Purpose: This laboratory study aimed at investigating the effect of setting expansion (SE), which could enlarge a wax pattern by concurrent exothermic reaction. Materials and Methods: Two phosphate-bonded investment materials (Rematitan Plus, T-invest C & B) and alumina-magnesia-based investment material (Titavest CB) were subjected to setting temperature and SE measurements (n = 10). Full-crown wax patterns were prepared from metal dies having the same design. Crown castings (n = 6) were made using a one-chamber high-pressure casting machine. Commercially pure titanium ingot (Japanese Industrial Standard Class II) was used for each casting. Dimensional accuracy of the cast crowns was expressed by marginal discrepancy for a pair of wax pattern and casting prepared from the same die. All results were then subjected to regression analysis. Results: Rematitan Plus gave the highest setting temperature (about 70°C) and the highest SE (1.16 ± 0.01%) almost concurrently. The result was that Rematitan Plus produced oversized crowns from the lowest thermal expansion (TE) value (0.53 ± 0.05%) reducing the linear correlation to 0.80 ( p < 0.05). No significant linear relationship was found between SE of investment material and crown-casting accuracy. Conclusions: The almost concurrent occurrence of high SE and high setting temperature generation in Rematitan Plus enlarged the wax pattern and effectively supplemented its low TE to produce oversized crowns. Despite this adverse effect, the correlation between TE and crown accuracy was still high. It is generally expected that the TE values given by manufacturers predict crown accuracy, when uniform TE, small SE, and minimum heat generation during setting are assured. 相似文献
ObjectivesThe author proposes to explore some of the characteristics of clinical practices and setting “at the limits.” Particular consideration is given to the underlying logics of co-construction and their implications for clinical work and the process of subjectivation.MethodClinical settings “at the limits” are defined as practices that are situated at the limits of psychological care or at the limits of the usually identified setting. They are specifically aimed at subjects with boundary problems and difficulties in subjectivation. Based on several types of setting, the dynamics of co-construction at work between patient(s) and therapist(s) and between setting and institution are studied, leading to the identification of some clinical benchmarks for the specificities of these treatments and the issues they raise from the point of view of the work of subjectivation.ResultsThe identification of the dynamic of co-construction specific to these clinical practices highlights the necessary congruence of these devices with the psychic needs of the subject, which implies a particular attention paid by the clinician to the effects produced in the therapeutic relationship by the setting. Three major characteristics of clinical settings “at the limits” are identified: unconditional welcome; appropriation of the setting; and sharing as a major organizer of the clinical encounter.DiscussionTaking into account the dimension of intersubjectivity and the singular use that the patient will make of the device makes it possible to underline the transitional virtues of the work of co-construction, notably in relation to the transference/counter-transference dynamic.ConclusionNowadays, clinical settings “at the limits” constitute a particularly heuristic and rapidly expanding field of research, contributing to refining and remodelling our clinical practices and theoretical models. 相似文献
Gypsum products are one of the most widely used materials in dentistry. The wide use of plaster of paris motivated a number of manufacturers to introduce different brands of the profession but their physical and mechanical properties were still questionable. The aim of this study was to access, compare and evaluate the physical properties of different brands of laboratory gypsum available in Indian dental market. Seven brands namely Calspar, Rajhans, Elephant, Horse, Lion, Johnson and Shree Niwas Chemicals were selected for the comparison of their particle size, consistency and setting time. The obtained data were tabulated and compared with Indian, Australian and US standard specification. Statistical analysis for comparative study was done. It was found that none of the brands were up to mark. The present study shall be able to provide some beneficial information regarding their quality control and guide the manufacturers for improving the standardization of their products so that most suitable type of material may be available to the profession. 相似文献
The School Setting Interview (SSI) is an internationally used client-centred interview assessment that specifically investigates the student–environment fit for students with physical disabilities. In this study the Rasch measurement model was used to examine validity of the SSI; specifically, whether or not the SSI measures a unidimensional construct. Data for analysis included SSI assessments of 87 Swedish students with physical disabilities aged between 8 and 19 years of age. The results of the Rasch analysis revealed that all items had acceptable infit MnSq and z values supporting evidence of construct validity of the SSI. The established order of the difficulty of the items was also shown to be in acceptable congruence with the theoretical basis for item development. In addition, the analysis revealed aspects of the SSI that need improvements, such as the need for more challenging items and refinements of the manual. Further investigations of validity in different cultural contexts are recommended. 相似文献
Women with pre-eclampsia have an increased risk of cardiovascular disease later in life. The aim of the study was to establish the presence and pattern of arterial stiffness in women previously with pre-eclampsia from a semi-rural region of South Africa. This was a prospective longitudinal study which involved 36 previously pre-eclamptic women and 86 non-pregnant controls (NPC) who had a past history of non-complicated pregnancy. Maternal wave reflection (augmentation index) and carotid-femoral pulse wave velocity were assessed noninvasively, using applanation tonometry with the SphygmoCor device. Endothelial function was assessed by EndoPAT 2000 device; pneumatic probes were fitted to the index fingers; induced flow-mediated reactive hyperemia; the ratio of the readings before and after occlusion was then used to calculate the score, the reactive hyperemia index (RHI) as a measure of endothelial function.
Pulse wave velocity remained significantly higher in previously pre-eclamptic women than non-pregnant controls up to three months after delivery (p < 0.05), then it reduced to nonsignificant values. All blood pressure indices (central and brachial pressures), were higher in previously pre-eclamptic women as compared to nonpregnant controls up to one year postpartum.
Regional (aortic) arterial stiffness, though it persists for some time after delivery, is transitory in previously pre-eclamptic women from the rural Africa setting. However, their increase blood pressure is an indication of compromised arterial compliance in women previously with pre-eclampsia. 相似文献
OBJECTIVES: The main objective is the characterisation of the setting reaction in glass ionomer cements based on experimental ionomer glasses with different fluorine content and a commercial glass ionomer cement liquid by using 13C CP/MAS-NMR, 29Si, 27Al and 31P MAS-NMR spectroscopy in order to receive information specifically about the cross-linking process. METHODS: Different fluorine containing glass compositions based on 4.5SiO2-3Al2O3-1.5P2O5-(5-z)CaO-zCaF(2) where z=0-3, were mixed with a commercially available polymer liquid to form glass ionomer cements. The cements were subjected to 27Al, 13C CP/MAS, 29Si, and 31P MAS-NMR analysis. RESULTS: The 27Al spectra showed clearly the formation of six-fold coordinate Al(VI), that may crosslink the carboxyl groups in the poly-acid molecules. A shift towards to more positive values of the carboxyl peak in the 13C CP/MAS-NMR spectra showed clearly the proton dissociation of the carboxyl groups. A shift towards more negative values was observed in the 29Si MAS-NMR spectra, suggesting formation of hydrated silica gel and consequently formation of additional Si-O-Si bonds. 31P MAS-NMR spectra also reflected changes in the coordination state around a PO4(3-) tetrahedron. Increasing the fluorine content of the glasses resulted generally in increased reactivity during setting, due to promoting cross-linking and repolymerisation of the silicate phase, followed by clear changes in the MAS-NMR spectra. CONCLUSIONS: The cross-linking process during the setting reaction of glass ionomer cements can be followed by MAS-NMR spectroscopy observing the conversion of Al(IV) to Al(VI). The acid base setting reaction is completed in 1 day and no further significant changes in the MAS-NMR spectra can be observed. Further study is required in order to understand the role of phosphorus. 相似文献