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2. Influence of Photoactivation Protocol and Light Guide Distance on Conversion and Microleakage of Composite Restorations.

Author

Fróes-Salgado, N. R. G., Pfeifer, C. S. C., Francci, C. E., and Kawano, Y.

Subjects
MICROLEAKAGE (Dentistry), LIGHT sources, PHOSPHORIC acid, DENTAL fillings, POLYMERIZATION
Abstract

Purpose: To evaluate the effect of light guide distance and the different photoactivation methods on the degree of conversion (DC) and microleakage of a composite. Methods and Materials: Three photoactivation protocols (600mW/cm² x 40 seconds; 400 mW/cm² x 60 seconds or 200 mW/cm² x 20 seconds, followed by 500 mW/cm² x 40 seconds) and three distances from the light source (0, 3 or 7 mm) were tested. Cylindrical specimens (5 mm diameter; 2 mm tall; n=3) were prepared for the DC test (FT-Raman). Class V cavities were made in 90 bovine incisors to conduct the microleakage test. The specimens were conditioned for 15 seconds with phosphoric acid (37%), followed by application of the adhesive system Prime & Bond NT (Dentsply/Caulk). The preparations were restored in bulk. The specimens were stored for 24 hours in distilled water (37°C) before being submitted to the silver-nitrate microleakage protocol. The restorations were sectioned and analyzed under 25x magnification. Results: Statistical analyses (two-way ANOVAs and Tukey test, α=0.05) found significance only for the factor distance (p=0.015) at the top of the composite for the DC test. Conversion was statistically lower for the 7 mm groups compared to the O and 3 mm groups, which were equivalent to each other. At the bottom of the specimens, none of the factors or interactions was significant (p<0.05). The Kruskal-Wallis test showed that, in general, the soft-start method led to lower microleakage scores when compared to the continuous modes, mainly when associated with a distancing of 7 mm (p<0.01). With the exception of specimens irradiated with 400mW/cm² that did not demonstrate variations on scores for the distances tested, higher microleakage was observed for shorter distances from the light source. Conclusions: Soft-start methods may reduce microleakage when the light guide distancing provides a low level of irradiance, which also causes a discrete reduction in the DC. [ABSTRACT FROM AUTHOR]

Published
2009
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3. Boundary element analysis for damage tolerance assessment of aircraft panels

Author

Aliabadi, M.H., Wen, P.H., and Salgado, N.

Abstract

In this paper, the application of the boundary element method to fracture mechanics of aircraft panels is presented. The panels are reinforced by longitudinal stiffeners which are attached to the skin by means of fasteners, bonded to it, or alternatively, machined to form an integral panel. The dual boundary element method used can model the crack growth processes automatically without any user interference. Crack propagation is performed for problems involving single or multiple cracks. The method is used to analyse the effect of both membrance and out of plane bending loads.

Published
2002

4. Boundary element analysis for damage tolerance assessment of aircraft panels

Author

Aliabadi, M.H., Wen, P.H., and Salgado, N.

Abstract

In this paper, the application of the boundary element method to fracture mechanics of aircraft panels is presented. The panels are reinforced by longitudinal stiffeners which are attached to the skin by means of fasteners, bonded to it, or alternatively, machined to form an integral panel. The dual boundary element method used can model the crack growth processes automatically without any user interference. Crack propagation is performed for problems involving single or multiple cracks. The method is used to analyse the effect of both membrance and out of plane bending loads.

Published
2002

8. THE ANALYSIS OF MECHANICALLY FASTENED REPAIRS AND LAP JOINTS

Author

Salgado, N. K. and Aliabadi, M. H.

Abstract

Abstract—A new Dual Boundary Element formulation is presented, which allows for the analysis of mechanically fastened repairs and lap joints. The method requires only the boundaries of the problem to be discretized and the fasteners location is simply defined by a set of internal points.

Published
1997
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11. The boundary element analysis of cracked stiffened sheets, reinforced by adhesively bonded patches

Author

Salgado, N. K. and Aliabadi, M. H.

Abstract

This paper presents a formulation based on the Dual Boundary Element Method and on the Dual Reciprocity Method for the analysis of thin cracked metal sheets to which thin metal patches and stiffeners are adhesively bonded. The stiffened cracked sheet is modelled with the Dual Boundary Element Method. Adhesive shear stresses are modelled as action–reaction body forces exchanged by the sheet and patches. The Dual Reciprocity Method is used to avoid the discretization of the patches attachment domain into internal cells. Several examples are presented to demonstrate the efficiency and robustness of the method developed. The examples include sheets with embedded or edge cracks, stiffened or not, to which single or double patches are adhesively bonded. © 1998 John Wiley & Sons, Ltd.

Published
1998
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