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Tooth Morphology (tooth + morphology)
Selected AbstractsPerformance of shark teeth during puncture and draw: implications for the mechanics of cuttingBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010LISA B. WHITENACK The performance of an organism's feeding apparatus has obvious implications for its fitness and survival. However, the majority of studies that focus on chondrichthyan feeding have largely ignored the role of teeth. Studying the functional morphology of shark teeth not only elucidates the biological role that teeth play in feeding, but also provides insight specifically into the evolution of shark feeding because teeth are often the only structures available in the fossil record. In the present study, we investigate the puncture and draw performance of three general categories of extant teeth, tearing-type, cutting-type, and cutting,clutching type, as well as three fossil morphologies, utilizing a universal testing system. Differences in puncturing performance occurred among different prey items, indicating that not all ,soft' prey items are alike. The majority of teeth were able to puncture different prey items, and differences in puncture performance also occurred among tooth types; however, few patterns emerged. In some cases, broader triangular teeth were less effective at puncturing than narrow-cusped teeth. There were no differences between the maximum draw forces and maximum puncture forces. Many of the shark teeth in the present study were not only able to perform draw and puncture equally well, but also many tooth morphologies were functionally equivalent to each other. The findings obtained in the present study lend little support to the belief that shark tooth morphology is a good predictor of biological role. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 271,286. [source] The esthetic outcome of autotransplanted premolars replacing maxillary incisorsDENTAL TRAUMATOLOGY, Issue 5 2002Ewa Monika Czochrowska Abstract ,,,Autotransplantation of developing premolars to replace maxillary incisors has been documented to provide physiologically sound results, but comprehensive studies of the esthetic outcome have not been made previously. In order to assess the applicability of this approach and to identify factors important for planning of treatment, 22 autotransplanted premolars reshaped to incisor morphology were compared to their natural, contralateral maxillary incisors by scoring of features considered important for esthetics (color, soft tissue appearance, tooth morphology, and position). The sum of scores for each feature was used to place the reshaped transplant in one of three categories , Match, Deviate, Mismatch. The 22 patients were asked to fill in a questionnaire which addressed the same features that were examined professionally, and the responses were categorized as either Satisfied, Acceptable, or Dissatisfied. Eleven of the 22 patients had received orthodontic treatment with fixed appliances following the transplantation. Most of the transplanted premolars matched the contralateral incisor, and the majority of patients were satisfied with the appearance of the transplant. Fourteen percentage of the transplants were categorized as Mismatch and 18% of patients reported dissatisfaction. The distribution in categories assessed professionally and by the patients was not significantly different. The color and gingival width of the transplanted tooth were scored as different from the natural incisor in about half of the bilateral comparisons. For those teeth categorized professionally as Mismatch and by patients as Dissatisfied, a potential for esthetic improvement could be identified, as allocation to these categories was primarily due to suboptimal positioning and restorative build-up of the transplant. Inter-disciplinary planning is important for successful esthetic results. [source] Root canal morphology and its relationship to endodontic proceduresENDODONTIC TOPICS, Issue 1 2005Frank J. Vertucci The hard tissue repository of the human dental pulp takes on numerous configurations and shapes. A thorough knowledge of tooth morphology, careful interpretation of angled radiographs, proper access preparation and a detailed exploration of the interior of the tooth are essential prerequisites for a successful treatment outcome. Magnification and illumination are aids that must be utilized to achieve this goal. This article describes and illustrates tooth morphology and discusses its relationship to endodontic procedures. A thorough understanding of the complexity of the root canal system is essential for understanding the principles and problems of shaping and cleaning, for determining the apical limits and dimensions of canal preparations, and for performing successful microsurgical procedures. [source] Scanning Electron Microscopy Study of Dental Enamel Surface Exposed to 35% Hydrogen Peroxide: Alone, With Saliva, and With 10% Carbamide PeroxideJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 3 2003MARIANNE SPALDING MS ABSTRACT Several vital bleaching systems have been introduced in response to the demand in esthetic dentistry. The active agents are commonly hydrogen peroxide or carbamide peroxide used in at-home or in-office techniques. Although generally positive results have been reported concerning the whitening ability of these agents, concerns still remain as to their effects on dental tissues. The purpose of this investigation was to evaluate the effect of these bleaching agents on the enamel surface morphology. Twelve extracted teeth were used according to three experimental protocols. In experimental protocol 1, specimens were treated with 35% hydrogen peroxide. In experimental protocol 2, after treatment with 35% hydrogen peroxide the specimens were immersed in natural saliva for 1 week. In experimental protocol 3, 35% hydrogen peroxide was applied once and 10% carbamide peroxide was applied for 1 week (12 h of 10% carbamide peroxide alternating with 12 h saliva). Scanning electron microscopy evaluation revealed that regional variation in tooth morphology surface sometimes exceeded the effects of the peroxide used according to experimental protocols. Thirty-five percent hydrogen peroxide had a tendency to promote an increase in density of pits. Precipitates were observed on specimen surfaces immersed in natural saliva according to protocol 2. A smooth and shiny surface was observed in specimens treated according to protocol 3. The potential relationship between surface alterations and differences in enamel permeability is currently under investigation. CLINICAL SIGNIFICANCE The differences in various articles written on the subject cannot be reconciled because of the lack of standardization of baseline data regarding factors such as location on the tooth, type of tooth, eruption or noneruption, and age in the oral cavity. This article demonstrates that, despite changes observed in the enamel surface after bleaching, normal variation in tooth morphology may exceed the effects of 35% hydrogen peroxide and 10% carbamide peroxide on the teeth. Hence, considering the morphologic features of the tooth surface, bleaching, as described in this study, can be considered safe for enamel. [source] A new species of Creagrutus Günther (Teleostei: Ostariophysi: Characiformes), from the upper Rio Paraná basin, central BrazilJOURNAL OF FISH BIOLOGY, Issue 3 2004A. C. Ribeiro Creagrutus varii n. sp. is described based on material from the Rio São Marcos basin, in the upper Rio Paraná system, Goiás State, Brazil. This is the first record of Creagrutus in the upper Rio Paraná. The new species is proposed to be the sister group of the remaining species of Creagrutus. Creagrutus varii differs from congeners in the morphology of the maxilla, primordial ligament, premaxillary dentition and other features. The evolution of premaxillary tooth morphology in Piabina and Creagrutus and the biogeography of the Rio Paranaíba basin are discussed. [source] Morphological variations in a tooth family through ontogeny in Pleurodeles waltl (Lissamphibia, Caudata)JOURNAL OF MORPHOLOGY, Issue 9 2006Tiphaine Davit-Béal Abstract Most nonmammalian species replace their teeth continuously (so-called polyphyodonty), which allows morphological and structural modifications to occur during ontogeny. We have chosen Pleurodeles waltl, a salamander easy to rear in the laboratory, as a model species to establish the morphological foundations necessary for future molecular approaches aiming to understand not only molecular processes involved in tooth development and replacement, but also their changes, notably during metamorphosis, that might usefully inform studies of modifications of tooth morphology during evolution. In order to determine when (in which developmental stage) and how (progressively or suddenly) tooth modifications take place during ontogeny, we concentrated our observations on a single tooth family, located at position I, closest to the symphysis on the left lower jaw. We monitored the development and replacement of the six first teeth in a large growth series ranging from 10-day-old embryos (tooth I1) to adult specimens (tooth I6), using light (LM), scanning (SEM), and transmission electron (TEM) microscopy. A timetable of the developmental and functional period is provided for the six teeth, and tooth development is compared in larvae and young adults. In P. waltl the first functional tooth is not replaced when the second generation tooth forms, in contrast to what occurs for the later generation teeth, leading to the presence of two functional teeth in a single position during the first 2 months of life. Larval tooth I1 shows dramatically different features when compared to adult tooth I6: a dividing zone has appeared between the dentin cone and the pedicel; the pulp cavity has enlarged, allowing accommodation of large blood vessels; the odontoblasts are well organized along the dentin surface; tubules have appeared in the dentin; and teeth have become bicuspidate. Most of these modifications take place progressively from one tooth generation to the next, but the change from monocuspid to bicuspid tooth occurs during the tooth I3 to tooth I4 transition at metamorphosis. J. Morphol. © 2006 Wiley-Liss, Inc. [source] A Skate in the Lowermost Maastrichtian of Southern SwedenPALAEONTOLOGY, Issue 3 2001Mikael Siverson A new skate, Walteraja exigua gen. et sp. nov., is described from the lowermost Maastrichtian Belemnella lanceolata Zone of Balsvik quarry, Kristianstad Basin, southern Sweden. It is the earliest known skate with a largely modern tooth morphology and the only known pre-Cenozoic rajoid displaying a very marked gynandric heterodonty, comparable to that in many living forms. The occurrence of W. exigua in the basal Maastrichtian at Balsvik coincides with a mass occurrence of the small ,deep-water' squaloid shark Proetmopterus hemmooriensis. Most living skates, and virtually all extant squaloids closely related to P. hemmooriensis, inhabit deep and/or cool water environments and do not occur in warm temperate to tropical coastal waters. The Walteraja/Proetmopterus association in a marginal, relatively shallow-water facies of the B. lanceolata Zone adds to other, recently described, unexpected occurrences of Late Cretaceous rajoids and etmopterids/centroscymnids in warm temperate to subtropical shelf environments. [source] Performance of shark teeth during puncture and draw: implications for the mechanics of cuttingBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010LISA B. WHITENACK The performance of an organism's feeding apparatus has obvious implications for its fitness and survival. However, the majority of studies that focus on chondrichthyan feeding have largely ignored the role of teeth. Studying the functional morphology of shark teeth not only elucidates the biological role that teeth play in feeding, but also provides insight specifically into the evolution of shark feeding because teeth are often the only structures available in the fossil record. In the present study, we investigate the puncture and draw performance of three general categories of extant teeth, tearing-type, cutting-type, and cutting,clutching type, as well as three fossil morphologies, utilizing a universal testing system. Differences in puncturing performance occurred among different prey items, indicating that not all ,soft' prey items are alike. The majority of teeth were able to puncture different prey items, and differences in puncture performance also occurred among tooth types; however, few patterns emerged. In some cases, broader triangular teeth were less effective at puncturing than narrow-cusped teeth. There were no differences between the maximum draw forces and maximum puncture forces. Many of the shark teeth in the present study were not only able to perform draw and puncture equally well, but also many tooth morphologies were functionally equivalent to each other. The findings obtained in the present study lend little support to the belief that shark tooth morphology is a good predictor of biological role. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 271,286. [source] | ||||||||||||||||