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Fibre Placement (fibre + placement)
Selected AbstractsInfluence of fibre position on the flexural properties and strain energy of a fibre-reinforced compositeJOURNAL OF ORAL REHABILITATION, Issue 7 2003A. Ellakwa summary, The introduction of laboratory-processed composite systems and fibre reinforcement techniques have increased the possibilities for the prosthetic replacement of missing tooth tissues. Laboratory fabrication variables may significantly influence the properties of the final prosthesis. During the construction of a fibre-reinforced bridge it is necessary to place the fibre at some distance from the fitting surface of the restoration in the pontic region. No guidelines are available for optimal fibre placement in this respect. The purpose of this study was to assess the influence of placing ultra high molecular weight polyethylene (UHMWPE) fibre at five different distances from the tensile side of test samples on flexural properties and the strain energy stored within the dental composite. The results of this investigation showed that whilst moving the fibre reinforcement away from the tensile side by up to 1·5 mm led to a significant reduction in flexural strength, there was no significant decline in the increase in strain energy stored within the tested composite until this distance was exceeded. [source] The influence of fibre placement and position on the efficiency of reinforcement of fibre reinforced composite bridgeworkJOURNAL OF ORAL REHABILITATION, Issue 8 2001A. E. Ellakwa The effect of placement of ultra-high molecular weight polyethylene (UHMWPE) fibres on the flexural properties and fracture resistance of a direct dental composite was investigated. The UHMWPE fibres are increasingly being used for the reinforcement of laboratory fabricated resin composite crown and bridgework. The aim of this study was to assess the effect of a commonly used laboratory fabrication variable on the in vitro strength of beam shaped specimen simulating a three-unit fixed bridge. Four groups (10 specimens per group) of Herculite XRV were prepared for flexural modulus and strength testing after reinforcement with UHMWPE fibres. Two groups of control specimens were prepared without any fibre reinforcement. Half the specimen groups were stored in distilled water and the other groups were stored dry, both at 37 °C for 2 weeks before testing. The results of this study showed that placement of fibre at or slightly away from the tensile side improved the flexural properties of the composite in comparison with the unreinforced control specimen groups whilst the mode of failure differed according to fibre position. Scanning electron microscope (SEM) investigation revealed that placement of the fibre slightly away from the tensile side favoured crack development and propagation within the resin bridging the interfibre spaces in addition to debonding parallel to the direction of fibre placement. Laboratory fabrication variables may effect the strength of fibre reinforced bridgework significantly. [source] Diverse optical characteristic of the prostate and light delivery system: implications for computer modelling of prostatic photodynamic therapyBJU INTERNATIONAL, Issue 9 2005Jerzy Jankun OBJECTIVE To explore the use of photodynamic therapy (PDT) as a minimally invasive form of treatment for organ-confined prostate cancer, for although there are several therapies, ablative treatments are associated with significant morbidity. MATERIALS AND METHODS Using the photosensitizer tin etiopurpurin, dogs were treated with interstitially placed laser fibres in an effort to validate PDT for treating prostate cancer. Earlier models assumed a uniform distribution of light output from a cylindrical fibre and a uniform attenuation coefficient throughout the prostate. Subsequent observations show that this model was too simple and that light radiance is not linear. To overcome under-treatment, a computer program to complement real-time fibre placement was developed. RESULTS As light radiance from interstitially placed laser fibres varies significantly from the commonly assumed ideal cylindrical emission, a predictive mathematical model of prostate PDT needs to consider the real emission. Also, the optical properties of the prostate, e.g. absorption and scattering of light, are anisotropic. Differences in the attenuation coefficient (combining absorption and scattering of light) also varied among different animals. Incorporating all these variables into a computer program produced a virtual model of the photo-ablated zone within ± 2 mm of that observed in animals. CONCLUSION PDT of the prostate is not trivial and should benefit from computer-aided methods as it is developed for clinical use. [source] | ||||||||||