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1.
Braz Dent J ; 33(2): 12-21, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35508032

RESUMO

The purpose of this in vitro study was to evaluate the shaping ability of reciprocating and continuous rotary systems after root canal retreatment. After preparation and root canal filling, mesial canals of 54 mandibular molars were distributed into 3 groups (n=18), according to the filling material removal and re-instrumentation protocols: WOG group - WaveOne Gold system; PTN group - ProTaper Next system; and PTU group - ProTaper Universal system. Cone-beam computed tomographic (CBCT) images acquisition of the mesial root canals was performed at different moments: (1) before instrumentation (unprepared root canals), (2) after preparation and filling, (3) after filling material removal and (4) re-instrumentation. The apical transportation (AT), centering ability (CA) and change in root canal diameter were assessed by CBCT analysis. The remaining filling material quantification was performed by radiographic examination. The statistical analyses were performed using the 3-way ANOVA, Tukey-Kramer, Kruskal-Wallis and Dunn multiple Comparison tests (p<0.05). The tested instruments did not show full CA (=1.0). PTN group had greater AT at the 5th mm in comparison with the WOG group (p<0.05). After re-instrumentation, WOG group had greater root canal diameter change at the 1st and 5th mm than PTN and PTU groups (p<0.05). There was no significant difference among groups when comparing the amount of remaining filling material after re-instrumentation (p>0.05). The tested systems provided minimal alteration in root canal morphology at the apical portion after root canal retreatment. However, WOG promoted greater change in root canal diameter.


Assuntos
Materiais Restauradores do Canal Radicular , Tomografia Computadorizada de Feixe Cônico Espiral , Cavidade Pulpar/anatomia & histologia , Desenho de Equipamento , Dente Molar/anatomia & histologia , Dente Molar/diagnóstico por imagem , Retratamento , Obturação do Canal Radicular , Preparo de Canal Radicular/métodos , Microtomografia por Raio-X/métodos
2.
Eur Rev Med Pharmacol Sci ; 26(8): 2861-2866, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35503630

RESUMO

OBJECTIVE: For a successful root canal therapy, it is necessary to locate all the canals debride and seal them with an inert filling material. The clinician must be aware of the internal morphology and variations in a permanent tooth. Mandibular first molars are widely studied to identify variations in the anatomy of the pulp space. In this study, the primary objective was to measure the distance between the mesiobuccal (MB) and mesiolingual (ML) canals in patients with and without a middle mesial canal (MMC) using cone-beam computed tomography (CBCT). The secondary objectives were to assess the tapering degree of the mesial root and to measure the dentinal thickness in relation to the danger-zone area in patients with and without an MMC. MATERIALS AND METHODS: A total of 200 CBCT scans were evaluated for the presence of an MMC. Two observers performed the observations, and the results obtained were subject to statistical analyses. RESULTS: The results revealed the prevalence of MMC was 5%. The average distance between the MB and ML canals was higher when there was an MMC [M(SD) = 3.61 (0.6) vs. 2.69 (0.66)]. However, there were no differences between the groups in the distance to the danger-zone area and the tapering degree of the mesial root. On CBCT images, the MMC was clearly visible 3 mm apical to the level of the cementoenamel junction; beyond 3 mm, the MMC could not be traced. CONCLUSIONS: Based upon the results of this study, the average distance between the MB and ML canals was higher when there was an MMC. A lesser degree of taper would be preferred to prepare the MMC than to prepare the other canals. It is recommended that careful examination of the canal 3 mm apical to the cementoenamel junction should be carried out when attempting to detect an MMC.


Assuntos
Mandíbula , Dente Molar , Tomografia Computadorizada de Feixe Cônico/métodos , Cavidade Pulpar/diagnóstico por imagem , Humanos , Mandíbula/diagnóstico por imagem , Dente Molar/anatomia & histologia , Dente Molar/diagnóstico por imagem , Raiz Dentária/anatomia & histologia
3.
Stomatologiia (Mosk) ; 101(2): 19-24, 2022.
Artigo em Russo | MEDLINE | ID: mdl-35362698

RESUMO

OBJECTIVE: To study the coupling of age-related systemic changes in inflammation-mediated apoptosis with the features of the anatomy of the pulp system of the first mandibular molars in patients with chronic pulpitis and periodontitis. MATERIAL AND METHODS: The study included 55 patients of both sexes from 18 to 75 years of age in three age groups - young (18-44 years) (n=17), middle (45-59 years) (n=18), elderly (60-74 years) (n=20) with indications for endodontic treatment. Diagnostic measures were supplemented with New Tom 3G cone-beam tomography. The concentration of anitapoptotic protein Bcl-XL and tumor necrosis factor-a (TNF-a) was determined in the blood, and the level of the nuclear transcription factor NF-KB subunit p65 was determined in the lysates of mononuclear cells. RESULTS: As a result of the analysis of the sections, significant obliteration of the pulp was revealed throughout and an increase in the frequency of occurrence of slit-shaped channels in the distal root of the first molar of the mandible in elderly patients. CONCLUSION: The pathogenetic factors leading to a change in the morphology of the pulp system include old age and an imbalance in the system of anti-inflammatory cytokine transcription mechanisms, which contributes to increased apoptosis and the protracted nature of inflammation.


Assuntos
Cavidade Pulpar , Dente Molar , Adolescente , Adulto , Idoso , Tomografia Computadorizada de Feixe Cônico , Cavidade Pulpar/anatomia & histologia , Feminino , Humanos , Masculino , Mandíbula/diagnóstico por imagem , Dente Molar/anatomia & histologia , Dente Molar/diagnóstico por imagem , Raiz Dentária/anatomia & histologia , Adulto Jovem
4.
ScientificWorldJournal ; 2022: 4766305, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35087327

RESUMO

The aim of this study was to evaluate the root canal morphology of permanent maxillary molars by cone-beam computed tomography (CBCT) using the classifications of Weine et al. and Vertucci and to correlate the findings with sex, age, position in the dental arch, and prevalence of a second canal in the mesiobuccal root (MB2). A total of 414 scans were evaluated, corresponding to 1,000 teeth. The assessment consisted of coronal, axial, and sagittal reconstructions using i-CAT Workstation®. Type 0 was assigned when neither classification could be applied. The data were entered into an Excel spreadsheet and analyzed using SPSS. The chi-squared test or Fisher's exact test was used to compare the distribution of root canal morphology classified using the two systems. Analysis of the distribution of Weine types showed a predominance of type III in mesiobuccal roots, while type 0 predominated in distobuccal and palatal roots. Vertucci type IV predominated in mesiobuccal and distobuccal roots and type VII in palatal roots. There was no difference in the distribution of morphological canal types in permanent maxillary molars evaluated by CBCT according to sex, age group, or position in the dental arch of the patients. MB2 canals were identified in 68.4% of the teeth evaluated.


Assuntos
Variação Anatômica , Tomografia Computadorizada de Feixe Cônico/estatística & dados numéricos , Cavidade Pulpar/diagnóstico por imagem , Maxila/diagnóstico por imagem , Dente Molar/diagnóstico por imagem , Adolescente , Adulto , Idoso , Criança , Cavidade Pulpar/anatomia & histologia , Feminino , Humanos , Masculino , Maxila/anatomia & histologia , Pessoa de Meia-Idade , Dente Molar/anatomia & histologia
5.
Folia Morphol (Warsz) ; 81(1): 212-219, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-33330969

RESUMO

BACKGROUND: The aim of the study was to analyse the morphology of the apical foramen in permanent maxillary and mandibular human teeth. MATERIALS AND METHODS: The anatomic parameters include shapes (rounded, oval, uneven, flat and semilunar) and location (centre, buccal/labial, lingual/palatal, mesial, and distal) of the apical foramina was evaluated. The shapes and locations of apical foramen were analysed based on tooth type (central incisor, lateral incisor, canine, premolars, and molars) arch type (maxillary and mandibular), and position (anterior and posterior). All the teeth were investigated for the apical foramina shape and location using a stereomicroscope at a magnification of 10×. Descriptive statistics performed using SPSS (Version 21.0, IBM, NY, USA) at p value less than 0.05. RESULTS: The common shape of apical foramina was round (65%) and location was centre (32%). The frequency of deviation of apical was 68% in overall teeth. Apical foramina in maxillary anterior teeth showed more deviation while posterior teeth in mandibular teeth. The most common shape of apical foramina was round (65.1%) followed by (31%) and flat and semilunar shapes are very rare in studied subjects. CONCLUSIONS: The most frequent direction of deviation is the distal surface, followed by the mesial surface. The variation is more common in mandibular posterior teeth, while maxillary posteriors showed the least difference. The commonest shape of the apical foramen is of a round shape, followed by the oval. The oval shape of the apical foramen is most frequent with central incisors.


Assuntos
Dente Molar , Ápice Dentário , Dente Pré-Molar , Humanos , Mandíbula , Maxila , Dente Molar/anatomia & histologia , Ápice Dentário/anatomia & histologia
6.
Folia Morphol (Warsz) ; 81(1): 203-211, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-33511624

RESUMO

BACKGROUND: This study examined the root morphology of mandibular first molars (MFMs) with radix entomolaris (RE), which presents diagnostic and therapeutic challenges for clinicians. MATERIALS AND METHODS: A total of 17 three-rooted MFMs were taken from a collection of extracted teeth. Root lengths and levels of furcations were measured with a digital calliper. The pulp floor configuration, root canal systems, and RE canal curvatures were evaluated using the cone-beam computed tomography scans. RESULTS: Radix entomolaris was either located disto-lingually, with its coronal portion fixed to the distal root (n = 16) or mid-lingually (n = 1). A literature search identified four additional cases of MFMs with RE located mid-lingually. In the present study, RE was significantly (p ≤ 0.001) shorter than the distal root (DR) and the mesial root, on average by 2.04 mm and 3.15 mm, respectively. The level of the distal furcation was significantly (p = 0.003) lower than that of the mesiodistal furcation, on average by 1.39 mm. The average divergence angle formed by the cervical portions of the RE and DR canals was 53.14°. All RE canals were severely curved (> 25°) in buccolingual direction. The RE orifice was located slightly disto-lingually to considerably mesio-lingually from the DR orifice. CONCLUSIONS: The traditional assumption of a disto-lingually located RE needs to be changed, even though this is the most prevalently found variant of this anatomy. The additional variant includes the presence of a mid-lingually located RE, which has implications for the endodontic access cavity design.


Assuntos
Mandíbula , Dente Molar , Tomografia Computadorizada de Feixe Cônico , Cavidade Pulpar/diagnóstico por imagem , Mandíbula/diagnóstico por imagem , Dente Molar/anatomia & histologia , Dente Molar/diagnóstico por imagem , Raiz Dentária/diagnóstico por imagem
7.
J Anat ; 240(1): 66-83, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34333769

RESUMO

Molar morphology is shaped by phylogenetic history and adaptive processes related to food processing. Topographic parameters of the occlusal surface, such as sharpness and relief, can be especially informative regarding diet preferences of a species. The occlusal surface can however be deeply modified by wear throughout an animal's life, potentially obliterating other signals. Age being difficult to assess in wild populations, especially small rodents, experimental studies of wear through age in laboratory populations may constitute a powerful way to assess its impact on molar geometry and topography, and to validate descriptors of molar morphology that could mitigate this issue. Molar morphology was therefore quantified using 3D geometric morphometrics and topographic estimates in four groups of house mice: wild-trapped mice, lab-bred offspring of these wild mice, typical laboratory mice, and their hybrids. Three descriptors of the molar morphology were considered: the surface of the whole molar row, the surface of the first upper molar, and a truncated template of the first upper molar mimicking advanced wear. Increasing wear with age was demonstrated in the different groups, with a more pronounced effect in the wild-trapped population. The geometry of the molar row is not only modified by wear, but also by the relative position of the late developing molars on the jaw due to loading during mastication. As a consequence, the alignment of the molars is modified in wild mice, showing a qualitative difference between wild animals and their lab-bred offspring. Results obtained from the lab should thus be transferred with caution to the interpretation of differences in wild populations. Topographic estimates computed for the first upper molar seems to provide more stable parameters than those based on the whole molar row, because issues related to non-planar occlusal surface along the molar row are discarded. The truncated template was proven efficient in discarding the wear effect to focus on genetic differences, allowing an efficient characterization of the hybridization signature between wild and lab mice. Dominance of the wild phenotype for the first molar shape supports that the lab strain evolved in a context of relaxation of the selective pressures related to nutrition.


Assuntos
Laboratórios , Dente Molar , Animais , Dieta , Mastigação , Camundongos , Dente Molar/anatomia & histologia , Filogenia
8.
Scanning ; 2022: 4886993, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35360525

RESUMO

Endodontic treatment is basically dependent on knowledge of the root canal anatomy. The goal of this study was to use cone-beam computed tomography (CBCT) imaging to examine the C-shaped canal configuration of mandibular and maxillary second molars in an Iraqi subpopulation. The prevalence and configurations of C-shaped canals were evaluated in 368 mandibular second molars and 369 maxillary second molars using CBCT scans. The effects of gender, age, and unilateral/bilateral on the presence of C-shaped canals were investigated. Chi-square and Fisher's exact tests were used to determine the level of significance (p ≤ 0.05), and kappa value was used to check reliability of results of the research. In mandibular second molars, the prevalence of C-shaped canals was 17.4%. The prevalence was significantly higher in females (23%) than males (10.4%) using the chi-square test. There is no significant difference in the prevalence of C-shaped canal depending on age and tooth position. The C2 type was the most common (56.3%). This prevalence did not differ with gender, age, or tooth position. In maxillary second molars, C-shaped canals were present in 7.9%. Type I (subtype C) (fusion of 2 root canals MB-DB) was the most common type of fused root (65.5%). There is no significant difference in the prevalence of C-shaped canal depending on the type of fused root, age, and tooth position. The majority of C-shaped canals in mandibular second molars were bilateral in both genders, but unilateral presence was more common in maxillary second molars in both genders. Within the limits of this study, C-shaped canals were found to be more common in mandibular second molars than in maxillary second molars in an Iraqi subpopulation.


Assuntos
Dente Molar , Raiz Dentária , Tomografia Computadorizada de Feixe Cônico/métodos , Feminino , Humanos , Iraque , Masculino , Dente Molar/anatomia & histologia , Dente Molar/diagnóstico por imagem , Reprodutibilidade dos Testes , Raiz Dentária/diagnóstico por imagem
9.
Sci Rep ; 11(1): 23863, 2021 12 13.
Artigo em Inglês | MEDLINE | ID: mdl-34903785

RESUMO

Our study aimed to describe the root and canal morphology of mandibular second molars in Emirati population and to study the prevalence and types of morphological change in C-shaped canal configuration along the root length in an effort to describe C-shaped molars as a unit. Cone beam computed tomography (CBCT) scans of Emirati patients were analyzed in multiple plans and root and canal configuration of mandibular second molars were evaluated. Moreover, specific types of morphological change in C-shaped canal configuration along root length were studied and reconstructed using 3D reconstruction software. A total of 508 mandibular second molars were evaluated. Among the non-C-shaped mandibular second molars, two separate roots were the most prevalent root morphology (78.3%). The mesial root's most common root canal configuration was Vertucci Type II (46.5%), and in the distal root, Vertucci Type I (90.5%). The prevalence of C-shaped mandibular second molars was 17.9% and was significantly prevalent (P < 0.001) in females. Specific types of morphological change in C-shaped molars along the root length were observed and described for the first time, in which the most common types of morphological change were C1-C2-C3d (18%), C1-C3c-C3d (15.4%), C4-C3c-C3d (7.7%), and C3c-C3c-C3d (7.7%). This study showed wide variations in the root and canal morphology in mandibular second molars in Emirati population with a relatively high prevalence of C-shaped canal configuration (17.9%). Moreover, specific types of morphological change in C-shaped configuration were detected and described for the first time in this population.


Assuntos
Variação Anatômica , Cavidade Pulpar/anatomia & histologia , Mandíbula/anatomia & histologia , Dente Molar/anatomia & histologia , Adolescente , Adulto , Idoso , Tomografia Computadorizada de Feixe Cônico , Cavidade Pulpar/anormalidades , Cavidade Pulpar/diagnóstico por imagem , Feminino , Humanos , Masculino , Mandíbula/diagnóstico por imagem , Pessoa de Meia-Idade , Dente Molar/diagnóstico por imagem , Emirados Árabes Unidos
10.
Sci Rep ; 11(1): 16480, 2021 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-34389746

RESUMO

The Baka Pygmies are known for their short stature resulting from a reduced growth rate during infancy. They are peculiar also for their teeth erupt earlier than in any other African population, and their posterior dentition is larger than in non-Pygmy populations. However, the Baka's dental morphology, like several other aspects of their biology, is still understudied. Here, we explore the variation of the Baka's deciduous upper and lower second molars (dm2s) in comparison to a geographically heterogeneous human sample by means of 3D geometric morphometrics and analysis of dental traits. Our results show that the different populations largely overlap based on the shape of their dm2s, especially the lower ones. Their distal region and the height of the dentinal crown differ the most, with the Baka showing the most extreme range of variation. Upper and lower dm2s covary to a great extent (RV = 0.82). The Baka's and South Americans' dm2s were confirmed among the largest in our sample. Despite the Baka's unique growth pattern, long-lasting isolation, and extreme dental variation, it is not possible to distinguish them from other populations based on their dm2s' morphology only.


Assuntos
Variação Anatômica , Dente Molar/anatomia & histologia , Dente Decíduo/anatomia & histologia , Feminino , Humanos , Lactente , Masculino
11.
Proc Natl Acad Sci U S A ; 118(23)2021 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-34083433

RESUMO

Development has often been viewed as a constraining force on morphological adaptation, but its precise influence, especially on evolutionary rates, is poorly understood. Placental mammals provide a classic example of adaptive radiation, but the debate around rate and drivers of early placental evolution remains contentious. A hallmark of early dental evolution in many placental lineages was a transition from a triangular upper molar to a more complex upper molar with a rectangular cusp pattern better specialized for crushing. To examine how development influenced this transition, we simulated dental evolution on "landscapes" built from different parameters of a computational model of tooth morphogenesis. Among the parameters examined, we find that increases in the number of enamel knots, the developmental precursors of the tooth cusps, were primarily influenced by increased self-regulation of the molecular activator (activation), whereas the pattern of knots resulted from changes in both activation and biases in tooth bud growth. In simulations, increased activation facilitated accelerated evolutionary increases in knot number, creating a lateral knot arrangement that evolved at least ten times on placental upper molars. Relatively small increases in activation, superimposed on an ancestral tritubercular molar growth pattern, could recreate key changes leading to a rectangular upper molar cusp pattern. Tinkering with tooth bud geometry varied the way cusps initiated along the posterolingual molar margin, suggesting that small spatial variations in ancestral molar growth may have influenced how placental lineages acquired a hypocone cusp. We suggest that development could have enabled relatively fast higher-level divergence of the placental molar dentition.


Assuntos
Evolução Biológica , Mamíferos , Dente Molar , Odontogênese/fisiologia , Animais , Mamíferos/anatomia & histologia , Mamíferos/fisiologia , Dente Molar/anatomia & histologia , Dente Molar/fisiologia
12.
PLoS One ; 16(5): e0251309, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33970963

RESUMO

Dental wear analyses have been widely used to interpret the dietary ecology in primates. However, it remains unclear to what extent a combination of wear analyses acting at distinct temporal scales can be beneficial in interpreting the tooth use of primates with a high variation in their intraspecific dietary ecology. Here, we combine macroscopic tooth wear (occlusal fingerprint analysis, long-term signals) with microscopic 3D surface textures (short-term signals) exploring the tooth use of a historical western chimpanzee population from northeastern Liberia with no detailed dietary records. We compare our results to previously published tooth wear and feeding data of the extant and continually monitored chimpanzees of Taї National Park in Ivory Coast. Macroscopic tooth wear results from molar wear facets of the Liberian population indicate only slightly less wear when compared to the Taї population. This suggests similar long-term feeding behavior between both populations. In contrast, 3D surface texture results show that Liberian chimpanzees have many and small microscopic wear facet features that group them with those Taї chimpanzees that knowingly died during dry periods. This coincides with historical accounts, which indicate that local tribes poached and butchered the Liberian specimens during dust-rich dry periods. In addition, Liberian females and males differ somewhat in their 3D surface textures, with females having more microscopic peaks, smaller hill and dale areas and slightly rougher wear facet surfaces than males. This suggests a higher consumption of insects in Liberian females compared to males, based on similar 3D surface texture patterns previously reported for Taї chimpanzees. Our study opens new options for uncovering details of feeding behaviors of chimpanzees and other living and fossil primates, with macroscopic tooth wear tracing the long-term dietary and environmental history of a single population and microscopic tooth wear addressing short-term changes (e.g. seasonality).


Assuntos
Comportamento Alimentar/fisiologia , Dente Molar/patologia , Pan troglodytes/fisiologia , Desgaste dos Dentes/patologia , Animais , Costa do Marfim , Morte , Dieta , Fenômenos Ecológicos e Ambientais , Feminino , Libéria , Masculino , Dente Molar/anatomia & histologia , Reconhecimento Automatizado de Padrão/métodos , Estações do Ano
13.
Sci Rep ; 11(1): 9432, 2021 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-33941828

RESUMO

The aim of this study is to investigate the accuracies and the agreements of the 3D Endo software, conventional CBCT software Romexis Viewer at three voxel sizes, and the EAL ProPex Pixi in endodontic length measurements. Three hundred and twenty-nine root canals in 120 intact human extracted molars were accessed. The actual lengths (AL) and electronic lengths (EL) were measured using the ruler and electronic apex locator (EAL), respectively. Teeth were scanned using the CBCT at different voxel sizes (0.075, 0.10, and 0.15 mm). Root canal lengths were measured using 3D Endo with proposed length (3D-PL) by software, corrected length (3D-CL), Romexis Viewer. The Fisher's exact test, paired t-test and Bland-Altman plots were calculated to detect the agreements of the four methods with AL measurements. The ProPex Pixi measurements obtained the highest accuracy in the range of ± 0.5 mm. There was agreement between the 3D-PL and the 3D-CL with AL measurements at voxel size of 0.15 mm and at voxel size of 0.10 mm, respectively. The CBCT Romexis Viewer measurements agreed with AL at three voxel sizes. The conventional CBCT measurements using Romexis Viewer and dedicated software did not reach to the 100% accuracy in the range of ± 0.5 mm.


Assuntos
Tomografia Computadorizada de Feixe Cônico/métodos , Cavidade Pulpar/diagnóstico por imagem , Dente Molar/diagnóstico por imagem , Odontometria/métodos , Ápice Dentário/diagnóstico por imagem , Cavidade Pulpar/anatomia & histologia , Cavidade Pulpar/fisiologia , Endodontia/métodos , Humanos , Dente Molar/anatomia & histologia , Dente Molar/fisiologia , Odontometria/instrumentação , Software , Ápice Dentário/anatomia & histologia , Ápice Dentário/fisiologia
14.
Naturwissenschaften ; 108(3): 23, 2021 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-33993371

RESUMO

The Langenberg Quarry near Bad Harzburg has yielded the first Jurassic stem therian mammal of Germany, recovered from Kimmeridgian (Late Jurassic) near shore deposits of a palaeo-island within the Lower Saxony Basin of the European archipelago. The new stem therian is represented by one lower and three upper molars. Hercynodon germanicus gen. et sp. nov. is attributed to the Dryolestidae, a group of pretribosphenic crown mammals that was common in western Laurasia from the Middle Jurassic to the Early Cretaceous. The new taxon is characterised by small size, a reduced cusp pattern in the upper molars lacking a metacone, and enhancement of the shearing crests paracrista and metacrista. Phylogenetic analysis identified Hercynodon gen. nov. as sister taxon of Crusafontia from the Lower Cretaceous (Barremian) of Spain. Both taxa belong to an endemic European clade of dryolestids, including also Achyrodon and Phascolestes from the earliest Cretaceous (Berriasian) of England. Despite its greater geological age, Hercynodon gen. nov. is the most derived representative of that clade, indicated by the complete reduction of the metacone. The discrepancy between derived morphology and geological age may be explained by an increased rate of character evolution in insular isolation. Other insular phenomena have earlier been observed in vertebrates from the Langenberg Quarry, such as dwarfism in the small sauropod Europasaurus, and possible gigantism in the morganucodontan mammaliaform Storchodon and the pinheirodontid multituberculate mammal Teutonodon which grew unusually large.


Assuntos
Fósseis/anatomia & histologia , Mamíferos/anatomia & histologia , Mamíferos/classificação , Filogenia , Animais , Alemanha , Dente Molar/anatomia & histologia
15.
Sci Rep ; 11(1): 7594, 2021 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-33828193

RESUMO

In the last decades, several discoveries have uncovered the complexity of mammalian evolution during the Mesozoic Era, including important Gondwanan lineages: the australosphenidans, gondwanatherians, and meridiolestidans (Dryolestoidea). Most often, their presence and diversity is documented by isolated teeth and jaws. Here, we describe a new meridiolestidan mammal, Orretherium tzen gen. et sp. nov., from the Late Cretaceous of southern Chile, based on a partial jaw with five cheek teeth in locis and an isolated upper premolar. Phylogenetic analysis places Orretherium as the earliest divergence within Mesungulatidae, before other forms such as the Late Cretaceous Mesungulatum and Coloniatherium, and the early Paleocene Peligrotherium. The in loco tooth sequence (last two premolars and three molars) is the first recovered for a Cretaceous taxon in this family and suggests that reconstructed tooth sequences for other Mesozoic mesungulatids may include more than one species. Tooth eruption and replacement show that molar eruption in mesungulatids is heterochronically delayed with regard to basal dryolestoids, with therian-like simultaneous eruption of the last premolar and last molar. Meridiolestidans seem endemic to Patagonia, but given their diversity and abundance, and the similarity of vertebrate faunas in other regions of Gondwana, they may yet be discovered in other continents.


Assuntos
Arcada Osseodentária/anatomia & histologia , Mamíferos/classificação , Dente/anatomia & histologia , Animais , Dente Pré-Molar/anatomia & histologia , Evolução Biológica , Osso e Ossos/anatomia & histologia , Chile , Fósseis/história , História Antiga , Dente Molar/anatomia & histologia , Filogenia , Crânio/anatomia & histologia , Anormalidades Dentárias/classificação , Erupção Dentária/fisiologia
16.
Am J Phys Anthropol ; 174(4): 804-811, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33543780

RESUMO

OBJECTIVES: One role of dental pulp is in the upkeep and maintenance of dentine. Under wear, odontoblasts in the pulp deposit tertiary dentine to ensure the sensitive internal dental tissues are not exposed and vulnerable to infection. It follows that there may be an adaptive advantage for increasing molar pulp volume in anthropoid primate taxa that are prone to high levels of wear. The relative volume of dental pulp is therefore predicted to covary with dietary abrasiveness (in the sense of including foods that cause high degrees of wear). MATERIALS AND METHODS: We examined relatively unworn lower second molars in pairs of species of extant hominoids, cebids, and pitheciids that vary in the abrasiveness of their diet (n = 36). Using micro-CT scans, we measured the percent of tooth that is pulp (PTP) as the ratio of pulp volume to that of the total volume of the tooth. RESULTS: We found that in each pair of species, the taxa that consume a more abrasive diet had a significantly higher PTP than the closely related taxa that consume a softer diet. CONCLUSIONS: Our results point to an adaptive mechanism in the molars of taxa that consume abrasive diets and are thus subject to higher levels of wear. Our results provide additional understanding of the relationship between dental pulp and diet and may offer insight into the diet of extinct taxa such as Paranthropus boisei or into the adaptive context of the taurodont molars of Neanderthals.


Assuntos
Polpa Dentária , Dieta/veterinária , Hominidae , Desgaste dos Dentes/patologia , Animais , Antropologia Física , Polpa Dentária/anatomia & histologia , Polpa Dentária/fisiologia , Hominidae/anatomia & histologia , Hominidae/fisiologia , Dente Molar/anatomia & histologia , Dente Molar/fisiologia
17.
J Morphol ; 282(4): 563-573, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33547822

RESUMO

We present a topological analysis of the third upper molars (M3) using the recently developed ICAMER nomenclatural system as a way to understand the dental morphological similarity in sigmodontine rodents, the most speciose subfamily of cricetids. The method is explored in Scapteromys aquaticus and Abrothrix olivacea, taxa belonging to two diverse tribes, Akodontini and Abrotrichini, respectively, which exhibit high similarity regarding several craniodental traits as well as external anatomy. Both species show morphologically similar M3 in adults characterized by cylindrification and the isolation of a large central fossette arising from the marginal fusion of the anterior and posterior lobes. The results indicate that, before the wear, these rodents have a strongly different topological pattern at the cuspal level, mostly involving production of the connection between the main cusps. The central fossette derives from the isolation of part of the metaflexus in Scapteromys, while in Abrothrix it originates from the hypoflexus. The topological analysis provides a new approach to sigmodontine systematics, including the ability to detect diagnostic characters of both tribes. More important, it constitutes a new step toward an integrative phylogeny of fossil and living cricetids.


Assuntos
Filogenia , Sigmodontinae/anatomia & histologia , Dente/anatomia & histologia , Animais , Dente Molar/anatomia & histologia , Especificidade da Espécie
18.
Homo ; 72(1): 1-16, 2021 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-33585856

RESUMO

Crenulated occlusal surfaces have previously been described on maxillary and mandibular molars; however, the occurrence of crenulations on premolars is only anecdotally supported. This study applies a modified version of a recordation scale developed for molar crenulations to record the frequency of crenulated premolars on the maxillary and mandibular premolars of modern individuals from a variety of populations: African, African American, Asian, Australian, European American, Latino, and Malay (n = 1238). Crenulations on the molars of the same individuals were also recorded to assess the relationship between occurrences on premolars and molars. Observations were compiled into frequency tables and analyzed using chi-square tests and correspondence analysis; relationships among teeth were quantified with polychoric correlation coefficients. Although crenulated premolars are observed rarely overall, the frequency of occurrence is significantly associated with group membership. Crenulated premolars occur most frequently in African, African American, and Australian samples and are observed least often among European American and Malay samples. Additionally, there is a strong relationship between third and fourth premolars, particularly within a jaw, and between fourth premolars and the molars in the same jaw. Interestingly, crenulations in premolars are most strongly associated with Grade 2 crenulations on molars. The observed differences between populations, and the associations between crenulated premolars and molars are evaluated with respect to function, tooth size, and dental development. Based on the results presented here, we recommend the addition of premolar crenulations to existing dental morphological traits used to study human population variation.


Assuntos
Maxila , Dente Molar , Austrália , Dente Pré-Molar , Humanos , Dente Molar/anatomia & histologia
19.
Mol Med Rep ; 23(4)2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33604680

RESUMO

MicroRNA­21 (miR­21) is a small non­coding RNA that is differentially expressed during tooth development, particularly during amelogenesis. Although orthodontic tooth movement and the innate immune response are impaired, miR­21 knockout mice demonstrate no obvious skeletal phenotype. However, the consequence of miR­21 knockout on tooth phenotype and corresponding alveolar bone is unknown. The current study utilized landmark­based geometric morphometrics to identify anatomical dissimilarities of the three lower and upper molars, and the corresponding alveolar bone, in miR­21 knockout and wild­type control mice. The anatomical structures were visualized by microcomputer tomography. A total of 36 and 38 landmarks were placed on mandibular and maxillary molars, respectively. For the alveolar bone, 16 landmarks were selected on both anatomical sites. General Procrustes analysis revealed significantly smaller molars and dimensions of the alveolar bone in the mandible of the miR­21 knockout mice when compared with wild­type controls (P=0.03 and P=0.04, respectively). The overall dimension of the mandible was reduced by the lack of miR­21 (P=0.02). In the maxilla, the dimension of the alveolar bone was significant (P=0.02); however, this was not observed in the molars (P=0.36). Based on principal component analysis, no changes in shape for any of the anatomical sites were observed. Dental and skeletal jaw length were calculated and no prognathism was identified. However, the fluctuating asymmetry of the molars in the mandible and the maxilla was reduced in the miR­21 knockout mice by 38 and 27%, respectively. Taken together, the results of the present study revealed that the molars in the mandible and the dimension of the respective alveolar bone were smaller in miR­21 mice compared with wild­type littermates, suggesting that miR­21 influences tooth development.


Assuntos
Tamanho Corporal/genética , Mandíbula/anatomia & histologia , MicroRNAs/genética , Dente/anatomia & histologia , Animais , Humanos , Mandíbula/crescimento & desenvolvimento , Maxila/anatomia & histologia , Maxila/crescimento & desenvolvimento , Camundongos , Camundongos Knockout , Dente Molar/anatomia & histologia , Dente Molar/crescimento & desenvolvimento , Dente/crescimento & desenvolvimento
20.
Sci Rep ; 11(1): 93, 2021 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-33420202

RESUMO

This study aimed to analyze the root anatomy and root canal system morphology of mandibular first premolars in a Chilean population. 186 teeth were scanned using micro-computed tomography and reconstructed three-dimensionally. The root canal system morphology was classified using both Vertucci's and Ahmed's criteria. The radicular grooves were categorized using the ASUDAS system, and the presence of Tomes' anomalous root was associated with Ahmed's score. A single root canal was identified in 65.05% of teeth, being configuration type I according to Vertucci's criteria and code 1MP1 according to Ahmed's criteria. Radicular grooves were observed in 39.25% of teeth. The ASUDAS scores for radicular grooves were 60.75%, 13.98%, 12.36%, 10.22%, 2.15%, and 0.54%, from grade 0 to grade 5, respectively. The presence of Tomes' anomalous root was identified only in teeth with multiple root canals, and it was more frequently associated with code 1MP1-2 of Ahmed's criteria. The root canal system morphology of mandibular first premolars showed a wide range of anatomical variations in the Chilean population. Teeth with multiple root canals had a higher incidence of radicular grooves, which were closely related to more complex internal anatomy. Only teeth with multiple root canals presented Tomes' anomalous root.


Assuntos
Dente Pré-Molar/diagnóstico por imagem , Cavidade Pulpar/diagnóstico por imagem , Mandíbula/diagnóstico por imagem , Dente Molar/diagnóstico por imagem , Adolescente , Dente Pré-Molar/anatomia & histologia , Chile , Cavidade Pulpar/anatomia & histologia , Feminino , Humanos , Masculino , Mandíbula/anatomia & histologia , Dente Molar/anatomia & histologia , Microtomografia por Raio-X , Adulto Jovem
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