Correlation between microtensile bond strength data and clinical outcome of Class V restorations.

OBJECTIVE: To determine if the results of resin-dentin microtensile bond strength (µTBS) is correlated with the outcome parameters of clinical studies on non-retentive Class V restorations. METHODS: Resin-dentin µTBS data were obtained from one test center; the in vitro tests were all performed by the same operator. The µTBS testing was performed 8h after bonding and after 6 months of storing the specimens in water. Pre-test failures (PTFs) of specimens were included in the analysis, attributing them a value of 1MPa. Prospective clinical studies on cervical restorations (Class V) with an observation period of at least 18 months were searched in the literature. The clinical outcome variables were retention loss, marginal discoloration and marginal integrity. Furthermore, an index was formulated to be better able to compare the laboratory and clinical results. Estimates of adhesive effects in a linear mixed model were used to summarize the clinical performance of each adhesive between 12 and 36 months. Spearman correlations between these clinical performances and the µTBS values were calculated subsequently. RESULTS: Thirty-six clinical studies with 15 adhesive/restorative systems for which µTBS data were also available were included in the statistical analysis. In general 3-step and 2-step etch-and-rinse systems showed higher bond strength values than the 2-step/3-step self-etching systems, which, however, produced higher values than the 1-step self-etching and the resin modified glass ionomer systems. Prolonged water storage of specimens resulted in a significant decrease of the mean bond strength values in 5 adhesive systems (Wilcoxon, p<0.05). There was a significant correlation between µTBS values both after 8h and 6 months of storage and marginal discoloration (r=0.54 and r=0.67, respectively). However, the same correlation was not found between µTBS values and the retention rate, clinical index or marginal integrity. SIGNIFICANCE: As µTBS data of adhesive systems, especially after water storage for 6 months, showed a good correlation with marginal discoloration in short-term clinical Class V restorations, longitudinal clinical trials should explore whether early marginal staining is predictive for future retention loss in non-carious cervical restorations.

Correlation of photodynamic activity and fluorescence signaling for free and pegylated mTHPC in mesothelioma xenografts

Rapport de synthèse : Introduction : Les premières applications cliniques de la thérapie photodynamique (PDT) remontent à plus d'une vingtaine d'années. Basée sur l'activation d'un médicament photosensibilisateur par une source lumineuse à une longueur d'onde spécifique, la PDT permet la destruction sélective de tissus contenant le produit actif. Ce procédé a été expérimenté dans le traitement de cancers en raison de la propriété du médicament à se concentrer dans les tumeurs tout en épargnant les structures normales contigües. Cependant, les photosensibilisateurs utilisés jusqu'à ce jour n'ont pas démontré une accumulation exclusive dans les tissus néoplasiques mais également dans les structures saines avoisinantes induisant une destruction tissulaire non sélective. Notamment, d'importantes complications ont été rapportées suite à l'utilisation de la PDT dans la cavité thoracique après la résection de mésothéliomes pleuraux, et ce malgré l'arrivée de photosensibilisateurs de secondes générations. De ce fait, plusieurs études expérimentales ont été menées afin d'améliorer la sélectivité tumorale du médicament en modulant différentes conditions de traitement et en modifiant la structure du photosensibilisateur par pégylation. Le but de cette étude expérimentale est de corréler l'activité photodynamique, la phototoxicité et la distribution du m-tetrahydroxyphenylchlorin (mTHPC) et de sa forme pégylée, le PEG-mTHPC. De ce fait, un modèle de souris nues porteur de xenogreffes de mésothéliome humain a été utilisé pour étudier les deux photosensibilisateurs. De récents travaux avec ce modèle ont montré que la mesure de la concentration tissulaire du mTHPC et de sa forme pégylée par HPLC restait limitée afin de prédire l'activité photodynamique. De ce fait, nous pensons que les mesures de fluorescence peuvent être plus appropriée. Le signalement fluorescent est mesuré dans le tissu tumoral et dans une région contrôle de la peau afin d'étudier la distribution et l'intensité des deux sensibilisateurs. Méthode : Des souris nues (cd1nu/nu mice) de 8 semaines ont été transplantées avec des fragments de mésothéliome malin humain (H-meso-1). Ces derniers ont été obtenus à partir d'une suspension cellulaire. Au moins trois passages ont été faits dans les animaux, avant que le traitement soit initié. Deux groupes de 6 souris chacun ont été utilisés pour l'injection intraveineuse par la queue du mTHPC à 0.15 mg/kg et du PEG-mTHPC à dose équimolaire. Après trois jour, la tumeur ainsi qu'une région contrôle de la cuisse ont été illuminées sur une surface d'un diamètre de 1.2 cm et pendant 133 secondes avec un laser à une longueur d'onde à 652 nm (fluence 20 J/cm2, fluence rate 150 mW/cm2). Les animaux ont été ensuite sacrifiés 72 heures après l'illumination. L'étendue de la nécrose tumorale et de la région contrôle ont été déterminées en aveugle par histomorphometrie par un pathologue (HJA). La fluorescence microscopique a été évaluée dans 12 souris à une concentration de 0.15 et 0.5 mg/kg pour le mTHPC, et à doses équimolaires pour le PEG-mTHPC. Trois animaux ont été injectés avec le mTHPC à 0.15 mg/kg, 3 autres à dose équimolaire avec la forme pégylée et 6 souris avec le mTHPC à 0.5 mg/kg et à dose équimolaire. Les animaux ont été sacrifiés 72 heures après injection. L'intensité fluorescente des sensibilisateurs a été mesurée dans la tumeur et la région contrôle. Suite à cela, les coupes ont été fixées par H&E et superposées aux images fluorescentes, afin de localiser la distribution des deux photosensibilisateurs dans les différents compartiments tissulaires. Six souris transplantées n'ayant ni été injectées avec les sensibilisateurs ou illuminées ont servi de groupe contrôle. Résultats : Trois jours après l'illumination, la PDT provoque une nécrose tumorale de 10 ±5.4 mm2 pour le mTHPC à 0.15mg/kg et 5.2 ± 4.6 mm2 pour sa forme pégylée à dose équimolaire. Cependant, la nécrose tumorale induite par les deux formulations du sensibilisateur est significativement plus élevée que dans le groupe contrôle (0.33 ± 0.58 mm2) (P=0.02). Toutefois, le mTHPC pégylé provoque une photosensibilité cutanée moins importante que la forme non-pegylée. Dans les deux groupes, aucune nécrose n'a été observée dans la cuisse des animaux. Trois jours après l'injection du mTHPC et de la forme pégylée à 0.15 mg/kg, aucune activité fluorescente n'a été détectée. Cependant, à 0.5 mg/kg, la fluorescence microscopique révèle une distribution hétérogène des deux photo-sensibilisateurs dans le tissu tumoral avec une accumulation prédominante dans les régions peri-vasculaires. Les deux médicaments montrent une distribution intracellulaire homogène dans le cytoplasme et une absence de signalement dans le nucleus. La mesure de l'intensité fluorescente du mTHPC à 0.5mg/kg ne montre pas de différence significative entre le tissu tumoral et la région contrôle. Par contre, le PEG-mTHPC montre une intensité fluorescente supérieure dans le tissu tumoral que dans la peau (ratio tumeur- peau 0.94 pour le mTHPC et 1.73 pour le PEG-mTHPC). Conclusion : L'utilisation du mTHPC à 0.15mg/kg induit une nécrose tumorale similaire à celle du PEG-mTHPC à dose équimolaire. Cependant, ce dernier démontre une photo-toxicité plus atténuée de la peau. La fluorescence microscopique permet de localiser les deux sensibilisateurs dans les différents compartiments tissulaires à partir d'une dose de 0.5 mg/kg. Le PEG-mTHPC induit un signalement fluorescent supérieur dans le tissu tumoral par rapport à la peau. La mesure du signalement fluorescent a le potentiel de prédire l'activité photodynamique du mTHPC et de sa forme pégylée dans les xénogreffes de mésothéliome humain dans un modèle de souris nue.

Correlation Studies BPR Type Roughometer vs. PCE Type Road Meter, MLR-68-2, 1968

The BPR type Roughometer has been used by the Iowa State Highway Commission since 1955 for the evaluation of the relative roughness of the various Iowa road surfaces. Since the commencement of this program, standardized information about the roughness of the various Iowa roads with respect to their type, construction, location and usage has been obtained. The Roughometer has also served to improve the economics and quality of road construction by making the roughness results of various practices available to all who are interested. In 1965, the Portland Cement Association developed a device known as the PCA Road Meter for measuring road roughness. Mounted in a regular passenger car, the Road Meter is a simple electromechanical device of durable construction which can perform consistently with extremely low maintenance. In 1967, the Iowa State Highway Commission's Laboratory constructed a P.C.A. type Road Meter in order to provide an efficient and reliable method for measuring the Present Serviceability Index for the state's highways. Another possibility was that after considerable testing the Road Meter might eventually replace the Roughometer. Some advantages of the Road Meter over the Roughometer are: (1) Road Meter tests are made by the automobile driver and one assistant without the need of traffic protection. The Roughometer has a crew of four men; two operating the roughometer and two driving safety vehicles. (2) The Road Meter is able to do more miles of testing because of its faster testing speed and the fa.ct that it is the only vehicle involved in the testing. (3) Because of the faster testing speed, the Road Meter gives a better indication of how the road actually rides to the average highway traveler. (4) The cost of operating a Road Meter is less than that of a Roughometer because of the fewer number of vehicles and men needed in testing.

Iowa's CHLOE Profilometer Correlation Procedure, MLR-87-10, 1987

The Iowa DOT has been correlating its roadmeters to the CHLOE Profilometer since 1968. The same test method for the Present Serviceability Index (PSI) deduction from the pavement condition (crack and patch) survey has also been used since 1968. Resulting PSI measurements on the Interstate and Primary Highway Systems have had good continuity through the years due to these test procedures. A computer program called PSITREND has been developed to plot PSI versus year tested for every rural pavement section in the State of Iowa. PSITREND provides pavement performance trends which are very useful for prediction of rehabilitation needs and for evaluation of new designs or rehabilitation techniques. The PSITREND data base should be maintained through future years to expand on nineteen years of historical PSI test information already collected.

Correlation of the Roughometer to the High-Speed Laser Profiler, MLR-97-7, 1997

The Iowa Department of Transportation has been using the Bureau of Public Roads (BPR) Roughometer as part of its detour analysis process for more than 20 years. Advances in technology have made the BPR Roughometer obsolete for ride quality testing. High-speed profilers that can collect the profile of the road at highway speeds are the standard ride instruments for determining ride quality on pavements. The objective of the project was to develop a correlation between the BPR Roughometer and the high-speed laser South Dakota type Profiler (SD Profiler). Nineteen pavement sections were chosen to represent the range of types and conditions for detours. Three computer simulation models were tested on the profiler profiles. The first model is the International Ride Index (IRI) which is considered the standard index for reporting ride quality in the United States. The second model is the Ride Number (RN) developed by the University of Michigan Transportation Research Institute and the third model used is a quarter-car simulation of the BPR Roughometer (ASTM E-1170) which should match the speed and range of roadway features experienced by Iowa's BPR Roughometer Unit. The BPR Roughometer quarter-car model provided the best overall correlation with Iowa's BPR Roughometer.

Correlation of Locally-Based Performance of Asphalts with their Physicochemical Parameters, Task 1 Report, HR-298, 1988

This is the first report of 6 tasks to be performed in an effort to establish locally-based quality and performance criteria for asphalts, and ultimately to develop performance-related specifications based on simple physicochemical methods. Three of the most promising chemical methods (high performance liquid chromatography (HPLC), thermal analysis, and X-ray diffraction were selected to analyze 4 different types of samples. The results will indicate the fundamental asphalt property variables that directly affect the field performance in Iowa. The details of the materials and procedures employed are described, and the results of the tests are presented.

Freeze-Thaw Durability of Concretes with Infilling of Ettringite in Voids, Phase 2, MLR-94-9, 1997

Examination of field portland cement concrete cores, from Iowa pavements with premature deterioration, reveals extensive infilling of calcium sulfate aluminum (CSA) compound in their air voids. A previous study (Phase I) has shown some evidence of the correlation between freeze-thaw durability of concretes and ettringite infilling. To further verify the previous observation, a more extensive experimental program was conducted in this Phase 2 study. A total of 101 concrete mixes were examined. Seven cements, six fly ashes, two water reducers and three coarse aggregates were used in the concrete mixes. Specimens were under moist curing for up to 223 days before being subjected to the freeze-thaw cycling. An environmental treatment consisting of three consecutive wet [70 deg F (21 deg C) in distilled water]/dry [120 deg F (49 deg C) in oven] cycles was applied to some specimens. Immediately prior to the freeze-thaw cycling, most specimens were examined by a low-vacuum scanning electron microscope (SEM) for their microstructure. The results obtained further demonstrate the correlation between concrete freeze-thaw response and CSA compound infilling in the air voids. The extent of the infilling depends on the period of moist curing as well as the wet/dry treatment. The extent of the infilling also relates to materials used. Concrete mixes with extensive infilling are more vulnerable to the freeze-thaw attack. Based on the obtained results, material criteria on cements and fly ashes for mainline paving were proposed for minimizing potential infilling of CSA compound in concrete.

Service Correlation of the Traffic Simulator, HR-100, 1967

A study was undertaken by the Bituminous Research Laboratory of the Engineering Research Institute at Iowa State University, under the sponsorship of the Iowa Highway Research Board, project HR 100, to ascertain the effects of a number of characteristics and properties of asphaltic concrete mixes upon the service behavior of the mixes as evaluated by the Traffic Simulator and by field observations. The study included: Investigations of the relations, of gradation, fraction and resistance to wear of aggregates; of stability, cohesion, per cent voids and asphalt content: of a number of laboratory and field mixes to service behavior as indicated by the Traffic Simulator under various test conditions. Based upon the results of the tests and the relationships noted, tentative criteria for the Traffic Simulator test were devised, subject to verification by observations and measurements of field service behavior of the mixes.

The making of frozen-hydrated, vitreous lamellas from cells for cryo-electron microscopy.

There has been a long standing desire to produce thick (up to 500 nm) cryo-sections of fully hydrated cells and tissue for high-resolution analysis in their natural state by cryo-transmission electron microscopy. Here, we present a method that can successfully produce sections (lamellas in FIB-SEM terminology) of fully hydrated, unstained cells from high-pressure frozen samples by focused ion beam (FIB) milling. The samples are therefore placed in thin copper tubes and vitrified by high-pressure freezing. For transfer, handling and subsequent milling, the tubes are placed in a novel connective device (ferrule) that protects the sample from devitrification and contamination and passes through all operation steps. A piezo driven sample positioning stage (cryo-nano-bench, CNB) with three degrees of freedom was additionally developed to enable accurate milling of frozen-hydrated lamellas. With the CNB, high-pressure frozen samples can be milled to produce either thin lamellas (<100 nm), for direct imaging by high-resolution cryo-TEM or thicker lamellas (300-500 nm) for cryo-electron tomography. The sample remains vitreous throughout the process by using the presented tools and methods. The results are an important step towards investigating larger cells and even tissue in there natural state which in the end will enable us to gain better insights into cellular processes.

3D solutions in transmission electron (Cryo) -microscopy in biology

One of the main problems in transmission electron microscopy in thebiological field is the tri-dimensionality. This article explains the technicalprocedures and requirements to prepare biological specimens preserving themclosest to their native state to perform 3D reconstruction of the macromolecularcomplexes and cellular structures in their natural environment.

Transmission electron microscopy in cell biology: sample preparation techniques and image information

Transmission electron microscopy is a proven technique in the field of cell biology and a very useful tool in biomedical research. Innovation and improvements in equipment together with the introduction of new technology have allowed us to improve our knowledge of biological tissues, to visualizestructures better and both to identify and to locate molecules. Of all the types ofmicroscopy exploited to date, electron microscopy is the one with the mostadvantageous resolution limit and therefore it is a very efficient technique fordeciphering the cell architecture and relating it to function. This chapter aims toprovide an overview of the most important techniques that we can apply to abiological sample, tissue or cells, to observe it with an electron microscope, fromthe most conventional to the latest generation. Processes and concepts aredefined, and the advantages and disadvantages of each technique are assessedalong with the image and information that we can obtain by using each one ofthem.

Electron energy loss spectroscopy: physical principles, state of the art and applications to the nanosciences

In the present work we review the way in which the electron-matter interaction allows us to perform electron energy loss spectroscopy (EELS), as well as the latest developments in the technique and some of the most relevant results of EELS as a characterization tool in nanoscience and nanotechnology.

Precession electron diffraction in the transmission electron Microscope: electron crystallography and orientational mapping

Precession electron diffraction (PED) is a hollow cone non-stationary illumination technique for electron diffraction pattern collection under quasikinematicalconditions (as in X-ray Diffraction), which enables “ab-initio” solving of crystalline structures of nanocrystals. The PED technique is recently used in TEMinstruments of voltages 100 to 300 kV to turn them into true electron iffractometers, thus enabling electron crystallography. The PED technique, when combined with fast electron diffraction acquisition and pattern matching software techniques, may also be used for the high magnification ultra-fast mapping of variable crystal orientations and phases, similarly to what is achieved with the Electron Backscatter Diffraction (EBSD) technique in Scanning ElectronMicroscopes (SEM) at lower magnifications and longer acquisition times.