Tooth displacement due to occlusal contacts: a three-dimensional finite element study.

The use of the Finite Element Method (FE) is an appropriate way to study occlusal forces and tooth movement. The purpose of this study was to evaluate the effects of different occlusal contact patterns on tooth displacement in an adult dentition using a three-dimensional FE model of a human maxilla and mandible. Initially, images of a computerized tomography scan were redrawn in a computer program (CATIA) followed by the FE mesh construction. The MSC/Patran software was used to develop the FE mesh comprising 520,445 elements and 106,633 nodes. The MSC/Nastran program was utilized as pre and post-processor for all mathematical calculations necessary to evaluate dental and mandibular biomechanics. Four occlusal patterns were tested: FEM 1 - standard occlusal contacts; FEM 2 - removal of mesial marginal and mesial tripoidism contacts; FEM 3 - removal of distal marginal and distal tripoidism contacts; FEM 4 - similar to FEM 3 with added contacts between upper and lower incisors. Small changes in the standard distribution of occlusal contacts resulted in an imbalance of occlusal forces and changes in dental positioning. All simulations tested showed mesial displacement of posterior teeth. The most significant changes were registered in the model presenting unstable occlusal contacts when the anterior teeth were in occlusion (FEM 4). These findings may explain mandibular incisors crowding and maxillary incisors flaring as a result of small variations in dental contacts.

Low-dose chemotherapy combined with an antiangiogenic drug reduces human glioma growth in vivo.

This study evaluates the efficacy of the combination of an antiangiogenic drug and conventional chemotherapeutics for the treatment of experimental human gliomas. As an antiangiogenic, we used recombinant human PEX, a fragment of matrix metalloproteinase-2 that we have previously shown to have a significant antimitotic, anti-invasive, and antiangiogenic properties against human glioblastoma in vitro and in vivo. We used carboplatin and etoposide as the two chemotherapeutic drugs routinely used in our institution (Ospedale Maggiore de Milano) for the treatment of malignant gliomas. Conventional chemotherapeutic drugs were administered at high dose or at a low and semicontinuous regimen. Combined treatment of high-dose chemotherapy and PEX did not produce an improvement of survival in comparison with chemotherapy alone, but it was associated with a decrease in tumor volume, vascularity, and proliferative index and an increased apoptosis. All of these animals experienced severe side effects. The longest survival was documented in animals submitted to low and semicontinuous chemotherapy and antiangiogenic treatment. This regimen was associated with no side effects, marked decrease in tumor volume, vascularity, and proliferative index, and an increased apoptosis. Our data suggest that low-dose chemotherapy in combination with PEX can be successfully used against human malignant glioma in vivo.

The response of Aeromonas hydrophila to oxidative stress induced by exposure to hydrogen peroxide.

Aeromonas hydrophila, an opportunist human pathogen of low virulence, was shown to display a high degree of sensitivity upon exposure to hydrogen peroxide. As with other species, Aer. hydrophila is able to develop the capacity to resist loss of viability induced by such oxidative stress. Development of stress resistance follows the archetypal profile where pre-exposure of a population to sub-lethal levels of H2O2 stimulates onset of tolerance to further exposure. Acquisition of tolerance critically requires nascent protein synthesis. Further analysis demonstrated population growth phase influences the degree of sensitivity of the organism. Late stationary phase cultures demonstrate a decreased sensitivity compared with younger populations. Significantly, it was also determined that stock culture age influenced the level of sensitivity of the derived experimental culture, where an increased stock culture age corresponded with enhanced resistance to H2O2. These data show that Aer. hydrophila population phenotype is influenced by the phenotype of the donor stock culture.

Incidence of mesophilic Aeromonas within a public drinking water supply in north-east Scotland.

The motile mesophilic Aeromonas are ubiquitous to a wide variety of aquatic environments including drinking water distribution systems. Concern over the presence of mesophilic Aeromonas in public drinking water supplies has been expressed in recent years as it has been regarded as a pathogenic organism of importance in gastroenteritis. A major drinking water distribution system in north-east Scotland was monitored over a 12 month period to determine the prevalence of mesophilic Aeromonas. These data were examined in relation to chlorine concentration, pH, temperature, rainfall and the standard bacteriological indicators of water quality. Aeromonas were isolated to varying degrees from 21 of the 31 reservoirs investigated. The maximum recovery observed during the study was 605 cfu in 300 ml. The probability of isolation generally decreased with increasing levels of chlorination, although this oxidant was found to be ineffective in many reservoirs. Certain reservoirs with poor chlorination profiles yielded very few isolates, whereas some highly chlorinated sites liberated Aeromonas frequently and in relatively high numbers. A seasonal pattern in the incidence of Aeromonas emerged with infrequent isolation during the winter period increasing to a peak during the summer, with most isolates recovered when water temperature was > 12 degrees C. An association was demonstrated between the pattern of Aeromonas isolations and that of rainfall. No relationship was apparent between incidence of Aeromonas and total heterotrophic plate counts.

False-positive coliform reaction mediated by Aeromonas in the Colilert defined substrate technology system.

The Colilert defined substrate technology system allows specific, one-step detection of both coliforms and Escherichia coli while claiming to suppress the influence of non-coliform heterotrophs. The Colilert assay was examined in order to determine whether organisms from the genus Aeromonas could interfere and cause production of a false-positive coliform result as aquatic Aeromonas are known to constitute a fraction of the heterotrophic population found in drinking water. Results obtained clearly demonstrate that Aeromonas sp. can elicit a positive coliform type reaction at very low densities. Cell suspensions as low as 1 x 10(1) cells 10 ml-1 were observed to yield a positive reaction using Colilert reagent 4 weeks short of shelf-life expiry. Use of aged Colilert for monitoring water quality could lead to overestimation of coliforms as Aeromonas have been identified in many treated drinking water supplies.

[The visual field of pseudophakic patients. Perimetric and statistical study]. / Le champ visuel du pseudophake. Etude périmétrique et statistique.

One hundred and twenty two visual fields were studied in 98 pseudophakic subjects, using cinetic perimetry according to Goldmann, in order to plot the internal (I1), medium (I2) and peripheral (I4) isopters. Computerized processing of data provided average results, allowing the following conclusions: In general, 20% of the total surface is lost in pseudophakia. This loss, as a consequence of prismatic effects of lenses, involves the internal isopters (26%) rather than the peripheral isopters (15%). Individually, these data can be modified by the location of the lens or by the diameter of its optical part: the more anterior or the smaller is the optical part, the narrower does the visual field become. Additional correction, particularly if exceeding 2 diopters is a supplementary factor of reduction. The perimetric consequences of pseudophakia are functionally latent. Nevertheless, the prismatic effects of intraocular lenses could account for the difficulties met in examination of peripheral fundus.