traits with significant heritability also tended to produce higher estimates. Genetic correlations were unremarkable, in part, because they were underpowered. However, M1 results may provide insight into the complex relationship between genes, environment, and development in determining ultimate crown form.


Assuntos
Afro-Americanos , Dente Canino/anatomia & histologia , Coroa do Dente/anatomia & histologia , Afro-Americanos/genética , Afro-Americanos/estatística & dados numéricos , Antropologia Física , Feminino , Humanos , Masculino , Odontometria
18.
Am J Phys Anthropol ; 168(3): 510-520, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30586150

RESUMO

OBJECTIVES: We present a new distance-based exponential regression approach based on published histological data to refine the objectivity, accuracy, and precision of age estimates of LEH defect formation on the anterior dentition. METHODS: Published histological data of anterior tooth crown growth for two samples (northern European and southern African) were fitted with exponential trendlines to construct exponential regression equations for each tooth type. A theoretical comparison of the age estimates produced by two commonly used methods (decile chart and linear regression), and those based on the exponential regression equations presented in this article were undertaken. Paired-samples t-tests were used to determine whether the estimates obtained by these methods differed significantly. RESULTS: Exponential regression equations were able to accurately replicate age estimates produced by the decile-chart method. For defects that fell precisely on a decile, estimates differed by 1-23 days. Estimates based on the linear regression method were consistently younger by 4.5-16 months. For defects that fell within deciles, the exponential regression equation estimates, when different, were 12 days to 4 months older than those yielded by the decile method. CONCLUSIONS: By combining currently published histological data on anterior tooth crown growth with a regression approach, it is possible to produce more accurate age estimates than yielded by methods that do not rely on histological data. Furthermore, this approach also greatly improves the objectivity, precision and replicability of results, especially for defects that fall between deciles, when compared to the decile chart method.


Assuntos
Hipoplasia do Esmalte Dentário/patologia , Incisivo/anatomia & histologia , Fatores Etários , Antropologia Física , Pré-Escolar , Dente Canino/anatomia & histologia , Humanos , Lactente , Odontometria , Análise de Regressão , Coroa do Dente/anatomia & histologia
19.
PLoS One ; 13(11): e0207070, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30439977

RESUMO

Although genes on the human X chromosome reportedly influence tooth crown morphology, little is known about X chromosome activation or inactivation systems relevant to morphological variations. We assessed the relationships between tooth crown size and crown morphological traits in females with Turner syndrome, the variants of which include complete absence of one X chromosome, lack of the short arm (Xp), or duplication of the long arms (Xq), and then estimated the functions of Xp and Xq in the process of unilateral X chromosome inactivation during tooth crown development. The mesiodistal and buccolingual diameters in the maxillary first (M1) and second (M2) permanent molars were compared among X chromosome karyotypes by multiple regression analyses, and their relationships with the development of Carabelli's cusp and the distolingual cusp were analyzed using logistic regression analysis. The crown sizes increased in the order of the 46,X,i(Xq) karyotype, 45,X and 45,X/46,XX karyotypes, and control group. A lower frequency of Carabelli's cusp and higher frequency of a reduced distolingual cusp in M1 were characteristics of Turner syndrome. The overall M1 and M2 crown sizes differed among the X chromosome karyotypes, whereas a smaller crown size was associated with a reduced distolingual cusp but not with Carabelli's cusp. Considering the differences in chromosome arrangement among females with Turner syndrome and the process of unilateral X chromosome inactivation, the observed results can be considered in terms of quantity or number of promoters/inhibitors during tooth crown development. The X chromosome karyotypes have a strong influence on the overall crown sizes of the M1 and M2 molars because those karyotypes with variable numbers of active gene regions directly influence tooth germ development in an early stage of human odontogenesis. The later forming cusps, such as the distolingual cusp and Carabelli's cusp, may be affected by this developmental prerequisite.


Assuntos
Cromossomos Humanos X/genética , Maxila , Dente Molar/anatomia & histologia , Coroa do Dente/anatomia & histologia , Humanos , Cariótipo
20.
PLoS One ; 13(11): e0204737, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30383758

RESUMO

Scholars have debated the taxonomic identity of isolated primate teeth from the Asian Pleistocene for over a century, which is complicated by morphological and metric convergence between orangutan (Pongo) and hominin (Homo) molariform teeth. Like Homo erectus, Pongo once showed considerable dental variation and a wide distribution throughout mainland and insular Asia. In order to clarify the utility of isolated dental remains to document the presence of hominins during Asian prehistory, we examined enamel thickness, enamel-dentine junction shape, and crown development in 33 molars from G. H. R. von Koenigswald's Chinese Apothecary collection (11 Sinanthropus officinalis [= Homo erectus], 21 "Hemanthropus peii," and 1 "Hemanthropus peii" or Pongo) and 7 molars from Sangiran dome (either Homo erectus or Pongo). All fossil teeth were imaged with non-destructive conventional and/or synchrotron micro-computed tomography. These were compared to H. erectus teeth from Zhoukoudian, Sangiran and Trinil, and a large comparative sample of fossil Pongo, recent Pongo, and recent human teeth. We find that Homo and Pongo molars overlap substantially in relative enamel thickness; molar enamel-dentine junction shape is more distinctive, with Pongo showing relatively shorter dentine horns and wider crowns than Homo. Long-period line periodicity values are significantly greater in Pongo than in H. erectus, leading to longer crown formation times in the former. Most of the sample originally assigned to S. officinalis and H. erectus shows greater affinity to Pongo than to the hominin comparative sample. Moreover, enamel thickness, enamel-dentine junction shape, and a long-period line periodicity value in the "Hemanthropus peii" sample are indistinguishable from fossil Pongo. These results underscore the need for additional recovery and study of associated dentitions prior to erecting new taxa from isolated teeth.


Assuntos
Esmalte Dentário/anatomia & histologia , Dentina/anatomia & histologia , Fósseis/anatomia & histologia , Hominidae/anatomia & histologia , Dente Molar/anatomia & histologia , Animais , Ásia , Fósseis/história , História Antiga , Humanos , Paleodontologia , Pongo/anatomia & histologia , Coroa do Dente/anatomia & histologia , Microtomografia por Raio-X
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