12 research outputs found
Root dentinal microcracks: a post-extraction experimental phenomenon?
Aim
To investigate the prevalence, location and pattern of preâexisting microcracks in nonâendodontically treated teeth from fresh cadavers. Microâcomputed tomography (microâCT) technology was used as the analytical tool enabling full screening of the root dentine with the teeth retained in their original alveolar socket.
Methodology
As a pilot study and to validate the present method, a series of 4 highâresolution scans were performed on one boneâblock specimen with teeth collected postâmortem: (i) entire boneâblock including the teeth, (ii) second molar tooth extracted atraumatically from the boneâblock, (iii) extracted tooth dehydrated to induce dentinal defects and (iv) entire boneâblock following reinsertion of the extracted tooth into its matching alveolar socket. In the main study, fortyâtwo dentoalveolar maxillary and mandibular boneâblocks each containing 3â5 adjacent teeth (a total of 178 teeth) were collected postâmortem and scanned in a microâCT device. All crossâsection images of the 178 teeth (n = 65 530) were screened from the cementoenamel junction to the apex to identify the presence of dentinal defects.
Results
In the pilot study, the microcracks observable when the dehydrated tooth was outside the boneâblock remained detectable when the entire boneâblock plus reinserted tooth was scanned. This means that the screening process revealed the presence of the same microcracks in both experimental situations (the tooth outside and inside the maxillary boneâblock). From a total of 178 teeth in the boneâblocks removed from cadavers, 65 530 crossâsectional images were analysed and no dentinal microcracks were detected.
Conclusions
This in situ cadaveric model revealed the lack of preâexisting dentinal microcracks in nonâendodontically treated teeth. Thus, the finding of dentinal microcracks observed in previous crossâsectional images of stored extracted teeth is unsound and not valid. It should be assumed that microcracks observed in stored extracted teeth subjected to root canal procedures are a result of the extraction process and/or the postâextraction storage conditions. Therefore, as a consequence, the presence of such dentinal microcracks in stored extracted teeth â observable in crossâsectional images of the roots â should be referred to as experimental dentinal microcracks
NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics
Xenarthrans â anteaters, sloths, and armadillos â have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset
Root canal preparation does not induce dentinal microcracks in vivo
Introduction: This in vivo study aimed to evaluate the development of dentinal microcracks after root canal preparation of contralateral premolars with rotary or hand instruments using microâcomputed tomographic technology. Methods: Sixty contralateral intact maxillary and mandibular premolars in which extraction was indicated for orthodontic purposes were selected and distributed into positive (n = 6, teeth with induced root microcracks) and negative (n = 6, intact teeth) control groups as well as 2 experimental groups (n = 24) according to the instrumentation protocol: ProTaper rotary (PTR) or ProTaper hand (PTH) systems (Dentsply Maillefer, Ballaigues, Switzerland). After root canal preparation, teeth were extracted using an atraumatic technique and scanned at a resolution of 17.18 ÎŒm. A total of 43,361 cross-sectional images of the roots were screened for the presence of dentinal microcracks. The results were expressed as the percentage and number of root section images with microcracks for each group. Results: All roots in the positive control group showed microcracks at the apical third, whereas no cracks were observed in the specimens of the negative control group. In the PTR group, 17,114 cross-sectional images were analyzed, and no microcrack was observed. In the PTH group, dentinal microcracks were observed in 116 of 17,408 cross-sectional slices (0.66%) of only 1 specimen. These incomplete microcracks extended from the external root surface into the inner root dentin at the area of reduced dentin thickness. Conclusions: Root canal instrumentation with PTR and PTH instruments of contralateral maxillary and mandibular premolars did not result in the formation of dentinal microcracks in vivo
Root dentinal microcracks: a post-extraction experimental phenomenon?
Aim
To investigate the prevalence, location and pattern of preâexisting microcracks in nonâendodontically treated teeth from fresh cadavers. Microâcomputed tomography (microâCT) technology was used as the analytical tool enabling full screening of the root dentine with the teeth retained in their original alveolar socket.
Methodology
As a pilot study and to validate the present method, a series of 4 highâresolution scans were performed on one boneâblock specimen with teeth collected postâmortem: (i) entire boneâblock including the teeth, (ii) second molar tooth extracted atraumatically from the boneâblock, (iii) extracted tooth dehydrated to induce dentinal defects and (iv) entire boneâblock following reinsertion of the extracted tooth into its matching alveolar socket. In the main study, fortyâtwo dentoalveolar maxillary and mandibular boneâblocks each containing 3â5 adjacent teeth (a total of 178 teeth) were collected postâmortem and scanned in a microâCT device. All crossâsection images of the 178 teeth (n = 65 530) were screened from the cementoenamel junction to the apex to identify the presence of dentinal defects.
Results
In the pilot study, the microcracks observable when the dehydrated tooth was outside the boneâblock remained detectable when the entire boneâblock plus reinserted tooth was scanned. This means that the screening process revealed the presence of the same microcracks in both experimental situations (the tooth outside and inside the maxillary boneâblock). From a total of 178 teeth in the boneâblocks removed from cadavers, 65 530 crossâsectional images were analysed and no dentinal microcracks were detected.
Conclusions
This in situ cadaveric model revealed the lack of preâexisting dentinal microcracks in nonâendodontically treated teeth. Thus, the finding of dentinal microcracks observed in previous crossâsectional images of stored extracted teeth is unsound and not valid. It should be assumed that microcracks observed in stored extracted teeth subjected to root canal procedures are a result of the extraction process and/or the postâextraction storage conditions. Therefore, as a consequence, the presence of such dentinal microcracks in stored extracted teeth â observable in crossâsectional images of the roots â should be referred to as experimental dentinal microcracks
Sazonalidade de variĂĄveis biofĂsicas em regiĂ”es semiĂĄridas pelo emprego do sensoriamento remoto Biophysics variables seasonality on surface in semiarid regions by using remote sensing
Para investigar alteraçÔes no albedo, no Ăndice de Vegetação por Diferença Normalizada (NDVI), no saldo de radiação e no fluxo de calor no solo, em decorrĂȘncia do regime pluviomĂ©trico no semiĂĄrido cearense, desenvolveu-se um estudo na bacia do Rio Trussu - CearĂĄ, empregando-se sensoriamento remoto. Foram utilizadas duas imagens Landsat 7 ETM+, datadas de 25-10-2000 e 24-7-2001, sendo as variĂĄveis estimadas pelo emprego do algoritmo SEBAL (Surface Energy Balance Algorithms for Land). Os resultados mostraram que as variĂĄveis investigadas apresentaram alteraçÔes entre as duas estaçÔes, sendo os maiores valores de albedo registrados na estação seca. O NDVI apresentou maior sensibilidade ao regime hĂdrico, mostrando alto potencial de recuperação da vegetação ao efeito da precipitação. As margens do Rio Trussu apresentaram NDVI superior a 0,39, sendo indicativo de preservação da mata ciliar. A vegetação da bacia mostrou alto poder resiliente expresso pelo incremento nos valores de NDVI para o ano de 2001. A estação chuvosa exerceu tambĂ©m influĂȘncia marcante sobre o saldo de radiação e fluxo de calor no solo, confirmando o efeito da estação climĂĄtica na modificação do balanço de energia sobre a bacia.<br>To investigate the rainfall regime effects over the albedo, NDVI (normalized difference vegetation index), net radiation and soil heat flux in a semiarid region (Northeast of Brazil), a study in the Trussu watershed was developed by using remote sensing. The study focuses on two images (Landsat 7 ETM+) provided by Instituto Nacional de Pesquisas Espaciais (INPE), from October 25, 2000 and July 24, 2001, each of them having a different rainfall regime (dry and wet seasons). The images were analyzed by using the SEBAL algorithm (surface energy balance algorithm for land). The results showed that the amount of rainfall affected the investigated variables, and the highest values of albedo were registered during the dry season. The NDVI presented high sensibility to rainfall regime, pointing out a high vegetation potential recover during the rainfall season. The NDVI along the Trussu River was up to 0.39, expressing the repair zone preservation. The watershed vegetation showed a high resilience power expressed by NDVI values in the year of 2001. Net radiation and soil heat flux were greater in the dry season, in this way expressing the effect of humidity on the energy balance